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1x9ues
|
why did the guitar become the go-to instrument for rock and the blues?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1x9ues/eli5_why_did_the_guitar_become_the_goto/
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"I think it's because the guitar, and it's variations, are one of the few instruments you can sing with while playing. Try doing that with a saxophone or violin. Adding on to that, it's a fairly easy instrument to learn and allows for easy of movement and performance, so its an easy fit.",
"It's also not prohibitively expensive, like say... a grand piano.",
"Simple, cheap, portable. "
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7ldxsa
|
why do lithium ion batteries degrade over time?
|
Why do lithium ion batteries capacity diminishes after each cycle? I'd like to know what happens chemically or structurally.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7ldxsa/eli5_why_do_lithium_ion_batteries_degrade_over/
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"Entropy.\n\nYou already know that batteries are a chemical process. It reacts one way to generate electricity which we use to power your devices. When you run electricity into it, it reverses the chemical process so that it can react another day. But nothing ever happens *perfectly*. Something's gotta give. In our case, the electrodes get slowly eaten away in the process and eventually the performance falls below what we find acceptable for running our devices and we get a brand new one.",
"If i replace an old phone battery, should the phone be almost back to normal?",
"Most traditional batteries have an anode and a cathode. The anode and cathode material is pasted or painted on a current collector. Lithium cobalt oxide is a popular cathode material and carbon/graphite is a popular anode material. Lithium ions are the positively charged particles that intercalate (move) from the anode to the cathode during discharge and from the cathode to the anode during charge. Charge has to be maintained, so electrons flow from current collector to current collector to balance the movement of lithium, resulting in electricity/current flow. During this cycling, some of the lithium ions irreversibly react with other species in the battery and are no longer available to move back and forth between the anode and cathode. This is what causes a loss in capacity. These side reactions can vary, but generally involve lithium moving from an ion in the liquid phase to its solid state or the development of dendrites. A secondary method that can cause capacity loss is the breaking of electrical contact between the anode or cathode material and their respective current collectors because there are some stresses associated with the lithium movement. ",
"Entropy is the answer for the degradation. \n\nChemically batteries give up and gain electrons.\nThis is called oxidation and reduction. The element giving up the electron is OXIDIZING and the element gaining the election is REDUCING. When the electron leaves an element and goes to the other element that creates voltage.\n\nIf we look at zinc and copper the voltage given off from an electron leaving zinc and going to copper we would get 1.1V (at standard conditions). To “recharge” you apply current which causes the electrons to move back to the zinc and then flow towards the copper again.\n\nAs a reaction occurs the elements actually lose and gain mass. So a zinc copper battery has electrons leaving zinc and going towards copper. At the end of the reaction the copper cathode(positive side of battery) will be bigger than when it started and the anode (negative side of battery) will be smaller.\n\nDue to entropy and us living in an imperfect world after so many charges there will be an abundance of electrons on one side or another causing a cathode or anode to be bigger.\n\nThe cathode and anode sit inside a solution of its own salt. So the zinc will sit in something like ZnNO3 and the copper will be in CuNO3. These are electrolytes because they both disassociate to form Zn + NO3 and Cu + NO3. So as the reaction occurs and electrons are transferred to the cathode the Cu is taken out of solution and forms onto the solid copper. Thus making the cathode bigger.",
"I am a battery test engineer. There are many ways lithium batteries can degrade, but since this is ELI5, I'll stick to one main method. \n\nBatteries have a few main parts: the anode (negative), the cathode (positive), a separator between them, and some stuff in between (usually a liquid) that conducts ions. When you charge a battery, you are cramming a whole bunch of lithium ions into the anode, kind of like absorbing water into a sponge. When you use the battery, these ions flow to the cathode, generating electric current. Over time, by cramming the ions in and out of the anode and cathode, you begin to damage the 'sponge', so it can't hold as many ions any more. So your efficiency goes down.",
"While there are people here who are knowledgeable about this - why do some batteries of well-known producers inflate?",
"For anyone interested in making their batteries last longer. For lithium ion batteries (not other kinds that retain a “memory”), your battery will live longer if you don’t allow it to discharge all the way, say you always kept it above 60%, it may last as much as 3 times longer ",
"How a Lithium-ion battery works:\nA lithium-ion battery consists of a negative electrode, a positive electrode, and an electrolyte. The two electrodes are seperated by a porous (to allow electrolyte through) seperator. Each electrode consists of particles that lithium can be stored in and a porous (to allow electrolyte through) polymer binder which holds these particles together and ensures electrical contact between the particles. When an lithium-ion battery is fully charged, almost all lithium is stored in the negative electrode particles. When you connect an external wire between the positive and negative electrodes, lithium travels to the surface of the negative electrode particles where a chemical reaction occurs producing a lithium ion and an electron. The lithium ion travels through the electrolyte to the positive electrode but the electron cannot travel through the electrolyte and so travels through the electrode particles, polymer binder, and external wire (producing a current) to the positive electrode. The lithium and electron then recombine through another chemical reaction to produce lithium stored in the positive electrode particles. This process occurs in reverse when you apply a voltage to charge the battery. \n\nDegradation: \nThe most important degradation mechanism is the formation of the solid-electrolyte interphase (SEI). The SEI is a layer that is formed on the surface of the negative electrode particles from the products of a range of different unintended chemical reactions. One of the chemicals used to make this layer is lithium. Therefore the more SEI, the less lithium there is to move between the positive and negative electrode particles and so we can store less charge in our battery (the is called capacity fade). One other effect of the SEI is that it is slightly harder for lithium to travel through than if it wasn't there. This means the SEI increases the resistance of the battery which results in power fade. \n\nA second mechanism is lithium plating. This occurs when one tries to charge the battery too quickly, which corresponds to forcing too much lithium into the electrode particles too quickly. Once the concentration of lithium reaches some critical level, the lithium no longer inserts itself into the electrode particles as desired but instead plates itself to the surface because it has nowhere else to go. Because of the properties of pure lithium (instead of lithium inside the electrode particles) it is then common for dendrites (long chains of lithium) to form. These dendrites can become very long, and can form in such a way as to penetrate the porous separator and connect the negative and positive electrodes. This results in a short circuit that can lead to thermal runaway and rapid degradation of the battery.\n\nFinally, throughout the charge/discharge cycle the amount of lithium contained in a single electrode particle changes. This results in the particle swelling and contracting. This can cause the particle to fracture (or parts break off) which may result in some of the particle and lithium contained in that broken off part being lost (capacity fade). The SEI may also fracture and break off, leading to a new surface where more SEI can form (accelerating the capacity fade). Furthermore the swelling of the particle can result in some of its surfaces becoming detached from the porous binder through which electrons must travel to the wire. This leads to higher current densities (and so higher temperatures which generally accelerates other degradation mechanisms) and potentially loss of electrical contact with that particle (capacity fade). \n\nThere are many other degradation mechanisms but hopefully this gives a brief overview of some of the most important ones.\n\nTLDR: Its complicated but a good portion of degradation is a result of undesired chemical reactions consuming lithium leading to capacity fade.",
"Pinging /u/Mooch315, aka BatteryMooch of /r/electronic_cigarette fame. This question is right up his alley. He is an EE, with extensive knowledge of Lithium Ion batteries, both from designing and manufacturing bespoke electronic devices utilizing Li-Ion batterypacks, as well as from testing Lithium Ion cells used in E-cigs, to insure the safety of the vaping community.\n\nHe has forgotten more about Lithium Ion cells, than most ever have learned, yet still knows more about them than most. To boot, he is both a gentleman and a scholar, and there’s damn few left of them. He can explain things so everybody, including me (and there are a lot of five year olds way smarter than me), can understand it.\n\n",
"Basically there are two main problems. \n\n1 leeching. Well johnny there two little things in a battery called electrodes. They sit in a liquid called electrolyte. Now imagine the electrodes are cookies and the electrolyte is milk. If you did the cookies in the milk enough times some of the cookie falls apart about stay the in milk. So basically every time to charge / discharge your phone it's like dipping the cookie into the milk again. \n\n(As for why leeching occur this can be caused by a ton of different things. In the research I did it has to do with the electrode materials changing oxidation states thus pushing the new oxidation state ions into solution because the solubility is different than the normally oxidation state)\n\n2 solid electrolyte interphase formation. Okay Johnny imagine you have a sticker. If you stick it the puppy (charging) it will stick pretty well. Then if you pull it off (discharge) you see some hair is stuck to the sticker. Then you stick it back to the puppy and pull it off again. You keep doing this till the whole sticker is covered in hair so it won't stick to the puppy any more \n\n\n(Yes I know not my best analogy. I'll keep thinking about it and try to come out with something better. Basically when you go through charge cycles a film forms on the cathode which holds onto the lithium ions instead of release them back into solution when dis charging. This also blocks the surface from allow ions to attach when charging lowering you capacity)\n\n\nSource : did 2 years of research on electrode materials in lithium ion batteries "
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89zyk2
|
why do our fingers curl up when the hands are laid down on a horizontal surface, instead of them laying flat as well?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/89zyk2/eli5_why_do_our_fingers_curl_up_when_the_hands/
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"our muscles resting position are when our fingers are curled to make our fingers straight you gotta extend them and to curl it more you gotta shorten them",
"Short answer, multi joint muscles and tendons.\n\nThink of it as a game of give and take. When one joint is extended it stretches the tendons like a rubber band. Tendons to be in a slack position when not in use.\n\nA wieldy concept to put into words but I hope that helped",
"the how is covered, now to the why: a strong grip is more important than a strong finger-straightening. having your tendons balanced in a way that causes the fingers to curl by default means you get a little extra force to your grip\n\nit's kinda like the springs in a garage door that naturally pull up, so lifting the door doesnt take much more strength than pulling it down",
"Resting muscle tension (tonus) is stronger in the flexor muscles than the extensors, simply because the muscles used for gripping and holding are stronger than those used for releasing the grip.",
"Your hands are evolved for grasping round objects, like sticks. Notice how your fingers are not all the same length when straightened? Now, curl your fingers like you were grabbing something or checking dirt under your fingernails. Pretty cool how all your fingers are roughly the same length at that point, huh? Your natural hand position is grasping things, not lying flat like a paw.\n\nEdit: one repeatedly autocorrected word: like/lime"
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133pqh
|
why were we attacked on 9/11
|
there are people who say it is because they hate our values (like how we dress and whatever) but that seems too simplistic. What were the real events that led to the attack? Did America do something specifically bad? I hope this doesn't sound insensitive to the victims of 9/11 but i just wanna know if there is another side to the story that we probably don't hear about.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/133pqh/eli5_why_were_we_attacked_on_911/
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"* You have to go back to the origins of the Cold War. \n* The US made allies with some not-nice dictators because the US needed allies and resources to stay even keel with the USSR. \n* One of those dictators was the Shan of Iran, who gave us cheap oil. \n* Many of his people hated him, because he was sometimes brutal to them. The fundamentalist Muslims were particularly upset with him. \n* In the 1970s, the Shah got deathly ill. He came to the US to get medical care. \n* Then there was a fundamentalist revolution in Iran, and they wanted the Shah back to put him on trial. \n* The US said no, and then the Shah died. \n* Around the same time, two things happened. 1) The USSR invaded Afghanistan. 2) Iraq invaded Iran. \n\n* The US supported Iraq (led by Saddam Hussein) against Iran, and started training an underground militia in Afghanistan (including a young bloke named Osama bin Laden) to fight against the USSR\n* Eventually, the Iraq Iran war ended in a stalemate. And the Afghan rebels forced the USSR to leave Afghanistan.\n* The US then forgot all about Afghanistan, and let fundamentalism take over that region.\n* Low on funds because of the lengthy war against Iran, Iraq decided to invade Kuwait (for its oil). \n* In a surprising 180 degree policy change, the US (led by GWH Bush) began calling their former friend Saddam Hussein evil. The US put together a military coalition to push Iraq out of Kuwait.\n* But where to put the US troops? The only place available was Saudi Arabia (Osama bin Laden's homeland, and the site of Islam's most sacred sites). Note: Fundamentalist Muslims consider it blasphemous for non-Muslims to set foot on Saudi soil. \n* Fundamentalist Muslims from Iran, Saudi Arabia and Afghanistan wanted the US off of Saudi land. \n* Two years after the US pushed Iraq out of Kuwait, Muslim fundamentalists blew up a car bomb in the basement of the world trade center. 6 people died. 1000 were injured. The US military continued its presence in the Middle East, including Saudi Arabia.\n* A few years later, Osama bin Laden and Ayman al-Zawahiri co-signed a fatwa in the name of the World Islamic Front for Jihad Against Jews and Crusaders which declared the killing of North Americans and their allies an \"individual duty for every Muslim\" to \"liberate the al-Aqsa Mosque (in Jerusalem) and the holy mosque (in Mecca) from their grip\".\n* Later that year, hundreds of people were killed in simultaneous truck bomb explosions at US embassies in the major East African cities of Dar es Salaam, Tanzania and Nairobi, Kenya. (they were linked to Osama bin Laden). The US increased its military presence in Middle East, including in Saudi Arabia.\n* Two years later in Yemen, a small dingy carrying explosives rammed the destroyer U.S.S. Cole, killing 17 sailors and injuring 39 others. Supporters of Bin Laden were involved. The US continued its military presence in Saudi Arabia, and its support of Israel.\n* None of these terrorists attacks got the attention of US foreign policy. \n* The attack on 9/11, a few years after the attack on the Cole, had nothing to do with the fundamentalist muslim terrorists hating our values or our clothes or our music. These fundamentalists wanted the US off of Saudi soil, and out of Israeli affairs. The US would have none of that. \n* Take note: They did not target the Statue of Liberty. They did not target Disneyworld. They did not target the Olympics. Their attacks were on embassies in the Middle East, military sites, globalization financial centers, and the CIA head quarters.",
" > What were the real events that led to the attack? Did America do something specifically bad?\n\nIt's a big and complicated subject, but there were three major motivations.\n\n- The US had interfered extensively with politics in the Middle East, including [overthrowing democratically-elected governments and replacing them with US-friendly dictators](_URL_0_), to the rage of many in the area.\n\n\n- The US had bases and forces stationed on what the attackers' group considered to be sacred ground, which was seen as blasphemy.\n\n- The US had a history of supporting Israel with financial aid and arms deals. The Israel situation is, again, big and complex, but basically, most of the Middle East sees Israel as an invading force attacking peaceful Muslim areas and occupying the land, including holy land.\n\n9/11 came not as an individual event, but as part of a whole series of attacks against US installations, embassies, bases and materiel, mostly throughout the Middle East and Africa.",
"A better way to ask this might be, what motivated the 911 attackers? I remember reading about the this and learning that \nthree causes for anti-western attitudes in the middle east are:\n\n1)US troop presence in Saudi Arabia (Holy Land)\n\n2)US support for foreign dictators (especially the ones we propped up like Saddam Hussein or Mubarack)\n\n3)US support for Israel\n",
"The US had bases in Saudi Arabia and bin Laden thought that was an abomination. He thought that if we were attacked, people would notice, land decide that it was not worth keeping bases there. He was surprised when the reaction was anger.",
"Out of curiosity, OP, how old are you?",
"\"The Power of Nightmares\", a BBC documentary series by Adam Curtis gives an interesting background and perspective on all the mad political movements starting 60 years ago that ultimately lead to this."
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3yxn94
|
how did scientists think of the formulae for physics and chemistry?
|
Equations such as Ek=1/2mv2 and N=M/GFM.
And the strange triangles that somehow work flawlessly no matter what you need to find out.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3yxn94/eli5how_did_scientists_think_of_the_formulae_for/
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"Too broad for ELI5.\n\nThere's hundreds to thousands of different formula in those two sciences, more if you include mathematics and geometry in the mix. \n\nThe way the formulas were created differs from formula to formula. Some were developed using a mix of repeatable observation and testing, and then using math formulas to determine constant elements like the constant G used in formulas pertaining to gravity. Others were created using calculus or algebra changes to existing formulas. Others are based on how we define terms, with distance = velocity * time being a classic example.\n"
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2q0to2
|
when i get pulled over, how can i tell if the guy who pulled me over really is a cop and not someone who is impersonating one?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2q0to2/eli5_when_i_get_pulled_over_how_can_i_tell_if_the/
|
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"If you're feeling unsafe, call 911, give them the details about where you are, and ask them to verify that the car behind you is a real police car. You can also ask them to send a marked car with a uniformed officer to meet you. "
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2o9owh
|
given that 9,223,372,036,854,775,807 is the limit for a 64-bit integer, how is it that my computer can work out 9,223,372,036,854,775,807 + 1?
|
I saw on /r/programming that YouTube had to start using 64-bit integers after Gangnam Style reached 2,147,483,647 (!) views, which is the limit of a 32-bit integer. If 9,223,372,036,854,775,807 is the limit of a 64-bit integer, how does my 64-bit computer work out 9,223,372,036,854,775,807 + 1 (or, indeed, any value past that)?
**Thanks guys - I think I understand it now :P**
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2o9owh/eli5_given_that_9223372036854775807_is_the_limit/
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"That is the highest integer that can be stored as a complete number. If anything is bigger, the computer simply performs multiple operations to split the number up into fewer digits then calculate the result and finally reassemble the parts.",
"Your computer can easily represent gigantic numbers by using more than one 64 bit signed integer.",
"Your computer isn't *incapable* of doing math with numbers larger than one word; it just can't do them in *one operation* any more. \nMost programming languages offer some facility for numbers of arbitrary size and/or accuracy of representation\\*. These slow down processing relative to using 'primitives' which have hardware support, so programmers use them when those features are necessary. Otherwise, they use simpler solutions. \n\n\n\\* In hardware-supported math, not all decimal numbers can be represented. This leads to weird things like how 0.2 + 0.1 = 0.30000000000000004 unless you use extra computation power on arbitrary-precision floating point math.",
"Depending on what the programming language decides, it can:\n\n\n* roll it over to -9,223,372,036,854,775,808\n* convert it from a 64 int to a BigInt, an arbitrary precision format that users more storage as integer size increases\n* convert it to a floating point value, losing precision",
"If a program needs to deal with numbers bigger than that they can represent numbers using multiple 64 bit pieces.\n\nNumbers of \"unlimited\" size can be created by using more 64 bit \"blocks\". The downside is that the more blocks it uses, the longer operations will take. It's also not truly unlimited because it's limited by how much memory there is, and most implementations would probably just use a 64 bit value to keep track of the number of blocks. But the limit is so unimaginable huge it might as well be unlimited."
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d3fpwn
|
when trying to sleep, how can one position be so comfortable when you first get into it, but then uncomfortable after 5 minutes?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d3fpwn/eli5_when_trying_to_sleep_how_can_one_position_be/
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"What's nice for your muscles and what's nice for your bones and ligaments isn't always the same thing, especially if you have posture problems.\n\nYou might have a tight shoulder for example, and being in a particular position might relieve that. But the same position could put stress on your spine. So you lie down and feel shoulder relief, but a few minutes later your spine starts hurting.\n\nIf you have persistent problems with sleeping comfortably, you may want to get checked out by a physiotherapist. Especially if it's back or joint pain.",
"Get a decent memory foam mattress (doesn't have to be expensive!). I can sleep for hours without moving, the mattress cradles me wonderfully.",
"your body isnt generally meant to stay in the same position forever. almost every position a human body can take on a surface slows the bloodflow of at least one area to less than optimal, and the simple act of staying still or being in a position can cause joints and muscles to tighten up in a way that might cause pain if held too long, and that can be relieved by simply shifting a bit.",
"Like everything in life, hence suffering. Try watching the same thing you like over and over again (eyes). Try listening for your favorite song over and over again (ears). Try eating your favorite dish every day (mouth). Try feeling the same texture every day (body). Try thinking of the same thing over and over again (thinking). 2 things that govern us. mind and body. The body deteriorates. While the mind can be trained."
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45mdgs
|
how can some sea creatures camouflage correctly without having conception of self?
|
Like the angler fish
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/45mdgs/eli5_how_can_some_sea_creatures_camouflage/
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"I asked a similar question on here the other day and [this](_URL_0_) was the response I got, perhaps it will be of some value to you as well.",
"Natural selection is the easiest way to explain. Over generations of specimens, the ones with unfit variations were more likely to be eaten, starve, or not reproduce.\n\nThe ones what survive and reproduce would pass on their adaptation to offspring which would then have the advantage their parent exhibited. Take that natural process over many generations and you now have a species that exhibits a camouflage pattern that it has no concept of possessing.\n\nIf you want to look at something like the cuttlefish (which exhibits a more active camouflaging), it's the same concept but contains an element of neurological and physiological response - certain variants of arousal (fear, sex, curiosity, etc) could possibly have elicited a random pattern until one was used and the specimen survived a pivotal moment. "
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|
1f7o1p
|
why water makes a shock so much worse.
|
Why does water make a shock so much worse, how and why does it amplify the shock?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1f7o1p/eli5_why_water_makes_a_shock_so_much_worse/
|
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"Don't be misled by common knowledge, water itself doesn't conduct much electricity. The thing is: water we use everyday to wash stuff, drink and other purposes has charged substances mixed in it, and they act like a bridge to the eletrons (electricity -- the shock) go through the water body. Picture a glass full of clean, translucent water. Now imagine salt being poured over it. When it comes to touch the water, the sodium and chlorine atoms that once were together break apart and get charged + and -, respectively. Since electricity is made of moving eletrons and those are negative, it needs a bridge made of positive atoms in order to spread through the water.\n**tl;dr: Water doesn't conduct electricity if it isn't mixed with stuff (not enough to make the shock worse)**\nNow answering to your question: Since the surface of your body is dry and neutral of charge (most solid and dry stuff are), it's harder for the electricity to spread across your body, so when you are struck by a shock while wet, the bridge the water forms makes it easier for it to affect a larger area of your body, making it seem worse, though its intensity is the same. Though, as Scottydoesknowbro said, when the shock is strong enough to pierce flesh and affect vital organs, the water on the surface of your body may redirect it to reach only the areas closer to the skin, making it actually better than being struck directly.\n\nEDIT: Clarifying."
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41rk1e
|
are energy harvesting roads a real thing?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/41rk1e/eli5_are_energy_harvesting_roads_a_real_thing/
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"So since you seem to be talking about a piezoelectric method instead of the solar roadway thing that was popular a few months back (which in theory *could* work even though it isn't really wise) this one is in fact taking energy from the cars. The thing about these \"sensors\" which they are using to create electricity is that they don't simply produce power by having weight on them. They make it because they deform when weight is put on them. As soon as it has finished deforming it will stop producing. As someone pointed out, if they made it just by having weight on them we could simply make these and then put a bunch of rocks on them for our power plants.\n\nThe reason this takes energy from the cars is that when we compare the section of road that a car is on to the bit just in front of it, because the sensors it is sitting on got ever so slightly squeezed, that bit of road will be ever so slightly lower than the section right in front of the car, and as such it will take every so slightly more energy (in this case the energy from gasoline) to lift that car onto the next sensor. The amount that it slows the car might not even be measurable by your instruments, but the amount of energy you get from each car is also very very small. Think about walking on a trampoline. Since you are pushing the spot you are on down, no matter which way you walk, it's just a bit up hill.\n\nBasically you are crowd sourcing power generation. You could totally argue that this is fine, and that the tiny amount of extra gas used is the cost of using the road, with all its lights and signs and such. You could argue that it has such a low impact on each individual that although it is *technically* taking their energy, it is *practically* free. You could also say that using someone else's energy without telling them, and instead implying that the energy is free, is a way of duping them regardless of the amounts at hand. \n\nI won't make a judgment about which of the above views is correct, but I will say that *practically*, there are much more cost effective ways to crowd source energy. For one you could just tax the people who use the road and then buy some electricity with that money, which we do. Or make it a toll road, and buy the power with that money. Or just use whatever money you were planning on using to tear up the roads and install this system to instead by some solar panels and batteries. In that case the energy itself pretty much would be free.\n\nTL:DR: It would take a tiny amount of energy from each car. You can say this ok, or not. Regardless, there are most likely cheaper and easier alternatives."
