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If I put helium in my rectum, will my farts be high pitched?
| 370 |
Short answer: yes.
Long answer: the reason your voice is high-pitched when you inhale helium is that the speed of sound in helium is faster than the speed of sound in air. When the pressure waves that make up the sound of your voice move from the helium in your lungs and throat and into the air, the change in speed also changes the wavelength and thus the pitch of the sound.
As long as the source of the sound is in a helium-rich environment, it will be higher-pitched when it is heard in air. If you actually filled your rectum with helium, your farts would, in fact, be higher pitched.
| 151 |
|
[Marvel Universe] If Bruce Banner proves himself to be worthy of wielding Mjolnir, would the Hulk be able to wield it as well?
|
I'm asking in terms of before the two personalities merge into one. This is strictly the doctor and giant green rage monster scenario.
| 41 |
I think the answer is no.
In movies, we've seen hulk beat his enemies but he dont care if anyone else got smashed under his giant foots.
If Bruce Banner became worthy, the Professor Hulk can become worthy as professor hulk has the body and strength of hupk but Bruce is fully conscious in him.
| 33 |
Should we be worried about SF6 as green house gas as it has ~20,000 time more global warming potential than CO2?
| 28 |
It's much more potent, but much, much less common. SF6 exists at about 7 parts per *trillion* in the atmosphere, CO2 is measured at 400,000,000 parts per trillion (400 ppm).
So, the effect would be roughly equivalent to 140,000 ppt of CO2, less than a thousandth of what's actually there.
| 18 |
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how can birds like parrots or ravens be so intelligent ; given their small brains ?
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Also , even though other birds have brains similar in size to the parrots and crows , they're not as intelligent . why?
| 44 |
>even though other birds have brains similar in size to the parrots and crows , they're not as intelligent . why?
Just a quibble -
We recognize certain things that corvids and psittacines do as "intelligent", partly because they're similar to things that we do. (E.g. "Manipulate physical objects")
But we should keep in the back of our minds the possibility of different kinds of intelligence that aren't obvious to us - for example many birds make multi-thousand-kilometer migrations, through different sorts of environmental conditions, and doing navigation that most humans would find a challenge with training and high-tech instruments.
| 23 |
ELI5 - When people lose weight, where does it go?
|
So, you go out, you exercise a lot, you eat less food and what you do eat is healthier. At the end of the week, you are 5 lbs lighter (just a guess). What happened to that 5 lbs of fat? Is it converted directly to energy? Do you have to wait until you next defecate to actually "lose" the weight?
| 38 |
The way your body uses food is that it burns it with oxygen, much like wood in a fireplace burns. The reaction in your body is a lot more controlled, which is why you don't go up in flames. But it does produce some of the same byproducts, namely heat, carbon dioxide, and water.
The same is true for your fat stores. They get burned up with oxygen as well, just like if you ate a piece of fatty meat. So where does the fat go? You breathe it out as carbon dioxide, and urinate it out as water. So imagine that next time you're in the gym. Every breath you exhale is some of your fat leaving your body.
| 25 |
If telomers get shorter with every split of a cell, doesn't this mean we can pretty accurately calculate when someone will die of old age?
| 7,244 |
The concept behind the question is an interesting one and the idea of predicting the lifespan of an individual based on biological indicators is indeed a popular research topic.
Long story short specifically for telomeres, the answer is "not really". Different cells divide at different speeds. Also, many cells do not divide any further at all. If someone got even a minor injury or a mildly traumatic event or some weird habits, that would affect cell division as well. And then there are the individual differences in telomere lengths. Given all these, it will be virtually impossible to predict the "endpoint" of cell division in the real-time scale, let alone predicting one for an individual based on a few cells.
Also, generally telomere length is not the limiting factor for humans. There's some evidence that it can be a contributing one, but it is not really a major factor (the correlation was not practically significant and causation is somewhat dubious). There are many other ways a person can die "of old age" depending on the definition, including cancer, neurological disorders (Alzheimer's etc.), osteoporosis, cardiovascular diseases, kidney failure, weak immune system etc. etc., all of which are very much age-related. There are even sayings that most people don't have Huntington's Disease because we die before we reach the age of developing one.
| 2,678 |
|
Are photons "immortal"?
|
If a beam of light doesn't hit anything, does it just keep on going forever?
| 19 |
This question is kind of hard to answer.
To say whether or not a photon is "immortal" implies, that there is some kind of reference frame of the photon in which time passes at a measurable rate.
It turns out, though, that we cannot do that. You may know, that the speed of light is constant in all frames of reference. Thus, photons move at c relative to **all** valid frames of reference. However, this renders it impossible to define a frame of reference in which the photon is at rest.
Since the rate at which time passes depends on the relative velocity between object and observer, it really makes little sense to talk about the passage of time of an object that has no rest frame.
Thus, photons have no perspective. Not even theoretically. Since photons have no valid "perspective", it is not possible to define a rate at which time passes from their perspective. Without a rate at which time passes, it is impossible to say how "old" they are.
I suppose they are immortal in the sense that they travel at a straight line until they hit something. Space is not a perfect vacuum though, so they will eventually interact with a hydrogen atom floating randomly through space.
| 13 |
ELI5: Do plants get cancer? Why or why not?
| 1,083 |
Plants get tumors, but it's debatable whether they qualify as cancer. Examples of a tumor on a plant include a burl or crown gall. The tumors are uncontrolled and abnormal growth of cells, which is one definition of cancer. But tumors don't spread throughout the body (called metastasizing) in plants like they do in humans because plant cells have cell walls that make the structure rigid and lock cells in place. Some definitions of cancer include that it spreads, so in that sense the term wouldn't apply.
| 1,102 |
|
[Pacific Rim] Why would the aliens invade a planet by sending single monster expeditions at predictable intervals over a twelve-year period?
|
That just seems wildly inefficient given their level of technology
| 22 |
We don't know how their portal technology works, and what its limitations/capabilities are. One theory recently placed forth by one of our top physicists suggests that the portal is slowly turning on, like a flickering light bulb. Over the years of the Kaiju war, as the portal "powers up", the portal opens more frequently (and for longer, which allows for the double and triple events that we see in the closing months of the War). If this is to be believed, then had the war not ended when it did, the portal may have become fully open, allowing Kaiju to come to Earth at any rate they wish.
| 31 |
ELI5: The Saudi Arabia / Yemen conflict?
|
I keep seeing a war of sorts between Suadi Arabia and Yemen on the news. I can't understand the topic at all and it seems very complicated. Could someone please offer an ELI5 version? Thanks
| 15 |
Religion in Yemen is split roughly 60-40 between Sunni Muslims (~56%) and a branch of Shia Muslims called Zaidis (~42%). The Constitution of Yemen makes no provision for freedom of religion, and as result the Zaidis have felt oppressed and targeted by the Sunni majority government for a while. Tensions between a Zaidi rebel group called the Houthis (officially *Ansar Allah*) and the government have been growing since the 1990s until an off-an-on war broke out in 2004. The war has since escalated, and the Houthis took control of the Yemeni capital Sana'a in 2015, forcing the president, Abdrabbuh Mansur Hadi, to flee the country.
Yemen is now divided into roughly three parts: the west, controlled by the Houthi rebels, the south and east, controlled by the government still loyal to president Hadi, and the center, controlled by various militant groups including Ansar al-Sharia, al-Qaeda, and ISIS.
Kind of like the Korean War was first and foremost a war between North Korea and South Korea, but secondarily a proxy war between the capitalist USA and the communist USSR, the Yemeni Civil War is first and foremost a war between Houthis and Hadi loyalists, but secondarily a proxy war between the mostly-Shia Iran and the 100% Sunni Saudi Arabia. These two states have been bitter rivals pretty much since the current Islamic Republic of Iran came into existence. There a number of reasons why they're hostile to each other, like stance towards the USA (Saudi Arabia is our friend, Iran hates us), oil export competition, and especially a difference in religious majority, which is exacerbated by an extremist approach on both sides. Diplomatic relations between Iran and Saudi Arabia have been getting worse and worse and worse, and this is just one more arena where they can try to assert their dominance over the other. Where the sides are drawn is very clear: Iran, being mostly Shia, supports the Zaidi Shia rebels. Saudi Arabia, being Sunni, supports the Sunni Hadi-lead government.
| 20 |
[DBZ] How can the collateral damage be so low?
|
All fighters are ridiculous strong. Even at the beginnings of DBZ people are strutting about destroying planets without even trying very hard.
Even Piccolo could do it and he was nothing compared to Goku or Vegeta.
How the hell is it possible that people that can do something like that spend their time fighting each other with punches or their standard ki-attacks.
If you have the power to vaporize a planet why hold back so hard?
| 45 |
They're not holding back. Their powers revolve around Ki. Having more Ki makes someone stronger, faster, more durable, and more powerful. When they fight they enhance their physical/energy attacks with Ki and can control the size/power of their blasts. So instead of just using huge beams/balls of energy they can put all of the energy into a smaller beam and still cause maximum damage in a smaller area. Check out Vegeta 's sacrifice against Majin Buu for an example of this -- when he expends all his ki he reduces the area of effect to avoid collateral damage but still delivers almost all his damage output in that area. If he didn't control the explosion it would easily have destroyed the planet but decreasing the area/size of the blast avoids that damage but still allowed him to concentrate his maximum damage output in a smaller attack/area.
| 47 |
ELI5: Why do some people's personalities completely change when they are drunk?
|
I am a very easy going guy but when I got blackout drunk I had the tendency to become an overly aggressive jackass. I have since quit drinking but the question remains; why do some people become different when they are drunk?
| 450 |
Alcohol basically has an anti anxiety effect. A person's level of anxiety is a huge part of their personality. Some people (I am one of them to an extent) are extra nice because they feel if they are even a bit rude, people would stop talking to them. Now, when one gets drunk, this filter disappears, and they lose the need to try to impress people and be honest about what they feel.
For someone who has a higher anxiety level, this sudden loss of anxiety can be a new and unnatural state and causes a "too free" or aggressive behaviour. While someone who doesn't have huge anxiety levels in regular life will be more comfortable in this state.
