query_id
stringlengths 3
6
| question
stringlengths 1
299
| goldenAnswer
stringlengths 3
35k
| doc_id
stringlengths 36
36
|
|---|---|---|---|
c13moa
|
How can one small sound become super loud when more people make the same sound?
|
Sounds are waves if you superimpose one waveform on top of another the amplitude of the wave increases as you add the two waves together. Increases in amplitude are an increase in the loudness of the noise.
|
93bcb641-dc9b-4a97-91c1-2c469ce87a56
|
c13qg9
|
What happens when a cetacean, like a whale or dolphin, accidentally inhales water?
|
If they inhale water they drown like any other mammal. But they have adaptations to avoid breathing in water in the first place.
Their blowholes can be voluntarily controlled, so they close them underwater and only open them to breathe. They also breathe out strongly to expel water away from the blowhole before breathing in.
They also have separate respiratory and digestive systems, meaning they don’t risk water getting into their lungs when they eat.
|
5f448cec-6224-4501-a2b2-08bda5783279
|
c13srh
|
-How do rockets work?
|
A fire or explosion needs 3 things to go: heat, fuel, and oxygen.
oxygen and fuel are fed into the bell(the part that the fire comes out of) where they explode, the force of the explosion pushes against the part you don't see, pushing the rocket, while the rest of the explosion goes out the other side which is opened up that you can see. They go straight up because it's inefficient to try to make them fly using lift, and so they need to get out of the air asap... they then turn into the Earth's curve to use the Earth's rotation to move faster.
When they move as fast as they fall, that's orbit.
|
b73dd858-64e1-4b25-b507-ce21ba479899
|
c13xko
|
What is the difference in brain chemestry between being drunk and being high?
|
Drunk and high are not scientific terms. Two categories that drugs can be classified as are stimulants and depressants. Stimulants increase nerve activity and depressants decrease nerve activity.
Ethanol is a brain depressant, it activates receptors for the neurotransmitter GABA which inhibits brain activity.
THC acts on cannabinoid receptors and can cause depression of brain activity among other effects.
|
732fea89-a0e5-4869-bb09-cbe378078acd
|
c140hn
|
Why does the body have panic attacks and anxiety when it's completely productive (I.e. paralyses the person in the face of a challenge)?
|
Think of a cat freaking out when it sees a cucumber.
It's an automatic flight or flight response that gets triggered by things your brain thinks is a threat - but isn't.
The heart beats faster, pumping adrenaline around the body, making you feel anxious and want to run away or fight. Or turn to ways of dealing with it, like alcohol (which makes anxiety worse in the long run, leading to a vicious cycle).
This automatic response is part of the 'animal' part of your brain, which also deals with hunger, anger, loneliness, tiredness. It reacts quicker than the 'logic' part of your brain - the part that makes you, you. A technique to reduce anxiety is to do a quick scan of whether you're hungry, angry, lonely or tired... or scared by cucumber. This puts the 'logic' part of your brain - you - back in the driving seat. Learning to control anxiety in this way is a skill that can be learnt, like any other skill.
Anti anxiety medication (like propranolol) works by stopping adrenaline from moving around your bloodstream as quickly. The cat has time to realise that the cucumber is just a cucumber.
Talk to your doctor. Anxiety is an actual thing that people have. It can be treated.
|
72b0a34c-5a0b-40c2-8a2e-4bbfb977c255
|
c143sv
|
Why/How does the human body produce tears when seeing something that makes you sad (also happy)?
|
The emotional centers of the brains have a connection to the superior salivatory nucleus, which is the area of the brainstem responsible for tear production. This nucleus outflows as cranial nerve 7 and triggers the lacrimal gland in your eyes to produce tears.
|
64023b8b-a8c1-4dd6-8410-074c238a4254
|
c14fn2
|
Is every individual sperm a potentially different child with different attributes?
|
Yes
Each cell in your body has 2 copies of 23 chromosomes, 23 from mom and 23 from dad. Sperm has a single set of 23 chromosomes, each one randomly picked from mom or dad.
In addition, chromosome from mom and dad also exhange information. So even if you get a chromosom from your mom, it might have some Dad's genes in it.
Add the fact that the egg also does the same thing means that there are many many many different combinations of offspring possible.
|
1faac964-0549-4a0b-80e6-39e4d8ad8f91
|
c14fsu
|
How does the human brain immediately remember the lyrics to a song you havent thought of in 20 years?
|
A terabyte SD card can probably hold 200 thousand songs and is much smaller than a warehouse.