]
}
|
[] |
[] |
[
[]
] |
||
3wayxx
|
how can countries like north korea test their alleged hydrogen/nuclear weapons without others finding out?
|
I heard once they may test underground. If they test underground wouldn't that decimate the underground cavern or whatever they dug up?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3wayxx/eli5_how_can_countries_like_north_korea_test/
|
{
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"cxuryoo",
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10,
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"text": [
"They can't. Testing underground causes unique seismic reactions which are picked up and identified by equipment used to report/study earthquakes. When somebody tests a nuclear weapon, it's known.\n",
"There's no reason to want other countries not to find out. The point in having nuclear weapons is not to use them, but rather to threaten to use them. Other countries just about put up with North Korea right now, and may be willing to grant concessions for not using, not developing, or destroying any nuclear weapons they have. If North Korea were ever to actually attack someone with a nuclear weapon - and theirs are not hydrogen bombs, they are much less powerful if they even exist at all - they would be in for a world of hurt. They do test underground for a number of reasons, and yes, that does make a heavily damaged cavern, but other countries are easily able to detect these detonations. All of which to date have been pretty small. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
euwedn
|
if we humans are hunter/gatherers, why is it risky to eat exotic/wild animals?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/euwedn/eli5_if_we_humans_are_huntergatherers_why_is_it/
|
{
"a_id": [
"ffrw6ht",
"ffsrgd5"
],
"score": [
8,
3
],
"text": [
"We haven’t been true hunter/gatherers for a very long time. Who’s his why we are so susceptible to food borne illnesses. We now have to cook the germs out of everything when it wouldn’t have been as necessary thousands of years ago. \n\nWe isolate ourselves from germs any way we can with clean food and water and showers and medicine. and our immune systems can’t fight them off like they used to. \n\nBut we live past 35 so it’s probably for the best.",
"What do you mean by risky? There's always a risk some animal has a disease or a parasite that we can get from eating it. That hasn't changed. It's true now and it was true 20,000 years ago. We just have modern medicine, hygiene, and clean kitchens to prepare food with that minimize the risk of getting sick. It's also a lot easier to spread diseases now because of how many people there are, how close together we all live, and how much we travel. 20,000 years ago, that was not the case. \n\nIt's also important to note that predatory animals can get sick from food just like we do. A tiger, for example, can get a parasite from eating an infected gazelle just the same as we can."
]
}
|
[] |
[] |
[
[],
[]
] |
||
6co10i
|
why do we sometimes think a word is misspelled when we are certain it isnt?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6co10i/eli5_why_do_we_sometimes_think_a_word_is/
|
{
"a_id": [
"dhwm6ut",
"dhwmg8k"
],
"score": [
4,
2
],
"text": [
"I have no accreditation to back this up and made this up just now thinking about it. But I will share it since no one has commented. I would guess it has to do with how our brains recognize words as a whole and not a series of letters (think of thsoe misesplled but you can sitll raed it thnigs). It stands to reason that if you focus too hard on the letters, you stop recognizing the word as a whole.\n",
"It's called wordnesia, and no I didn't just make that up. There isn't an identifiable reason that it happens, to be honest. It's just one of those weird human things, like sleep and highway hypnosis."
]
}
|
[] |
[] |
[
[],
[]
] |
||
damymp
|
how does the body " decides " when the growth is finished ?
|
What is the biological mechanism responsible for the change from " actually growing " to maintaining your size and silhouette ?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/damymp/eli5_how_does_the_body_decides_when_the_growth_is/
|
{
"a_id": [
"f1rkcq8"
],
"score": [
9
],
"text": [
"So, its pretty complicated. Growth isn't determined by one singular thing. Your genetics affect your potential growth, but external things, like nutrition or illness during your growing years, can play more of a role than your genetics. In other words, poor nutrition or being sickly can mean you never reach your potential adult height - your body just isn't able to grow as much as you could have, so you end up shorter. \n\nBut in terms of what controls growth besides genetics, its hormones (like growth hormone and testosterone) as well as your bones themselves. Your two fastest periods of growth are in utero, as a fetus, and during puberty. During puberty, all the hormones that trigger developmental changes also trigger growth spurts. A couple of years into puberty, the growth plates on your bones mature and then close, so your bones stop growing. This happens at about 14 for girls and 16 for boys, but worth noting that's just height. Both continue to mature and fill out for years after. And of course, it's based on puberty, not age. Totally possible for boys who are late bloomers to still be having growth spurts in college. \n\n\nFun fact, your growth plates don't all stop at once. Your hands and feet stop first. Then your limbs. Then your torso. Your spine is the last thing to reach full adult height... Length? Size."
]
}
|
[] |
[] |
[
[]
] |
|
1ah8mi
|
why 120hz tvs are so easy to find but 120hz computer monitors are not?
|
This bugs the hell out of me. High refresh rate TVs have been available for some time and it comes standard on most TVs. But the technology is very much absent on computer monitors where it would be of great use to gamers who have to deal with screen tearing or enable Vsync. The process for creating TVs and Monitors is largely the same isn't it? So why is this piece of technology only available on ultra high end monitors?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1ah8mi/eli5_why_120hz_tvs_are_so_easy_to_find_but_120hz/
|
{
"a_id": [
"c8xii32"
],
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2
],
"text": [
"Monitors, as they are designed to be seen from close up, have different specification. Due to different types of panels being used (no, one LED panel is not the name as another), you get some pretty significant differences. Pixel density is one, resolution being another. You'll get more pixels per square inch in a monitor, and as such will get a better resolution on a screen the same size. You'll also usually get better viewing angle and colours, but that depends heavily on the specific product.\n\nSo basically, what I'm saying is monitors and tvs are *not* basically the same. Saying a monitor and a TV is the same because they're both LCD screen is like saying a Veyron is the same as a 911 just because they're both fast cars. "
]
}
|
[] |
[] |
[
[]
] |
|
7330pg
|
[sports] how do newspapers know the actual numbers of transfer fees, when those numbers are listed as "undisclosed to the public"?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7330pg/eli5_sports_how_do_newspapers_know_the_actual/
|
{
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"dnniz9p"
],
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"text": [
"I am a sports journalist myself.\n\nWe usually keep a very close distance to management/coaches/staff of the clubs we report about. They will oftentimes not give you an exact number but when confronted with some, they'll tell if you're close or way off. While this then is not an official press statement, we still get the answer we are looking for. Sometimes, they'll just \"drop\" the number during a convetsation and act like nothing happened, because media attention is good attention.\n\nAnother way we often use to get information is to see which people are involved in the deal and find any that are not aligned with either club (mostly player agents or a relative) and get the information from them. They know that being present in press is a good thing for the player and will oftentimes leak the intel. \n\nThere are also some football leak pages simmilar to wikikeaks that oftentimes leak contracts to the press or even make them public. \n\nSometimes it's a combination of the above, mixed with an educated guess that more often than not hits the right fee +/- a few percent, which is often good enough. If the actual fee is €51.355.500, it doesn't really matter if you call it \"Little over 50M\", \"about 51M\" or \"almost 52M\" - your consumers will be satisfied."
]
}
|
[] |
[] |
[
[]
] |
|
1wajye
|
why do conventional schools continue to teach language in the seemingly most ineffective way possible, when there are existing methods that allow you to be at least conversational within a few months?
|
Most people I know claim to have taken x amount of years of a language in high school or college, but have no clue how to get by with said language despite having done well in their respective course.
Why do some schools continue to teach language using the old textbook method when it provides little practical use to the students? Wouldn't it make sense to teach students how to be conversational first and then get more grammatically detailed rather than the reverse?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1wajye/eli5_why_do_conventional_schools_continue_to/
|
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"it's an area resistant to change, largely because one of the main things with language learning is personal input. if you dont put effort into it, and you dont *want* to learn it, then it's not going to happen. and generally, kids dont want to learn the language. if anything they just want to know it already. \n\nthat being said, you're definitely right. there'd be a lot more interest if the teaching methods were a lot more interactive, the way they should be in language learning. the easiest and most measurable approach for schools is to just stamp vocabulary in there. if the students can then spit out the required vocab, they're happy. due to how broad the subject of conversation is, that's difficult to test. you'll always end up setting a set convo, and going through that. so again the students simply need to be taught to mechanically spit out set sentences, in order to pass school exams.\n\npersonally, I'm fluent in 5 languages. I've had school lessons in 4 of them, and yeah, they managed to completely squash my interest for the duration of the course. one of the main issues for me was that everyone was always supposed to stay at the same level, and nothing interesting was set as a goal to progress to, and nothing interesting was left to do if you did get ahead.\n\ntl dr; we need better teachers and variable testing methods to improve things.",
"ELI5: It's more expensive for schools and more time consuming all around to teach students that way. It's far easier to grade them primarily on written things, especially with the current focus on standardized \ntests.\n\nAlso, if budget cuts exist, language programs are often a favorite to cut as English is a global language.",
"As a teacher, I can state pretty confidently that the main reason for this is timetabling. An 11 year old kid has (in the UK) 5 hours of lessons per day, one of which per week is languages. Some (lucky) kids have 2. Either way, a kid who takes a GCSE in languages (at age 16) has had something like 270-360 hours of tuition.\n\nWhen the kids have so much else to fit into their brains, they can't cope with the more intensive practise the courses you suggest require. As a result, schools teach in a way that they think kids are most likely to retain, rather than most likely to help them progress. As kids are learning how to use tables and such like in other lessons, they (we) try to teach kids in a way that gives them the best chance of retaining the fundamentals.\n\nIt's sad, because you're absolutely right, two hours a day for even three months would see these kids performing at conversational level in whatever target language they chose. The problem is that they would have to have fewer Maths and English lessons, and the school would have to commit to finding two hours a day for languages. A three month intensive (and by intensive I mean this two hour a day, five days a week idea) course would last 120 hours, but critically this would not be spread out over five years, and would not have the downside of having to relearn the previous lesson's work in the first twenty minutes of this week's lesson. This is, of course, talking only about contact hours. If you could convince the kids to study at home, then you could push it up to around 200 hours just through private study.\n\nAfter 120 hours, the Alliance Francaise say that you ought to be somewhere between A1-A2, which equates to an average to high level pass on a GCSE paper.\n\nAnother 100 hours should see progress up to somewhere between A2 and B1, which is equivalent to an AS approximately, and is more or less the minimum level you would need to emigrate to the country.\n\nIn short, you could cram all language teaching they normally do in six **years** into two terms if schools were able to timetable it for two hours a day every day. But they aren't.",
"The \"methods\" you're talking about require far more time than you imply. \"Within a few months\" is great and all, but what you're not saying is that those months involve very, *very* intensive immersive experiences. Hours per day.\n\nMost traditional school environments can afford to spend maybe two or three hours a week on foreign language instruction, max. Not the two or three hours per *day* that an immersive approach would require. There's just not enough time for that. But it is barely enough time to get something done the textbook way if the student applies himself. \n\nLike any class, you get out of it what you put into it. ",
"For most people you can't do it in a few months.\n\n",
"Languagey person here -\n\nIt depends on your age when you start learning. As a youngin, you can get by with just learning it conversationally, because that's how you're learning everything else anyway.\n\nThe older you get, the more focused you are on learning via adult methods, which generally require you to understand what you're saying (grammar) before you say it (conversation).\n\nAlso, everyone learns differently. Some people can do the whole conversational thing well. I need rules, otherwise I don't feel confident in what I'm saying at all, and tend to say nothing until I've figured them out.\n\nI can (and have) learned [Portuguese] just by grabbing a dictionary and reading newspapers and books - after having a strong foundation in Spanish. I've also learned [French] simply by reading a grammar textbook.\n\nAnd I've learned [Arabic] by being in an immersion environment where I *have* to speak it, whether or not I'm comfortable with it.\n\nAs to why people claiming to have taken x years of whatever in high school or college - they took the class, they didn't study the subject."
]
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|
[] |
[] |
[
[],
[],
[],
[],
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|
ax1lqp
|
why are lobsters commony sold live, while shrimp are commonly sold dead?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ax1lqp/eli5why_are_lobsters_commony_sold_live_while/
|
{
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"text": [
"Lobsters are sold and boiled alive because Vibrio bacteria. They are a certain kind of bacteria that take only hours to appear after a lobster dies. It became popular in 1880 when American chefs discovered it reduced the risk of severe food poisoning and made it look and taste better. \n\n\nShrimp, do not have this issue, and thus are not sold/cooked alive. ",
"All shellfish go bad very quickly after death, so they need to either be eaten very fresh, or frozen immediately. Freezing affects the taste somewhat, so freshest is best. \n \nLobsters are the most expensive common shellfish, because they take many years to grow to substantial sizes. So to get the best from them, you want them alive when you start cooking.\n \nMore common that cooking them alive is killing them immediately before cooking. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
epjfbc
|
radiocarbon dating is based on the half-life of c14 but how are scientists so sure that the half life of any particular radio isotope doesn't change over long periods of time (hundreds of thousands to millions of years)?
|
Is it possible that there is some threshold where you would only be able to say "it's older than X"?
OK, this may be more of an explain like I'm 15.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/epjfbc/eli5_radiocarbon_dating_is_based_on_the_halflife/
|
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"Theres a few lines of evidence.\n\nOne is a constant half life means it follows first order kinetics, which means there is no dependence on the number of atoms around it, its a process that only involves that atom and happens randomly. You dont need to make a super long term observation to determine the kinetics if its first order, it will be apparent pretty quickly.\n\nThe second reason is that scientists subjected radioactive atoms to pressure changes, radiation, and all kinds of things and the half life never changed. This is good evidence that the decay rate will be constant in nature as well",
"Anything is possible, if only really, really, really unlikely.\n\nThere has been no recorded evidence that any physical constants have been inconstant during any time that matters on a geological or biological scale.\n\nYour question, which concerns to two of the three fundamental forces of the universe, is equivalent to asking if time has ever varied or gravity turned off in the past... If such things had happened, everything in the universe would be different.\n\nVery long-lived radioactive elements that decay infrequently or very short-lived radioactive elements that only exist in minute quantities can both have relatively large error bars and low precision, because it can be hard to get enough decay events for good statistics. However, there has never been any evidence that the half-lives actually changed from say 500 years to 450 years.",
"As I understand it, they aren't sure. Confirmation of scientific theory requires direct observation of the proposed phenomenon. Since we can't go back a million years and measure the decay rate of carbon back then we can't directly observe that its half-life hasn't changed. But, in the absence of any evidence suggesting it has, we assume it hasn't and base other scientific findings on that assumption. \n\nA contrasting example would be studying past climate conditions by drilling ice cores out of ancient ice deposits. The climate conditions that deposited the ice long ago has just been sitting there under other ice for hundreds of thousands of years, so by digging it up, scientists can directly observe the chemical makeup of environmental conditions back then.",
"That threshold exists, but not because half-lives change. Radiocarbon dating is only useful up to around 50,000 years ago, after which the quantities of carbon-14 in a sample are generally so small that they can’t be reliably measured. There are a variety of other dating methods that archaeologists, paleontologists, etc., use for things older than that threshold, including other radiometric dating methods that use different elements.",
"It's also worth noting that there are multiple dating methods that overlap. As an example pulled from thin air, one method has a range of 10-400 years, one that's most accurate at 100-5000 years, one for 300-10000 years. A sample dated 350 years ago by all 3 methods means the date is fairly well supported. It also means that the methods are fairly reliable as well. Now multiply this by hundreds of thousands or maybe even millions of samples, each corroborating together to increase the confidence by some amount. Over the years, this builds a really high confidence in the methods.",
"Supernova light decay studies. Astronomers can observe supernovas at extreme distances, which also means they can observe them a various points in the past, extending back billions of years. While the light from the initial supernova blast doesn't tell us anything about radioactive decay, the supernova creates a large number of radioactive elements that have relatively short lifespans, as in minutes to months. We can observe the changing light patterns from the supernova, and measure the speed at which various radioactive elements are decaying out of that light curve. Radioactive decay rates of elements differ by element, but they all depend on the same fundamental physical constants, so a change in rate for one element would imply a change in rate of all elements. Because we can see the same decay curve at different points in history, we can establish that those physical constants are either unchanged over time, or the change is too small to be detected over billions of years.",
"That's an interesting question, the answer is that it isn't possible to know for 100%. Rather, due to statistical data from decay events we can get a really high level of centrainty > 99%. The process of radioactice dacay is completely random and unpredictable for specific atoms in a population. For example, say you have 100 C-14 atoms and you wish to predict exactly which atoms will decay and when, you have a 1/100 chance of predicting correctly in the next decay. Now let's say you wish to predict how many atoms will decay in amount of time 't', this can be closely approximated using a decaying exponential, #decay=#original*e^(-h/t), Where h is some decay constant. The only reason we can do this, is that we are taking the probabalistic nature of the decay and aren't trying to quantify exactly what atom is decaying and when. So what we can infer from this is, the larger the decaying population the more accurate your prediction. This also applies to the half-life (time it take for half the atoms in the population to decay) of a compund, by the time of the half-life roughly half the population will have decayed, either a little over or a little under half. We can assume this variance from half to be random, so that over many,many half lives, the random deviation will roughly cancel out, allowing a fairly accurate prediction to be made.",
"They can compare the carbon 14 ages to stuff like growth rings of long lived trees to compare and verify that their ages are mostly correct. Radiocarbon isn’t useful after 60,000 years because it decays to such a small amount it can’t be detected.\n\nI think atomic bombs added carbon 14 to the atmosphere and altered ages on the surface, but I’m shaky on that fact.",
"Can someone explain the question like I'm five?",
"Because we have a pretty good grasp on nuclear and particle physics. \n\nFor half-lives to change over time, some very fundamental physics has to change too, and that would have an incredible knock-on effect for everything we've already learned about physics. \n\nWhen we look back at the most distant (and therefore oldest galaxies), physics looks the same. Gravity looks the same, and electromagnetism (where the light comes from) looks the same. While these aren't responsible for radioactive decay, they're still intrinsically linked and allow us to infer that physics as a whole hasn't really changed. \n\nWe can say with as much confidence as possible that such physical interactions haven't changed over time. \n\nOf course, nothing is ever 'certain', but the stockpile of evidence and research gathered since the dawn of modern science points toward the notion that half-lives are constant everywhere and at all times. \n\nTl;dr: Physics.",
"Basically you can produce calibration curves that account for varying radiocarbon through time. This can be done through methods such as analyzing ice cores or calibrating against organisms that were known to have live at a specific date. For example, you can use dendrochronology to get an exact chronometric age of a tree, then use that data to help calibrate your radiocarbon analysis.",
"About 85% of this response comes from a Stuff You Should Know episode I listened to recently: [_URL_0_](_URL_0_) \n\n1) You don't have to wait 50,000 years to measure half-life - if it is a constant then you can calculate what level of isotope decay one would expect to see in a given time frame and measure that. The more often you do that and the more corroborating evidence you have the more confident you can be that your assumption about the rate of decay is accurate, and that has now happened thousands (millions?) of times so we feel pretty good about it. \n\n2) Carbon Dating is always relative, by definition. What folks are actually measuring is the amount of decay in a given sample relative to the carbon levels found in 1950 - meaning that an object found to be 50,000 years old is really 50,000 years old plus however many years away from 1950 we are. \n\n3) Isotope decay has recently been discovered to NOT be constant. Several factors affect different elements differently, so syncing up the various methods of data is a big undertaking right now. By doing that we should be able to account for fluctuations, but some poor sucker has to do all that work. \n\n4) For reasons I do not understand we basically eliminated the possibility of using this method of dating for anything after the detonation of the first atomic bomb. Future humans digging up our remains won't be able to use this method to determine how old we are."
]
}
|
[] |
[] |
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[],
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[],
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"https://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm"
]
] |
|
4inohm
|
what it means when x approaches either negative infinite, zero or positive infinite in the subject of calculus.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4inohm/eli5_what_it_means_when_x_approaches_either/
|
{
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"text": [
"It means exactly what it sounds like.\n\nLet's consider the function f(x)= e^x\n\nNegative infinity: as x gets more and more negative, getting closer to an infinitely large negative number, what happens to the value of f(x)? If you look at the graph of that equation, and look all the way left (towards more and more negative x), you'll see that f(x) gets closer to 0. So, we say that the limit of f(x) as x approaches negative infinity is 0.\n\nZero: now we look at what happens as x gets closer and closer to 0. For this one, we have to consider what happens as x approaches 0 from the left (0-) and the right (0+). Again, looking at the graph, we see that in both cases, f(x) gets closer and closer to 1 as x gets closer to 0 from both sides. Thus, the limit of f(x) as x approaches 0 is 1.\n\n\nPositive infinity: as x gets larger and larger, what happens to f(x) now? Again, looking at the graph, we see that f(x) exhibits \"unbounded\" behavior, which means that f(x) keeps getting bigger and bigger as x gets bigger and bigger. It does not approach some finite value like it does when x gets more and more negative. Thus, we say that the limit of f(x) as x approaches infinity does not exist. "
]
}
|
[] |
[] |
[
[]
] |
||
29arlq
|
why do the homeless tend to stay out of affluent areas, even when they are nearby?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/29arlq/eli5_why_do_the_homeless_tend_to_stay_out_of/
|
{
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],
"text": [
"Probably because they just aren't welcome there.\n\nJust because the people have more money, doesn't mean they will give up more, or give it up more often. Most people who pay a lot of money to live in a nice neighborhood don't enjoy seeing homeless people in the streets.",
"Cops harass them more. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
2zkm3s
|
what is an equinox?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2zkm3s/eli5_what_is_an_equinox/
|
{
"a_id": [
"cpjr45t"
],
"score": [
3
],
"text": [
"As the tilt of the Earth changes, the lengths of day and night change in the different parts of the world. Day gets longer in some areas, shorter in others.\n\nThe equinox for a part of the world is the two times of year when the day is as long as the night. They are equal. Equinox."
]
}
|
[] |
[] |
[
[]
] |
||
1zzt5a
|
do tranquilizer darts really take instant effect? how is that possible?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1zzt5a/eli5_do_tranquilizer_darts_really_take_instant/
|
{
"a_id": [
"cfygzb9",
"cfyre1d"
],
"score": [
4,
2
],
"text": [
"No, they aren't instant, they are fast, but not instant.\n\nGenerally when you see an animal (or person) get hit by one, immediately they go a little loopy, then as the drugs work their way to the heart and brain they get more loopy, and then they fall unconscious as their brain gets drugged.\n\nIt happens because the tend to hit their target so the drugs go straight to the heart and/or brain, meaning a very quick release.",
"We used to tranquilize animals when I was in the Army, and they don't take immediate effect. It always bugged me in movies when they would, or when they shot people in the necks. That's a huge no-no. There's many different ways a drug can be injected. Here's some of the most common in order of slowest to fastest:\n\nIP (into the stomach)\n\nSubQ (under the skin)\n\nIM (in the muscle)\n\nIV (in the vein)\n\nIC (in the heart)\n\nDarts have to be IM because it's the only thing you can hit with any precision from a distance. IM shots take about 15 minutes to start taking effect, and 45 minutes to peak. IRL you shoot an animal and do not give immediate chase, but rather just wait half an hour for it to go to sleep on its own.\n"
]
}
|
[] |
[] |
[
[],
[]
] |
||
dwja28
|
round-robin tournaments
|
I just don’t understand how it works.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dwja28/eli5_roundrobin_tournaments/
|
{
"a_id": [
"f7jmk6c"
],
"score": [
6
],
"text": [
"Every team plays every other team, the winner is the team that wins the most matches.\n\nThe pros are that it seems \"fair\", it doesn't matter that some other team got \"an easier schedule\" because everybody plays everybody. Also, there is a constant number of matches each round for fans to watch, so you don't have fans drop out when their team is eliminated.\n\nThe con is that it takes a lot of games: n/2 • (n-1) for n teams. In a sport where players can wear out, that's a serious problem."