Simply put it depends how much anxiety you have in your sober state.
| 499 |
[DC] What would Joker think of Joe Chill, if he found out that Chill was the one who caused Batman to exist?
|
Joe Chill cannot reveal that Batman is Bruce Wayne because the other criminals would kill him for creating Batman, but what about Joker, who loves Batman as an archnemesis?
| 67 |
Joker isn't going to "respect" him or anything. Joe Chill is just a common street thug so Joker can't get anything of value out of his skills.
If Joker can use Joe Chill in some sort of way to torture Batman, he will. Otherwise, he's just giving him a sarcastic thanks and shooting him in the head.
In the Three Jokers, the Jokers kidnap Joe Chill and plan to dump him in Joker Venom to transform him into an Ultimate Joker but Chill is saved by Batman.
| 82 |
ELI5 When a beverage is advertised as "More hydrating than water," how could that be physically possible? Or is that just marketing nonsense?
| 549 |
This is marketing nonsense that stems from a tiny grain of truth.
**The grain of truth**
To be properly hydrated, you don't just need water, you also need salt and other electrolytes. As an example, when you sweat, it is salty, so if you sweat a lot, just drinking water won't fully replace what was lost, you also need ~~sweat~~ **salt**. Realistically, the vast majority of people do not lose enough electrolytes to need to use these "extra hydrating" electrolyte beverages. But if you are exercising super, duper hard, or if you have really bad food poisoning, they can help.
**The marketing nonsense**
Not sure how it works elsewhere, but in the US, companies are allowed to say anything about their product as long as they are not claiming it treats a specific disease. If you look closely you will notice lots of vague but healthy sounding statements such as "more hydrating than water" or "supports (body part/system) health." These are meaningless phrases.
| 790 |
|
ELI5: Why do we feel compelled to hit/break stuff when we are angry?
| 119 |
fight or flight response
humans when confronted with problems have a fight or flight response - animal nature. You choose to fight and tackle the problem, or flight and avoid it.
When you get down to the most basic instinct, you want to solve the problem by destroying it. If you're angry at something you can't hit or break, you still want to break something.
TL;DR; ELI5;
HULK SMASH.
| 133 |
|
ELI5: So, what exactly WOULD happen to the body in the event portrayed in this gif? (All the body's water Into red wine).
|
http://giant.gfycat.com/ImportantEmbellishedBushbaby.gif
I'm extremely curious.
| 21 |
Exactly what happens in the GIF, dead. Imagine each cell of your body, all fluids, instantaneously turning to wine which is full of alcohol, sugars, proteins, etc. which your body normally processes slowly. Now your body is suddenly overwhelmed with these substances with no way to process them. Dead.
| 22 |
ELI5: What does the Arkenstone actually do?
|
Everyone wants it. What's it for?
| 21 |
If you read the Silmarillion, you find out just how old the Arkenstone actually is. Basically, it's a family heirloom over a couple of millennia. It also glows of its own accord, which suggests that it was formed in the ages before the sun and moon.
| 16 |
I believe the dream that freer markets will solve all our problems is flawed. I believe hoarding defeats the system. CMV.
|
I'm no expert on economics or ideologies, but...
The point I keep hearing is that all problems come back to price manipulation in one way or another. "The government interfered, artificially inflating..." and so on.
I don't see how a private entity hoarding resources (money) isn't price manipulation.
* I've heard the argument that you eventually have to stop hoarding to buy stuff that you need, but that only ensures a trickle. If you love money (resources) more than good food, you can save $10 and spend $1.
* Allowing “some” inflation, as I understand it, is price manipulation and not a free market. I’m not sure “some” inflation is even a barrier as investment vehicles keep up with inflation.
* I've heard that hoarding money doesn't hurt the economy and everything still works regardless, the values just shift. But if that's true, that's just acknowledging that you can manipulate over time.
Here’s my analogy: Let's picture a small island with a few thousand people. They use a commodity standard so that money approximately matches resources, is finite, and government isn't assigning any monetary values. Let's call this time "A". Then, one guy comes along who is good with the free market and very committed, hard working, etc. He loves nothing more than to own more money and resources, a money hoarder.
He piles up 10% of the money on the island before anyone notices through diligent saving (or hoarding, depending on your perspective) and sacrificing anything but basic needs. Eventually, 10% of the money is out of circulation, so the price of everything falls by 10%. Nobody cares because all prices fell together. Let's call this time "B". However, one person is different. Our beloved hoarder can now buy goods using his stockpile at 90% its previous price. This makes collecting more even easier, and eventually 10% becomes 20% becomes 90%.
He can control prices over time. Price manipulation, by a private individual. He has power of coercion over other individuals granted to him entirely through the free market.
Finally, to relate to our world: Consider that most wealthy individuals keep only a tiny fraction of their wealth "liquid" and a slightly larger fraction "semi-liquid".
**Edit**: I'm not precluding investing as part of the hoarding, but I was trying to keep it simple. A large percentage of our real world wealth is owned by a small fraction of individuals, which I believe proves that it is plausible - although the real world is much more complex than Thought Experiment Island.
| 60 |
You cant "hoard" money unless you have a stack of bills in front of you that you do not touch. As this is not what happens, "hoarding" is a ridiculous reason to not believe in markets.
If you out money in a bank the bank lends out that money. It is invested. It doesnt just sit in a vault looking pretty. This is the entire concept of fractional reserve banking.
| 27 |
ELI5: Why does it feel warmer when it's snowing outside, compared to it just being cold without snow?
| 29 |
Bunch of wrong answers here...
Snowfall implies negative degrees celcius (otherwise it would rain). As the temperature drops below zero, the humidity in the air quickly drops aswell. Dry air is much easier to shield yourself against than humid air.
This is why 1 degree celsius above zero is such an awful temperature. You get all the cold with the humidity.
| 13 |
|
Too deep of a function hierarchy makes debugging difficult?
|
I was talking with a more junior developer on my team last Friday, and we were having a discussion about some code that he had written (Javascript in React). I was concerned that his function was a little too big and was trying to do too much, so I recommended moving functionality pieces into their own functions.
He pushed back some, basically saying that if the function hierarchy gets too deep, it's difficult to debug and understand, whereas if the logic is all in the same place, it's easier to debug and understand.
I had never heard anyone push back against breaking functionality out into separate functions, and off the top of my head, I didn't really have anything to come back with. I've thought about it over the last few days, and I'm still not sure how I can impart what I'm trying to.
Is there a better way to explain the importance of what I'm trying to get across, or perhaps I'm not looking at this the right way? I'd appreciate any input. :)
| 23 |
I think the junior dev's view is simply due to inexperience. The whole point of moving common pieces of code into a function is to *reduce* cognitive load by wrapping that chunk up into a single call the programmer no longer needs to think about. The logic is still all there but now it's in a single (testable!) place and can be re-used anywhere.
Maybe come at this from a maintenance perspective. Take some code you've recently worked on, manually inline as many function calls as you can, and ask the junior dev to debug it. Then show him the original and ask which he prefers.
| 24 |
CMV: Sansa Stark is the most useless Stark
|
I don't see how Sansa Stark is useful at all. Arya Stark learned to fight and has become an assassin. Bran learned how to see the past and future. Jon took his skill to The Watch and became a fine solider, eventually becoming the lord commander and a king. He fought off skilled White Walkers and came back to life. Sansa has...well...not much. I can only say she is good at sewing stuff, which isn't a special skill. Any woman in Westeros would know the basics, men know it because battle and travel usually isn't nice to clothing, even kids know how.
She was forced into one marriage and got tricked into another. No useful.
She was naive enough to tell Cersei about her fathers plans and got him killed. Not useful
She believed stupid songs and poems, letting it blind her to Joffery and the south. Not useful.
She has to be saved by others, not men because Brienne, and can't survive on her own. Not useful.
She has no special skills, never gained any, isn't physically strong, can't fight, can't manipulate people well, can't cook or make things. Not useful.
She withheld valuable info from Jon for the BOTB. Not useful.
She sold out Arya and Nymeria, called her father out as a traitor, calling for her mother and brother to recognise Joffrey and pledge loyalty. This got them killed (not Arya and Nymeria) and was not useful.
Arya was able to escape KL and survive, Sansa seemingly can't be sneaky or run very fast. Not useful.
She's always the victim and is never able to contribute to the story or her family. Not useful.
She doesn't add much to the plot. She's done nothing to affect the story. Even crippled Bran can contribute. Not useful.
I can't seem to find a way she helped her house, influence the plot, or did anything besides make people upset.
Please change my view.
_____
> *This is a footnote from the CMV moderators. We'd like to remind you of a couple of things. Firstly, please* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!*
| 18 |
Are you just talking about the show? In the books, as a point-of-view character, she is often our only insight into the goings-on of the castle and the lives of the King and Cercei until Cercei herself becomes a POV character in book 4. So definitely not useless.
Also, in the show she sent for the Vale to help Jon in the Battle of the Bastards. She also seems to be handling her role at Winterfell in Jon's absense well.
| 23 |
What about an actively burning star prevents its mass causing it to collapse in on itself?
|
Was wondering about this last night at the Paramount Science Summit featuring Michio Kaku, Brian Greene, and S. James Gates Jr.
When a star of sufficient mass dies it collapses in on itself to form a black hole (or other things). What prevents this from happening while the star is still burning?
| 119 |
*Pressure.*
When the star is still alive, there is fusion in the core, producing thermal energy which creates a thermal pressure, which pushes back against the pressure from gravity which compresses it.
Imagine it like a concert, where everyone wants to go to the center of the dance floor. They're all squeezing *inward.* The people in the middle might be crushed if they stand still. But suppose they are moshing. The constant bouncing and shoving pushes back against all the people pushing in, and so they can keep the mosh pit open. If they stop moshing or slow down or the song ends, then without anything to push back the crowd the other people will come in and the crowd will compress.
In the same way, fusion in the core of the star is like the moshers. They get the energy to push back against the crowd from fusion. Once they've exhausted the fuel, they can't push back, and they get compressed.
| 121 |
How do you find conferences to attend?
|
Early PhD student here. My advisor has suggested that I attend my first conference next year and provided a few possibilities. However his suggestions are not as relevant as I would like and he has said I'm free to suggest alternatives.
​
Any suggestions on where to look to find conferences? My field is interdisciplinary, biology/nanomaterials.