Memories are stored in different areas of the brain, long term memories are thought to be stored in the frontal cortex. Memory is stored as a system of connections between neurons and distant memories can be recalled using context clues. For example, hearing the beat of the song and perhaps watching the video allowed your brain to find the lyrics to the song. If someone had just told you the song title, it could have been much harder to recall the lyrics.
|
66c0c7a5-85b1-4c44-952e-c7ead41c1beb
|
c14lxw
|
How is it that your nose can produce an almost endless amount of snot when you are sick, even after you blow your nose dry?
|
We've got pretty big sinus cavities inside our cheeks and foreheads. It can seem like your blowing your nose *forever* when you're sick, but we underestimate the amount of snot our noggins can store. Plus, if you're fighting an infection, your body's gonna keep producing more mucous to try and flush it out.
|
56aa3fc6-87a0-4aef-a826-6783a2747d45
|
c14rda
|
Why does dark colors tend to be much hotter in the sun compared to lighter ones?
|
Dark colors absorb light and therefore heat with the sun while light colors reflect them and don't get as hot.
|
8c74771d-ada5-4b83-a61b-65ad5925911c
|
c14tdh
|
Why aren't TV's correctly adjusted out of the box?
|
Because "correctly adjusted" TVs don't sell. Manufacturers have found that consumers prefer to buy TVs with very bright, contrasty, colour-saturated, sharp images so that's how they're configured out of the box. They can't trust the stores and sales staff to change the out-of-box settings to a special sales mode, so out-of-the-box *is* sales mode. Even having sales mode in people's homes helps sell the brand to people who see them.
Often there is something like an accurate mode that can be accessed via a TV's menu for people who care. So the question is then: why isn't that mode calibrated? I suspect there are two reasons. Firstly and obviously, cost, especially when only a low percentage of people will ever use this mode. Secondly, the people that do care and who use an accurate mode actually want better calibration than the factory can provide.
|
65a29e77-1283-4b83-8072-c24eeaaf341c
|
c14y50
|
What is a “squatcheloid” and how is it used to compute the ascent load on a space vehicle (like the shuttle) during launch.
|
There's a pretty good explanation here:
_URL_0_
It is product of dynamic pressure and an angle. The full squatcheloid is a graph around 360 degrees of the vehicle. But just looking at the Q-alpha (angle of attack) limit it is measured in Pa-rads (pressure times angle) in metric. Typical values would be around 1000-4000 Pa-rads for real vehicles. If MaxQ was around 50 kPa then a 2000 Pa-rad Q-alpha limit would equate to:
2000 Pa-rad / 50000 Pa * 180 deg / 3.14159265 rad = 2.29 deg
Earlier or later in the flight when the pressure was 25 kPa:
2000 Pa-rad / 25000 Pa * 180 deg / 3.14159265 rad = 4.58 deg
A symmetrical rocket should have a symmetrical squatcheloid. The shuttle was highly asymmetrical, and it flew upside down with a negative angle of attack (which upside-down should mean nose-up relative to the horizon) to catch some lift (but not too much!). Rockets should all try to fly with zero sideslip and roll into the wind, but there will be a distribution of wind velocities that it actually experiences.
It is a name that was invented for this graph, for the space shuttle in particular (I suspect its sort of a half-joke like "quark" or "color"):
> Because the shuttle is a winged vehicle, the high dynamic pressure regime was a major analysis problem to adequately predict rigid-body vehicle response to winds and thrust-generated, vehicle-induced loads, which included all system parameter variations as well as wind statistics. This was accomplished in an efficient manner through the creation of squatcheloids (Tom Modlin’s work) which was qα and qβ plotted continuously for nominal parameters as the wind direction varied. These squatcheloids are generated for each Mach number. A set is also generated for 3σ system parameter variations and becomes the basis for the design criteria (figs. 46 and 47). This work has been extended to the use of alpha, beta, and “q” combinations instead of the rigid boundary of the squatcheloid, providing more freedom in trajectory shaping and the tailoring of the day-of-launch I-loads updates to increase launch probability.
_URL_1_
|
5e568f82-0d58-4c6f-b34f-be87543b8469
|
c150il
|
why fast food advertisements don’t need disclaimers saying the food you get won’t look anything like the food in the advertisement.
|
There's is a law in the US requiring that the food being pictured is the actual food being served. But...
I was on set for a cereal photo shoot once and saw a team of people shifting through dozens of boxes of the product looking for The. Perfect. Corn flakes. One by one they picked up each corn flake with tweezers, inspected it, and discarded 99.9% of them. It's legal because the corn flakes they ended up picturing **were** the real food.
Another interesting note from that day - the "milk" they put the perfect corn flakes in for the photography was actually glue-like substance. That was legal because they were not advertising the milk, so it didn't need to be there actual product. Only the corn flakes needed to be real.
Edit: clarified a sentence
|
98c665c5-e2cd-41a6-a7cf-e3843a2ab41f
|
c159wp
|
cc % charges
|
If you don't have a balance from the previous month, you are not charged interest on the purchases you make this month.
If you do have a balance due from the previous month, you are charged interest on that amount.
Depending on the card you have, purchases made this month may also accrue interest, but usually there is a 'grace period' during which the new purchases don't accrue interest. You have to read the agreement to find out.
|
c89ac497-c2ac-4b48-afa9-f6f5180e96f9
|
c15d4s
|
How do riots and protesting achieve anything?
|
Well, the riots did function. They got the law makers to change their minds on the implementation of the proposed law.