]
}
|
[] |
[] |
[
[]
] |
|
8tcqkx
|
why can’t our devices simultaneously connect to 2 wifi networks to provide an even faster internet connection?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8tcqkx/eli5_why_cant_our_devices_simultaneously_connect/
|
{
"a_id": [
"e16h8om",
"e16iv42",
"e16kqr8",
"e16lka3",
"e16lug0",
"e17nfxz"
],
"score": [
39,
4,
4,
4,
4,
2
],
"text": [
"Fundamentally there is only the hardware available to talk on one frequency at a time. It can be adjusted to hop between channels but at any given time it needs to be on only one.\n\nConceptually you could use two sets of antennas and associated hardware to communicate over two separate channels at the same time, but you would need to use the same router to coordinate the transmission of information otherwise you would just be duplicating your effort. At this point we are proposing a heavily modified device on both ends of the process and it probably isn't even helpful because it is rarely the limiting factor in connection speed anyway.",
"In general the limiting factor is not the amout of wi-fis you connect to that governs your Speed but the quality of said wi-fi and the transfer rate your device can handle. ",
"It has to do with all of the layers of technology necessary for networks to work.\n\nWhen an application calls to the Transport layer, that is usually bound to a single Physical layer device - in this case, a wireless network interface. So, even though you have multiple network connections, your web browser or whatever is only using one of them at a time.\n\nThink of it as filling several buckets of water, but each bucket can only be filled by one spigot. Adding another spigot doesn't do much to help any given bucket get filled.\n\nNow, there are devices called multiplexers and demultiplexers. These devices consolidate and coordinate traffic such that multiple physical connections can be consolidated into one. However, there is some overhead in doing this that most likely makes the overall connection speed even slower in some cases.",
"Depending on what you mean by fast, this is possible, but it’s not terribly useful in practice. \n\nThe ELI5 is that you could have Hulu and Netflix both running, and make each one use a different WiFi connection and this would sort of get you what you want. You would have a harder time making Netflix alone use both, and would probably require some changes by the Netflix engineers. \n\nThere are other techniques for getting a faster connection (plugging in a wired connection) but most of the time WiFi is fast enough. ",
"Because 99.9% of consumers don’t want devices which are more expensive, bulkier, heavier and have shorter battery life.",
"When I get home I'll eli5 this, but the short answer:\n\nNetwork code wasn't really designed to smoothly handle you having two addresses. Imagine your house is on a corner and you decide to use both streets as home addresses. But also imagine you don't tell anyone this, you just randomly send them mail from each.\n\nYour computer is designed to setup holes like mail slots called ports that all are tied to your final physical address, and if your physical address changed constantly it can't maintain that connection. \n\nThere are ways to make it work, but it requires a decent knowledge of routing, special software, or a special router. \n\nIt would be far easier to break down the two connections to handle different tasks but leave each task alone on that 1 connection. \n\nIn the end, it's far easier to increase the bandwidth or speed of 1 frequency than add a whole second one, similar to how using a longer bus is easier than using 2 busses. "
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[]
] |
||
1omdqa
|
how can encryption be cracked?
|
I don't understand how encryption can ever be cracked, as long as it's random. I was thinking if you had a message, let's just say "Hello" and you added random encryption, how could it ever be deciphered **without** actually stealing the encryption method?
For example, "Hello" is my message, so that's 8 5 12 12 15. Now if I added random numbers to that, let's just say 2 4 9 1 3 (those are made up by me, I guess technically not random). You end up with 10 9 21 13 18. Now "hello" turns into "JIUMR" (I hope I counted everything right).
So you see "JIUMR," you know it's encrypted, but how would you ever go about unencrypting that? To me it seems like it could be any other 5 letter word, and if you wanted to get fancy with your encryption it could probably have different length encrypted forms vs. unencrypted forms. Seems pretty fool proof to me :/
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1omdqa/eli5_how_can_encryption_be_cracked/
|
{
"a_id": [
"cctdtqb",
"ccte4vw",
"cctfe8k"
],
"score": [
2,
5,
4
],
"text": [
"The example encryption scheme you outline is essentially a one-time pad. To use it, duplicate set of pads are made up and distributed so that each pair of correspondents has a set. However, distributing and maintaining the secrecy of these pads is pretty difficult, especially when a correspondent is under deep cover in hostile territory. If the pads can be intercepted en route, it would be easy to make copies and then send them on their way.\n\nTo avoid this, book codes might be used, in which an innocuous-seeming book that is readily available might be used as the seed. Certain dates would correspond to certain pages, or there might be another mechanism to determine the sequence of letters chosen. But while there are a lot of books, it's not impossible to narrow things down, especially if you can get access to the correspondent's library, even for a fairly short period of time.\n\nSo yes, randomness is good, but it's not actually easy to generate and distribute random sets of letters securely. Loads of these codes have been broken not by breaking the algorithm itself, but by intelligence work of one kind or another.",
"First, you are actually correct. If you use a truly random sample to create what a \"one time\" key, then it is impossible to break the encryption. No amount of brute force or fancy algorithm (other one that steals the key) can break the encryption because, since the key is really random and is used only once, there's no mathmatical way to distinguish the \"right solution\" from a wrong solution. \n\nThe catch is that, if the key isn't really random (if there's even a slight bias) or if its reused enough times, then with a large enough data set and a big enough computer, you can eventually ferret out patterns and determine the underlying message. \n\nThe other answers are very good on encryption generally, but thought you should get credit for being correct. A one time, true random key, actually is unbreakable. ",
" > I don't understand how encryption can ever be cracked, as long as it's random.\n\nYou are describing an encryption scheme called one-time pad. One-time pad is unbreakable under two conditions.\n\n1. Your pad (in this case \"2 4 9 1 3\") is truly random. \n2. You use your pad once and only once.\n\nLet's look at rule number 2. What happens if you use the same pad twice?\n\nTo be clear, I will use A=0, B=1, ... Z=25. It makes the math come out much cleaner. \n\nIn your example, you have the plain text 'HELLO'. We will use *m* to denote a plain text message. Your pad is 'CEJBD'. We will use *k* to denote the pad (also known as a *key*). Your coded message, or cipher text, is 'JIUMR'. We will use *c* to denote a cipher text.\n\nThe way to state this mathematically is *m* + *k* = *c*. To get the original message back, we can just do *c* - *k* = *m*. It's pretty much normal algebra. OK, now what happens if we use the same pad a second time.\n\nI'm going to encode the plain text 'APPLE' with the same pad. What I get is the cipher text 'CTYMH'. In math notation this would be *m'* + *k* = *c'*. Notice I'm using a little tick mark to show that the plain text and cipher text are different. But the pad is the same, so I use the same variable.\n\nWhat happens if we re-arrange these equations? We can do this.\n\n*m* + *k* = *c* \n*k* = *c* - *m*\n\n*m'* + *k* = *c'* \n*k* = *c'* - *m'*\n\nWe rearranged both equations so that *k* is all alone on one side of the equals. That means we can set the other two sides equal to each other.\n\n*c* - *m* = *c'* - *m'* \n*c* - *c'* = *m* - *m'*\n\nThat means that if we subtract one cipher text from the other, we get the same answer as if we subtracted one plain text form the other. Let's see what that gives us.\n\n JIUMR\n - CTYMH\n -------\n HPWAK\n\nThat may not look very helpful, but now we actually have a lot more information. 'HPWAK' is no longer an English word plus some randomness. It is one English word minus another English word. Also, look at the fourth letter. It is an 'A'. That means that if you subtract the fourth letter of one word from the fourth letter of the other word, the answer is zero. That means those letters are the same. You can do something similar with the other letters. Because the first letter of our answer is 'H', we know that the first letters are 7 letters apart in the alphabet ( [A, H], [B, I], [C, J], etc.). Since the second letter is P, we know that the second letters of the plain texts are 15 letters apart in the alphabet ( [A, P], [B, Q], etc.). With this information and some patience, you could probably figure out both plain texts, especially if they were as long as a paragraph.\n\nThat's one example of how codes get cracked."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
7g0p8e
|
why are we still capable of “active” listening while asleep? do we actually retain knowledge of things we listen to or hear in our sleep?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7g0p8e/eli5_why_are_we_still_capable_of_active_listening/
|
{
"a_id": [
"dqfug39"
],
"score": [
2
],
"text": [
"You are not actively listening while you sleep. You are unlikely to retain any influencing spoken when you are unconscious. Any suggestion otherwise is a myth."
]
}
|
[] |
[] |
[
[]
] |
||
d3szm6
|
if the moon's gravity affects the tide then does it also affect the orbit of man made satellites?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d3szm6/eli5_if_the_moons_gravity_affects_the_tide_then/
|
{
"a_id": [
"f04wsvs"
],
"score": [
2
],
"text": [
"Yes, but the effect is very small, and satellites have to use thrust periodically to adjust/maintain their orbits anyway."
]
}
|
[] |
[] |
[
[]
] |
||
1o1t5c
|
what is digg and its relation to reddit?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1o1t5c/eli5_what_is_digg_and_its_relation_to_reddit/
|
{
"a_id": [
"cco285w"
],
"score": [
5
],
"text": [
"Digg used to be a website very similar to Reddit. People would post links & vote on them to figure out what was popular & they'd talk about it. A bunch of bad things happened to make people unhappy with the site (like people cheating to get top stories visibility). When everyone was already unhappy, they tried to do a major redesign of the site that nobody liked. They ended up losing so many users they went out of business.\n\nA lot of the users that left came to Reddit.\n\nToday, Digg is back as a completely different site run by new people."
]
}
|
[] |
[] |
[
[]
] |
||
8ttyqy
|
- why cant appliances work on both ac power or dc power?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8ttyqy/eli5_why_cant_appliances_work_on_both_ac_power_or/
|
{
"a_id": [
"e1aa1oh"
],
"score": [
2
],
"text": [
"It's all about cost, except for motors. AC and DC motors have completely different designs. Most things are AC because we have AC outlets in our homes & offices. There aresometimes DC versions made, for mobile homes for example."
]
}
|
[] |
[] |
[
[]
] |
||
17rqrr
|
how does the skin-crawling optical illusion work?
|
_URL_0_
stare at the centre of the first image for 30 seconds, then look away. Whatever you look at will appear to rotate, similar to the gif
Why?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/17rqrr/eli5_how_does_the_skincrawling_optical_illusion/
|
{
"a_id": [
"c88by41",
"c88c90c"
],
"score": [
2,
3
],
"text": [
"Yours eyes try to compensate for all sorts of images, including how light or dark the image is, what colors your brain is expecting in the image, and motion. The spiral creates the illusion of motion and your eyes compensate for it. When you look at a non-moving image, your eyes take several seconds to react to the new image, during which they try to compensate for motion that isn't there.",
"At the back of your eyes are your retinas. They are made up of special brain cells (neurons) that detect light and fire when light hits them. Behind these are other neurons that detect patterns of firing neurons on the retina. Some detect for things like horizontal lines and others for vertical lines. The farther back you go the more complex the pattern detectors. There are also neurons that detect for movement. For any of the pattern detectors, the longer you are seeing that particular pattern, the less they fire. In other words the longer you are seeing the same thing, the less your brain cares about it. In this example, the spin detectors in your brain are firing. To allow itself to focus on things that change and the important things, the brain begins to inhibit the pattern detectors firing with special inhibitory neurons. So as soon as you look at something else, the front line neurons are firing in a different pattern. The spin detectors stop firing, but there is a lag in when the inhibitory neurons stop firing. You experience this as an opposite movement in the stationary image. Lets say you were staring at a clockwise spin, the inhibitory neurons were causing you to experience a slight counter-clockwise spin at the same time to make the spin seem less noticeable. As soon as you look at the stationary picture your brain makes you see it spin counter clockwise for a few moments. With this illusion, however, the spin is complex with parts that spin clockwise and parts that appear to spin counter clockwise. So lots of pattern detectors are all firing and arguing with each other and the inhibitory neurons are likewise going nuts. So the abrupt stop means it takes the inhibitory neurons longer than normal to stop overcompensating. \n\nTL;DR:Your brain is overcompensating for the movement and when it stops there's a lag till your brain realizes in can stop overcompensating. "
]
}
|
[] |
[
"http://imgur.com/a/VIeMk"
] |
[
[],
[]
] |
|
27jggc
|
why do some people work better with background noise that they tune out?
|
Some people (myself included) will turn on music or the TV as "background noise" and ignore it while we do something else. Why? What is it about having something in the background to tune out that helps some people work better?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/27jggc/eli5_why_do_some_people_work_better_with/
|
{
"a_id": [
"ci1f3g6"
],
"score": [
4
],
"text": [
"I think its because then, if a random sound enters the fray, it will automatically be ignored because you are already ignoring the rest of the background noise. \n\nIf it were silent, then any stray noise would disrupt your work."
]
}
|
[] |
[] |
[
[]
] |
|
91lmga
|
why are wetsuits dark instead of brightly colored for high visibility?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/91lmga/eli5_why_are_wetsuits_dark_instead_of_brightly/
|
{
"a_id": [
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],
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3,
6,
8,
3,
3
],
"text": [
"Actually I don't know. After certain depth colors are not visible. They get filtered out. Blue wavelengths remain mostly. So your yellow wetsuit would look gray anyway.",
"I'm assuming you are referring to wetsuits used for diving.\n\nWhen you are deep in the water you don't really see colour so it won't make much of a difference.\n\nPeople are more likely to go with black because the colour lasts longer, a bright pink wetsuit would fade a lot faster with all the sea water and sun light etc.\n\nThere's also an argument for fashion I suppose, black is easy, it goes with anything. This saves manufacturers having to keep up with fashion trends etc.\n\nI think it's also cheaper, most suits are made of neoprene which is naturally black. On more expensive suits this isn't usually exposed but you would still be able to see it through the other colours anyway.\n\nProbably a lot more reasons, or an actual reason that I don't know about but gave it a shot.",
"Scuba diver here. Dark wetsuits became popular because of military and navy seals. But for recreational diving you will see blue yellow pink black mix. Shiny and reflective stuff will make you enticing to attacks by big predators such as baracuda as they will think you are a shiny fish.",
"Surfer and for many of us it's that black absorbs heat from the sun as well. Let's you have a thinner suit for more flexibility.",
"The natural color of neoprene and similar wetsuit materials is black.\n\nThere *are* [brightly-colored wetsuits available,](_URL_0_) and lots of people wear them. There are also [Search and Rescue wetsuits colored red or orange.](_URL_1_)\n\nThese suits are normally colored by bonding thin colored fabric over the black neoprene. Cut the suit open, the cross-section will be black, neoprene does not take dye very well (obviously: the material is supposed to keep liquid OUT).\n"
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"https://i.ytimg.com/vi/RkcpeNkCaAU/hqdefault.jpg",
"https://www.ndiver-military.com/assets/images/thumbnails/product_default/northern-diver-rescue-wetsuits-search-and-rescue-wetsuit-01-1000x1000-Nxm4.jpg"
]
] |
||
w93ir
|
maglevs and high speed rail?
|
Why aren't maglevs more popular? Wouldn't it make sense to build maglevs more since they use less energy and are faster? They would pay off wouldn't they? ELI5 please.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/w93ir/eli5_maglevs_and_high_speed_rail/
|
{
"a_id": [
"c5bdws0"
],
"score": [
2
],
"text": [
"As of now, they are much more expensive to build. Considering energy must be constantly expended to levitate them, they are also relative energy hogs. \n\nSo no, they really wouldn't pay off. In fact, most infrastructure never pays off its building cost."
]
}
|
[] |
[] |
[
[]
] |
|
71qztl
|
how are kids in their 20s better with computers than parents in their 40s and 50s?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/71qztl/eli5_how_are_kids_in_their_20s_better_with/
|
{
"a_id": [
"dncqmty"
],
"score": [
6
],
"text": [
"We grew up with computers, while they didn't get them until they were well into their 20's. You learn a lot more a lot faster when you're young. "
]
}
|
[] |
[] |
[
[]
] |
||
2qmsbr
|
what was so awesome about 1969 that there are so many songs that mention that year?
|
So I've been listening to some amazing songs recently, and a lot of them have references to the year 1969, like "Summer of '69" and "Hotel California". As a new millennial kid, I'm kinda oblivious to what happened in 1969 and what made it so special.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2qmsbr/eli5_what_was_so_awesome_about_1969_that_there/
|
{
"a_id": [
"cn7iizc",
"cn7imv1"
],
"score": [
4,
3
],
"text": [
"Woodstock, moon landing, all sorts of cool stuff.\n\n_URL_0_",
"I can think of two major things off the top of my head:\n\n1. The first human walked on the moon (In the summer of '69, to be specific!)\n\n2. The US started pulling troops out of Vietnam.\n\n(Edit: Punctuation, and also adding: The first was amazing and cause for excitement all over the world, not just the US. Well, except for the Soviet Union, I guess. In either case, it was a big \"U-S-A! U-S-A!\" moment. As for the second, the war in Vietnam was hugely unpopular, so the withdrawal of troops was a big relief for many.)"
]
}
|
[] |
[] |
[
[
"http://en.m.wikipedia.org/wiki/1969"
],
[]
] |
|
9156ru
|
if i was 66 million light years away from earth and had a telescope strong enough would i be able to see the dinosaurs if i faced it towards earth?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9156ru/eli5_if_i_was_66_million_light_years_away_from/
|
{
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"text": [
"Technical yes but practically it would very very hard. Earth is not large and 66 million light years is very far away and there is a lot of light that could potentially cover up earth in space and not to mention the star right next to earth. So if you could pin point earth you could see dinosaurs.",
"Think in terms of photons.\n\nTo see a dinosaur light would have to reflect off of that dinosaur and travel to your telescope. Light spreads out, so the further away you are, the fewer photons will reach you.\n\nAt 60 million light years away the number of photons reaching you from that particular dinosaur are basically zero. If the dinosaur were very well lit, and didn't move, and the earth didn't move, and you took a photo over several millenia, it would still be a very dark picture. \n\nAlthough then you'd have worry about other light sources (like stars and galaxies in the way), space dust, and the fact your telescope would need to be the size of a galaxy to bring the dinosaur into focus.\n\nSo I'm going with... No. Not really possible, even with a big telescope (and a well behaved dinosaur). ",
"If you had a telescope that was powerful enough to resolve objects the size of a few meters from 66 million light years and way and to see all of this in the visible light spectrum without interference from our own sun any stars in between, and any large clouds of gas and dust, then yes, theoretically that's what you'd see. In practice, there is no telescope capable of doing this. ",
"Yes, in theory. If you were there right now you would be seeing earth as it appeared 66 million years ago. The problem with that is no matter how powerful your telescope is you wouldnt get the full picture. Every pun intended. There are alot of things that would get in the way. Planets, moons, meteors, stars, other light, etc... At that distance even dust would block the image. Imagine standing in your back yard trying to take a picture of a flea standing on Pluto. That's essentially what you're talking about doing. Even if you had a camera that could see and focus that far away the chances of you getting that shot are next to nothing. Another easy example. Hold your hand out in front of you with one finger pointing up. Close one eye and try to notice what is blocked from your vision by that finger. Now bring your finger in closer to your face, notice how more and more is blocked from view? Now imagine having 100,000,000,000 fingers, all at different distances, moving at 25,000 km/h back and forth through your field of vision. Can you see? ",
"No. Not even theoretically. \n\nEver wondered why the telescopes they use to see far away objects are the size of an actual building? You need to capture enough light, and focus it to see something. \n\nThe further away you want to look, the bigger lens you need.\n\nHere's a formula:\n\n`Earth Radius/Distance = 1.22 × Wavelength / Lens Diameter`\n\nTrex was greenish (at least in cartoons), so lets use the wavelength of green - about 500nm.\n\nTo see earth from 66 million years away, your lens needs a diameter of 6*10^10 meters. That's 6 with 10 zeroes, or about 1/3 of the way to the sun - imagine that, a lens so big, light needs 3 minutes just to get from one end to the other. \n\nAnd this wouldnt show you any dinosaurs - you would only see earth as a speck of dust. Dinosaurs are, on average, smaller than the Earth. To see a dinosaur, replace earth's radius with the size of a dinosaur; lets just assume 10 meters. That gives you a **lens size of about 4 light years in diameter** - the distance between sun and the closest other star. If at this point your lens doesnt turn into a black hole (which it will), you would see a very confused looking dino.\n",
"Ok going to start afresh since I have seen some of the answers and supplementary questions.\n\nThe light that left our planet from the time of the dinosaurs is still travelling out into space. However....\n\nComparatively there was not that much light leaving our planet, before it left some was blocked and distorted by our atmosphere, so that even a detailed image of the ground is hard to get from something as close as the international space station. As the light moves away from our planet it is doing so in all directions meaning that as you get further away less of the light from the Earth is reaching you (inverse square law - _URL_0_ ) 66 million light years is a huge distance about 300 times the length of our Milky Way almost all the stars you can see with the naked eye are all in the Milky Way, the only exceptions are some nearby galaxies which though they are clusters of billions of stars, to the naked eye just appear to be a single star. The light from the Earth is also being drowned out from that distance by the light from the Sun and the relative motions of the Earth and you observation point would make any kind of close focus equally difficult.",
"The problem with that is, light spreads as it travels. You can test this yourself with a flashlight; shine it on something very close and it creates a small circle of light, but aim it at the other side of the room and it spreads into a much bigger circle. \nThe same thing happens on a cosmic scale. \nHypothetically, you could capture all of the photons that were emitted from a dinosaur, but you would need a telescope of galactic proportions to do so.",
"All the comments are saying you'd need a super good telescope, but in theory you're correct. The light would have been traveling for 66 million years to get to that point. It's also kinda funny to think that if the sun randomly blew up we would have no way of knowing for 9 minutes.",
"Lets try to imagine the light bouncing off the dinosaur in 2 dimensions to simplify the situation.\n\nDraw a circle with 12 points marked around it evenly like the hour marks on a clock. The circle is our dinosaur.\n\nNow project those marks outward from the centre of the circle. These will represent our light rays bouncing off the dinosaur.\n\nImagine our astronomer trying to see our 2D dinosaur is some distance from the circle with a light bucket ready to catch some of the light from the dinosaur.\n\nYou can see that the further away the astronomer is the larger the light bucket needs to be in order to make sure they catch one of those light rays.\n\nIn 3 dimensions the problem is even worse. In reality there are many more than 12 light rays but as we look out over vast distances, even in a perfect vacuum the light spreads out so thinly that our light buckets (telescopes) pick up very few light rays (photons).",
"Funny I had this same weird idea long time ago, something like could we send a telescope out into space *faster* than light speed, look back and see dinosaurs - so profound, yet so dumb",
"So somewhere in the universe, you can see earth in the past. Very cool, the light itself is digital data that recorded our entire history.",
"What if we put a mirror two light years away? If we looked at it would we be able to see four light years into the past?",
"How about if we had a telescope from say 1 light month? away. Does that mean we would be able to watch the past, in the present?",
"Can we change the question so it isn’t limited by the technology that is a telescope. I’m more interested in the theory of his question. \n\nIf we were 66 million light years away from earth and had the technology to see earth clearly, what would we witness on earth? Would it be present day time or would we see dinosaurs?",
"I think the question assumes it is possible to take a picture and the question is more to do with whether you'd see dinosaurs if it was possible. The answer is yes. Essentially the light from the planet would be 65 million years old, you'd see dinosaurs etc. Some stars that we see today no longer exist. Even the images we have of the sun are 8 minutes (I think) old. The sun could disappear and we wouldn't know for a short while.",
"If you went 66 million lightyears and say 5 seconds away, Could you see the light from the explosion of the asteroid IF that is what killed the dinosaurs?",
"Theoretically yes, practically no.\n\nHowever, I would advise you watch this video.. It might not be possible now.. But could be in the future.\n\n_URL_0_ ",
"I believe the implication of your question has to do with speed of light and time and observing past events and not the practical possibility of actually doing so. So yes, if you were 66 million light years away and with all conditions right, you would be observing what happened here 66 million years ago.",
"Everybody's talking here about the giant lenses needed for the telescope but there's a different approach, using a pinhole camera system.\n\nI remember there was a proposal many years ago that involved two satellites with precisely synchronized positions. The first satellite would be a large field of light-absorbing material with a small hole in the middle. The second satellite would be the sensor. It was calculated that we would be able to see the continents on the closest exoplanets with this setup.\n\nAll we have to do is place the pinhole satellite somewhere between the Earth and the sensor satellite, carefully synchronize their positions, maybe improve the tech a little and use several systems.\n\nAny thoughts?",
"_URL_0_\n\nThis pretty much explains the same idea and also has a cool animation.\nTLDW: no you couldn’t ",
"Theoretically Yes it is possible. \n\nAssuming some alien has his super giant 9000 telescope faced towards us with awesome technology and materials and he happens to be 66 ly away then he would see T-rex and his friends.\n\nPractically No. It is not possible with our current technology of lenses\n\nThe lens would have to be so big it would collapse on its own weight and create a black hole.\n\nThis question was answered before but i cannot find the link I think it was a physics subreddit ",
"Follow up question because I've thought about this a lot, too.\n\nI've never thought about dinosuars, though, I've thought about using it to veiw historical events. We could see how the pyrmids were built, who shot JFK, etc.\n\nWould this work at:\n\n10,000 light years? \n\nAt 5,000? \n\nAt 2,500?\n\nAt 1,000?\n\nAt 500?\n\nAt 250?\n\nAt 100?\n\nAt 50?\n\nAt 20?\n\nAt 1?",
"This is funny bc I tell everyone this. It’s a fascinating topic. Of course we can’t imagine a telescope that can be that powerful.\n\nWe are just saying the theory is if you did indeed have a telescope powerful enough, and you are 66 million light years away and decided to look at earth.\n\nYou would see dinosaurs roaming, the cool thing is while they see dinosaurs we are currently existing as well.\n\nThe past, present, future are all existing at the same time.",
"(copied from my answer to another post)\n\nLet's say that I want a 100×100 pixel image of a dinosaur, the dinosaur is 10×10 meters large, and I want a monochrome images. Furthermore, let's assume that the dinosaur is standing on the equator at noon, and I can get away with a 1 second image, that I need 100 photons per image on average, and that the average albedo of the dinosaur is 0.5.\n\nSo, I want to image pieces that is 10cm×10cm. The insolation is around 1000 W/m^(2), or 10 W per pixel. Let's say half of that is visible,and half of *that* is reflected (albedo). So each pixel sends out 2.5 W of visible light, or 2.5J/s. The energy of a visible photon is around 5\\*10^(-19) J, so the pixel sends out 5\\*10^(18) photons per second. So I need to catch 1/(5\\*10^(16)) of the photons.\n\nThe area of my lens must be 1/(5\\*10^(16)) of the area of a 65 million light year radius half sphere, which is 2.5 \\* 10^(16) square light years. So my lens needs to be around one light year in diameter.\n\nEdit: my calculations cover getting enough light. Further down, it is shown that you would need a 4 light year baseline to see 10 meter objects, so you would need a 400 light year baseline to see 10 xcm objects. So four lenses, each .5 light years in diameter, 400 light years apart, should do it.",
"Of course, and haters saying it’s impossible do not think of the endless of possibilities of space time. Light can move faster than the speed of light if space time is bent, there could be some curvatures of space time, or wormholes, that make imaging dinosaurs possible...",
"But if you could see the dinosaurs you can't because you're not 66 million light-years away and there's no way of getting there. You can't catch up with the dispersing light. \n\nIt occurs to me that if there happened to be some accidental natural mirror with some really convenient positioning and focusing perhaps positioned 33 million light-years away it's conceivably possible that something could be bouncing images of the Dinosaurs back to Earth. That would be fun."