Edit: lots of great suggestions in this thread! Thanks everyone!
| 59 |
It may sound silly, but Google it. There are many conferences that are bad advertised that appear on Google searches. Also, try to find a newsletter on your field that gives you the latest information on call for papers for journals and conferences. Keep in mind deadlines. Some conferences have deadlines almos 6/8 months before the actual conference. Start a calendar of conferences as you discover then and check it regularly, so every year you know what conference is coming.
| 35 |
[Star Wars] Sometimes they can’t enter or exit entire planets? Does that mean the empire has ships all around the planet?
|
In Star Wars there are moments where a whole planet is locked down by the empire. (Like lothal in rebels) people can’t go in nor out. Does that mean the empire has ships or stations all around it? Wouldn’t that take an insane amount of resources? Yet, when they try to sneak in you can only see a a “small” empire fleet.
| 16 |
It means that the empire are blocking the hyperspace lanes. There are only a few parts of a solar system were you can safely enter hyperspace block them and they can't leave. That way you can blockade a planet with a few ships
| 24 |
ELI5: Why cheap cars always have to look ugly, it's just a shape of the metal, producing Ferrari looking bumper shouldn't be that more expensive or challenging.
|
I'm talking just about the exterior
| 55 |
Well because the exterior has to fit around the interior. With a car like a Ferrari, it's all about performance and flash. The shape of the body helps generate downforce to keep the car on the road at high speed. But this means sacrificing space inside. With a "normal" family car, the interior is more important because it's used on a daily basis. Room to sit comfortably, room for the kids and groceries and dog and golf clubs etc etc etc. Performance and looks aren't as important as comfort and reliability in that case.
| 35 |
ELI5: How is Tesla worth more than Ford?
|
My question comes from this news article: [Tesla is worth more than Ford](http://money.cnn.com/2017/04/03/investing/tesla-ford-market-value-gm/index.html)
Ford sells more vehicles in 2 days than Tesla sells in a year. Ford sold 17.55 million vehicles in 2016 while Tesla sold 76,000.
The article even says that Tesla is losing money. How can Tesla be worth more than Ford?
| 40 |
Stock price and market cap are based on projection for growth. Ford is a mature auto maker fighting in saturated markets full of uninspiring vehicles, with 100 years of legacy costs and overhead -- older, less efficient plants, retiree pensions, etc.
Tesla has a new exciting product that's revolutionary because it runs on electricity, yet doesn't suffer from the negative perception other "green" cars did/do. And they are investing billions in building state of the art factories to build their cars and -- of great importance for electric cars -- batteries. Tesla has only sold small numbers of expensive vehicles since their launch... not only did they have to win people over to electric cars, but they also had to do so with people willing and able to pay $60-100k to buy one.
Once their upcoming Model 3 -- starting at $35k -- is released, and these plants are up and running to allow for greater capacity to produce cars, they will be selling many times the number of cars they do today, and their investment in building that capacity will have been made. So a company selling tens of thousands of cars could be selling a million in a few years, and the stock price anticipates that kind of growth for Tesla.
Meanwhile, Ford is selling millions of vehicles but where's the growth opportunity for them? Maybe their next ___ model is more popular than Toyota's similar model and they grow that one model by 20% vs. it's previous version? That's not a lot of growth relative to the whole company...
| 31 |
[Mad Men/Batman] The Gotham tourism board go to Sterling Cooper to create an ad campaign to attract more tourists and visitors. With the very public battles Batman has with his rogues gallery, what kind of ads does Don Draper create that brings people to Gotham?
|
Since the 60's I'd guess with go Adam West Batman or the Batman comics from that time but Batman and his biggest villians are well known.
| 18 |
The 60's show with Adam West was the brain child of Don Draper and produced by Sterling Cooper to make the borderline psychotic vigilante fighting a wave of costumed supervillains who were bent on the subjugation of the city seem like harmless, campy fun.
| 23 |
ELI5: Why did crypto (in general) plummet in the past year?
| 7,675 |
People are mostly interested in crypto to make money. They pile in while it is going up in price and run away when the price stops going up. You can look at the price history of bitcoin and see every 4 years we’ve gone through a clear bubble.
The last year has been a combination of the crypto bubble popping again, the interest rates rising and some shady crypto exchanges going down.
| 9,487 |
|
Why does it take our eyes longer to adjust from light to dark than from dark to light?
|
Turning off lights in a room, will take eyes a few minutes to adjust and start to make out objects. turn light on and after initial sudden flare in eyes we can see everything.
| 22 |
The pigment protein in the rods of our retina, rhodopsin, is responsible for our low-light vision capabilities. When it absorbs light, it photobleaches, becoming inactive, until it is recharged by the biological processes in our eyes. When we are in bright light, all of the rhodopsin is photobleached and the rods no longer function, and our vision is dominated by the cone cells (which work in bright light). So, when dark conditions occur, the rhodopsin has a chance to regenerate, but this takes time (around 30 minutes or so to fully regenerate). Thus it takes some time before our ability to see well in the dark begins to work well again.
Photopsin, the pigments that work in our cones, have a similar process but they are much less light-sensitive. However, with really bright sources of light they can photobleach too, which is why when you see something really bright, it can leave a dark spot in the place where the bright image was for awhile. All the photopsin pigments in that area have photobleached out and need time to regenerate to re-enable normal vision.
| 17 |
ELI5: Why if prostitution is illegal, hookers do not simply go through a motions of 'borrowing' money upfront and then pretending to want have sex afterwords?
|
I know it obvious what they're doing, but it still would technically be within the law. Is there something else I should know?
| 23 |
The legal loop hole I've seen is to hire the girl as a 'model' for nude photos.
That way there is a legal excuse for a exchange of currency, and you can tell if the girl is an undercover cop if she doesn't agree to the 'photo session' before any talk of sex beings.
| 21 |
Why are truly random numbers significantly advantageous to pseudorandom numbers?
|
I understand the way that truly random and pseudorandom numbers differ (for what it's worth, [there's a good explanation here](http://www.reddit.com/r/science/comments/s9k51/researchers_have_developed_the_fastest_random/c4cc1m4)) and how difficult it is to generate truly random numbers, but why do people value true randomization?
For instance, [cbswe commented that truly random numbers are often sold online](http://www.reddit.com/r/science/comments/s9k51/researchers_have_developed_the_fastest_random/c4c8ndd). But I can only think of a few disciplines, like cryptography on a massive scale, where they can come in handy. In other fields, why do they hold a significant advantage to the use of pseudorandom numbers?
In other words, since they seem to not be significantly different from pseudorandomization in the majority of circumstances, how large is the demand for numbers with a higher strength of randomization, and who is comprised in this demand?
| 63 |
That part about selling random numbers online was a joke. Hardware RNGs are cheap, and having someone else generate your random numbers and send them over the internet would defeat the purpose of having secure RNG in the first place.
Good pseudo random generators (called cryptographically secure) produce a sequence of numbers that is not in practice distinguishable from truly random sequence. This means that for all practical purposes those numbers are as good as truly random numbers.
However, pseudo random generators still need a truly random seed for them to be secure. Here is why it is important: let's say you are generating a 128-bit encryption key using a pseudo RNG. You might think that your key is secure because there are 2^128 possible encryption keys and it cannot be broken in a billion years. However, if your pseudo RNG uses current second as a seed, there are only 86400 different keys it can produce in a given day! Suddenly, the encryption key becomes absolutely insecure.
Thus, one of the main uses of hardware RNG is generating truly random encryption keys. This is why if you used TrueCrypt it asks you to randomly move your mouse when generating a new encrypted disk - it uses YOU as a hardware RNG :)
| 30 |
How was the Euro's initial value determined?
|
A lot of charts I see of EUR/USD go back to 1979 even though (I thought) the Euro didn't become a currency until 1999. What's the reason for this? Did the Euro supersede another currency? And how was the Euro's initial value determined? Or did it just adopt the value of the currency it superseded?
| 60 |
Before the Euro, every country has its own currency - e.g. French franc, Deutsche mark, Italian lira, etc. However, there was something called the European Currency Unit which was part of the European Exchange Rate Mechanism or "snake in the tunnel".
The ECU was a basket of European currencies (including currencies which ultimately did not join the Eurozone like Denmark and the UK - and not including currencies which did join the Eurozone like Austria and Finland) used to effectively peg every European currency to each other, and the Euro replaced the ECU on a 1:1 basis. In practice, due to relative economy sizes, it was heavily dominated by Germany, France, the UK, and the Netherlands - with large contributions from Belgium and Italy.
It was called a snake in a tunnel because each currency (the snake) was meant to fluctuate within an upper and lower limit (the tunnel) vs the ECU. The range was quite small at ±2.25%, except for Spain/Portugal/UK which was allowed ±6%. The ratios of each country's weighting was fixed, so this effectively kept them fixed to each other within the range. The ECU never actually traded and was never used for anything else other than determining this mechanism.
This system actually worked decently well at limiting the variance of each currency vs the other currencies. One major issue was that it required countries to defend that range, which was easier when countries were actually part of an integrated European economy, and very difficult when they weren't. The UK joined the tunnel in 1992, but had a much worse economy than the rest of Europe, featuring high interest rates and high inflation. Ultimately, within just 2 years it couldn't afford to defend the bottom end of the range and was forced to leave, triggering Black Wednesday.
| 109 |
[Jurassic World] [Spoilers] How powerful is Indominus Rex's bite force?
|
The pod vehicle's glass can stop a 50 caliber bullet from penetrating. How powerful would Indominus' bite have to be to break it so effortlessly?
| 17 |
Considering the Indominus' base genetic code was said to be that of a T. Rex, it would probably be safe to assume that Indominus had a similar bite force; somewhere between 35 and 57,000 Newtons, if not more. Compare this to the high end of .50 caliber ammunition at around 18,000 Newtons and it's obvious why the hamster ball would break, even discounting the damage our had already taken from being smacked by an ankylosaur and the Indominus' claw. It wasn't designed to stand up to larger predators. A few bumps from a triceratops, maybe. A bite from something tyrannosaurus size, not so much.
| 22 |
ELI5: Would an overweight person or a skinny person last longer without food? Does stored fat have an effect on lasting more without food intake?
|
I'm talking about an abrupt stop in food consumption.
| 16 |
Assuming they have water and no food the overweight person would last longer.