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42hn11
|
do people actually smoke in movies, or is it some kind of trick?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/42hn11/eli5_do_people_actually_smoke_in_movies_or_is_it/
|
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"They actually do (pretty sure), I don't think they would CGI something like that. Probably not a cigarette that you buy at a gas station, they use like a non-nicotine herbal ones. Imagine having to smoke in multiple takes, it would be way too much.",
"There are harmless blends of herbs that give off the correct look when smoked but actors who smoke in real life typically opt to smoke cigarettes. Helena Bonham Carter said her favorite movie to shoot for was Fight Club because it gave her an excuse to smoke around three packs a day.",
"Its a real sign of the times to even ask that question. Just watch any documentary about the Kennedy assassination where they show everyone smoking cigarettes all over the place. Nobody was putting on any act. That's just the way they were.",
"Its depends if they are smokers, but usually they can junt inhale not in lungs but just to mouth",
"As an extra on a 2nd World war movie they snap the filters off normal cigarettes and encouraged smokers and non smokers alike to smoke them. They didn't threaten that we would get less work for doing so or not.",
"Depends on the actor and whether they want to. There are often less harmful alternatives to real cigarettes since, especially in the digital age, you can be doing a take for an entire day. \n\nBut if you're an actor, you kind of understand and accept that you're going to get some roles where you may have to smoke and you will have to smoke a lot. Part of the job. ",
"Another thing a lot of people here aren't mentioning is that sometimes they use real cigarettes, but don't inhale. You can tell that by the opacity of the smoke usually; more opaque means they're just mouth drawing and blowing it out. Less, and they're probably inhaling. Or using an alternative",
"Background extras get extra money for smoke - it is called Smoke Pay. \n\n_URL_0_\n\nIs there a section on the employment contract to indicate working in smoke?\n\nYes. The employment contract contains a check-off box indicating work in smoke. Additionally, the producer must provide each performer with a Material Specification Data Sheet (MSDS) no later than the first day of employment when work in smoke is required. An extra performer is entitled to additional compensation in the amount of $46.95 per day for work in smoke, wet, snow or dust (or any combination of these conditions). ",
"I read a Mad Men article where in California it is illegal to smoke in workplaces or something so therefore pretty much alive and movie shoots in the state they smoke Clove cigarettes ",
"It depends. William B. Davis opted to smoke real cigarettes for The X-Files because smoking was the entire trademark look for the character and he wanted the realistic look. He eventually switched to the herb stuff other people are talking about.",
"In live theatre, they make fake cigarettes that puff out a bit of powder when you blow, and they have a neon orange piece of metal just within the edge that catches the light. \n\nBut some directors have us smoke, and they often prefer it if you are willing. Source: had never smoked, but was asked if I would be willing to at a call back. Said yes, got part, director asked the rest of the cast to teach me how using a hooka. Good times.",
"also, what do they do for marijuana smoke? I was pretty convinced by all the smoke in Pineapple Express...especially the cross joint",
"There's an additional problem- as you continue filming, the cigarette shortens, and if the scene continues, you eventually have to replace it.\n\nIt's a major technical annoyance. Having a cigarette short then long then short does get noticed and detracts from the scene. Also, it's not uncommon to come up with a whole different sequence of out-of-order cuts in editing, so you don't even know for sure what the final correct chronological sequence is while filming.\n\nThis is also one reason why very few movies feature eating or drinking. Bite after bite will not be consistent. Quentin Tarantino makes it a point to break that rule. Of course, an actor getting full after eating 30 bites of strudel during a prolonged shooting session is also an issue.",
"I wish I knew a good trick because everytime i smoke in the movies the people with the flashlights come and asked me to leave",
"You can buy dollar store \"gag cigarettes\" that look real enough... some people smoke real cigs, some people pretend to smoke fakes. Depends.",
"Funny but relevant story. I was an extra in an independent film called Lonesome Jim. It was directed by Steve Buscemi. It was a bar scene, and Steve Buscemi asked the extras one by one if they smoked. First and second guy said yes. Third guy said no. Steve said, \"You're fired\". Then cracked a smile and said, \"Just kidding\". Got to the fourth guy, and he said no too. Steve just looked at him and said, \"Didn't you hear what happened to the last guy\". \n\nSo to answer your question, yes the people actually smoke cigarettes.",
"Ghostbusters still holds the record for the most cigarettes smoked in a movie. Real cigarettes.",
"When I was a kid, I had a similar question: Are they really cussing, or just saying a word that sounds *really* close to the actual cuss word?",
"Can't you just suck the smoke into your mouth and not inhale it? Sure its not entirely harmless but at least most of it isn't going in your lungs that way",
"I can recall a few movies where you can look at whoever is smoking and just tell it's digitally added smoke... it was still pretty well done and would fool most people because they don't know what to look for. \n\nWith small form factor e-cigs these days that offer nicotine free \"juice\" that's another alternative, as long as you aren't in a closeup shot of the cigarette itself to witness the combustion, a few sound effects is all it would take to complete a standard smoking situation. ",
"Smoking man from X-Files smoked real cigarettes the first 2 seasons and then switched to herbal ones because he quit in real life: _URL_0_",
"As others have said, it varies from actor to actor and production to production. Interestingly, in Avatar Sigourney Weaver's character Grace smokes, and in some scenes the cigarette was completely CGI (I think smoke would have interfered with the 3D effects in the live action filming). In the deleted scenes on the deluxe Blu-ray set, you can see scenes where she is puffing away with nothing in her hand."
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||
6hkcx3
|
how does the nose spray prevent my nose from running?
|
When I get a flu, my nose runs endlessly and I have to blow it every ten minutes. My snot is very watery and transparent and only one brand of nose spray is able to stop it (Otrivin Comp if you are familiar with it). What does it do that's different from other sprays?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6hkcx3/eli5_how_does_the_nose_spray_prevent_my_nose_from/
|
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"The active ingredients in that product are xylomethaline and ipratropium.\n\nThe xylomethaline is a decongestant that constricts/tightens the blood vessels and prevents more blood from getting to the area. This makes your nose feel less stuffy because when you're congested, there is a lot pf bloodflow to your nasal passageway, making tge area tight/kind of swollen and harder for air to get through.\n\nIpratropium is anticholinergic that works by relaxing the muscles in your throat and chest, allowing more air to get to your lungs when you take a breath."
]
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[] |
[] |
[
[]
] |
|
e0i3zl
|
what’s datamining in the context of leaking content from new video games?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/e0i3zl/eli5_whats_datamining_in_the_context_of_leaking/
|
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"Let’s use fortnite as an example as most people know what it is. So new pickaxes, skins, Emotes and other such items are added into the game by the developers before they are released to the public.\nSo a new skin that’s going to be released in the upcoming weeks can be added to the game much before then. We are just not able to see it. Data miners will go deep into the game files and find these skins. It’s similar to just opening up all your computer documents and just finding new documents that have been added to your computer. Basically anything new added to the game is usually in the game before it is released.",
"Game datamining is someone digging through the files of a game to find hidden content or information.\n\nThe datamining we hear about on news sites is usually people trying to find what's going to be added or changed in a game before the publisher or developer announces it. For example, in Pokemon Go, dataminers discovered the new Pokemon named Meltan before Niantic announced the event.\n\nDatamining is also used to find cut or beta content in games. Pokemon Ruby, Sapphire, and Emerald are full of old beta content ranging from unused tiles to whole maps. One of them even containd the entire soundtrack from Fire Red and Lead Green."
]
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||
4shoiy
|
i'm trying to overcome my fear of cliff jumping, so how deep would i go into water if i jump from 16 feet?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4shoiy/eli5_im_trying_to_overcome_my_fear_of_cliff/
|
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"You will most likely not go more than 4m deep into the water, and certainly no deeper than 5m. [Here's an AMA](_URL_2_) from a professional high diver stating that professional diving pools are 5m deep, and that the closest he's ever come to hitting bottom was to tap it with his foot after slowing down.\n\nThe height that you jump from matters less than you think. It matters a little bit, but it's not like doubling the cliff height doubles your dive depth. Your dive depth depends on hydrodynamic [drag](_URL_1_), and the force of drag increases the faster you go. Once you dig through all the math, you start getting serious diminishing returns on dive depth the more you increase your cliff height.\n\nTo give you a direct number answer, [this post from StackExchange](_URL_0_) actually did the math for you. 16 feet is close to 5m, and the guy calculated a dive depth of **3.39m, or 11.1 feet** for such a dive.\n\nBut if you doubled that to a 10m cliff? Your depth would only increase to 3.65m, or 12.0 feet. Really not much difference. Your force of impact into the water would be much higher, yes, but hitting bottom really isn't an issue."
]
}
|
[] |
[] |
[
[
"http://physics.stackexchange.com/questions/146010/platform-diving-how-deep-does-one-go-into-the-water",
"https://en.wikipedia.org/wiki/Drag_equation",
"https://www.reddit.com/r/IAmA/comments/1fbz00/i_am_gary_hunt_3_times_world_champion_cliff_diver/"
]
] |
||
1k5eml
|
how did evolution through small mutations cause the creation of the eye or other complex organs that serve no beneficial purpose until completion?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1k5eml/eli5_how_did_evolution_through_small_mutations/
|
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"Simple answer: it's false to assume they served no useful function until completed. This idea is called [irreducible complexity](_URL_1_), and is simply wrong - it's mostly used by creationists and intelligent design proponents, and they use it because they don't have any actual valid arguments based on sound science. It's all they have, so they are loathe to abandon it.\n\nNobody has yet found an example of an organ or system that is actually irreducibly complex. Take the eye - is it really true that having an organ that can detect light and the direction it is coming from is completely useless? Having an eye that can't focus on anything but can detect light is still incredibly useful compared to not having one at all. The fact is, we know quite a lot about the [evolution of the eye](_URL_0_), which has happened independently a whole bunch of times throughout the earth's history. The same is true for pretty much all the other systems that these people have claimed to be irreducibly complex. ",
"The idea that \"an eye serves no beneficial purpose without being fully evolved\" is incorrect. Throughout the animal kingdom and the fossil record (and even in some plants) we see various forms of proto-eyes which serve useful purposes and could represent earlier steps in eye evolution.\n\n_URL_0_",
"It's wrong to say that complex organs like the eye don't serve any purpose until they're are completed, because they're never completed. Human eyes may seem perfect to us but there are many functions they don't possess because as a species, we had no specific advantage encouraging their development.\nOn the other hand, there are many more \"primitive\" examples of \"eyes\" (but let's call those \"light perception organs\") in nature. Some are only able to distinguish between darkness and light. One might see those as \"unfinished\" versions of our eyes, but the species that have them have yet to be confronted to an incentive to develop those.",
"Just FYI, there is no such thing as \"completion\" in evolution. We are not necessarily the best model possible and our evolutionary path is not optimizing us.\n\nEdit: the point of my comment is to elucidate the fact that the efficacy of an adaptation is entirely dependent on the environment of the organism. Yes, you can say a hawk has \"better\" eye sight. But it still doesn't mean anything. Is it correct to say the hawk's eye has advanced in its evolutionary path farther than humans? Absolutely not; that presumes natural selection has a goal or a plan. It does not (see: vestigiality). Furthermore, this inadequate understanding of evolution is what led to scientific racism. ",
"There is this saying: \"In the land of blind, a man with part of an eye survives.\" Or something like that.\n\nImagine a creature that evolved some light receptors. Without rest of an eye it can detect only light/no light. It's still better than being clueless of your surrounding. It could jump out of the harms way when shadow of a predator approached.\n\nWhen the light receptors start growing in a concave, the creature will get more of an idea where the light is coming from. It's not perfect, but much better than detecting only light and darkness.\n\nWhen the concave grows, it becomes more and more accurate until the nerve receptor structure eventually becomes a pinhole camera, capable of producing blurry pictures. There are some animals that still use this, like nautilus for example. Water can flow in and out of its eye freely.\n\nThen a bit of transparent film evolved over the pinhole, to keep receptors clean and infection away. Then it got more and more specialized, until it became a lens.\n\n----\n\nAnother example you might hear about is complexity of a wing. You cannot fly with half of it. It's kind of ignorant assumption, because there are plenty of animals that use half a wing to survive. \n\nWhen you live in high places, the extra bit of skin connecting your arms and torso may mean life or death in case you fall.",
"Here is a very good video about the evolution of the eye and it's uses at the different stages of evolution by David Attenborough.\n\n[_URL_0_](_URL_0_)\n\nEdit: Some clarification",
"This assumes that the eye only has functionality when complete.\n\nThe general theorized way that the eye evolved, was that some mutation happened that caused an animal to have cells that could detect heat/light (probably one mutation for heat that slowly specialized for light, I am uncertain). Over time, the animals with more ability to detect light were favored by conditions. The ones that could make out more information from this light were even more favored because they could use this information to make better decisions (is my food jumping left or right?). As the light sensing organ got better and better, and the brain got more and more capable of processing the information, the modern eye slowly came into being.",
"OP, is it your understanding that evolution can be separated into 'micro' and 'macro'? That may explain your difficulty. ",
"Here's a great explanation by Richard Dawkins. \n_URL_0_",
"There is an excellent video from the BBC [here](_URL_1_). That lays out, much more clearly, the ideas I will try to summarize. \n\nAs others in this thread have pointed out it is wrong to assume that intermediate steps leading up to a lens-eye like those seen in humans do not provide an advantage in selection. The first step would simply be a patch of light sensitive cells which could allow an organism to detect if some object was between it and a light source. This would provide a huge advantage over totally blind organisms Next, slight curving inward of the part of the organism covered in these cells would allow different cells to respond to changes in light in certain directions, again providing a huge advantage even with just slight curving. As this curving continues over evolutionary time a small hole is left allowing for relatively good visual acuity (at least compared to creatures with only a slight dip inward). Next this cavity inside the pinhole could be filled with some sort of secretion creating a very primitive lens without any huge leaps in complexity. Around the same time we might imagine muscles evolving to help the eye such as changing the size of the hole to help maintain visual acuity when the amount of light changes (like the [Iris sphincter muscle](_URL_2_) which controls out pupil dilation) or to aim the eye in different directions without moving the whole body, like the [Extraocular muscles](_URL_0_). Finally over time the lens could become contained in some sort of sheath and its shape tweaked by selection until a very effective eye remains. Ta-da! We arrive at a modern I with no huge jumps in complexity and a consistent idea of the advantages provided by each small change.\n\n",
"That's because evolution does not just occur through random mutations. It also takes into account \"survival of the fittest\". Simply meaning, that mutations that make an organism more suited to its environment are more likely to be passed on. Another thing most people don't realize is that these mutations and selections occur over millions/billions of years. What started out most likely as a single photo-sensitive cell, over billions of years, evolved into what we see today as the eye. This does not mean that the intermediary forms were useless, indeed, if that was the truth, then the organisms would have probably died out in favor of a different mutation that would have been more beneficial to the propagation of the species. Hope this helps.",
"I'm sure someone is about to give a far better answer but as I'm here, I'll bash out a couple of quick paragraphs for the ~~simpler~~ busier folk.\n\nYou are wrong to assume the eye had no purpose and that there were no benefits to organisms before it was finished. And a quick pedantic note, the eye isn't 'finished' in any sense - it just has it's current form because it's evolved to be, it may very will evolve into something else in the future.\n\n\nSO! Here is an incredibly crude summary of the beginnings of the eye. [Here is a picture explanation.](_URL_0_)\n\n\n- Simple organisms first evolved light sensitive cells, like binary - there is either light or there isn't. This meant they could tell the difference between light and dark. These cells started to form in clusters, so now organisms had patches of light sensitive cells. This could be beneficial for feeding, avoiding predators, achieving shelter, all sorts of shit.\n\n- These patches of light sensitive cells started to become ever so slightly concave. These meant that because light only travels in straight lines, a sense of direction was became apparent. Now organisms are capable of telling what direction the light source is. This would be beneficial as you'd now know where the Sun is, what direction prey is coming from, etc. Organisms that had this stage of 'eye' as opposed to the last stage obviously had an advantage and survived to pass on their gene to the next generation.\n\n- The light sensitive cells become ever more concave and form a chamber with a narrower entrance for the light. These allows for far more precise understanding of direction. Higher definition direction if you like. Obvious this is just a step up from the last stage.\n\n\n\nNow, sorry for the abrupt end but hopefully you can see how benefits were apparent from the start. If there were no benefits it would not have developed. Organisms with eyes survived much better than their competitors, the same goes for skin, lungs, noses, hair, ears, buttholes, knees, etc - we are the most efficient creature on the planet, because we earnt the right to be.",
"What you speak of is a concept called Irreducible Complexity, which is the idea that a functioning unit will cease to function if one of its parts is removed. At first this seems self-evident, especially for wings and, like you mentioned, eyes. ‘What is the use of half an eye?’ you ask, along with ‘ What is the use of the half-wing that each small mutation passed through to get to a full wing?’ However, you are framing the question incorrectly; thus begging the question, or assuming a premise that entails a certain conclusion. I guarantee you that there has yet to be discovered a truly irreducibly complex structure, because as soon as we give these assumptions a moment of thought, we immediately see how foolish the concept is.\n\nLet’s think of wings first before I get to eyes. So the question is how did evolution jump from zero wings to the wings of an eagle, as certainly any option in between would lead to the organism being unfit for the environment, right? Wrong. Half a wing is indeed not as good as a whole wing, but it certainly is better than no wing at all. Half a wing can save your life by easing your fall from a tree of a certain height. Furthermore, 60% of a wing could save you from a fall from a slightly taller tree. Whatever fraction of a wing you have, there is a fall from which it will save your life where a slightly smaller winglet would not. So it is easy to see that in theory there should be a smooth gradient of advantages from 1% of a wing to 100%. And we can see this theory in action – there are many animals in the forest with parachuting or gliding capabilities that illustrate in practice every step of the way up this particular gradient.\n\nSo now let us use the same analogy on the development of eyes, and we’ll find it is easy to imagine situations in which only half an eye would save the life of an animal where 49% of an eye would not. Smooth gradients are provided by variations in lighting conditions, variations in the distance at which you catch sight of your prey – or your predators. Just like going out into the forest to find animals that illustrate the intermediates pertaining to flight, the same can be done for eyesight. A flatworm has an eye that can be considered ‘less’ than a human eye. Yet, the Nautilus’ has an eye that is an intermediate in quality between the flatworm and the human. Unlike the flatworm’s eye, which can detect light and shade but see no image, the Nautilus’ eye acts as a pinhole camera and can see a real image; but it is a blurred and dim image compared to ours’. It would be ridiculous to deny the benefits a flatworm’s eye would have over having no eyes at all. What about dogs, whom aren’t capable of seeing the color ranges we humans can – they have eye sight that is considered worse than ours, and yet they still benefit from them? Even more, I am color blind – I have difficulty differentiating blacks/blues/purples and browns/reds/greens/oranges, and yet I’d much rather be colorblind with sight than to have no eyes at all. Now think of it from a hawk’s perspective – Humans have horrible sight compared to them; from a hawk’s perspective we have “half an eye” because we can’t see miles away like they can – but does that make us unfit for survival?\n\nAnd so the answer you are looking for is stated within your question – Complex organs/organisms/mechanics evolved through ‘small mutations,’ or better put: small incremental steps along a graduate slope of development.",
"Natural selection pushes for function following form, not the other way around - which seems counter intuitive to a lot of people. The mutation develops first, then nature experiments with it to see if it can work.\n\n\nThe first \"eyes\" were most likely rudimentary sensor organs that may have been nothing more than a cluster of a few cells. Some of these organisms had more sensitive organs than others, so much so that they triggered responses from exposure to light. Such a simple organ may seem like nothing, but in a world of blind organisms - this made whatever evolved eyes (primitive or not) - king.\n\nThe first 'eyed' organism were most likely predators. The advantage would be too huge to not take advantage of. Nearly all Ediacaran fauna (635 - 541 million years) did not survive into the following Cambrian Period. I think the development of these primitive eyes could very well have played a part in this evolutionary bottle-neck, as Ediacaran life was blind soft-bodied organisms just sucking up bacteria on the sea floor.\n\nWhat followed in the Cambrian Period was an [explosion](_URL_0_) of life, most of which was both eyed, and armor plated. This shouldn't come as a surprise, as there was no need for a shell when everything was blind and mucking about on the seafloor.\n\nI love talking about the dawn of complex life! Sorry if I got on a tangent. The point is, the first eyes were most certainly very primitive - but they could at the very least permit such an organism to be able to orient itself, no which way is up, and whether it's night or day. Once such a feature proves not only that it's not detrimental to the organism - but actually beneficial, natural selection takes over and continues to refine the design.",
"Your question is based an a pretty big false assumption that a lot of people have; that evolution has a goal or \"finished\" point. It doesn't. \n\nAlso, one cannot consider a single physical trait, organ, or characteristic as an individual component; an organism exists and evolves as a whole. The collective genes that make up an eye are also used to make up nearly every other part of the creature. A mutation in a gene that, for example, builds a protein would effect every part of the organism that utilizes that protein. \n\nIn the case of an eye, at every stage of evolution (which is a misnomer as there are no stages but you have to draw a line somewhere) the eye is functional and beneficial to the organism. Eyes first evolved in simple worm- like animals as a nerve cluster that just happened to be sensitive to light exposure. This helped the organism sense light which, in conjugation with an evolved behavior to react favorably to light exposure, could give it a survival or reproductive advantage - survival of the fittest.\n\nOver time subtle gene mutations could make the light sensing cluster more or less functional; providing either an advantage or disadvantage. With enough time and successful reproductive cycles/ mutations a very complex structure will emerge. This is a universal effect that applies to just about everything and is called 'entropy'.\n\nMost people who have heard about entropy believe it only describes the degradation of a complex system over time, given the lack of energy input; and it does describe that. But it also describes the increasing of complexity in a system given a constant energy supply and the ability of the system to process that energy. Given that the sun has provided constant energy to the Earth, and it's complex chemical system, for around 4.5 billion years - that's more than enough time + energy + reproductive cycles to get a human eye.",
"You have three types of mutations; silent, deadly and beneficial. If you get a deadly mutation it generally leads to a disease or death, a beneficial one gives you an edge against other members within your species, for example a longer neck as a giraffe allowing you to reach higher berries. A silent mutation is one that can does not give a distinct benefit or disadvantage because it codes for the same amino acid sequence (amino acids are the building blocks of proteins which in turn create everything within a cell, its structure, enzymes and mechanisms like gateway channels), like GUU mutating to GUC which both code for valine. \n\nEach mutation leading to an eye will serve to benefit the organism in some way, and even if it does not, the organism can carry on breeding until further mutations along its line of offspring produce an eye. However, the organism with the most beneficial mutation will be the one to survive as others die out. it is believed that giraffes were in fact pretty much a horse like animal until a mutation resulting in the longer neck occurred, but this was not any single mutation but a group of mutations.\n\nThe eye is probably my favorite mutation as it is one organ that other animals have developed to a much higher standard than humans, rain deer in Finland have overcome the problem of snow blindness by developing an eye to see in ultraviolet and therefore can see through the snow. Colossus squids have square eyes that can see much further than many eyes of the animal kingdom and is one of the largest, this is because it must be able to see in near pitch black darkness. There are even cases of human beings having mutated eyes, such as the Asian kid with eye equivalent to a cat and some people being able to see ultraviolet because their cornea has not formed correctly. There is an artist that painted what he saw in ultraviolet and flowers really do look more amazing than in natural light. "
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Evolution_of_the_eye",
"http://en.wikipedia.org/wiki/Irreducible_complexity"
],
[
"http://en.wikipedia.org/wiki/Evolution_of_the_eye"
],
[],
[],
[],
[
"http://www.youtube.com/watch?v=HTg3TrDyZ20"
],
[],
[],
[
"https://www.youtube.com/watch?v=Nwew5gHoh3E"
],
[
"http://en.wikipedia.org/wiki/Eye_muscles",
"http://www.youtube.com/watch?feature=player_detailpage&v=mb9_x1wgm7E&t=129",
"http://en.wikipedia.org/wiki/Sphincter_pupillae"
],
[],
[
"http://upload.wikimedia.org/wikipedia/commons/b/b6/Diagram_of_eye_evolution.svg"
],
[],
[
"http://en.wikipedia.org/wiki/Cambrian_explosion"
],
[],
[]
] |
||
2n7c1c
|
how would a financial crisis in europe or asia affect the us economy?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2n7c1c/eli5_how_would_a_financial_crisis_in_europe_or/
|
{
"a_id": [
"cmb2kug"
],
"score": [
4
],
"text": [
"A financial crisis in those areas would affect US exports to those areas. Depending on the severity it can result in a temporary drop in sales or up to another recession in the US."
]
}
|
[] |
[] |
[
[]
] |
||
aru4ak
|
what is post-colonial literary theory and why is it important?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/aru4ak/eli5_what_is_postcolonial_literary_theory_and_why/
|
{
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"text": [
"This is a massively complicated question to answer fully, so I will keep this as ELI5 as I can.\n\nPost-colonial literary theory is essentially the study of literary texts which deal with some form of event(s) or issue(s) stemming from after a group of people or a nation were colonised by foreigners, or during that time. Basically the setting or the characters are in that context in some way or another - such as the time period immediately after a particular people achieve political or cultural independence following colonisation. \n\nSome great examples of post-colonial literary texts include:\n\n“Disgrace” by J.M Coetzee (set in post-apartheid South Africa).\n\n“Midnight’s Children” by Salman Rushdie (set immediately after India’s independence).\n\n“Benang” by Kim Scott (set during a period of Australian history where the English colonialists established dominance over indigenous Australians). \n\nIt often falls into the bracket of post-modernism too because generally it deals with ideas of identity and internal politics as well as how we contextualise our own persona in the world we live in and experience. \n\nThe “theory” aspect is all about the themes and ideas that that context can explore: the ethics of colonisation, the impact that has on different groups, the impact that has in the future, the human experience of being “different” to others, how we can perceive ourselves to be in a global context, and what it means to be culturally independent. \n\nPost-colonial literary theory is massively important because we live in a post-colonial world right now. The political, social, and moral implications of a post-colonial world are vitally important; they are complicated social and artistic realms that we can experience and apply today and forever in the context of human history. \n\nIssues of race, immigration, religion, and identity are all the proverbial political hot-topic in the contemporary political climate. Post-colonial literary theory provides significant artistic and literary commentary on that. \n\nWithout reading post-colonial texts and associated journal articles about them you will probably struggle to grasp fully what it is exactly though, so I would recommend the novels I mentioned above and any others you have been recommended :)\n\nSource: have a degree in English Literature. "
]
}
|
[] |
[] |
[
[]
] |
||
2u5upj
|
so why am i as a (american) "victim" still paying 9-11 security fee every time i book a flight, and how long will they keep charging me for it?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2u5upj/eli5so_why_am_i_as_a_american_victim_still_paying/
|
{
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"score": [
2,
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4
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"text": [
"Security was expanded at airports following 9/11. This isn't free. The people who use the service are charged in order to pay for it.\n\nThere's no sign that the TSA will go away anytime soon.",
"You got the memo about capitalism and free enterprise ? Yes ?",
"If we stop paying the fee, the terrorists win."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
2t4326
|
how does isil post videos anonymously at this age?
|
How is it that they can upload videos and we cannot track them down?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2t4326/eli5_how_does_isil_post_videos_anonymously_at/
|
{
"a_id": [
"cnvigoh",
"cnvj5au"
],
"score": [
3,
2
],
"text": [
"Internet cafe, public wifi, making a hard copy of a video and delivering it to the media. Using Tor. Really, if you get caught doing anything on the internet, it's because you're not trying very hard to be secret. ",
"Methods can include everything from dropping it in the mail to a media outlet, to using TOR to publish it, to walking into an internet cafe."
]
}
|
[] |
[] |
[
[],
[]
] |
|
3n69nj
|
explain the syria situation as if i was a russian.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3n69nj/eli5_explain_the_syria_situation_as_if_i_was_a/
|
{
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"cvl7h6v"
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"text": [
"My country backs the FSA, free syrian army, your country backs the current regime, Assad's regime.\n\nThe US thinks Assad is bad for the area and replacing him would let the US have a stronger control over the area and probably get something we want at a better price. Also he kills lots of his own people.\n\nYou're country supports Assad because he supports the russian army in his country and works with russia with regards to providing better prices on resources. It's also a staging ground and has important russian territories to counter-invade in the middle east.\n\nSo yea it's all a bunch of shit though. Neither side helped early enough to put an end to ISIS and now the place is all fucked up."
]
}
|
[] |
[] |
[
[]
] |
||
3kmsaq
|
federal law supersedes state law.
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3kmsaq/eli5_federal_law_supersedes_state_law/
|
{
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" > But then federal law says they don't car if you can put up a 10 commandments statue but a state can go beyond that. \n\num. what? basically, anything that federal law doesn't specifically cover, the states can decide on their own. and anything that federal law does cover, the states can not make a contradictory law. [technically the states can pass a contradictory law, but the federal gov't would have to exercise their enforcement powers to get that law repealed]",
"* If a state makes something illegal, it is illegal.\n\n* If the fed makes something illegal, it is illegal.\n\n* If the fed makes something illegal, and the state does *not*, it is still illegal.\n\n* If the state makes something illegal, and the fed does not, it is still illegal, *unless*...\n\n* If the fed *makes it illegal for the state to make something illegal*, the state **cannot make it illegal**.\n\n* If the fed makes something illegal, and the state says that it *is* legal, it is still illegal, *unless*...\n\n* If the fed chooses not to *enforce* a law, it is **still illegal** but the state can choose to \"legalize\" it until such time as the fed chooses to enforce it again.\n\nIn the case of gay marriage, the fed has specifically said that states cannot make a law against it. It can't be illegal.\n\nIn the case of legalizing marijuana, the fed has specifically said that it is *still illegal*, but so far has not been enforcing that. The states that have legalized it are just saying that they will not enforce it at the state level: a state trooper can't arrest you for possession. However, a federal officer still *can* (they just...don't...at the moment...). The fed could, at any time, compel those states to enforce the law, at which time state troopers would be obligated to arrest you.",
"In the examples you cite, it's not a federal law, it's the constitution. No law can violate the constitution. The constitution is the foundation of the laws, whether state or federal. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
3xgw9z
|
what drives people to post movie spoilers?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3xgw9z/eli5_what_drives_people_to_post_movie_spoilers/
|
{
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"the same thing that drives people to key nice cars, or vandalize someone else's property: not enough hugs from mommy as a child. I got at least 2 messages sent to me yesterday containing a big star wars spoiler. ",
"So you really have to understand the psychology of self esteem and self image. They are playing this game where they're smarter than you and better than you, and to win they make you mad. Recently, studies have debunked the idea that bullies secretly have low self-esteem. Turns out, no, they're usually very narcissistic, and narcissists aren't covering for anything. They really believe they're that much more important and better than everyone else. \n\nSo put it all together and you get someone who thinks the brief enjoyment they get by making you angry (by spoiling a movie) is more important than the enjoyment you would have gotten from the movie. It's also just a lack of empathy - they are literally incapable of putting themselves in your shoes to understand how terrible it would make them feel, so they don't care how you feel. They're not stupid, they know how it makes you feel, but the mentality is, \"Yeah, but it's not happening to me, so it doesn't matter.\"\n\nTake solace in the fact that studies have also shown that having a movie, show, or book spoiled usually *increases* your enjoyment of it. So if someone does ruin Star Wars by telling you that Darth Vader is Luke's father, you'll probably still enjoy the movie just fine. "
]
}
|
[] |
[] |
[
[],
[]
] |
||
8k4bob
|
why do tinted windows almost look like a grid when you wear sunglasses?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8k4bob/eli5_why_do_tinted_windows_almost_look_like_a/
|
{
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"text": [
"Polarization. Simply put: Sunglasses with polarized lenses align the light in one direction. The tint is an imperfect film that has certain polarizing effects on light as well. When you have the shades on, you’re able to see the alignment of the tinted application. \n\nTry this with cheap shades. You won’t see anything. Any sunglasses with polarized lenses will show off other polarized items. Even the aftermarket screen protectors on some phones are polarized, you’ll see the pattern as well. ",
"Light travels as a squiggly line, going up and down, side to side or in any other diagonal direction. A polarization filter is basically something with very tiny slits in it that only lets light pass if it squiggles in a certain way, blocking all other light.\n\nNow if two filters are behind each other, it depends on how the slits are angled to each other. If they are nearly the same, lots of light pass through both. If they're different, less or even no light at all passes through them both.\n\nNow, glass is made in a way that polarizes light, which changes throughout the pane. If you see light polarized through glass through another polarizing filter, like a good pair of sunglasses, the different angles make that pattern visible because different amounts of light pass through. ",
"Polarization. \n\nBecause you are wearing polarized sunglasses and the car window has partial spotty accidental polarization. A second polarization filter further reduces the visible light creating the effect you describe. So it has nothing to do with the “tint” of the film used for making your car windows look fly. \n\nFurther explanation:\n\nThe tint is like a volume knob on your TV. Overall light is reduced after passing through the “tint” filter. \n\nKeeping the same analogy, polarization is more of like a specific or fine tuning of the bass or treble knob. \n\nLight is made up of unpolarized waves that go up and down. You can thinking of a uniform squiggly line that a 5yo might use to represent the ocean in a drawing. \n\nA polarization filter is like a white picket fence. You could pass the drawing through the picket fence on its side but the paper would not pass through the picket fence if it were “flat” like it would be sitting on a desk. \n\nThis means that the polarized filter only lets certain waves of light through to your eyes or effectively reduces the amount of light you see. \n\nSo when looking at the ocean with polarized glasses, some of the light you would generally see without a filter that makes up blinding glare is eliminated. Net result is you can see the surface of the water and what might be directly below the surface better. Like a fish. \n\nOr when driving into the sun, the glare coming off the road is reduced. \n\nPolarized sunglasses work great for reducing the glare when fishing or driving but things can get funky when you have more than one polarizing filter. For example, a lot of LCD displays use a polarizing filter - to reduce glare on your GPS while driving. So when you look at your phone or the dashboard display with polarized glasses on... too much light is getting filtered and you get a weird visual effect. \n\nNow for automobile glass that has been “bent” or “curved” to match the contour of a vehicle, like the windshield or especially the rear window... the “stressing” of the glass can create a second “accidental” polarized filter. This further reduces the amount of light you see and creates the “grid” effect. \n\nGet two pairs of polarized sun glasses and line them up so you can look through both lenses at a light source like a lamp or outside. The visual effect will be similar to looking through a single lens - only darker. But if you turn one pair of sunglasses on it’s side. You’ll see almost a complete filtration of all the light. You can imagine trying to pass the 5yo wave drawing through a single picket fence. Or even two single picket fences but if one fence is turned on it’s side - you ain’t passing that drawing through the fence. \n\n\n\n\n\n",
"Spots on glass are caused by the glass in that spot being under direct contact from a cooling fan and the glass cooling quicker in that spot. Thus altering how the light waves pass through those spots, which is noticeable through polarized glasses. Not related to the tint. \n\nThis is only the case on tempered automotive glass (anything that isn’t a windshield) due to the manufacturing process. This is why people associate the “spots” or “grid” with tint, since people don’t normally tint windshields and only tint the tempered glass. \n\nSource: work for an automotive glass manufacturer. ",
"The grid is caused by the tempered glass. The tempering process places a grid pattern of stress in the glass itself. Those regions of stress cause light to twist as it passes through. Your polarizer lets you see those patterns of twists. If you go to Google Images and search for \"polarized light stress analysis\", you'll see some beautiful images of this effect.\n\nThis [stack exchange article](_URL_0_) has a photo of this effect that probably closely matches what you're seeing.\n\nI don't know what window tinting has to do with it unless it served to darken the glass enough to let the grid pattern be obvious."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[
"https://physics.stackexchange.com/questions/273439/grid-pattern-on-a-car-window-when-viewed-through-polarized-sunglasses"
]
] |
||
3thqar
|
how is scientific research actually conducted? who pays for the majority of scientific research?
|
For example, does the government research or fund cures/treatments for diseases such as cancer? Where is this research done? Or is it mostly done via private companies? Who does the most research between private companies/organisations and the government?
Any sources you could provide would also be a great help.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3thqar/eli5_how_is_scientific_research_actually/
|
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"text": [
"The National Science Foundation, the Department of Energy, the National Institute of Health, the Department of Defense, and NASA are the larger federal government organizations that support scientific research. Many professors and others at universities apply for grants from these organizations to support their research. There are also private foundations, like the Carnegie Foundation or the Bill & Melinda Gates Foundation, that may provide grants to researchers. And of course college tuition dollars indirectly support at least some academics' research. (Strangely, though, many academics are expected to acquire grants that pay for much, if not all, of their own salaries, plus an \"overhead cost\" that goes to the University)\n\nOf course, there's lots of research going in on the private sphere, too. Microsoft, Google, etc., all employ folks to do research that can be applied to their products pretty much immediately. Drug companies spend billions (one drug company, Pfizer, for example, spends more than the whole budget of the National Science Foundation, which funds basic research on a number of sciences, on R & D).\n\n",
"A lot of research, particularly academic research, is government-funded. Researchers apply to various government agencies to receive grant(s) to help fund their studies. Other sources of funding for academic research include universities, non-profit research groups/organizations, and private donors.\n\nIn addition to academic research, there is also corporate-sponsored research. That's when businesses fund their own research studies because they hope the research will demonstrate that their product/services have proven scientific benefits or are less harmful than assumed.\n\nIf the scientific research is conducted properly and is peer reviewed, then it shouldn't matter where the source of funding comes from... but in reality it does still matter because for-profit research groups (e.g. corporations studying the effects of their own products) have a vested interest in only publishing research that shows the benefits of the products/services they're researching and ignores data that minimizes or contradicts negative findings.\n\nAll scientific journal articles / research studies will report where their funding came from, so at least there is transparency and you will know whether or not the researchers could have potentially been biased through financial interests / corruption.",
"Most scientific research that doesn't have a specific product as an end goal is done by universities or the national labs. The national labs, obviously are funded by the federal government. Most are part of the Department of Energy and originated from the Manhattan Project. Some of them still do nuclear weapons research. There are also NASA labs and some associated with the Department of Defense that do scientific research. \n\nAt universities, professors apply for grants, from agencies like the National Science Foundation or National Institute of Health. The grant proposal outlines the general plan of their research and is reviewed by other scientists for merit, broader impact, and feasibility. However, most of the actual work in the labs is done by graduate students, postdoctoral fellows, and technicians. Professors spend so much of their time writing grant proposals (I think the NSF funding rate is ~15%), teaching classes, writing journal articles and book chapters, reviewing articles, and doing required administrative work, most don't have much time to work in the lab.\n\nOf an actual research grant, about half goes to the university to pay for \"overhead\" expenses, which covers everything from maintaining copy machines to paying for all the journal subscriptions the library carries and computing clusters. Some goes toward the professor's salary and the grad student's stipend and tuition. Some will be used for travel expenses to present at academic conferences or do field work. The rest goes toward actual research expenses - buying supplies and using equipment. Things may vary from institution to institution, but where I did my PhD, our lab had to buy everything we used from our grants - chemicals, equipment, paper towels, gloves, tools. I probably bought as many things from industrial supply stores as I did from lab supply/chemical companies. Really expensive instruments like electron microscopes are typically in shared labs that charge a usage fee. The instrument itself is typically bought using a special grant just for that, the usage fees cover training and maintenance. The cheapest thing I routinely used (a magnetometer with liquid helium cooling that could go to 1.8 K) was $20/hour. The most expensive (a combination scanning electron microscope/focused ion beam) was $65/hour. \n\nProfessors typically have to submit quarterly or annual reports to the funding agency, but generally have wide latitude for actually conducting (or overseeing) the research. \n\nAlso, when a new professor starts at a university, they typically get a \"startup package\" that funds their initial lab equipment and research until they can get a grant. And established professors can get \"endowed chair\" positions that may come with some unrestricted funds from an endowment set up by a big donor. \n\nCompanies used to do a significant amount of basic science research (Bell Labs was the most well-known), but that's been mostly eliminated as the return on investment for basic research is too long-term for companies focused on quarterly earnings reports which unfortunately is most of them now. It's more common now for companies to partner with universities for funding. Senior research/design projects in engineering colleges are often sponsored by companies. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
4016gw
|
when mouthwash says 'kills germ for 12 hours'
|
That just means in a lab setting this liquid fending off any bacterial growth right? It really means nothing in relation to being used in your mouth, right?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4016gw/eli5when_mouthwash_says_kills_germ_for_12_hours/
|
{
"a_id": [
"cyqmgve"
],
"score": [
2
],
"text": [
"It is just an approximate of the tests done in the lab. It doesnt mean your mouth will be free of bacteria for 12 hours. The cleansing power decreases with time and rarely lasts for 12 hours. Usually after a meal the effectiveness is reduced considerably "
]
}
|
[] |
[] |
[
[]
] |
|
ab9a6n
|
how much of an effect do daily vitamins have on someone? is it ever noticeable?
|
I take one of those daily vitamin/calcium tablets every day cuz I'm sort of a picky eater and I just keep wondering to myself how much they really even do cuz it kinda seems like they don't do anything.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/ab9a6n/eli5_how_much_of_an_effect_do_daily_vitamins_have/
|
{
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"score": [
73,
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11,
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"text": [
"Assuming you're eating a reasonably decent variety and quantity of food, and have no other outstanding medical issues that would require a supplement, they don't do all that much. If your diet is unusually narrow or light, then they'll smooth things over a bit (i.e. you won't get healthier, but you won't get sick either). It's mostly a form of preventative medicine that covers gaps left by a bad diet to stop you from developing issues in the first place.",
"If you have enough vitamins it not notice anything as that is the normal state. The problem is if you have to little and that result in problems.\n\nTo much it not good either because high amount is toxic. \n\nIf you eat more vitamins that is need and less then the toxic amount the only result is:\n\n > Multivitamins provide “no benefit” to most people and instead just create “very expensive urine,” the president of the Australian Medical Association has said.\n\nYou body regulate the amount and excrete it if you eat to much. So most people that eat multivitamines have no benefit. It is only people with specific deficiency or very limited diet that need vitamin tables most people do not. The only way to know for sure is by tests. If that is the case for you is impossible to say without test but a sing multivitamine tablet per day can only hurt your wallet. Having more vitamins then is needed provide no benefit.",
"They can have a very positive effect for someone like my brother - severe digestive issues and a very sensitive stomach limit his diet to a pretty small collection of foods. Some people also have a hard time digesting certain vitamins, so they need to take more. \n\nFor a person with a healthy diet, they generally don’t do much, but it’s worth talking to your doctor about whether they might be right for you. ",
"They can be very useful if you are deficient in a vitamin. Most people are not deficient in a vitamin unless they have a problem absorbing that vitamin from the digestive system in which case, the multivitamins can't help. (this can be a problem with B12 as well as others). Multivitamins are considered very rarely useful as a preventive treatment but may be useful in cases where they are prescribed as a treatment.",
"If winter brings you down because of the lack of sunshine, on the west coast from Oregon north, take vitaimin D. Some dairy products are enriched with vitamin D, but the pills are cheap. I take 2000 i.u. every day all year, and I'm trying an increase to 3000 for the winter. It boosted my enthusiasm a great deal.",
"I think it's highly variable, dependent upon a person's body chemistry. I was having some health issues including severe fatigue and joint pain, so much so that I was convinced I had Lyme disease. After multiple doctor visits turns out I was vitamin D deficient. Crazy thing is I was a farmer and in the sun every single day but a vitamin D supplement cleared things up...the body is weird ",
"They are like magic pills if you are deficient.\n\nIf you aren't, you won't even notice em.\n\nAlso, alot of the viatmins and minerals don't play well together and restrict each other absorption, so a multi-vitamin can be basically useless for certain stuff."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[]
] |
|
b8h5fh
|
what is r/place, why did it stop and what is that pixel gif thing?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b8h5fh/eli5_what_is_rplace_why_did_it_stop_and_what_is/
|
{
"a_id": [
"ejxr1kr"
],
"score": [
4
],
"text": [
"Place was an April fools reddit made two years ago. Place was essentially a canvas consisting of 1 million pixels (1000x1000). Users could change one pixels colour every 5 minutes or so (the delay between placements changed). As it progressed over the next couple of hours users started to make drawings and images on it. The April fools this year is kind of the same - it's like r/place, just with gifs. Users can submit gifs and I think people can upvote them to put them onto a short sequence of other gifs. The result is a sequence of gifs one after another that make a movie. The April fools reddit pulls every year tend to be social experiments.\n\nEdit: r/place stopped two days after it was released on 1st April "
]
}
|
[] |
[] |
[
[]
] |
||
mpgjo
|
why do my knees hurt after long plane flights
|
Just took a trip across the Atlantic and for the first couple days back in the US, my knees are killing. Was wondering why this is: circulatory changes from siting, altitude issues...etc?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/mpgjo/eli5_why_do_my_knees_hurt_after_long_plane_flights/
|
{
"a_id": [
"c32syfj",
"c32syfj"
],
"score": [
3,
3
],
"text": [
"It could be from sitting for a long time, but there is a medical condition called decompression sickness or \"the bends\", which specifically results from changes in pressure on your body (most often due to altitude changes).\n\nIt can range from pretty minor, to very severe. The bigger the change in overall pressure, the more severe it is. People who recently went scuba-diving then go on a plane get it the worst.\n\nIn every case, it results from gasses dissolving into liquid at high pressure and then releasing in lower pressure environment. This causes bubbles of gas to build up in the tissues of you body, causing pain or other symptoms, depending on where they build up.\n\nMore info [here](_URL_0_)",
"It could be from sitting for a long time, but there is a medical condition called decompression sickness or \"the bends\", which specifically results from changes in pressure on your body (most often due to altitude changes).\n\nIt can range from pretty minor, to very severe. The bigger the change in overall pressure, the more severe it is. People who recently went scuba-diving then go on a plane get it the worst.\n\nIn every case, it results from gasses dissolving into liquid at high pressure and then releasing in lower pressure environment. This causes bubbles of gas to build up in the tissues of you body, causing pain or other symptoms, depending on where they build up.\n\nMore info [here](_URL_0_)"
]
}
|
[] |
[] |
[
[
"http://en.wikipedia.org/wiki/Decompression_sickness"
],
[
"http://en.wikipedia.org/wiki/Decompression_sickness"
]
] |
|
d55bar
|
what is the difference between sustainable and renewable energy?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d55bar/eli5_what_is_the_difference_between_sustainable/
|
{
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"f0jtfxc",
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8,
3
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"text": [
"They often mean the same thing, but 'sustainable' energy has an extra caveat that your usage doesn't cause a problem in the future. As an example, burning logs in a furnace uses a renewable energy source (trees) but clear cutting forests for power isn't necessarily sustainable. If one exercises proper forest management, however, using trees could be sustainable and renewable.",
"Generally speaking, the terms are used interchangeably but they are not the same; not all renewable sources are sustainable, and not all sustainable sources are renewable.\n\n- Sustainable energy is energy that, when used at a responsible rate, would last for the foreseeable future. For example, nuclear power is considered a sustainable energy source because we have such an abundance of nuclear material to use for fuel that it is unlikely we will run out for thousands of years.\n\n- Renewable energy is energy that regenerates over time, so that any amount that is depleted will eventually be regenerated. Solar is a good example of this, in that the sun will constantly provide additional solar radiation, no matter how much of it is captured."