When you enter starvation mode your body begins to burn fat for energy. The entire reason we get fat is for this situation, our body has more fuel than it needs so it stores it for emergency use.
| 18 |
[Star Wars] When Vader caught the blasts from Han Solo, was he using the Force, or was his cybernetic hand just powerful enough to absorb blaster shots?
|
Me and my friend are debating whether it took more power to do that, or if it took more power to do what Kylo Ren does in Episode 7, blocking a blaster bolt with the Force in mid-air. She thinks it was just Vader absorbing the hit with his cybernetic arm, but a DL-44 is a pretty heavy blaster pistol, and Han wasn’t too far away either, so I doubt his hand would have been as fine as it was.
| 113 |
Vader's armor is very strong, capable of even partially deflecting a lightsaber. Recall that in Return of the Jedi, Luke struck Vader in the shoulder with a lightsaber and it did not cut Vader in two. A similar lightsaber strike at Mos Eisley in the cantina resulted in someone else instantly losing an arm at the shoulder. Thats the difference Vader's armor makes.
There's that plus Vader's force powers. He was looking directly at Solo when Solo fired the blaster at him. And its just a robotic hand as well, so if it takes damage its not that big of a deal.
Had Vader survived the events of Return of the Jedi he'd have replaced his lost hand as soon as he had downtime and access to a machine shop.
| 87 |
Has all of the earth's land been discovered?
|
With the vast oceans and cartography been around since people could make them, have all lands been discovered and charted? Could there be a biome in the middle of nowhere with prehistoric plants/animals?
| 23 |
There are new islands forming regularly from volcanic activity, but none would contain prehistoric life. There are certainly cave systems that we have not discovered that may contain various animals and fossils. There is an island, North Sentinel Island, where the native inhabitants have developed their own society and they attack anyone who attempts to make contact with them. It is probably the closest thing fitting the description in your question.
| 17 |
ELI5: Will there ever be a cure for acne?
|
It's not cancer, but it comes with its own baggage.
| 117 |
Yes and no. Acne comedones are infections, and the pus is bacteria plus dead white cells trying to fight off the bacteria. Most acne treatments are designed to help remove dead skin cells from covering the pores that fill with bacteria so the infections in the pores can drain without making whiteheads. *but few acne treatments actually do anything about the bacteria!*
Killing off the bacteria on your face so it doesn't cause an infection and make a zit, is something you can do yourself, and attacks acne at its root cause..the bacteria on your face that gets into your pores and causes a pus-laden pocket of *infection.*
Get yourself a container of sulphur powder, also called Flowers or flour of sulphur. It's sold on amazon, and its cheap. It's not patented. And it kills bacteria...BEFORE we had antibiotics, infections were treated with sulfa drugs, up through the Korean war. Sulphur-based drugs are still used for people who can't take antibiotics or in containing antibiotic-resistant bacterias.
Mix 1 teaspoon of sulphur powder with 1 cup of rubbing alcohol in a glass or plastic container. (sulphur won't dissolve in water, but it suspends in rubbing alcohol.) Shake well. Twice a day, AFTER you have washed your face, shake up your sulphur solution and saturate a cotton ball with it. Using -firm- strokes, stroke the solution over your face. Make your strokes firm to help dig the bacteria out of your pores and get the sulphur into your pores. Leave it on. When it dries, if you have a little visible yellow dust, just brush it off with your fingertips.
Bacteria *can not live* in the presence of sulphur. As long as you have a light coating of sulphur on your face (light enough it can't be seen), bacteria will not be able to survive on your face or in your pores and since its not there, it will not multiply into infections. And the infections are zits. Therefore, no zits.
This won't make acne treatment companies any money. There is no patent on sulphur, its a common mineral. But it solves the problem. Give yourself a month of using it for any old discolorations to fade.
| 87 |
What percentage oxygen would mars need to have to support humans at its current atmospheric density?
| 154 |
No percentage would be enough at the current atmospheric density of Mars.
The atmosphere on Mars has less than 1% of the density of our own atmosphere at sea level. Our atmosphere has about 20% oxygen, so even converting the entire Martian atmosphere to oxygen (100% oxygen), you wouldn't come close to the oxygen density that we have on Earth.
| 223 |
|
[DC] Does Batman Fund the Entire Bat-Family?
|
I can see him setting up the various Robins with funds both above and under the table, but how is he supplying Batman level gear to all of Batman Inc?
| 82 |
I think you're underestimating his own personal wealth. He's a primary stock-holder of Wayne Industries, which is a conglomerate worth trillions.
To put it simply, Wayne isn't Jeff Bezos level of rich, he's *beyond* Bill Gates and Warren Buffett levels of rich.
In some continuities, he funds the entirety of the creation of the Watchtower (a *massive* space station with all sorts of crazy tech even by DC standards) by himself. And it's a blip in the operational budget of Wayne Technologies, which is just one of the many subsidiaries of Wayne Industries.
| 91 |
Faculty co-author stole my (PhD student) idea/project. What should I do?
|
I started working with a junior, tenure-track faculty member in my school from a related department (we are both in social sciences). We came up with an idea together, and jointly decided I would be first-author on the project and we would aim to publish in a journal in my field (hers is close, but people care which journals you publish in). We were meeting weekly and everything was going well. I then ran a pilot study, which didn't work, but the results were still promising.
She stopped responding to my emails, and after a few attempts at emailing her, she sent me this response: *"Hi! Thanks for checking in. Really sorry for being unresponsive. Could we pause this for now? I’m pretty stretched with upcoming teaching and a new phd student."*
I though working with another phd student was a weird excuse to be busy, but didn't think much of it because I figured she might be the primary advisor for that student (she isn't mine). I emailed her back that is was no problem and to just let me know when she was ready to pick our project back up.
Fast-forward 7 months later (to last week), she emails me a question, and I email her back a response and ask if she is ready to pick back up our project together. Her response was: *"On the [research topic] stuff, I’m actually pursuing a related set of questions with a [her field] graduate student, geared for a [her field] journal, so I worry there would be too much overlap."*
I send her back a nice response trying to gauge how much her project is overlapping with my ideas and whether it is okay to still pursue my own ideas. She responds to my email with one word *"Sure"*.
I then tried to set up a meeting to *"make sure I am on the correct page with everything"*. It has been over a week and she hasn't responded.
She does not seem like a malicious person at all, but I find it hard to believe that she is completely oblivious to the situation. Also, there is a small possibility that her related project may not be that related, and she is just bad at making up excuses not to work with people.
What should I do? If I try to force myself onto the paper (which I have no idea what stage it is in) there will be two problems: 1) it's targeted for a journal that I don't get credit for, 2) schools that might try to recruit me in the future will see her as a coauthor and probably will reach out to her to ask what my contribution was on the paper.
On a related note, I am much closer than her to the senior/administrative faculty in our school. She has only been here for two years (I have been here for 3), and my primary advisor (who I am very close to) is the director of research for our entire school.
**tl;dr: Faculty coauthor told me to pause our project together because she was too busy, and then proceeded to do the project on her own without telling me.**
| 21 |
I doubt there would be so much overlap that you couldn't continue to pursue your project and publish it in a journal in your own field. She likely wanted to have her own student and publish it in a journal in her field. It's kind of shitty on her part, but it *doesn't* impact in you any way except that you can't get her help.
Go ahead with your work, ask her to send you any grant proposal draft etc, and don't work with her again - she's unreliable if anyone asks.
tldr Unless you happen to be Kahneman your idea isn't big or original enough that it matters that two possibly similar studies get published in unrelated journals.
| 14 |
ELI5: Why can't alcohol commercials actually show anyone drinking the product?
| 92 |
Legally, they can show it, however unofficially, it is banned based off previous agreements and codes of conduct and network guidelines.
What does that all mean? It means while the govt hasn't specifically prohibited commercials from showing alcohol consumption, among advertisers and tv stations/channels its an official (but not legally binding) agreement that they simply do not show people drinking alcohol in a commercial, if you want your commercial to air. There is not much demand to change this, so it goes on.
| 35 |
|
[Harry Potter] Who decided what creatures where magical and not muggle?
|
So when the Wizards and muggles war split the world's and the Wizards went into hiding, how did they decide what creatures should be hidden as magical? Before they split dragons would have just been dragons, not magical dragons?
| 70 |
Magic isn't a subjective judgement in the Harry Potter verse: it's a concrete force that can be detected and studied. Dragons were always magical dragons, because they used magic.
The boring answer is the magical creatures are the ones that are magical. It's no more subjective then if we listed all the flying animals. Magical creatures are the ones who can use magic, and muggle creatures are the one that can't.
| 64 |
ELI5: Howcome when I drink salty sea-water I vomit but drinking water while eating heavily salted popcorn is fine?
| 731 |
There is much much much more salt in salt water. When you eat popcorn then drink water you are essentially diluting the salt content. When drinking salt water you aren't diluting anything, but you are increasing your body's salt content. (edit to fix auto correct - lol)
| 555 |
|
[40K] Why are all Daemons assholes? When a Daemon manifests into the material plane all the want to do is rape murder until they cant. How come there are no benevolent Daemons coming over here who just want to bake pies or go for a hike? Its just birth then murderrape
| 73 |
Because a very long time ago, eldritch psychic space frogs and undead Egyptian murder-robots and their star-eating vampire gods fought a war so violent that *it permanently damaged the afterlife.*
That's not an exaggeration. The Sea of Souls, as the Warp was known back then, was a relatively calm place before the War in Heaven. It was the negative emotion and psychic backlash birthed from the atrocities that occurred in that War that turned it into the infinite demonic hellscape that we know of today.
| 127 |
|
ELI5: Does having a prosthetic leg make it easier to run farther since it won't get tired?
|
Perhaps someone with some first-hand experience can enlighten me. I was wondering since the leg won't get tired, once you get used to having a prosthetic leg, is it easier to run farther distances? Or does it hurt more in the upper leg area? I get shin splints all the time and wonder if I would run farther if I didn't have shins...
| 24 |
You get a lot of strain on the thigh and some pretty rough chafing at the contact areas. It's hard to *walk* long distances with standard prosthesis, and nearly impossible to run(unless you have that springy thing, but that's more bouncing than running?).
| 13 |
[Sherlock Holmes/Limitless] What would happen if Sherlock Holmes took NZT-48?
|
Would it enhance his deductive skills even more, or would it have little to no effect since he's such a genius anyways? I remember someone saying that it works better if you're already smart.
| 40 |
Holmes mind is operating at close to the limits of human cognition. NZT-48 allows you to operate an order of magnitude beyond. Holmes' already exemplary deductive skills would become so fine as to appear psychic.