]
}
|
[] |
[] |
[
[],
[]
] |
||
d3zqnc
|
why is it when you are stopped in a car and the radio is completely static, you can then move the car a foot forward and it comes in clearly?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/d3zqnc/eli5_why_is_it_when_you_are_stopped_in_a_car_and/
|
{
"a_id": [
"f068tfm"
],
"score": [
3
],
"text": [
"Radio signals don’t necessarily require line of sight to work. But if you’re far enough out of range then minor obstructions will present a problem. \n\nThink of it sort of like a light beam but everything is a mirror. At close range, the beam of light hits everything pretty easily. Further away that beam of light is going to bounce off reflective surfaces and the light will degrade meaning you won’t get as much light until you move to an area (sometimes a foot in front of you where a building was obstructing the already weak signal). To further the example, various objects will have levels of “opacity”. The same thing happens when we talk about signals a building that isn’t built “heavy” will allow for better signal propagation than one that is heavily reinforced. So shifting your position one front forward might be just enough to allow that propagation to reach your receiver."
]
}
|
[] |
[] |
[
[]
] |
||
5rf38o
|
-why to grocery stores have refrigerated aisles of food without enclosures? wouldn't it be more economic to retain the cool air and save money?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5rf38o/eli5why_to_grocery_stores_have_refrigerated/
|
{
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"dd7ei7c"
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"text": [
"The fridges use a set of nozzles to create laminar flows of cold and hot air to separate the air inside the refrigerator from the rest of the shop without any physical barriers. It is a pretty cool system and can be quite efficient. Although not as efficient as an actual physical barrier. A shop may install transparent doors or flaps to save energy. And during night they often cover the refrigerators to make them more efficient.",
"They factor the refrigerated air dumped into the store out of the HVAC load. More open cases = less air conditioning needed",
"In a way they are enclosed by something called an air curtain, its basically a wall of moving air that separates the inside air from the outside air. At night many also have actual physical curtains that can be used. It also helps that cold air falls, so they are designed such that they trap in their own cold air.\n\n",
"I can't recall the term for the phenomenon right now, but I would guess it's because if people have to do extra actions, even minor ones, they're less likely to do the task at all. \n\nIf stores build a separate enclosure with a door to save a tiny bit on cooling costs, they're going to lose more than that due to fewer sales. ",
"with the open sections, customers are much more likely to grab more items, and thus spend more money. ",
"Because people are literally incapable of closing doors after themselves and it sets temperature alarms off.",
"It is rather energy inefficient; however, these displays encourage purchases, so what's lost in energy is made up for with profit at the checkout.\n\n",
"It's good marketing. Putting things behind windows helps slow down \"grab and go\", which is a part of good sales. And it also puts a barrier between the buyer and the goods. Seeing things fresh, up close inside of clear plastic, such as meats, tends to encourage lots more buying.\n\nalso works with pastas of the many kinds, which are mostly sold inside of clear plastic, or at least windows of plastic, too. We are visual critters, as our brains are organized around the visual systems we use, so that works best.\n\nIt's more real that way, too. Imagine how poorly chicken and steak would sell if the beef wasn't reddened with nitrites, and you couldn't see the meat, nor feel it either.\n\nImpulse buying and good marketing, all.",
"In the Netherlands, most supermarkets have [closed fridges](_URL_0_)."
]
}
|
[] |
[] |
[
[],
[],
[],
[],
[],
[],
[],
[],
[
"http://www.levensmiddelenkrant.nl/sites/default/files/styles/w620_h366/public/nieuws/koelingen_die_falen.jpg?itok=J22fazi0"
]
] |
||
86kmry
|
what is new materialism?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/86kmry/eli5_what_is_new_materialism/
|
{
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"dw6cp6u",
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],
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42
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"text": [
"Isn’t it weird that we were scared of the Jurassic Park dinosaurs? Like, they were just dead animals in the ground and with our huge scientific abilities we were able to create these living beasts once again, who immediately terrified us as soon as they got out of hand. What contributed to how we understood the dinosaurs?\n\nThey weren’t scary just because they were large killing animals, because Jurassic Park wasn’t any ordinary movie about lions\n\nThey weren’t scary because it was a kind of robots turning on us, because Jurassic Park wasn’t any kind of iRobot/Terminator/etc. movies\n\nInstead, Jurassic Park was scary because of their interplay. Technology allowed us to bring back this freak species from millions of ears ago back, that weird technological feat then stayed true to its natural origin and fight against its constraining conditions — us. So what were the Jurassic Park dinosaurs? They are the widest spread representation of what dinosaurs were. They weren’t just scary animals, and they weren’t just technology gone awry, they were both. \n\nNew Materialism would say that the Jurassic Park dinosaurs are a really good example of the “mutual construction” (fancy word for two ideas building off of each other, like twins growing up together and influencing one another) of technology and life. As we get more material control over life, as we can do more things/enact larger change/achieve greater precision, we make life more technological (phone addiction, prosthetics, FitBits, workplace efficiency measures). With life as an idea closer to technology than before, technology is also closer to life than before. Digital images can go “viral”, programs can have “artificial” intelligence, dinosaurs made in a lab can turn on you and eat you.\n\nThis is happening all over the world, and in a lot more contexts than just technology/life. How we lay the line dividing “nature” (green forests n jungles and stuff) from “culture”(all the not green stuff with humans), “subject” (thing that does something) from “object” (thing that is only ever pushed around), and “self” (me! In my entirety?) from “other” (literally everything else), are all questions taken up by New Materialism, which attempts to answer them by investigating the histories of how certain concepts came to mean what they do now.\n\nFor example, let’s talk about the idea of uploading your brain to the internet. Did you know that spiritualism exploded in the 19th century because telegraphs were invented? Before then, you always had some kind of physical contact with whoever you were talking to, even if it was just that they had mailed the letter you opened. Now that you could get messages from literally the other side of the world without ever having to interact with the other person, people thought that talking to the dead wasn’t too much of a stretch. At the time, they could talk to them as much as they could someone in Eurasia. The electrical world of communication was seen as this cool other plane where just like human energy and spirit could exist. Yes, obviously the telegraph mechanics knew how telegraphs worked, but to the vast public it was still a marvel. Fast-forward a century, there’s this super cool new technology called the Internet. It does the same thing telegraphs do, but now it’s on steroids (if you want a fun internet hole to go down, look up Technopagans). As we’ve sequenced the genome and neural research is getting increasingly advanced (read: technology is increasingly improving our control and understanding over life), we have the idea that we can not only talk through technology, but actually exist in it. The idea that the important parts (those that we care about to prove “aliveness”: consciousness, ability to communicate) of a human can be uploaded to technology is not a new idea. It comes culturally informed by a long reorientation of what “life” means and what this fuzzy thing called “technology” might change it, while nonetheless being bound by the facts of the world (new technology made this more possible, the brain is a hard thing to image, etc).\n\nNew Materialism says “hey, we have these ideas about what things are, we also know that these ideas have had different meanings in the past, and nobody really intentionally pushed these changes in the first place. So why’d they change? What mix of actions, reactions, and facts of the world (material conditions/the physical way things are) caused them? To bring it back to Jurassic Park, it says that it’s significant that humans *made* the dinosaurs and not discover them, and that we care so much about the process of *genetically coding* them so that they were that much more scary when they were set up to scare us, but it’s equally interesting that the way the dinosaurs looked/the method of creation used (genes)/the fact that we had never interacted with them was influenced by factors we don’t necessarily always consider to be actors (things that do things). Dinosaur bone structure, genetic chemistry, and the procession of time all don’t really choose to go out and do things, but they have influenced one of our main cultural touchstones for the interaction of technology and life. Seeing this picture in its entirety is New Materialism\n\nTLDR: new materialism is understanding that ideas/conceptions of things have complicated histories contributed to by not only people but also things.",
"New Materialism is a new body of theory that is still being developed. There are a lot of different thinkers that are part of this emerging field, and there isn't clear agreement between all of them. They come from many different disciplines as well (e.g. study of science and technology, philosophy, sociology, quantum physics, ecology). \n\nThe few things that they appear to agree upon:\n\n* The world, and everything in it is always changing. Nothing is stable -- whether that's the earth beneath our feet (e.g. constant tectonic plate movement, microbes helping to decompose soil), our social institutions (e.g. governments, religions, families), or ourselves (e.g. emotions, bodily mass, etc.) Because of this, new materialists don't focus their work on explaining what something IS, but what it DOES in this flow of constant change.\n\n* The world is not made of opposites (like good/bad, nature/culture, social/material, man/woman). The most fundamental of these opposites that new materialists reject is social/material. They feel that postmodernists focused too much on the social (e.g. using language, culture, or economics to explain too much), and so they want to bring the material realm back (but do so with some of the lessons of postmodernism in mind). This is why some new materialist theorists talk about an \"object-oriented ontology\" in which matter becomes central. [See Ian Bogost's definition.](_URL_0_)\n\n* Everything in the world has the capacity to impact the world. Sometimes this is referred to as \"affect\" or \"agency\". Humans are not the only ones with this capacity. This is why some new materialist theorists talk about \"post-humanism\" and use new materialism to discuss how humans can act more ethically in a changing world (e.g. with regard to animal rights, climate change, etc.). \n\nedit - grammar"
]
}
|
[] |
[] |
[
[],
[
"http://bogost.com/writing/blog/what_is_objectoriented_ontolog/"
]
] |
||
87fawn
|
sudan the northern white rhino breeding
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/87fawn/eli5_sudan_the_northern_white_rhino_breeding/
|
{
"a_id": [
"dwchl6l"
],
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2
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"text": [
"Most likely yes, it would be considered inbreeding. I learned this in freshman year so this info might be outdated but basically, they take genetic material from Sudan. Then they take on of the female’s genetic material. Then, the nucleus of Sudan’s cell will be sucked out, and then will merge with the female’s given cell. After the new “fertilized” (if you can even call it that) cell will be inserted into a host female so they can give birth to the animal. I do remember, and this might have changed by now because of genealogy advancements, that there is a very small chance the cell will take to its host mother, so it will die, or if it does live, it usually won’t live for very long. So all this taken into consideration, since one of the other rhinos will have to provide their genetic material, and another or the same rhino will have to carry the artificial baby rhino, yes it most likely would be considered inbreeding"
]
}
|
[] |
[] |
[
[]
] |
||
biholf
|
what's the difference between extra moisturizing lotion and regular lotion and why not just buy the one with the most strength?
|
Assuming they are both the same brand and same price.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/biholf/eli5_whats_the_difference_between_extra/
|
{
"a_id": [
"em0u4iy"
],
"score": [
2
],
"text": [
"There's almost no difference. Its marketing. They give each bottle a slightly different description or sub name depending on slight differences in ingredients. In most cases if you compare the ingredients they are identical. Companies do this all the time to rip you off.\n\nTake colgate or sensodyne for example. They have many different pastes that supposedly whiten or strengthen or clean but advertise it in a way that if you buy a basic paste that just says the company name and fluoride, that you are getting an inferior paste from the other more expensive ones with more flash on their design and artwork and things it says it does.\n\nThe reality is they are all toothpaste and they all contain fluoride, they do the same job of cleaning, strengthening and whitening your teeth.\n\nThey pry on the weaker minded or ignorant individual who will be gulable enough to believe if they spend more on a better advertised bottle they'll get more value for their money.\n\nIt happens a lot in England with the supermarkets own food brands. Tesco for example will sell you a frozen curry with nice packaging for say £3.50. But they'll also offer you the EXACT same curry in more basic packaging and cheaper use of film lid for £1.00. Comparing the ingredients on the back and tasting them both is close to identical."
]
}
|
[] |
[] |
[
[]
] |
|
2izgpt
|
why aren't soldiers sucked out of air planes when the door opens to skydive?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2izgpt/eli5_why_arent_soldiers_sucked_out_of_air_planes/
|
{
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"cl6wc7t",
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3
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"text": [
"the decompression you see in movies is mostly an exageration, and at the altitude of most parachute jumps it doesn't really happen at all",
"Equalized pressure between the interior and exterior of the aircraft.",
"Mythbusters did the whole \"Getting sucked out of an airplane\" thing, and it's a total myth. Even sat right next to a window that blows out at altitude, you just get buffeted slightly. That's the real reason. Getting sucked out of a plane is a movie myth. "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
83oep6
|
why are roads in snowy/icy areas still made with asphalt?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/83oep6/eli5_why_are_roads_in_snowyicy_areas_still_made/
|
{
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"text": [
"The only thing I can think of is overall cost. I’m interested to see what someone more experienced in the area will say. ",
"The reason potholes are so common in the north is due to a little thing called winter. As it gets cold out, the water that has seeped into the minute preexisting cracks in the road freezes, and as it turns to ice, it expands. This expansion causes the crack to widen. This process happens over and over forming larger and larger cracks that eventually develop into full blown potholes.\n\nThere are ways to make asphalt last longer as well. These techniques usually involve some sort of secondary layer pressed into/on top of the asphalt, adding additional strength. Concrete is more resistant to this process, as it is a more homogeneous mixture, giving it more strength.\n\nConcrete is very effective for defending against pothole formation, but it is not used very often because it is much more expensive than asphalt.\n\nTLDR: because the longer lasting materials (concrete) are more expensive."
]
}
|
[] |
[] |
[
[],
[]
] |
||
3tqxrw
|
what will the world do once bacteria become resistant to all currently available antibiotics?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3tqxrw/eli5what_will_the_world_do_once_bacteria_become/
|
{
"a_id": [
"cx8huza",
"cx8j0yg"
],
"score": [
2,
2
],
"text": [
"It's a circular race between technology and bacteria. We are constantly developing new ways to target bacteria, and the bacteria are constantly evolving. The worry is that our ability to develop new technologies will be slower than the bacteria's ability to evolve, in which case mortality rates from certain bacterial infections are likely to increase. ",
"The world will panic, and rush new antibiotics and other treatments through trials and into production.\n\nThe main reason why we don't have new antibiotics isn't because we can't find them. Any new antibiotic would immediately be quarantined to treat only cases where current antibiotics weren't working, and only under close medical supervision to avoid the issues that allow bacteria to develop resistance. The manufacturers know this, know that a new antibiotic won't earn them much money, so they don't put funds into taking new antibiotics from early *in vitro* (in glass, i.e. outside of an animal) or animal studies - or even funding those early studies at all.\n\nThis is one place where the capitalist model falls down.\n\nThat said, there are a fair few potential antibiotics waiting for funding to be studied and developed. A serious outbreak of a bacteria resistant to all our antibiotics would force funding into them. The only question is how many people would die before they become available, or from side effects from inadequate, rushed testing.\n\nOh, and most importantly, we may be able to get people serious about washing their hands - the single most effective treatment against any bacteria!"
]
}
|
[] |
[] |
[
[],
[]
] |
||
2vxw40
|
why can't you set cruise control below 25 mph?
|
In every car I've ever driven it wont let you turn on cruise control without meeting a 25MPH threshold.
Is this a safety thing?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2vxw40/eli5_why_cant_you_set_cruise_control_below_25_mph/
|
{
"a_id": [
"colufsa",
"colvi11"
],
"score": [
2,
2
],
"text": [
"What possible use could there be for cruise control at school zone speeds?\n\nYou should be more attentive on surface streets where pedestrians are present.",
"Whoever commented on this second is shadowbanned."
]
}
|
[] |
[] |
[
[],
[]
] |
|
1w21w2
|
how exactly do box tops help schools?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1w21w2/eli5how_exactly_do_box_tops_help_schools/
|
{
"a_id": [
"cexye8v"
],
"score": [
3
],
"text": [
"Inherently, they don't. But companies who produce the product agree to pay a school $.10 for every box top the school sends them as a community relations builder with the company. The company can also use it as an advertising point along the lines of \"buy our product and we'll help your school!\""
]
}
|
[] |
[] |
[
[]
] |
||
3hssgh
|
i eat fast food/unhealthy foods daily and yet i gain little to no weight. why is this?
|
I'm 19, 6'1, and 155lbs. I eat have eaten unhealthy foods my entire life but have never gained much weight. I'm not trying to gain weight or anything. I'm just a little confused.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3hssgh/eli5_i_eat_fast_foodunhealthy_foods_daily_and_yet/
|
{
"a_id": [
"cua8m5z",
"cua8mzr"
],
"score": [
3,
3
],
"text": [
"Just so long as you burn more calories than you take in, you will lose weight. If you managed to eat about 10,000 calories a day, but were active enough to burn 11,000 you would wither away in no thyme.\n\n\nFor instance, when training for the Olympics, [Michael Phelps had a daily caloric intake around 12,000 calories](_URL_0_), but because he exercised so much, he burned through all of that. If he had been sedentary with that intake he would have gained a few metric tons daily.\n\n\nMind you that eating just junk food can have other negative impacts on your health unrelated to weight gain...",
"Well you're 19 and 6'1\" which meant you've spent the past few years growing like all holy hell. If you're not aware, growing is not a cheap process - it takes a lot of energy and resources to do that. Like most teenagers, you are enjoying the benefits of a young metabolism. Give it ten years and it'll slow down a fair bit.\n\nSecondly, weight gain is more about how MUCH you eat, not what exactly you eat. You can eat McD's every day of your life but if you're not consuming more calories than you use in a day, you're not going to gain any weight."
]
}
|
[] |
[] |
[
[
"http://healthland.time.com/2012/12/12/the-most-popular-diets-of-2012-according-to-google/slide/michael-phelps-diet/"
],
[]
] |
|
2pl8ly
|
if i randomly find a suitcase full of money, can i legally keep it?
|
If I randomly find a suitcase or bag full of $100,000 cash, on the side of the road for example, would I legally be allowed to keep it? I'm speaking strictly from a legal standpoint, completely take morals out of the equation. It's most likely drug money, so I feel like that would factor into the equation at some point. I obviously couldn't just take the bag to my bank and randomly deposit $100,000. What would one do if they found themselves in this situation?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2pl8ly/eli5_if_i_randomly_find_a_suitcase_full_of_money/
|
{
"a_id": [
"cmxoliy",
"cmxp8mv"
],
"score": [
2,
4
],
"text": [
"I suppose it depends on if you decide to tell anyone. If not, 100% you get to keep it. If you do, you're an idiot. ",
"It depends on where you live. In many states/cities in the US there is an obligation to turn money into law enforcement so that they can try to find the rightful owner. If they can't, the money may go back to the finder or it may go to the government depending on the state/city. Also, if you have reason to believe the money is stolen and/or involved in illegal activity (and there's good reason to believe that $100,000 in cash sitting on the side of the road was stolen or involved in illegal activity) then the law may also require you to turn over the money to law enforcement or face criminal charges.\n\nYou're going to have be more specific about the jurisdiction to get an exact answer, though."
]
}
|
[] |
[] |
[
[],
[]
] |
|
59g4rt
|
i have in the past couple years discovered that if i think about a certain time i want to wake up by the next day, i will wake up pretty much at that approximate time with no alarm, or clock. how exactly does this work?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/59g4rt/eli5_i_have_in_the_past_couple_years_discovered/
|
{
"a_id": [
"d98a2pi",
"d98a5dt",
"d98af25",
"d98ahzy",
"d98bsge",
"d98bwdc",
"d98bzgh",
"d98c0mx",
"d98c4oq",
"d98c50s",
"d98c5aq",
"d98ccm3",
"d98cg14"
],
"score": [
18,
883,
68,
34,
3,
8,
3,
3,
2,
6,
7,
5,
2
],
"text": [
"This always happens to me if I focus on the time I need to wake up the next day a lot. I always set an alarm but I find myself waking up a few minutes before it goes off constantly. It is not because I am used to a certain time I go to sleep and wake up at different times everyday.",
"This is something that's been researched quite a few times, actually.\n\nSleep scientists at Germany’s University of Lubeck asked 15 volunteers to sleep in their lab for three nights. One night, the group was told they’d be woken at 6 a.m., while on other nights the group was told they’d be woken at 9 a.m.\nThe scientists lied, they woke everyone up at 6 a.m anyways. When they collected their results, they noticed that the group they told would be woken up at 6 a.m started releasing stress hormones at 4:30 a.m, meaning their bodies were preparing them for an early morning. Meanwhile, the group that was told would be woken up at 9 a.m woke up feeling groggy and tired.\n\nSo, simply put, when you anticipate waking up at a certain time, your body begins preparing you for it by releasing stress hormones so you can wake up feeling alert and ready. \n\nEdit - [Here's](_URL_0_) a source if anyone wants to read up and get a better understanding",
"For me, when I know I have something important to wake up for, or an early morning, I wake up periodically throughout the early hours of the morning until the time comes for me to get up.",
"I have the same thing. Just check the time before I shut my eyes and think \"Right, waking up at X am\" and it'll happen. Unless my kids wake me up earlier. Alarm clocks ain't got shit on wooden blocks being thrown against a hardwood floor.",
"Just this morning I had a dream about an alarm clock and I woke up. It was 7.59. I had an alarm at 8. That was so weird/cool",
"What I'm not seeing answered is how the body keeps track of time so accurately. When I set my alarm for 6:30am, I wake up at 6:29, every time. ",
"I started a new job this morning. Told myself I needed to be up by 5:45, woke up 2 minutes earlier than this with no alarm.\n\nStrange. ",
"This happens to me. As a kid, I was told I could watch the Grand Prix in the small hours IF I happened to be awake. \n\nI was - I woke 5 minutes before the race, and went downstairs to watch it. \n\nMy mother didn't believe I hadnt set an alarm. I promised I hadn't. Was punished anyway. \n\nNowadays when I wake, I think \"it must be about x o'clock\" and I'm usually right to within about 15 minutes - even waking in the night with no reference, when I could have been asleep for half an hour or half a day. \n\nIt's interesting since our natural body clock isn't on the same schedule as a 24 hour clock, so how come my body can do this? ",
"Circadian rhythms are biological clock manifestations. They can be triggered by the time of day, tides, moon phases. _URL_0_\n\n I myself am a winter time diurnal sleeper and I get sleepy at sunset and wake up at the first glimmer of dawn. Even if there are no windows.",
"Call me crazy but whenever I need to get up very early I sleep with my watch on. It's just a cheap Timex with indiglo but it ticks pretty loud for a little watch. \n\nIf my alarm is set at 4am I'll always wake by 3:55 if I'm wearing the watch. It's made me believe my brain is subconsciously counting ticks but heck after reading some of these comments it sounds like my brain may subconsciously keep time anyway. \n\nGonna have to experiment with and without the watch now. \n\n",
"I do this every day. Set an alarm for 7 am, wake up and check time at: 6:58. Often when I wake up before my alarm I'm like \"oh let's see how much time I have to snooze,\" just to realize it's like maybe a minute and a half. :(. ",
"I'm no expert, so I'll go with what I know. It's pretty common. My dad used to do it. He put an alarm but he'd wake up all by himself if he wanted to. \"I got work at 6AM, I have to wake up at 5AM\" and he was up at 5:01AM. And to an extent, I'm the same as I always sleepwalk at precise times. I think it has to do with our \"internal clock\". Our body knows when it's the day and when it's the night, as it's used to see the cycle go on and on again. And time is something he's getting used to. It's the same when you go to bed at various times but always wake up at that one precise time.\n\nDid you ever work on something for several hours, thinking \"it must be 6:30PM\" and finding out it's 6:28PM ? Or simply walking in town, seeing a clock in the corner of your eye without giving it much thought, and thinking 15 minutes later \"it must be 1:27PM\" for no reason, and asking the time finding out it's 1:27? Our brain remembers what time it is, and tries his best to keep count of the time by itself using everything it can. That's one of the reason winter surprises a lot of people. We're used, as a society, to the fact that at night we're supposed to be out of our working place/school and at home, so every single year, we tell ourselves \"goddamn. It's 10AM and it's still night out there.\" or \"Wait, it's 3PM, what are you doing sun?\", to the point that our body itself isn't sure if we should even be there in the first place. Also why a lot of people have trouble sleeping at regular times when winter arrives. We don't know how to deal with it because our brain is just as weirded out as our eyes.",
"In my experience, this only works for a few mornings. If you rely on adrenaline to wake you too often your body just eventually goes on strike. \nMy sleep pattern is often disrupted if I have to travel to early morning meetings or stay up late to study. I can do a 3am finish or a 5am wake-up a couple of times a week without problem but if I push it too much I'll eventually have a day when I just sleep through everything, no amount of alarms or phone calls will wake me until my body says it's ready. \n"
]
}
|
[] |
[] |
[
[],
[
"http://m.mentalfloss.com/article.php?id=53710"
],
[],
[],
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Circadian_rhythm"
],
[],
[],
[],
[]
] |
||
3716e0
|
whats going on in my brain when i suddenly perceive mundane things i'd never noticed in a different way?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/3716e0/eli5_whats_going_on_in_my_brain_when_i_suddenly/
|
{
"a_id": [
"criuprg"
],
"score": [
4
],
"text": [
"Nobody can give you an answer to this because frankly we just don't know how our brain works. We think we have an idea, for example, which part of our brains control certain functions etc, and then a case like [this](_URL_0_) comes along and blows conventional thought out of the water. By all accepted medical knowledge this woman shouldn't be able to walk, or really do anything for that matter, but she can, and so the human brain is still a complete mystery!"
]
}
|
[] |
[] |
[
[
"http://www.newscientist.com/article/mg22329861.900-woman-of-24-found-to-have-no-cerebellum-in-her-brain.html#.VWEPBNrBzGc"
]
] |
||
9fp4tm
|
what is prograde and retrograde motion?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9fp4tm/eli5_what_is_prograde_and_retrograde_motion/
|
{
"a_id": [
"e5y72am",
"e5zw8zf",
"e64qb41"
],
"score": [
8,
2,
2
],
"text": [
"Prograde = moving more in direction of travel\n\nRetrograde = moving against the direction of travel \n\nMost commonly use is space things and orbital mechanics.",
"Another way of putting it is prograde is the normal or \"expected\" way something will spin or rotate. Like how all the planets in the solar system spin the same way except for Venus (which has a retrograde day/rotation, but still in a prograde orbit) \n\nIt's used to describe storms too, tornadoes in the northern hemisphere typically always spin the same way, but under very specific and uncommon circumstances one can go \"the other way\" and this is a retrograde tornado (they tend to not be as strong as the prograde ones though)",
" \n\nOrbital motion of an object in terms of retrograde and prograde is described with respect to the movement of another object. In this case, the object which it’s orbiting.\n\nA *retrograde* orbit is one where a satellite revolves opposite to its parent body’s direction of rotation. A *prograde* orbit is its opposite—a satellite revolves in the direction of rotation of the parent object. The Moon orbiting the Earth is an example of a prograde orbit. Israeli satellites orbiting Earth is an example of retrograde orbit."
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
4fx1fk
|
why do we like to scare people, and in particular, why do we most like to scare the people we are in the closest relationships with?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4fx1fk/eli5_why_do_we_like_to_scare_people_and_in/
|
{
"a_id": [
"d2cr3kf",
"d2crchv"
],
"score": [
9,
23
],
"text": [
"I don't think that this is something that applies to everyone - at least not me? I don't get why people like scaring anyone and I can't remember the last time someone tried to scare me",
"Physically, our body responds to all strong emotions in the same way (e.g., heart beats faster, butterflies in the stomach, etc.). What we end up feeling, then, depends upon how we interpret the situation. \n\nStartling a loved one initially provokes a strong emotional response. But, when the person looks for cues to interpret that response, she or he see cues related to love and affection rather than fear. This then leads that person to interpret the emotional response as love instead of fear. This may be the same reason people take dates to horror movies.\n\nAn experiment called the [\"Love Bridge\"](_URL_0_) study tested this idea by measuring the attraction men felt toward a women on a sturdy bridge and on a rickety bridge. Results showed that, because men on the rickety bridge felt a greater amount of emotional arousal, they reported feeling more strongly attracted to the woman on the rickety bridge as well. \n"
]
}
|
[] |
[] |
[
[],
[
"http://www.spring.org.uk/2012/04/what-the-love-bridge-tells-us-about-how-thoughts-and-emotions-interact.php"
]
] |
||
2591mj
|
what's the deal with nutmeg?
|
If it can be used as a hallucinogenic drug, then why is it commonly used as a spice? Why is nutmeg legal as opposed to other hallucinogenic substances?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2591mj/eli5_whats_the_deal_with_nutmeg/
|
{
"a_id": [
"chevjws",
"chf08oh"
],
"score": [
2,
3
],
"text": [
"Its just the way people abuse it. If you think about it cough syrup is legal and people abuse that too. Just to get high man ;) ",
"When you use nutmeg as a spice, you only use a few sprinkle of it.\n\nWhen you get high, you need to eat *fucking mountains of nutmeg*. Like the whole bottle. It's like eating nutmeg flavored sawdust & gives you nutmeg burps for days. It's not like popping a pill, it's something that takes a lot of effort and time - most people will decide it's disgusting and give up on it.\n\nWhen you actually do get high, it's not \"hallucinogenic\" - you just feel fucked up for a few days. It's not pleasant, it's not fun & it's not something you're likely to ever try again.\n\nWhy isn't it against the law? Because it's a pretty tasty spice & most people aren't going to be able to actually eat enough to get high off of it."
]
}
|
[] |
[] |
[
[],
[]
] |
|
bzcpg9
|
how does a genetic mutation reach critical mass to become a new species?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/bzcpg9/eli5_how_does_a_genetic_mutation_reach_critical/
|
{
"a_id": [
"eqrhx4i",
"eqs6vvf"
],
"score": [
8,
2
],
"text": [
"\"Species\" is a nebulous term. Scientists usually define it as the point when two populations of animals can no longer breed with each other, but there are other definitions. \n\nFurther more, there's no \"critical mass\" of mutations; I am different from my parents, and they're diffferent from their parents, and so on. At one point, my many-many times great-grandfather was an ape-like animal, and before that, a lemur-thing, then a rat-thing, then a lizard-thing, then a fish-thing and a slug-thing and, all the way back, a single microbe. There is a completely unbroken line of descent from the first life all the way to me, with hundreds of species in between, and yet every single one of my forefathers was the same \"species\" as their immediate parents.",
"This isn’t ELI5 level reading, but this may help. This idea in evolutionary biology is basically the how-to for your question. The [Hardy-Weinberg Principle ] is a sort of list of ways genes can become more common in a population, eventually leading to new species. In the simplest terms, there are some conditions that make new genes more likely to catch on. For example, imagine a lone tortoise, laden with eggs, is washed out to sea along with some floating vegetation (hurricane or flood washout). She makes it to an island where she lays her eggs. If the island has no other tortoises, the ones who hatch are all siblings, and share a lot of the same genes, about half. So whatever genes the mother had, even her rare genes, are now the dominant type. According to the H-W principle, this small population (or genetic bottleneck) is one of those conditions that can lead to a new species. There are other conditions, of course. I hope this helps. \n(_URL_0_)"
]
}
|
[] |
[] |
[
[],
[
"https://en.wikipedia.org/wiki/Hardy%E2%80%93Weinberg_principle?wprov=sfti1"
]
] |
||
2m6151
|
how does someone stay in government despite being blatantly corrupt?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2m6151/eli5_how_does_someone_stay_in_government_despite/
|
{
"a_id": [
"cm18pke"
],
"score": [
3
],
"text": [
"Simply? Time tested facts?\nAll politicians are friends with all other politicians.\nThe \"arguments\" and 'sides' you're able to choose? Are bogus. \n\nThe politically powerful are also in cahoots with powerful people, the ones who paid their way, backed, and funded the politicians so they could become the RULE MASTERS.\nTo help the big guys, of course. \n\n\nLawyers, bankers, big business, regulators, government.\nTogether they make rules, break rules, and escape rules.\n\nIt's all a game. It's all corrupt. Votes don't matter. And most of all? You don't matter.\n\nIt takes a revolution to clean out a government.\n\nThen those people? Being the nasty, selfish, power hungry... humans we all are?\nbecome the corrupt. \n\nAnd it's a cycle that'll keep on keeping on, until we don't have men governing other men anymore. "
]
}
|
[] |
[] |
[
[]
] |
||
4eiota
|
why does volume on things seem to go from 0-100 in a small portion of the bar, leaving the majority of the scale at max volume?
|
[deleted]
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/4eiota/eli5_why_does_volume_on_things_seem_to_go_from/
|
{
"a_id": [
"d20ge7t"
],
"score": [
2
],
"text": [
"Humans interpret many of their senses, including sound, logarithmically; changes between small values are more noticeable than the same amount of change between large values. Unfortunately, the software developers often gloss over this and just make volume bars a constant amount of change for each tick. "
]
}
|
[] |
[] |
[
[]
] |
|
a9twxy
|
where can't you get cancer?
|
You hear about all types of cancer, from bone to eye cancer, but I was wondering if there is anywhere that you cannot get cancer? For example I have never heard of heart cancer, I don't know if that's a thing...
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/a9twxy/eli5_where_cant_you_get_cancer/
|
{
"a_id": [
"ecmf1e8",
"ecnzlck"
],
"score": [
8,
3
],
"text": [
"You can get cancer anywhere you have living, replicating cells because cancer is, broadly speaking, just cells growing out of control.\n\nSo you can't get finger/toe-nail or hair cancer because that material is already dead.",
"I would like to point out that although it is *possible* it is very *rare* to get cancer from the neurons in your brain, which do not reproduce after a certain point in your life. The vast majority of brain cancers come from glial cells, which *do* reproduce, albeit very slowly (which is why brain cancers are relatively rare). Because neurons never produce after a certain age, it's nearly impossible for them to become cancerous after that.\n\nGenerally speaking, cancer is going to be most common in tissues where the cells reproduce more often. For instance, that's why stomach cancer is so common - the cells lining your stomach are constantly being chewed up by the harsh chemicals in your stomach. They're pretty much being digested along with your food. So those have to be refreshed a lot, which means there are many more opportunities for cancer to form in those tissues."
]
}
|
[] |
[] |
[
[],
[]
] |
|
kso2r
|
what is an ulcer?
|
What is an ulcer? How are they formed/obtained?
I don't really know much about them, thanks!
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/kso2r/eli5_what_is_an_ulcer/
|
{
"a_id": [
"c2mxwih",
"c2mxwih"
],
"score": [
2,
2
],
"text": [
"I'm guessing you're specifically thinking of Stomach Ulcers, but lets talk about some other ulcers too!\n\nThe stomach ulcer is one of our oldest, most bemoaned friends. You get this, according to everyone, from everything. Spicy foods, Stress, the list is quite long. Interestingly enough, it's mostly not 100%, either! Heck, one of the most common 'stomach ulcers' actually occurs in your small intestine! But since it's so close to the stomach, and the pain is felt in a way that makes us think of the stomach, we still call it a stomach ulcer, even doctors are known to stick to this simple terminology when discussing it with patients. \n\nThe basics are that you've ingested something, picked up a sickness, or otherwise triggered a biological reaction that has caused agitation to the lining of your stomach or small intestine. If the agitation becomes persistent, it becomes an ulcer. The ulcer itself is basically just a sore of sorts. Think of a deep scrape wound on your arm. It's a thinning of the normal protective layers of the stomach. In severe cases, it becomes an open sore that opens all the way to the outside of the stomach or small intestine, and can allow half digested food (and stomach acid!) in to the rest of your body, which is an immediate medical emergency.\n\nUlcers elsewhere vary in cause, but they are all basically just inflamed flesh and open sores. Many people who stay in hospitals for a long time (especially coma patients) can be prone to getting bed sores. This is basically a type of skin ulceration where the constant pressure of laying in bed, never moving, starts to wear the skin thin. The sores turn in to ulcers at their severest point.\n\nMouth ulcers are also a very common ulcer. We often cause them ourselves: cheek chewing, bad oral hygiene, tobacco products, even nail biting has been linked to the mouth ulcer.\n\nIn fact, that's a great example, you know what canker sores are, yes? That's an ulcer! The stomach and skin ulcer is not much different, the mild stomach ulcer in fact is very similar, while the skin ulcer looks much more open-woundy.",
"I'm guessing you're specifically thinking of Stomach Ulcers, but lets talk about some other ulcers too!\n\nThe stomach ulcer is one of our oldest, most bemoaned friends. You get this, according to everyone, from everything. Spicy foods, Stress, the list is quite long. Interestingly enough, it's mostly not 100%, either! Heck, one of the most common 'stomach ulcers' actually occurs in your small intestine! But since it's so close to the stomach, and the pain is felt in a way that makes us think of the stomach, we still call it a stomach ulcer, even doctors are known to stick to this simple terminology when discussing it with patients. \n\nThe basics are that you've ingested something, picked up a sickness, or otherwise triggered a biological reaction that has caused agitation to the lining of your stomach or small intestine. If the agitation becomes persistent, it becomes an ulcer. The ulcer itself is basically just a sore of sorts. Think of a deep scrape wound on your arm. It's a thinning of the normal protective layers of the stomach. In severe cases, it becomes an open sore that opens all the way to the outside of the stomach or small intestine, and can allow half digested food (and stomach acid!) in to the rest of your body, which is an immediate medical emergency.\n\nUlcers elsewhere vary in cause, but they are all basically just inflamed flesh and open sores. Many people who stay in hospitals for a long time (especially coma patients) can be prone to getting bed sores. This is basically a type of skin ulceration where the constant pressure of laying in bed, never moving, starts to wear the skin thin. The sores turn in to ulcers at their severest point.\n\nMouth ulcers are also a very common ulcer. We often cause them ourselves: cheek chewing, bad oral hygiene, tobacco products, even nail biting has been linked to the mouth ulcer.\n\nIn fact, that's a great example, you know what canker sores are, yes? That's an ulcer! The stomach and skin ulcer is not much different, the mild stomach ulcer in fact is very similar, while the skin ulcer looks much more open-woundy."
]
}
|
[] |
[] |
[
[],
[]
] |
|
kbrm7
|
- heuristics (comp sci or other)
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/kbrm7/eli5_heuristics_comp_sci_or_other/
|
{
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"text": [
"Let's say you're walking home from school and it's about a 20 minute walk. Now, there are probably lots of different ways you can go. You could go through the park where it takes a bit longer but it's a nicer walk. Maybe the quickest way has a loud dog that you don't like walking past or something like that. You decide that the best thing to do is as you walk home each time, you should take note of which way you go and what was good/bad about it.\n\nOver time, you'll start to realise that some ways are better than other and your walk home becomes more efficient. You've managed to avoid the scary dog but it doesn't take you 40 minutes like it does when you go through the park. Each time you walk, you're learning more and more about all the different potential paths and why they're good or bad.\n\nYour brain does this with all sorts of things. When you see a girl, your brain remembers all sorts of experiences with girls and based on that, your brain will adjust how you act (you might want to touch them because of their cooties). These rules you make for yourself, based on experience, are called heuristics.",
"imnotjesus did a good job, but just to bring it back around (not LY5):\n\nin computer science, we use and study algorithms. Algorithms are lists of steps which deterministically and reliably transform an input into a desired input.\n\nFor instance, take the common sorting problem, which converts an arbitrary list of integers into a list of the same integers sorted in ascending order.\n\nThere are known algorithms which can be applied to any list of integers and it can be mathematically proven that you will end up with a sorted list.\n\nA heuristic lacks this determinism or reliability. That is, it cannot be mathematically proven that it will work in every case. Often times, there are known cases for which it does not work.\n\nLike all things, it's a trade-off. So what do you get in exchange for this reliability? Generally, improved running time (or memory consumption). So, you give up a little bit of reliability (which can be mitigated) for a (sometimes vastly) improved running time.\n\nThey are commonly used for things like facial recognition. In these cases, the computer need not be exactly correct in all cases because potential solutions can be verified by humans.",
"Let's say you're walking home from school and it's about a 20 minute walk. Now, there are probably lots of different ways you can go. You could go through the park where it takes a bit longer but it's a nicer walk. Maybe the quickest way has a loud dog that you don't like walking past or something like that. You decide that the best thing to do is as you walk home each time, you should take note of which way you go and what was good/bad about it.\n\nOver time, you'll start to realise that some ways are better than other and your walk home becomes more efficient. You've managed to avoid the scary dog but it doesn't take you 40 minutes like it does when you go through the park. Each time you walk, you're learning more and more about all the different potential paths and why they're good or bad.\n\nYour brain does this with all sorts of things. When you see a girl, your brain remembers all sorts of experiences with girls and based on that, your brain will adjust how you act (you might want to touch them because of their cooties). These rules you make for yourself, based on experience, are called heuristics.",
"imnotjesus did a good job, but just to bring it back around (not LY5):\n\nin computer science, we use and study algorithms. Algorithms are lists of steps which deterministically and reliably transform an input into a desired input.\n\nFor instance, take the common sorting problem, which converts an arbitrary list of integers into a list of the same integers sorted in ascending order.\n\nThere are known algorithms which can be applied to any list of integers and it can be mathematically proven that you will end up with a sorted list.\n\nA heuristic lacks this determinism or reliability. That is, it cannot be mathematically proven that it will work in every case. Often times, there are known cases for which it does not work.\n\nLike all things, it's a trade-off. So what do you get in exchange for this reliability? Generally, improved running time (or memory consumption). So, you give up a little bit of reliability (which can be mitigated) for a (sometimes vastly) improved running time.\n\nThey are commonly used for things like facial recognition. In these cases, the computer need not be exactly correct in all cases because potential solutions can be verified by humans."
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
1zvw81
|
how does a laser speed gun work to measure a car's speed?
|
I Googled; I didn't understand, I came here.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1zvw81/eli5_how_does_a_laser_speed_gun_work_to_measure_a/
|
{
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3
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"text": [
"Light moves fast. Really, really, fast. But it still has a measurable speed, so as long as your timer is quick enough all you need to do is fire a laser at something and start counting until the moment the reflected laser light comes back.\n\nBecause we know the speed of light is a constant, by counting the (very tiny) amount of time between when we fired the laser and when we get the reflection, we know how far away something is.\n\nSo that's how a laser measures *distance*. How does it measure speed?\n\nWell it's the same idea, only instead of firing a single beam of laser light it fires lots and lots of very short pulses. Each of those will reflect off the car and reflect back, and so we can calculate the distance the car was when each one reflects back. All that's then required is to calculate how quickly that distance decreases and that's the speed of the car."
]
}
|
[] |
[] |
[
[]
] |
|
7gav2e
|
why do babies need to be burped but adults don't?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/7gav2e/eli5_why_do_babies_need_to_be_burped_but_adults/
|
{
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"dqhsipf",
"dqhskux"
],
"score": [
2,
2
],
"text": [
"Burping is basically a learned behavior, meaning we develop the ability over time through practice or watching others do it; hence adults knowing how and babies not. It's not a killer if you don't burp a baby but they'll get fussy because it'll affect their stomach like it normally would for an adult if they had gas that wouldn't come out. ",
"Babies don't know how to burp. They haven't yet learned that muscle control. So a soft pat on the back helps release gas trapped in their stomach. Trapped gas can make babies uncomfortable and cranky and can also cause vomiting."
]
}
|
[] |
[] |
[
[],
[]
] |
||
1jyhzi
|
double clutch gearbox
|
I hear Jeremy Clarkson talk about them in nearly every episode of Top Gear. What are they and how are they different from a normal clutch in a regular car.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1jyhzi/eli5_double_clutch_gearbox/
|
{
"a_id": [
"cbjj7nd",
"cbjvaat"
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"score": [
3,
2
],
"text": [
"It's pretty much like having two transmissions in one. It has (as you would probably assume) two clutches that are both connected to a different shaft. One clutch connects to the odd numbered gears and one connects to the even. It allows the transmission to shift more quickly by allowing the transmission (through electronic control) to preselect the next gear in the sequence. Once it is ready to shift, it just switches the pressure from one clutch to the other allowing an almost instantaneous transfer from say second to third gear and so forth. \n\nEdit: [Here](_URL_0_) is a youtube video, [here](_URL_1_) is a description from \"how stuff works.\"",
"A double clutch gearbox has 2 clutches as the name implies. Each clutch is attached to different shafts in the transmission (one shaft within the other). Because there are 2 input shafts, the output shaft on the transmission can mesh with either one at any time depending on the clutches.\n\nAs others have mentioned, this means that when you are in one gear, the transmission can pre-select the next gear. By having 2 input shafts and 2 clutches, the beauty is that between shifts, the other clutch can already start grabbing before the first shaft has let go of the current gear. This is a significant advantage over a single clutch gearbox.\n\nThe only draw back is weight and complexity and reliability. Double clutch gearboxes are noticeably heavier, and due to complexity, arguably will cost more to maintain over time."
]
}
|
[] |
[] |
[
[
"http://www.youtube.com/watch?v=oOciX6kdexE&list=TLd9V9bcBnbYg",
"http://www.howstuffworks.com/dual-clutch-transmission.htm"
],
[]
] |
|
3zg397
|
how does the verdict of the supreme court's ruling on affirmative action (fisher v. university of texas) apply to the rest of the nation?
|
1. Since Fisher is only suing University of Texas, does that mean if Fisher wins the ruling only applies to them? All undergrads? All medical/professional schools?
2. If the Supreme Court rules in favor of University of Texas, is that a ruling in favor of affirmative action? Or just a ruling in favor of University of Texas's admission process.
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3zg397/eli5_how_does_the_verdict_of_the_supreme_courts/
|
{
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"text": [
"For almost any case the SCOTUS hears you can ask these two questions. For any decision, the majority has to decide not only their reasoning but how strongly they lay down the decision. For instance, in 2013 in the Windsor case, SCOTUS largely agreed with the plaintiff that a ban on marriage is unconstitutional but they did not go as far as they eventually did in Obergefell that any state ban on marriage is unconstitutional.\n\nI am trying to find an article that goes through possible outcomes, but it is my opinion that any number of things could slowly or quickly come from a ruling. Maybe AA will be upheld. Or maybe it could be found totally unconstitutional. Or perhaps the majority opinion would find some merit in Fisher's arguments that would eventually trickle down in future decisions and change the types of rules U of T and other schools use in admissions processes.\n\nSo to answer your questions:\n\n1. the ruling will apply as far as the majority writers seek to apply it and as precedent in future cases\n\n2. No, SCOTUS is really ruling for or against a lower courts rulings and not really for or against Fisher or the school. But how it decides the lower rulings will have effects (most likely) on admissions processes across the country.\n\n",
"Any ruling from the SCOTUS has broad reaching ramifications. Since a SCOTUS ruling is, in essence, a clarification of the constitution. So if they rule against the University of Texas, they are saying that the UoT admissions rules were unconstitutional, and anyone who had similar rules would also be considered unconstitutional.\n\nThere's generally some language in the ruling that details what exactly they thought violated the constitution that would give other schools a clue what they would have to change if anything, and any remaining confusion would likely be resolved in lower courts. \n\nTo answer your second question, a positive ruling for the UoT would state that the SCOTUS thinks that this sort of discrimination is not constitutionally prohibited, which would cause similar lawsuits against other schools to be dismissed unless they could prove that they were arguing a different constitutional point.",
"It makes it easier for other people to sue the same thing and win.\n\nbasically, when something goes to court, the largest job of the lawyers is to look up all the relevant past rulings so you can tell a judge \"These are all the times that the courts ruled in favor of people on my side of this kind of case, rule in my favor\"\n\nthere are hundreds of thousands of local court rulings, no one is looking those up. There are thousands of circuit court rulings, those are often cited, but can disagree*. There may be only one supreme court ruling, but if there is one that is relevant to your case, then the lower courts should rule based on that even if there are circuit court rulings in your favor.\n\n\\* a disagreement between circuit courts, often referred to as a circuit split, is one of the best ways to get a case seen by the supreme court"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
5fdasu
|
deep sea animals withstanding intense psi
|
I always wondered, if we could hypothetically bring up a deep sea animal (something from the Marianas trench) and keep it alive, if we then proceeded to hit it with a hammer of some other hand held object would it even hurt the creature? Seeing how it can take ~16,000psi in its natural habitat, would it even feel it?