The real issue is that he would quickly, and irrecoverably, become addicted.
Holmes already uses cocaine, both medicinally and recreationally. It gives him an extra bump when he's having trouble with a case, and lifts him up when his melancholy gets him down. Watson has had to intervene in Holmes' drug habits on more than one occasion.
NZT-48 would be the best thin Holmes ever snorted. He would be an absolute fiend, ingesting as much as he could, as quickly as he could.
And it would kill him. NZT-48 is fatal, eventually, and the vast majority of users were not, despite the cognitive advantages it provides, smart enough to figure out how to mitigate its negative effects. Nothing about Holmes' personality suggests moderation, and NZT-48 would almost certainly be fatal to him.
| 62 |
[Harry Potter] What would happen if a wizard joined the IRA?
|
On that note, how much of a shit storm would it cause if a wizard died in Bloody Sunday?
| 15 |
Assuming they were using magic to assist the IRA you can bet both the Ministry and the international wizarding community would shut that shit down as soon as possible. Breaches of the Statute of Secrecy is serious business and there's no better way to get the Muggle world involved than killing their citizens.
As for what would happen if a wizard was killed in an IRA attack, likely there would be a protest amongst wizards and perhaps a few would 'try to get revenge' but ultimately nothing huge would come of it.
| 17 |
ELI5: Why do very high resolution images/videos look "sharper" than reality ?
| 121 |
Reality is moving all the time. Your eyes can only handle so much resolution and your brain can only process so much at once, but with a high res picture you have a frozen image that you can study up close, so it looks razor sharp.
| 85 |
|
what is the problem with the syllogism "all B are A, all B are C, therefore some A are C"
|
my professor said something about going from a universal generalization to an existential generalization. i still don't understand why this is an issue. any answers are greatly appreciated!
| 76 |
Just because all B are A and all B are C doesn't mean that any B actually exist.
All unicorns are animals.
All unicorns are rainbow coloured.
Therefore, some animals are rainbow coloured.
The conclusion is only true if unicorns exist, but our premises don't tell us that.
| 224 |
ELI5: When the twin towers fell, what types of paper records were lost?
|
They called it the 'World Trade Center'.
Surely back in 2001 not much, if any, was backed up on computers (outside of the building).
Both buildings must have had hundreds of miles of paperwork that was lost and unrecoverable.
Did many businesses lose records? Did anyone's credit card debt disappear? Did the US government leave their bills to China in there?
I'm very curious as it seems to be a topic that is never covered.
Edit: Perhaps I phrased it badly, is it bad etiquette to change the title?
I was also thinking about whether there were offsite backups for the computer records.
| 21 |
You are mistaken about how computerized things were in 2001. All major businesses were deeply computerized by that time. In fact, you may recall there was something called the y2k crisis, in which businesses were terribly afraid their computers would go down when the year switched from 1999 to 2000.
| 19 |
[Green Lantern/Marvel] Who would a ring choose to be the GL of Sector 616 (the Marvel Universe)?
| 36 |
Unassailable will, powerful imagination, great builder, honest, dutiful, and noble: Victor Von Doom.
Before people start with "but he's a bad guy" lemme just say one thing, Thaal Sinestro of Korugar.
| 28 |
|
[D&D/Pathfinder] Why don't dragons rule the world?
|
Basically as above.
True dragons are- by a pretty overwhelming margin- stronger, tougher, smarter, richer, more skilled, more magically capable, longer lived and generally better then basically anything else in the setting short of the Gods. There are very few beings that can take them in *any* conflict, from combat to rap battling (genuinely- charisma of 16+ and huge social skill bonuses across the board)
So, why are they still sitting in caves eating sheep? Where are the dragon empires, or noble dragon kings? Where are the dragon mansions? Hell, where are the dragon *farms*?
Why are the most powerful beings in the world content to sit in a dungeon and roll around in coins all day?
| 45 |
They don't want to, for the most part. They like caves. They tend to sleep a lot, so ruling isn't really feasible if you're going to disappear for 150 years.
That said, plenty of areas live basically at the whim of a dragon, sitting in fear of the next random demand of sacrifice or gold. Why farm when the humans are already doing it for you?
| 66 |
ELI5: What happens if two people with Down's Syndrome have a child? Does their child also have Down's Syndrome? If they do, is it worse than their parent's?
|
I'm very confused. Pls help.
| 62 |
Downs is where you have 3 x chromosome no 21.
2 people with downs can produce an offspring with either 2, 3 or 4 no21's.
2 results in a normal child. 3 results in downs and 4 is incompatible with life so results in an early miscarriage.
| 72 |
How does vasoconstriction reduce blood pressure in haemostasis?
|
I'm a nursing student, and I'm currently studying my second physiology unit. My materials all say that when a blood vessel is damaged, vasoconstriction occurs to reduce the pressure and flow of blood, so that the platelet plug is not dislodged. This mostly makes sense to me, however it's my understanding that vasoconstriction means the same amount of blood flows through a smaller opening, thereby INCREASING blood pressure. Is there a different mechanism in place during haemostasis? Is the constriction occurring proximally to the clot, reducing the volume of blood? Is the heart output of blood changed? I can see the heart rate increasing in major injuries, thus lowering blood pressure, but what about for minor injuries?
| 30 |
The blood can go through more than just that blood vessel. If you have 2 vessels in parallel and one gets injured and constricts, the resistance in that vessel will increase. In that way, more blood will flow through the other vessel and less blood will flow through the injured vessel.
| 13 |
How does fire behave in zero gravity?
|
Besides the typical "flames are spherical in zero gravity", does fire expand, and if so, how and why? If you were to be in zero gravity with a flammable gas, and set fire to said gas, what would happen? Any other information worth mentioning would be appreciated as well
| 18 |
Some fires in zero gravity works differently than they do with gravity due to the lack of convective currents. As the warm air does not need to rise, there is no longer a source of fresh air constantly supplied to the fire.
This means if you have an oxygen limited fire (like a match or a candle), the fire will burn much more slowly via oxygen diffusion rather than convection.
In a oxygen limited fire the oxygen near the flame is used up, and this CO2 and CO diffuses outwards, while the oxygen around it diffuses inwards.
This means that you tend to get a spherical section where the diffused oxygen gets above the combustion limit and in this section you have a sustained flame.
However there are other types of fires, like a fuel limited fire, such as a lean engine, or a fuel mist being sprayed and ignited. However these types of fire do not look like what you normally think of as a fire, they tend to look like an explosion. They do not work much differently in zero g than a normal fire, and are incredibly dangerous.
| 16 |
ELI5: Why is it uncomfortable to stand with both legs straight for extended periods of time?
| 30 |
Muscles in the legs massage the veins when you're walking. This helps the veins return blood back to the heart.
If you're standing still all your muscles are tensed to keep you upright. This means they're not in a cycle of contraction and relaxation, like when you're walking. No cycle, no vein massage, which in turn leads to less back flow of blood to the heart. This causes your feet to swell with fluid that pools in your legs (if you've ever wondered why the elastic bands on your socks leave imprints on your skin after a long day, it's the same phenomenon).
Besides, your muscles don't particularly enjoy being contracted for very long amounts of time, because when they contract and tense up they tend to shut off parts of their own blood supply.
All of this contributes to the uncomfortable feeling you're describing.
| 49 |
|
[MCU] I have an objectophilic desire centered on my wife, a chair I have purchased from IKEA. Can I trade her life for the soul stone?
|
The Avengers felt it necessary to call me into action, and last night Captain America showed up to tell me that the only way we might save humanity and perhaps existence from Thanos would be if I brought my wife, Chairen, to the planet Vormir and sacrificed her to retrieve the soul stone. Apparently, only a love as strong and pure as ours can be sacrificed, which is why he needs my help.
Can I actually help the Avengers, or should I tell him to find someone else who might be of more use to them? I desperately love Chairen, and I'm not sure if I could withstand the emotional toll of losing her, though I suppose I understand the necessity.
| 146 |
Well, the soul stone needs there to be soul lost in the process. So if animist theories are correct, you will indeed be able to help the Avengers.
That being said, that does mean that you risk throwing Chairen off the cliff only to both lose the love of your life and learning that she really wasn't a person after all. Which is not the sort of one-two punch I'd wish on anyone.
| 148 |
ELI5: Why can we imagine images in our heads but we cannot see it but know every single detail?
| 319 |
You might remember it in detail, but it's not as relevant to your survival as the data that your sensory inputs are currently taking in.
In other words, your brain doesn't give it the bandwidth (or focus) you want it to, because hearing what's around you, feeling with your fingers, thinking logically, tasting, seeing, digesting, etc. are all much more important to your survival.
And because they're more important to your survival, your brain will expend more resources on those things.
| 45 |
|
what are the rules for emailing a professor at a university I do not attend?
|
I am currently a politics student who has applied for a history masters at another university. Whilst writing my dissertation I have come across an academic who’s work has helped me massively and I have discovered they’re a professor at the university I want to attend. What is the general consensus if I wanted to email their university email (which is their profile on the university website) and say I appreciate the work you have done and also low-key mention I wanna study at their university?
| 124 |
Professors get tons of emails. Don't "low-key mention [you] want to study at their University". Reach out, tell them you appreciate their work and why and tell them you are interested in working with them (assuming you're doing a thesis-based master's).
| 199 |
ELI5: Why do some people stop liking something when it becomes popular/mainstream?
|
Nirvana, Game of Thrones, Punk;
They all seem to have had fans who were passionate, and then as soon as these things became mainstream, some of those people just jumped off the ship.
Does anybody know the psychology behind it? Why do we often place emphasis on something being exclusive and 'alternative'?
| 41 |
Some people identify themselves as 'alternative' or 'underground' or whatever you want to call it, and things like music and clothing can be part of that identity. They can feel smarter or more 'involved' in the music scene if they listen to non-mainstream music. If something becomes popular it doesn't fit that identity anymore, so they stop liking it.
In the end, liking a band because they're popular (which also happens a lot) and not liking them because they're popular is pretty much the same thing; you let its popularity influence your opinion. Other people just like music because they like it, popular or not. One is not better than the other, people are just different like that.
| 29 |
[Death Note] I write someone's name into the Death Note and set his time of death to 23 days later. A week later I get tired of waiting and decide to just shoot him myself. Am I able to?
|
Writing someone's name into the Death Note guarantees that they'll die according to the time and method written down. If it is impossible for them to do so, they just get a heart attack and die 40 seconds after as usual.