On a somewhat related note, if we took a crab or shrimp that live around the edge of underwater volcanoes, would we be able to cook it using traditional means?
Thanks for your time!
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5fdasu/eli5_deep_sea_animals_withstanding_intense_psi/
|
{
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"text": [
"They are equalized by having water in them and forming in high pressure, and volcano shrimp would still cook like shrimp because the surrounding water is near freezing, they live in the thermocline",
"Deep sea animals do not feel water pressure. The pressure inside their bodies is the same as the pressure outside, so the net effect is zero. Atmospheric pressure is 14.7 psi; that doesn't mean you feel 14.7 pounds of pressure on every square inch of your skin. The pressure inside your body is the same as the pressure outside. ",
"To add to what others have said, the contain the pressure of all that water and the pressure inside them, many deep sea fish are smaller and thin "
]
}
|
[] |
[] |
[
[],
[],
[]
] |
|
6zucxs
|
why are there airbags attached to seat belts of older aeroplanes but not in newer ones?
|
I recently flew in a fairly old B777-300, and there were large, heavy [airbags](_URL_0_) attached to the right seatbelt. However, when I flew in newer aeroplanes there weren't visible airbags (I didn't even know the clunky thing *was* an airbag until I read the little warning tag) on the seatbelt.
Where are the airbags most often located nowadays, and why the change? I tried to look this up on Wikipedia to no avail, except for the picture ):
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6zucxs/eli5_why_are_there_airbags_attached_to_seat_belts/
|
{
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"dmy3kdm",
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2,
3
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"text": [
"Regulations changed. Impact requirement went from 9g to 16g. So until seats and interiors could be redesigned, some seats got airbags depending on what was in front of them. If there was a hard bulkhead in front or seat pitch below a certain distance, then the seat got an airbag.\n",
"I suspect you flew in business class, or in an economy seat where there was no other seat ahead of you. Often seatbelts will have airbags (or a chest strap) if there is a hard surface directly in front (rather than the top of a normal economy seat, which is \"soft\" enough), or if the distance between seats is too great to brace against the seat in front. This mostly happens in fancy seats."
]
}
|
[] |
[
"https://upload.wikimedia.org/wikipedia/commons/thumb/c/ca/Airplane_Airbag_Cathay_Pacific_Airbus_A330.jpg/1200px-Airplane_Airbag_Cathay_Pacific_Airbus_A330.jpg"
] |
[
[],
[]
] |
|
3t4j2z
|
how do tunnel builders know where they are going?
|
Like with the Channel Tunnel how did the French and English side meet up?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/3t4j2z/eli5_how_do_tunnel_builders_know_where_they_are/
|
{
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"text": [
"i dont know anything about that specific project, but in general there is an engineer that surveys in the centerline of the tunnel using a theodolite (_URL_0_). you basically move a known point down the tunnel using the previous point along the centerline as a reference. you offset each point from the actual centerline so that you can mark the actual points with a nail along the tunnel wall, out of the way.",
"I will start by saying that I have no experience with tunnel construction, but I will hazard an guess based on my experience with navigation. \n\n-You could use an inertial navigation system. That means that you have a gyroscope, a machine that has at its center rings that spin very fast and that are not fixed solidly to their container. Their spin tends to stabilize them, and so when the machine changes direction, the rings stay pointed the way they were going when you turned the gyro on. If you then measure the difference in angle between where the rings are lined up now and where they were when you started, you can tell where the machine is pointed in 3 dimensions. This solves finding direction. To know how far you've gone, you can just measure the length of the tunnel. \n-You could also use a laser or some other tool that keeps a straight line over long distances (taught string? Surveying scopes?) and a device that lets you measure angles to ensure you're going in a straight line and only turning as much as you want to. Again, measure the tunnel to see how far you've gone.",
"_URL_0_\n\nThis is episode one of a three part fly on the wall documentary called 'The Fifteen Billion Pound Railway' about the current construction of a new underground railway line underneath London. Especially interesting is the 'Eye of the Needle' segment whereby the new tunnel needs to be bored with just an 80cm gap to a neighboring existing tunnel. \n\nEpisodes 2 and 3 are also very good, all on youtube. "
]
}
|
[] |
[] |
[
[
"https://en.m.wikipedia.org/wiki/Theodolite"
],
[],
[
"https://www.youtube.com/watch?v=42-lJ2y6ddQ"
]
] |
|
2rwzsn
|
how do shots work?
|
Does it matter where in your body shots are used
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/2rwzsn/eli5_how_do_shots_work/
|
{
"a_id": [
"cnk26x4"
],
"score": [
3
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"text": [
"Yes.... in the sense of going into a muscle (or below the skin) versus going directly into a vein. Injecting something into a muscle will release the drug slowly and so the body sees its effects gradually with time. Injecting directly into a vein means the effects are close to immediate.\n\nThere really is no difference between getting a shot in your arm versus your butt."
]
}
|
[] |
[] |
[
[]
] |
|
6vtvf5
|
why is the 'information cannot be lost' principle so vital to physics?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/6vtvf5/eli5_why_is_the_information_cannot_be_lost/
|
{
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"text": [
"\"Information\" in physics is basically the thing itself, or whatever distinguishes one thing from another. It is important that this cannot be lost as it is similar to the principle of conservation of energy. A more simple statement would be that things don't just disappear. If a particles is moving at a speed then that momentum can be converted into other forms but it won't just vanish.",
"First off, I'd guess you saw the in a nutshell video, and to you I say good day well educated citizen, secondly as to the question, the principle that no information can ever be lost is vital in our current theory of relativity, while I am no expert in the nuances, the basic concept worked in is that you can, from a single atom, calculate every other atom in the entire universe. Psychics relies heavily on this, and in other seemingly made up explanations for the universe, life and everything. ",
"Cuz it would break science. Don't worry, Stephen Hawking once got this question wrong and a plumber bested him. \n\nIt goes to whether or not physics is determinate. Can I measure things perfectly today, and expect that there is a consistent system of rules (science) that tell me how it will look in 10 years? If so, I should also be able to measure things today and understand how it looked 10 years ago. If information gets destroyed, maybe I can't know everything about the past. \n\nAlso, philosophically, where would the information go? If matter is conserved and energy is conserved then that kind of conserves all the things that information would be made of doesn't it? What happened to the information?\n\n### Black Holes \nThe biggest challenge to this was black holes. What happens to things that fall in? Surely their information is destroyed. If you write a letter and toss it into a black hole, no one is going to be able to ever read it right? \n\nStephen Hawking thought so. So much that he bet made Kip Thorne a bet on it. But this plumber Susskind proved him wrong. Leonard Susskind was actually a real physicist too, but I believe he really once was a plumber. \n\nThe way he proved it was interesting too. Mathematically, the whole universe looks like a hologram on the edge of a 2D spherical shell with a diameter equal to that of the universe. We could be inside a black hole. \n\n",
"I am not a physicist, but my best understanding of it is that is where quantum mechanics and general relativity meet.\n\nIf a black hole does spit information (atoms) to a different part of the universe or to another universe (white hole) the information that is put in maybe discombobulated but not lost. It's the same concept that energy is never created or destroyed just changes. When you heat something up, some of the mass of the solid/liquid is lost in the form of gas. In theory, with enough time and energy, you could recapture the lost gas or let it disperse into a tube and chill it to form it back into a liquid, but even then some of the individual atoms might still be released into the air. \n\nIf I get thrown into a black hole and get spit out the other side all with all the atoms in tact, then I am still there in the essence of my atoms, but they are distributed in a different manner. \n\nThat's how I understand it. "
]
}
|
[] |
[] |
[
[],
[],
[],
[]
] |
||
37gvmm
|
why does the road seem to have 'water' or a 'mirror' like mirage whenever its really hot outside? and then goes away once you get closer to it?
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/37gvmm/eli5why_does_the_road_seem_to_have_water_or_a/
|
{
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"crmk4do"
],
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"text": [
"Normally, light waves from the sun travel straight through the atmosphere to your eye. But, light travels at different speeds through hot air and cold air.\n\nMirages happen when the ground is very hot and the air is cool. The hot ground warms a layer of air just above the ground.\n\nWhen the light moves through the cold air and into the layer of hot air it is refracted (bent).\n\nA layer of very warm air near the ground refracts the light from the sky nearly into a U-shaped bend. Our brain thinks the light has travelled in a straight line.\n\nOur brain doesn't see the image as bent light from the sky. Instead, our brain thinks the light must have come from something on the ground."
]
}
|
[] |
[] |
[
[]
] |
||
16af1p
|
warp drive or "the spaceship's engine will compress the space ahead and expand the space behind, moving it to another place without actually moving"
|
_URL_0_
I remember watching a documentary about this a couple years ago, but that didn't help a lot.
Please supplement your answers with images/videos if they could help me understand this concept.
Thanks
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/16af1p/eli5_warp_drive_or_the_spaceships_engine_will/
|
{
"a_id": [
"c7ublod"
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"text": [
"Imagine a rubber band, stretched out. If you let it relax, draw a line an inch long on it, and then stretch it out again, the line is now two inches long, even though it's still the same line.\n\nThis new warp drive (theoretically) works like that. Think of space as a stretched-out rubber band. This engine would compress the space in front of it, travel through the compressed space, and stretch the space back again behind it. So the ship would only travel, say, a light year relative to the space around it, but once that space stretches out again the actual travel distance would be 2 light-years.\n\nThe reason we're even bothering to do all this stretching of spacetime is because of the unbreakable speed limit of the universe; the speed of light. To reuse the rubber band analogy, you can only draw a line across the rubber band so quickly, but there are no rules (as far as we know) against stretching the rubber band all you want. So we can \"cheat\" and get from one place to another faster than light can while not ever exceeding the speed of light. Which would be great, since the universe is so freaking big that if we couldn't go faster than light, it would take decades or centuries to get anywhere outside of our solar system.\n\nOf course, this is all still in the theoretical stage. Basically, some bright spark found this loophole and said \"hey guys, there's nothing in the math that says we can't do this,\" and now people are starting to actually figure out if it's feasible, instead of just not physically impossible."
]
}
|
[] |
[
"http://gizmodo.com/5942634/nasa-starts-development-of-real-life-star-trek-warp-drive"
] |
[
[]
] |
|
1tuqb0
|
why is it so hard to breath when you fall on your back or get punched in the stomach.
|
Slipped at the pool tring to stop walking when someone stepped in front of me. Was laying there trying to breath in for what felt like 30 minutes. Just wanted to know what being "winded" really is and googling it didn't get me any relevant results.
|
explainlikeimfive
|
http://www.reddit.com/r/explainlikeimfive/comments/1tuqb0/eli5_why_is_it_so_hard_to_breath_when_you_fall_on/
|
{
"a_id": [
"cebmfxb",
"cebmhuv"
],
"score": [
2,
2
],
"text": [
"It is your diaphragm, the muscles that control your breathing, that gets hit. This makes them seize up and spasm. Which makes it hard to breathe.",
"You take a hit to a nerve (solar plexus) that controls the diaphragm, the muscle that controls most of your breathing. When it takes a hit it turns off for a short period of time and so you can only take short breaths by using your ribs. "
]
}
|
[] |
[] |
[
[],
[]
] |
|
8jedph
|
can humans accept blood donations from other species? why or why not?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/8jedph/eli5_can_humans_accept_blood_donations_from_other/
|
{
"a_id": [
"dyyzilm",
"dyyzpxy",
"dyzdyem"
],
"score": [
17,
2,
3
],
"text": [
"Generally speaking, no. Your body will detect proteins in the other blood as foreign agents and create antibodies to kill it, and that kind of reaction can be fatal.\n\nI mean look at just human blood. We can't even accept blood from specific blood groups based on our own blood type. Adding in the foreign proteins of animals would be a nightmare.",
"No.\n\nBlood is not a liquid, it's a liquid that's full of tiny living cells. It really can only be human cells for it to work, and not even any old human cells will work (see blood type).",
"Yes it is possible, but not very effective. If I recall, there was a research study using cow blood transfusions. The researchers had to remove all the antigens in the cow blood serum to prevent blood type mismatch (ie they made it O type blood so it’s a universal donor).\n\nThe cow red blood cells lasted for only 2-3 days because they were incompatible with the human body, but got the job done deviating oxygen. But because such a large amount of cow red blood cells were breaking down rapidly, they released a lot of Heme which put stress on the spleen to clear it up.\n\nThe procedure was performed here:\n_URL_0_"
]
}
|
[] |
[] |
[
[],
[],
[
"http://www.dailymail.co.uk/news/article-1383586/Cows-blood-saves-life-crash-victim-world-procedure.html"
]
] |
||
fk5pgd
|
; why can you not thaw ground beef then refreeze it and thaw it and then consume it?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/fk5pgd/eli5_why_can_you_not_thaw_ground_beef_then/
|
{
"a_id": [
"fkqsrxh",
"fkr07se",
"fkrivap"
],
"score": [
3,
5,
3
],
"text": [
"Not sure who told you you couldn't do that, but I've done it many times. As long as the meat doesn't rot and you cook it to a safe temperature (minimum 160F/71C), you should be fine, regardless of if it's been thawed and refrozen.",
"Answer: The refrigerator guarantees thawed meat didn't ever go into the Goldilocks zone for bacterial growth. **Technically** any thawing method is safe as long as it doesn't give bacteria time to multiply - this would be very hard for someone to do with a microwave unless they were trying to prove a point \"that it can be done\".",
"So long (as others have mentioned) as it was thawed safely, you can thaw and refreeze to your heart's content. The problem is, repeated thawing freezing can affect the texture of the meat. Each time it is frozen, ice crystals occur which literally cut the meat. AFter enough times, the super tiny cuts can add up and give the meat a \"mushy texture\"\n\nBut to repeat, the biggest issue is because people don't normally safely thaw meat and allow it to get to temperatures that can promote bacterial growth"
]
}
|
[] |
[] |
[
[],
[],
[]
] |
||
9oyqxh
|
what is a data ecosystem?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/9oyqxh/eli5_what_is_a_data_ecosystem/
|
{
"a_id": [
"e7xo05a"
],
"score": [
2
],
"text": [
"I get some data and sell it to you. You aggregate it with other data and sell it to Fred. I pay Fred to target my advertising super effectively. It's the circle-of-life."
]
}
|
[] |
[] |
[
[]
] |
||
911zrm
|
how does decaffeination work?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/911zrm/eli5_how_does_decaffeination_work/
|
{
"a_id": [
"e2uu669"
],
"score": [
10
],
"text": [
"It’s a lot like washing your face. The beans are steamed so that the pores open up and then they are washed with certain chemical compounds for hours until decaffeinated. "
]
}
|
[] |
[] |
[
[]
] |
||
5rib1n
|
why do spaceships need to travel at escape velocity to escape earth's gravity?
|
Let's have a fictitional situation. You have a spaceship with infinite fuel that doesn't weigh anything (thus your effect on Earth doesn't change when using it). The catch is that you move only about 10 miles/kilometers (doesn't really matter) per hour with it. At all times. It can't accelerate, so it takes a really, really long time to get anywhere. It is, however, affected by gravity, but whenever the gravity becomes lower, the fuel consumption recudes to keep you travelling at exactly 10 m/km per hour.
So here comes the question. If I have a spaceship that can go at a slow speed indefinitely, why can't it escape earth's gravity? Every spaceship thus far has had to move at at least 11.186 km/s or 6.951 mi/s. Why is that?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/5rib1n/eli5_why_do_spaceships_need_to_travel_at_escape/
|
{
"a_id": [
"dd7gb2f",
"dd7hdnd",
"dd7i1h3",
"dd7ihgx",
"dd7ir3j",
"dd7qj8d"
],
"score": [
3,
2,
2,
2,
2,
2
],
"text": [
"If you had infinite fuel you could just cruise on out in your scenario.\n\nIn reality, escape velocity is the speed you throw a rock for it to leave Earth's gravity well. In this case, spaceships are the rock as they burn the majority of their fuel to start their ascent and definitely don't continually burn fuel as they fly. They burn fuel until they can escape and then fuel is used for adjustments or the return",
"Here's the thing about orbit: gravity is still pulling you back, it's just that the Earth is \"falling\" away at an equal rate. If you don't have this lateral escape velocity, Earth is going to be beneath you when you come down. Now, with infinite fuel, it's moot because you won't come down, or if you got far enough away some other gravity well would pick you up (like the sun).",
"Well your example can't exist in our physical reality so how can we answer it really?\n\nAs for you question at the bottom, that I can answer.\n\n_URL_0_\n\nHere a little video. In it you see a cannon shooting a ball. The earth's gravity will attract it toward the ground. Whatever the speed at which you shoot it, it will always take the same amount of time for that ball to touch the ground. Let say for the sake of simplicity it take 1 second for the ball to touch the ground.\n\nThe faster the ball go, the more distance it will be able to travel in that second before it touch the ground right? So let say it can go really really fast. Fast enough that after one second the ball went further than the earth curvature and there is no ground under it. Congrats you launched the ball in orbit. The ball keep falling toward the ground, but it go too fast and keep missing it.\n\nAs the ball is in orbit there is two forces fighting each other. The kinetic energy of the ball 1/2*m*v² and the gravitational potential energy mV (V is the gravitational potentiel per unit of mass).\n\nAs long as the gravitational potentiel is higher than you kinetic energy then the earth's gravity will keep attracting you toward the earth bending your straight trajectory around the earth.\n\nBut if your kinetic energy is equal to the gravitational potentiel, then the earth's gravity is not strong enough to keep you from keep going on your trajectory. See that there is your mass in both equation. So for both equation to be equal you need to have 1/2*v² = V\n\nNow the only thing that is variable is your velocity (v). You can isolate that v in the formula and you get the escape velocity.",
"If your engine is constantly burning so that your spaceship moves away at 10mph, then yes, you could escape Earth.\n\nEscape velocity is the speed at which, if you shut down the engines at your current velocity, you would still escape from Earth. It changes with altitude, so as you get farther away, the escape velocity gets lower and lower. At 100ft off the ground, if were moving 10mph before you shut off your engines, Earth would pull you back down. But at 100,000,000mi off the ground, if you were moving 10mph, it wouldn't.\n\nAnother way to think about it is in terms of [delta-v](_URL_0_). Delta-v is a measure of the energy imparted to your spaceship by an engine burn. Out in deep space with no gravity, it's equal to the change in speed from your burn (i.e. a 5mph burn will take you from 0mph to 5mph). When you're escaping a gravity well, escape velocity is actually an escape delta-v. You can do it all at once, by starting out at escape speed (firing your ship out of a cannon), or you can do it with a constant low thrust, but either way the energy expenditure will end up equal.\n\nSpaceship fuel levels are often measured in terms of delta-v, because it makes stuff like this simple: \"do we have enough fuel to reach X altitude? Well, that would take a delta-v of Ymph, and we only have 70% of that in the tank, so no, we can't get there.\"",
"The trick you're missing is that escape velocity varies with altitude. The figure you quoted for earth is only accurate at sea level and the higher you go, the lower escape velocity will be. A slow vehicle could escape but it's a very inefficient approach using rocket technology. If we had a space elevator then a slow escape from the earth would become feasible.",
"Welp. There's an issue you got here with a lot of things, because not only is this situation fictional but its not helping you understand escape velocity.\n\nLets begin by starting with einstein then we will get less conceptual, more intuitive, and just use newtons 3 laws to explain this. \n\nSo first off if your rocket doesn't weigh anything and has any actual motion at all, its moving at the speed of light. Thats simply the universe and how mass, energy, and time are defined. So you need to understand escape velocity in its definition and how it works /must/ take into account mass.\n\nSo lets go simpler and talk about mass, and force, and acceleration, and velocity. I think you need to understand escape velocity isn't like some magic number, its actually an output, and it is different depending on the weight of the object (mass).\n\nForce = mass times acceleration, newtons second law, really puts into the account the issue. The \"force\" of gravity is created by a set acceleration (9.8) working on any mass around the gravity well of the planet. Since there is a force constantly acting on anything that wants to go out away from this pull of earths gravity, the force of the object must be matched with an acceleration that is to overcome the force being applied on the object with the acceleration of gravity. \n\nAcceleration is literaly defined as the change in velocity over time. To go out and away into space, your object must have an acceleration that greatly outpaces the acceleration that is applied from the force of gravity. \n\nSo you can find at the point at which this happens, and then you just integrate this acceleration down to velocity, and this will give you a set velocity at which point your object's acceleration counteracts the acceleration of the force of gravity, that now you are able to leave earth."
]
}
|
[] |
[] |
[
[],
[],
[
"https://www.youtube.com/watch?v=ymC6fuX03ns"
],
[
"https://en.wikipedia.org/wiki/Delta-v"
],
[],
[]
] |
|
b5k653
|
when you shut an engine off, why does the combustion process stop instantly?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/b5k653/eli5_when_you_shut_an_engine_off_why_does_the/
|
{
"a_id": [
"eje18v2"
],
"score": [
4
],
"text": [
"If it's a petrol/gasoline engine, then it's because there is no longer a spark being delivered to the cylinders where the fuel/air mix is burned. In these engines, compression is not enough to light the mixture, and once the ignition switch is off, the spark plugs no longer spark.\n\n(Different for diesel engines.)"
]
}
|
[] |
[] |
[
[]
] |
||
dp5a1v
|
why do some lights tinkle when they light up?
|
Okay so I'm not a native speaker so I hope I can translate my Question correctly.
Some older Lights Do this little high pitched sounds (kinda sounds like icicles falling on ground) when you switch them on/when they light up after. What produces that Sound?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/dp5a1v/eli5_why_do_some_lights_tinkle_when_they_light_up/
|
{
"a_id": [
"f5skjqd"
],
"score": [
5
],
"text": [
"If you mean fluorescent tubes, older fluorescent fixtures used a system which featured a bimetallic starter (the small, round, silver piece). Inside the starter is a bimetallic switch which \"pings\" when energized. Newer fluorescent systems, such as the \"preheat\" or \"rapid start,\" are rendering the \"ping\" a thing of the past."
]
}
|
[] |
[] |
[
[]
] |
|
53dgtm
|
what's the difference between a low end laptop and a high end notebook?
|
explainlikeimfive
|
https://www.reddit.com/r/explainlikeimfive/comments/53dgtm/eli5_whats_the_difference_between_a_low_end/
|
{
"a_id": [
"d7s43zp"
],
"score": [
16
],
"text": [
"A laptop is an electronically powered machine that is capable of running an operating system. The laptop does this by storing and retrieving the code for the operating system in its memory, and executing that code upon startup. After the operating system is running, you can then install additional modules of code referred to as \"software\". These are modules of code that provide you with the ability to input some information, and then the software uses that information to process you a particular result. You can think of this almost like a mathematical function. A user will input some information through the keyboard, mouse, or other input device (X value), the software then does something with X (the function itself doing a process), and finally the software spits out a result (Y value). Running code is the main function of a laptop, which ultimately is just a piece of hardware containing some form(s) of input, a temporary memory location (RAM) and permanent memory location (Hard Disk), a CPU for processing code, a motherboard for interconnecting all components, and some form of output device, such as a screen, or speakers. Additional hardware components do exist, such as NIC (for networking), USB ports, SD card ports, HDMI ports, FireWire ports, Speaker ports, etc. \n\nA high end notebook is simply some bounded amount of paper. The higher end versions you speak of usually contain several divided sections, a plastic back and front cover, built in folder pockets on the divider pages, and generally a higher quality paper than cheaper notebooks.\n\nHope this helps!"
]
}
|
[] |
[] |
[
[]
] |
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