In this situation I only make the decision to kill them a week after I've written their name down. Would a bunch of coincidences prevent me from doing so? Or is there some sort of determinism that causes my victim to die 40 seconds after I write their name in the notebook regardless of the extra stuff I've written because my future actions are destined to occur and have been accounted for by the Death Note?
| 133 |
you are indeed able to, the things written only happen as written if possible, it's impossible for a dead person to take any actions so nothing happens and it's changed to a heart attack, his heart is already not beating so that also doesn't happen.
| 96 |
ELI5: If an autonomous car, while driving, parking, etc. hits a person or another car, who is held responsible?
| 476 |
No one really knows. There is no established case law to settle the issue. The fact is that the first truly autonomous accident will likely make it's way to the supreme court before we have an answer to this question.
| 338 |
|
How high can you theoretically build a building?
|
Is there a point at which a building cannot be built any higher?
| 83 |
well, in theory, you could build a space elevator. Put a counterweight into orbit around the Earth, and drop down a 'ladder' to the Earth. This could work, only there isn't any material strong enough to withstand the strains of gravity pulling on it. Although carbon nanotubes theoretically do have the capacity to withstand the gravitational strain, but so far the longest carbon nanotube that's been created is still extremely tiny. Maybe someday though.
I can't think of anything much higher than a space elevator....maybe an Earth-moon elevator O_o
| 32 |
CMV: The Rebel Flag
|
As a young, 20 year old African American man, it's easier for me to accept gray areas as compared to my parents and grandparents. I'm growing in the golden age for progression, so my view on the world is different. But one thing that never sways is how I feel when I see somebody uplifting the rebel flag, celebrating it with claims such as "Southern Pride." I hail from Richmond, Virginia, the former capital of the Confederacy, which already sums up how much of this pride I've run into. Whether it's been on my high school football team going against the Lee Davis Confederates, seeing 'Grave Digger-esque' trucks with the flags waving from them, walking or riding through neighborhoods getting blank stares and hostile scowls signifying the fact that I don't belong. Hell even in the architecture through statues and memorials, I see the glorification of a nation that not only betrayed their brothers, but betrayed them to fight for their "right" to own other human beings, that they inhumanely deemed lesser just because of darker skin. A nation fueled and driven by hatred. I feel like the flag is a symbol of a nation that openly oppressed an entire race, and trying to pick and choose what the flag represents is disrespectful in my opinion. It seems like people are trying to justify the flag and their stance behind it by saying it's not about racism or slavery, when in my eyes it 100% is.
| 21 |
There are a few different way to view the rebel flag. To one of your points, one could argue the American flag or almost any other western flag represents a nation that has subjugated minorities. America has a history of slavery on both sides. It was only until the north separated itself from an agricultural economy that it felt it was ready to end the practice of slavery.
The actual rebel flag was never the flag of the confederacy. It was the battle flag of northern Virginia. It's worth noting that nobody is alive who remembers the flag in that context. A lot of the people who still fly the rebel flag remember it in a different context. To them, it was the flag on top of the Dodge Charger in the Dukes of Hazzard, the show they used to watch as a kid. It's the flag on t-shirts they saw at their first Lynyrd Skynyrd concert. To them, it never signified slave owners or anything racist. Yes, they are ignorant to history, but to them it really does mean something different. It can also be used as a rallying symbol for hate groups, and there's obviously no excusing that, but it's not true for everyone. For a lot of people, it's childhood and teenage memories.
| 12 |
Since the Sun is converting mass to energy, its gravitonal pull should be reducing. What kind of effect does this have on our orbit?
| 99 |
Not that much.
The sun emits a bit under 4 * 10^26 W of power. Dividing that by the speed of light squared shows that about 4.4 * 10^9 kg of mass is lost per second. That's 4.4 billion kilogram per second. That sounds like a lot. In fact, WolframAlpha conveniently tells me that that's about 2% of the total amount of trash produced by the US in one year. But that's besides the point.
How much is this in the grand scheme of things? Well, not so much it turns out. That's a fraction of 2.2 * 10^-21 of the total mass of the sun. But that's per second. Looking at it per year gives you a fraction of the total solar mass of 7 * 10^-14 . Still extremely small.
In fact, in its lifetime of about 5 billion years, the sun has only lost 0.035% of its total mass through emission of radiation.
Note: This assumes that its luminosity was constant throughout all this time, which it most likely wasn't. But that's a matter for someone with more experience in stellar evolution. There's probably also some mass gained by objects falling into the sun. Either way, it doesn't really matter for the main conclusion anyway: Mass-loss through radiation has a negligble effect on the gravitational pull of the sun.
| 77 |
|
ELI5: Why, when I'm horny, do I have questionable thoughts and make questionable decisions as to the things I would do and who I would do them with? When I'm of normal (not as horny) mindset I many times would write those thoughts or decisions off completely.
| 124 |
Priorities.
When your horny the only thing you really want at that time is sex, everything else is deemed much less important. So you tend to make questionable choices and have questionable thoughts as our brains try to satisfy this desire.
Once satisfied it isn't really important to us anymore so our priorities change and our brains turn to the next important thing beside food and sex, sleep and thus our brain stops having all these dirty thoughts since it has no desire for sex anymore.
As smart as brains are, there shitty at multitasking, so we tend to only focus on what is most important to us at that time. Also even tho humans seem to be complex creatures, we were really only built to have three main functions; eating, fucking and sleeping.
| 65 |
|
How do the temperature receptors in our skin work?
| 16 |
The nerve endings imbedded in the skin have an array of receptors that detect different ranges of temperature. Molecularly, they are temp-sensitive ion channels, and their opening/closing regulates ion flow across the membrane, and this current produces an electrical signal in the nerve, that will travel to the central nervous system.
Fun fact: some of these channels are both sensitive to temperature and to certain chemicals, and that is why some substances "taste" hot or cold (think mint, peppers)
| 22 |
|
CMV: Conservatives aren't being unfairly censored.
|
Conservatives aren't being censored. Racists, misogynists, homophobes, transphobes, conspiracy nut jobs, and (recently) insurrectionists are the ones being censored. There is nothing in the terms of service of Twitter, Facebook, YouTube, Reddit, or any other platform that explicitly discriminates against conservatives. If conservatives weren't any of those things I listed, they wouldn't be be banned. You can be a fiscal conservative, you can believe in the border wall and stricter immigration, you can be a Christian and hold traditional values and you won't be banned from these platforms on that basis. Even known white nationalists like Nick Fuentes are verified and remained unbanned from Twitter because they do their best to dogwhistle and stay within the limits of the TOS.
In addition, liberals and progressives aren't immune to censorship. If they break the TOS, they will be banned. And it has happened; notable left wing streamers and content creators have been banned from Twitter. The YouTube algorithm once unfairly demonetized LGBTQ content creators because it falsely flagged them as sexualized content.
My point is that political affiliation isn't something that any social media company takes into consideration for their terms of service. If anything, conservative companies like Parler are the ones using political affiliation to ban users. Any disproportionate censorship that conservatives face on Twitter, YouTube, etc. is their own fault.
I'd also add that these companies are almost purely driven by profit motive. They don't care civil rights, they don't care about LGBTQ, they don't care about cyberbullying, they don't care about disinformation. All they care about is their bottom-line, and conservatives pose a huge risk to it by jeopardizing their ad revenue. Facebook only started to crackdown on QAnon and antivaxx communities on its platform when they started posing a risk to their public image and ultimately their bottom line.
| 32 |
> Racists, misogynists, homophobes, transphobes, conspiracy nut jobs, and (recently) insurrectionists are the ones being censored
First of all: Why should this be censored?
Secondly, conservatives get called these things all the time. Since you seem to imply that the average conservative is not these things then this should make you realize that conservatives can get banned even tho they are not these things just cause Twitter thinks they are these things.
> I'd also add that these companies are almost purely driven by profit motive.
Censorship can happen for profit reasons. It's still censorship.
| 10 |
ELI5: why mkv is supplanting avi as the preferred video format
| 33 |
It is not a format. It's a container.
If AVI is a nice cube box, MKV is adjustable in all of its dimensions, and comes with all sorts of packing materials. There is much more flexibility about what you can put inside of it. It's not preferred, but the *actual* formats (e.g. h264, AAC, FLAC, xvid) are changing more rapidly than the AVI container can support in many ways.
| 43 |
|
How to read difficult philosophy books?
|
I'd like to delve deeper into philosophy, but as I read recommended text, I begin to get frustrated by how mentally taxing it is to comprehend. Often times I will get discouraged and stop reading. Given this, what kind of approach should lower level readers take when trying to understand philosophy?
| 38 |
I began by reading books that cover many philosophies by way of overviews and then you get a feeling for where your inclination lies. Your ability to focus on what you naturally relate to will make it more accessible. Plus you obtain a synthesis of different teachings.
| 25 |
eli5: What exactly is a spark, and how does it occur?
| 17 |
It depends on what kind of spark you're referring to. If you mean the sparks you get from a firework or from striking steel and flint for instance, the spark from a firework is a small mote of burning chemicals and the spark from the steel is a small piece of very hot steel. If you mean a spark like what jumps from your hand to a doorknob and gives you a shock; certain conditions can cause your body to pick up a static charge, essentially loose electrons from the environment. When you touch a conductor, like the metal doorknob, the electrons jump from you to the doorknob, causing a visible (and tangible) discharge.
| 18 |
|
Is it possible for meteoroids carrying microorganisms from Earth to travel to another planet, such as Mars, and seed life onto them?
|
And if possible, how likely is a situation like this to occur successfully?
| 17 |
What you're asking is basically the panspermia theory, that says life can spread between habitable planets when carried by meteors. Research has been done about this by taking extremophiles into space and exposing them to vacuum, radiation, extreme temperatures and direct sunlight. Survival rates were good enough.
The weak link in the theory is atmospheric entry. When the meteor burns up, any lifeforms it carries would be vaporized and destroyed. A possible exception is that lifeforms are carried in very deep a crack in the rock that isn't reached by the hot air outside. ESA has discussed experiments about atmospheric entry in these conditions but none have been performed yet.
| 25 |
Could a gas giant have an atmosphere? Where would the border be between "planet" and "atmosphere"?
| 34 |
Gas giants have very thick atmospheres, that is what the gas is. They are often said to lack solid surfaces, so the distinction between sky and ground may be less clearly defined than it is on our planet, though they may have a solid core.
| 15 |
|
I'm going to University in September (UK) to study Economics and am planning on learning some form of coding over the summer as I have a long break and want to do something productive. Does anyone have any advice on what would be the best language to learn that would be applicable to my degree?
| 131 |
I studied in the UK and we used Stata and R/ R studio Highly recommend the latter as it is free therefore easy access for you and your university and any potential employers which makes it very popular!
| 72 |
|
[Harry Potter] Dumbledore and the elder wand
|
So, ignoring the elder wand (and the other hallows) in the specific plans to defeat/trick Voldemort in the end...
​
How important was the elder wand to Dumbledore and his abilities in general? We are essentially told that Voldemort is the most powerful wizard, except for Dumbledore, though it seems pretty close. However, during this period, Dumbledore possesses/uses the elder wand as his wand.
​
How close of a match would the two be if Dumbledore never had the elder wand? How would the duel inside the department of mysteries gone if Dumbledore had a "regular" wand (lets still assume the "regular" wand is his and "matched" to him properly etc.)?
| 17 |
Dumbledore was apparently able to defeat Grindlewald while Grindlewald held the Elder Wand, which is supposed to be nigh impossible.
That alone would put Dumbledore up near to top of the list of wizards who ever lived, and even higher up the list of currently-living Wizards.
There's a reason Dumbledore is the only one Voldemort ever feared.
| 43 |
Does it take more energy in transmitting electricity uphill than it does downhill? Is the loss during transmission more in one of the two directions?
| 37 |
Very, very small difference, so small because gravity is so much weaker than electricity. An electron going through a potential of one volt is a convenient measure of energy called an electron-volt (equivalent to ~10^-19 Joules). An electron moving up one hundred meters requires an energy of about 5 billionths of an electron volt. So in terms of circuits, the voltage required changes by billionths.
| 21 |
|
There is no possible world in which the world does not exist. Does that mean that the world necessarily exists?
| 88 |
If we follow Lewis' conception of necessity and possiblity, then something similar to what you are talking about does follow.
According to Lewis, we analyze "Necessarily x" as "In all possible worlds, x". That means we would have to understand "The world necessarily exists" as "In all possible worlds, the world (that world?) exists", which would obviously come out as true.
But let's not get carried away with the result, which does not establish anything very interesting by itself. It does not, for example, establish that *this* world necessarily exists, or (generalized) that any particular world existst necessarily. Likewise, it does not establish that there are no empty worlds. Since in Lewis' framework, worlds are described in terms of sets, they don't "disappear" if they are empty.
But Metaphysics has moved on quite a bit since Lewis. While his account is still a useful way to analyze necessity and possibility, philosophers have become more sceptical that it's all there is to say about modality. Kit Fine, for example, introduced the notion of a non-worldly necessity in his paper "Necessity and Non-Existence" (2004). According to Fine, there are certain facts that are true regardless of the world at which they are evaluated, like your statement of "The world existst.", but there are also statements that do not need a world context to be meaningfully evaluated, like "2+2=4". You can see that, while "The world existst" is true in all world contexts, and thus necessarily true, it is not true regardless of there being a world context, and thus not (what Fine calls) transcendentally true.
There is good reason to think that there is more to modality than possible worlds, and you should not therefor put too much weight on your result. But it is a correct result, given Lewis' account.
| 51 |
|
[ATLA] Why did the Lion Turtles unconditionally help and protect the humans?
|
Humans have the troublesome habit of destroying nature and starting fights everywhere they go. Why did the Lion Turtles give them protection and bending powers in the Spirit Wilds, even if the humans were destroying the wilderness?
| 24 |
Humans have practically unparalleled abilities of creativity and ingenuity, and the lion turtles wanted to cultivate that.
It's also worth noting that nature is pretty good at destroying the natural world. Humans can destroy an entire forest, but so can a fire, or a volcano, or a tsunami etc.
| 37 |
[Superman] What is the easiest way to Kill a Kryptonian?
|
Completely hypothetical I have no wish to do harm to any Kryptonian at the moment. However they do pose a rather serious threat so what would be the easiest way to kill one if I was say a billionaire with a lot of friends in high places.
| 23 |
Easiest is relative, but the most reliable way would be a red-solar lamp to weaken them, and then some sort of kryptonite blade to finish them off. That's assuming you don't have access to anything magical.
| 26 |
[Man of Steel] [SPOILERS] What exactly is the Codex?
|
At first I thought it was just an ancient fossil of an early Kryptonian, but later it's said to contain the genetic material of all Kryptonians. This really got me confused.
The first interpretation I had makes sense for being a cracked skull, but then it lost the purpose.
| 27 |
Think of it this way: the Kryptonians are master geneticists, capable of genetic engineering on a level as complex as themselves, and possibly even creating entire new species to suit their purposes. It's likely that they discovered, in their development of advanced genetics, that the best way to store genetic information is in bone, organically. They tried digital data, they tried their mass storage technology (the Superman USB drive that was sent with Kal El), but in the end the old ways, the ways tried and tested by natural selection, are still the best.
So let's say you have to store incredibly important genetic information meant to represent the future of your species on a piece of bone... what bone do you use? If it were me, I'd find the skull of an ancestor, for the sake of connecting our future to our past and for it to be a physical incarnation of the concept of biological/genetic progress. You take the well-preserved skull of a Kryptonian hominid, an ancestor representing where the Kryptonians came from, and you encode the DNA into that skull, to represent the future of the Kryptonian race. t's not just the most functional scientific method, but it's also a powerful metaphor.
| 22 |
[Star Wars] So, I'm thinking about leaving the Jedi Order
|
Despite being a well-respected Jedi Knight, I never really felt comfortable with the Jedi-dogma's (no attachments, no friends, no family or love, ...). Recently, I fell in love with this really nice girl I met on a diplomatic mission, and since we don't a secret relationship (because, let's be honest, that's just asking for trouble isn't it?) I am thinking strongly about leaving the Jedi Order. I just want a simple life with a loving wife, kids and a few friends. But what are the consequences?
Are the other Jedi's going to hunt me down like I'm some kind of Dark Jedi or Sith? Will they keep an eye on me to be sure I'm not turning to the Dark Side?
Can they stop me from leaving? Will they try to make me change my mind?
Also, can I keep my lightsaber? After all, it's a danger universe out there (that Qui-gon Jinn guy was recently attacked by a Sith on Tatooine) better be able to defend myself.
May the Force be with all of you
| 306 |
You're fine. Leave the order and go to a backwater planet somewhere. No one's going to search you out and kill you. The galaxy is a big place and the jedi have too much on their hands to worry about someone who's not hurting anyone.
As for your lightsaber, who cares if they let you keep it? Just because you left the order, doesn't mean you forgot how to make one.
| 226 |
ELI5: why on videos of Jupiter can you not see cloud movement like you can on earth?
|
We can see clouds moving over our planet, but every video I see of Jupiter I don’t see movement in the clouds/swirls. Why is that?
| 99 |
The cloud bands you see on Jupiter are huge. The red storm you can see is larger than the entire Earth. Even with very high speed winds, the distances involved mean that the clouds are barely going to look like they are moving.
When a single pixel represents 100 miles, a cloud moving at 100mph is going to take an hour to show one pixel of movement.
| 209 |
ELI5:why do humans all look different facially but not animals?
|
people mostly distinguish each other from facial features (eyes, bone structures, cheek bones, nose), while animals all appear to have uniform features. Humans are all the same species so why do our faces vary so much?
I'm thinking of birds, sometimes cats (not counting fur markings)
Is it that the more advanced the animal is, the more variation there is per individual? insects all have the same face, but chimpanzees and gorillas should have more variety
| 16 |
You're using a brain wired to see the differences in humans and not other animals to state that humans look different and animals look the same.
>Is it that the more advanced the animal is
There is no concept of "advanced" in evolution. We are not more advanced than ants or mice. We're different at best you could claim more complex.
| 32 |
[SCP] Why would ANYONE work at the foundation?
|
I mean, it's literally the most dangerous thing you can work with, period. People meet fates worse than death so often that simply dying seems merciful. What kind of payment or motivation drives the staff?
| 36 |
>I mean, it's literally the most dangerous thing you can work with, period.
Prometheus labs collapsed in an orgy of unsafe crosstesting and Apeture-science-level poorly concieved ideas. The Chaos Insurgency flies blind, with their cells ping-ponging off each other on suicide missions ascribed by poorly understood, possibly non-existent higher-ups. The GOC routinely gets into literal wars with supernatural forces. Fucking up at Marshall, Carter and Dark can get you turned into a blood-bag that the higher-ups will use to extend their life. And good things rarely happen to people caught up in the Sarkicists, the Mekhanites or the Fifthists.
The Foundation is, in all honesty, a reasonably safe environment if you want to be on the cutting edge of research and development, in that it's at least nominally run by humans in service of human interests, with a strong culture of workplace safety and cautious, trial-and-error based analysis. If you've become aware of the anomalous world, and you want to throw in with any faction, I'd argue that the foundation is the least likely to get you killed as a matter of course.
| 69 |
[Star Wars] Aside from the turrets on clone gunships and the Death Star, why aren't laser beam weapons more common?
| 44 |
They're sophisticated, maintenance-intensive, power-hungry and prone to overheating, and not much more destructive than an ordinary particle gun. Why bother with them if your shipborne turbolasers can already slag entire cities?
| 51 |
|
[Star Wars] How did the Death Star blow up planets?
|
The primary weapon of the Death Star was a massive LASER array. LASER's don't have any kinetic force and only cause changes in temperature. Shouldn't it have just melted the planet instead of causing it to explode?
| 25 |
The primary weapon of the death star was NOT a purely laser weapon. Whilst referred to as a 'superlaser' this can easily be a slang term for the weapon, or a reference to a single portion of the weapons design. The characteristics of the weapon, such as the speed of the beam (which is much much much much much slower than the speed of light which a laser beam would travel at), and the 'converging' beams (which laser energy cannot do) show this amply. The same goes for the 'turbolasers' on Imperial Star Destroyers and other warships.
As far as the effects, pump enough energy into something and it'll go boom. Doesnt matter if its an energy based weapon on not.
| 18 |
ELI5:Why is the human body not sensitive to radio waves?
|
Why are humans not able to see,feel or hear radio waves? We are sensitive to the rest of the waves in the EM spectrum. If EM waves are composed of oscillating magnetic and electric fields, why am I not electrocuted by the electric constituent of the Radio waves?
| 19 |
Radio waves have wavelengths of several feet, so humans are virtually transparent to radio waves, like glass is transparent to visible light. If you have a piece of conductive metal the right length (an antenna), the waves WILL interact and make electricity move in it. Because the signal is so weak and humans are not as conductive as metal, we don’t notice any effect.
But if you stand really close to a powerful transmitting antenna, it can heat up your body (microwaves were discovered this way when a technician noticed the chocolate being melted in his pocket).
| 31 |
[Borderlands] Why are there so many Psychos on Pandora.
|
As in, I understand that Pandora isn't exactly the best place to live but that doesn't explain why there are so many people who have just gone completely insane.
| 151 |
Some of the companies that came to Pandora to mine its resources used prisoners and mental patients for manual labor. When the resources ran out and the companies left the planet it was more cost effective to leave behind much of the used equipment and all of their "labor force". The now free prisoners and psychopaths over ran the remaining population of people who moved to Pandora to make a fortune for themselves similar to people who flocked to California and established boom towns during the gold rush. When the companies left Pandora the whole world went to shit.
| 147 |
ELI5:Why is there sometimes a "choppy" noise when you only have one window open in the car?
|
Its hard to explain what it sounds like, but im gonna assume that you've heard it before.
| 33 |
air is rushing in the open window and the pressure builds up until it is strong enough to break through & some escapes out the open window, that reduces the pressure. that cycle repeats. its the flapping of air pressure
| 25 |
[Star Wars] What are the poltical impacts of building the Death Star?
|
I'm trying to understand how the empire is actually evil, what justifies the Death Star? It seems to me like a good weapon for defense rather than offense
| 21 |
The Death Star is meant as a weapon of terror. Tarkin explains its use right in ANH.
>**General Tagge:** But that's impossible! How will the Emperor maintain control without the bureaucracy?
>**Governor Tarkin:** The regional governors now have direct control over their territories. Fear will keep the local systems in line. Fear of this battle station.
It's not about defense or offense, it's about intimidating civilian populations and planetary governments with the threat of full-blown genocide.
| 23 |
[Star Wars] Is it really more economical to 'farm' moister on Tatooine than ship it in from off world?
|
Like spaceships seem to be all over the place, wouldn't bringing in some ice from Oort cloud be cheap and easy?
| 35 |
I mean, people are doing it. They're not exactly getting rich off it, but they're surviving, so there's at least enough of a market to support that.
Likely the situation is that nobody on Tatooine has all that much money, so bringing in small scale water shipments isn't really worth it, and doing something large scale would flood the market and crash prices such that it wouldn't support itself.
| 58 |
Why doesn't the n-body problem make the rotation curves of disc galaxies unpredictable?
|
The difference between the observed and expected rotation curves of disc galaxies is explained by the presence of dark matter.
But how do we even have a predicted rotation curve for disc galaxies?
Doesn't the n-body problem mean the radial velocities of the stars in a galaxy are completely chaotic and unpredictable?
| 212 |
The n-body problem doesn't mean that trajectories are completely ~~chaotic and~~ unpredictable. It just means that there is no known analytical solution for 3 or more bodies. We can still do numerical simulation to an arbitrary degree of precision -- limited only by our computational resources.
The general technique is to calculate the two-body solution on every possible pair of bodies in the simulation, and sum the effects on each body for a given time-step. The number of calculations is proportional to *n^2*, so it becomes time-consuming very quickly. Various methods are used to approximate the result with less complexity.
| 42 |
How likely is it that digital data we have right now (of music, movies, pictures, etc) are preserved and recoverable thousands of years into the future?
| 40 |
Such a question is difficult if not impossible to answer. There are too many variables; what country are you talking about for example, as a war or conflict could destroy data storage infrastructure. Which company because of how likely they would be to preserve data through acquisition or financial ruin. What is the nature of the data; financial data is virtually assured of destruction within the next few decades simply for legal reasons. Ultimately the web of supposition becomes too thick for any level of reasonable conclusions to be drawn.
| 20 |
|
ELI5 Video Compression
| 25 |
The next time you watch a movie or TV show look at how little changes from one frame to the next. For example, if you have two people talking to each other the background isn't going to change much. So, instead of storing a picture of the background twice they simply include the pieces that changed. Then they can throw out the rest of the data.
Next, imagine a really chaotic action scene with multiple, fast cuts. No image is on screen long enough for your eyes to really focus well. So, you can throw out a lot of the data and use lower quality images since it's all moving too fast to notice.
These are just two examples of how they compress video. There are numerous other tricks they use to remove non-critical information.
| 15 |
|
ELI5: If there is such a dire global shortage of helium, why do we still use it to fill up balloons?
| 188 |
The "helium shortage" is actually a reaction to massive helium stockpiling of the US starting with the Helium Act of 1925 for use in airships and later on as a coolant during the Cold War and the Space Race. The idea was that it may be a critical natural resource similar to oil, but the progression of technology determined that it wasn't really that important and it was decided that the billion cubic meters of the gas we had collected should be sold off.
This dramatically dropped the price of helium for decades, as the US government was selling a seemingly unlimited supply off at bargain prices. The "shortage" is that the US is coming to the end of their fire sale of helium which means the price will begin to rise to the actual cost of production, which means applications designed around the historically low cost of helium now are looking at a big price bump.
| 137 |
|
Eli5: How are the different types of "athletic" muscle different?
|
I've seen so many different builds on the "muscular" spectrum, ranging from barrel-shaped power lifters, to wiry, waifish dancers and acrobats, to really chiseled and defined bodybuilders. I know they're all strong and ripped in their own way, but what's the difference as far as approach and training?
| 18 |
You pretty much answer your own question. Power lifters need to have high force output which is accomplished by large muscles, dancers need long, lean, fast twitch muscle for quick movements and lots of flexibility. Your primary training is always by doing the activity you are training for, weight lifters lift larger weights, runners run, climbers climb. Each group targets strength training in a similar philosophy as the sports they are training for.
| 12 |
ELI5, Why is the amount of water required for producing something (food, clothes, etc..) used as a measure of sustainability?
|
I get that if it’s produced somewhere where water is scarce it’s important not to waste it but where I live freshwater is incredibly abundant why does it still matter?
| 84 |
Industrial production tends to use massive amounts of ressources. If not well managed, even the most abundant of ressources can become depleted given enough time.
Another reason is that industrial processes often cause pollution and if not managed (often mandated by law), polluted water could be dumped back into the environment. The water may not be reusable without (heavy) treatment, therefore not sustainable for the long term.
Another reason could be that a big corporation could set up shop in an area, exploit the ressources without caring about the environment. Once the ressource is depleted or the market has dried up, the corporation leaves. The local inhabitants are now left economically deprived in a degraded environment which could have been better preserved when the moneyed corporation still had an interest in the area.
| 85 |
[MCU] Why was Sandman in "sand form" through out No Way Home?
|
Through out the entire movie, when not fighting Marko stays in this humanoid sand form, unlike Spider-Man 3 where he can give himself colour and appear like an ordinary person.
Was this some sort of voluntary choice or was this the reason he "needed" to be cured? Cause if it was the former, I don't really understand why he had to br cured, unlike Norman, Otto and Connors, his powers didn't have an effect in his personality, the same you could say about Max to a lesser extent, both can control their powers and could live normal lives.
In fact, taking his powers would make his life worse since he is a wanted criminal and would have more trouble slipping awat and visiting his daughter.
| 133 |
I figured Flint didn’t feel comfortable walking around as his normal self in a strange new universe with magic and crazy technology, a different Spider-Man, and two of his NYC’s most dangerous criminals hanging around alongside a giant lizard and some dude with electricity who all died fighting a superhero.
As for his powers getting taken away, it doesn’t seem like MCU Peter was making him a cure or planned to, but when all hell broke loose and Flint left he and the other Peters couldn’t take the chance he would cooperate after he’d already been stuck there so long, an assumption proven correct. Given some of the other things going on it seems like he came back from 2024 like Raimi Peter did, so it’s possible the latter would seek him out to make sure he is handling the transition alright. Electro also definitely needed his powers taken away, as we see in TASM2 they were severely warping his mind-he may have been more stable in the MCU with its energy, but coming back there’s no guarantee.
| 121 |
What CPUs do cars run on?
|
Sorry if this is the wrong sub for this. But yeah, do cars have brand-name CPUs from Intel or AMD? I just got curious, because I was thinking about it, and when it comes to futureproofing for vehicle-to-vehicle communications, they would want some decent hardware in there. But then again, I'm sure cars in the 80s and 90s had some Atari-grade CPUs to handle whatever KBs of data they had to process.
| 55 |
Broadbrush info - there are exceptions...
1. There are no x86 (Intel/AMD) processors, they take too much power and get too hot and they're a bit fragile in an auto environment
2. Japanese cars use NEC, Hitachi (Renesas) etc. American cars use US brands, the Germans use European brand like Infineon.
3. In the past all the semconductor companies designed their own CPUs but these days they almost all license ARM cores.
4. Most of the CPUs in current cars are actually 8 and 16-bit and mostly do simple jobs but the overall trend is toward 32-bit ARM processors.
5. It's a massive and growing market so the manufacturers are desperate to get their chips in cars but the software is growing 10x faster so the tools are more important than the CPU - ARM has the biggest tools and engineer base.
| 54 |
ELI5: How do people initially determine the amount of protein, carbohydrates, and fat in a food item?
| 23 |
Foods are pretty complex, so the tests used also get complicated pretty quickly, but there are a couple basics. For fat, you can weigh the food first, then wash out the fat with special liquids (solvents). You can remove the solvents from the fat to get the weight of fat alone.
For protein, people usually look for the element nitrogen. There are specific measuring methods to get the amount of nitrogen in the sample, and then a mathematical formula is used to convert that to an amount of protein.
Carbs are kind of assumed to be what's left over from the other two kinds of tests.
| 24 |
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