The trick is that law makers need the people to support them. In democracies, that's "If all of these protesting and rioting people vote for my opposition, I'm screwed. I had better present policies that all of these people, if not agree with, aren't super angry at. "
But on some level, if they realize that the average people are against what they are doing, they know that it's going to be VERY difficult to continue running the government. They'll face inconveniences and protests and strikes and enough to make their jobs impossible.
& #x200B;
Politicians are humans, and if everyone they are trying to rule over hates them, they can't continue to do their job.
|
d20b1767-6f03-43f9-a45e-401ca1c7509b
|
c15i9y
|
Why does the brain forget things? What decides what gets forgotten and what doesn’t?
|
As we go through the day we experience lots of things, if we were to remember all of it we would be simply overwhelmed.
It is important to realise that there are different types of memory: there is our short term memory and our long term which consists of "declarative" (basically facts like remembering what time your favourite restaurant opens) and "procedural" (like motor skills: riding a bike or doing tasks)
There is also no specific one place in your brain where memories are stored. Different areas of the brain play roles in different parts of memories. For your question specifically the answer is our emotional response to things happening. Our memory is dependent on our limbic system (which helps control emotions) so if we are super happy about something we are much more likely to remember it than remembering something that is meh and boring.
Example: you'll remember getting a puppy on a specific day and you might not remember eating a bowl of cereal a week ago.
The same goes for memories that upset us or anger us.
Our hippocampus is the area of the brain that helps us consolidate our memories from short term into long term. If we learn something we think is interesting and form some kind of emotional response to it we are more likely to remember it. Which is why I remember lots about science and barely anything about history.
|
ba5326fb-0ae7-4b08-afbe-0370ff487a8f
|
c15kf3
|
what causes the "mind blown" feeling?
|
It's your brain processing the fact the a great deal of information it has stored is suddenly wrong and struggling to process and rewrite all of it.
|
19760704-cd0e-403c-9286-d20a4951c3fc
|
c15pnk
|
An article today said using your phone battery below 20% and charging it routinely above 80% reduces battery life...what causes this and is it the same process at both ends of the range?
|
ELI5: Discharging a battery too deeply causes its structure too break down, increasing the potential for a short circuit. Overcharging has a similar effect, but can also result in the battery catching on fire. Discharging from 80-20 slows the breakdown.
Full Answer:
When discharged below its safe low voltage (exact number different between manufacturers) some of the copper in the anode copper current collector (a part of the battery) can dissolve into the electrolyte. The copper ions then in turn can stick on to the anode during charging by chemical reduction and cause dendrites. The dendrites might cause a short circuit inside the battery. So basically discharging too much is as bad as charging too much. But the dendrites caused by overcharging is formed out of lithium.
Normally the battery pack should have some sort of supervisory circuit that disconnects the cells from the charger or load when the cells are above or below the recommended voltages.
|
aa918f53-4260-4e6b-903a-c25f57e5a8c7
|
c15wgx
|
How do activity trackers know when I'm asleep? How they deduce REM sleep, deep sleep etc?
|
They detect movement through either an accelerometer or by using a microphone to listen out for movements (as programmed by the software). Since each sleep cycle lasts roughly 30 mins, the tracker is really only guessing which stage of sleep you are in based on the time in bed and any movement detected throughout the night.
|
7faca125-e7df-44f1-b3bd-42688f9e2893
|
c16952
|
Why do your eyes tear up really badly when you bump your nose, or when you pull out nose hairs?
|
I'm not entirely sure, but am pretty confident that it has to do with the naso-ocular reflex path. Your eyes and nose are connected by certain nerves, which cause the other to react when one is irritated. When you pluck a nose hair, you irritate the nasal mucose membrane, and the body reacts by trying to "flush out" the irritant via increased fluid secretion. Similarly a jab to the nose warps the mucosa causing similar irritation and secretion. The reflex nerve pathway will make your eyes secrete as well, and thus tears are produced, which will flow into the nasal cavity to help with the flush.
It's also complicit in the eye symptoms due to allergies, and likely to contribute to ACHOO-syndrome (I kid you not, look it up!), also known as sun-sneezing.
|
1d4074cd-c389-4b45-b34f-55e8c7c60bcf
|
c16a2n
|
Why do some companies create multiple apps for the products they offer instead of using one app? Uber and Uber Eats, Google Home and Google Assistant are two examples.
|
Marketing. You get more people to use your app/product if you have different versions targeted to specific groups. It's why there a separate varieties of cold medicine in spite of all of them having identical ingredients. If presents with a choice between something generic and something that seems tailored to their specific needs, people will choose the specific one most of the time, even if there's no actual difference.
|
79406574-37ff-4e95-b475-8e9d9a9bb248
|
c16fsb
|
Why didn't we ever get immune to colds if it's so common?
|
The rhinovirus (aka common cold) is always changing/mutating into new strands. One person’s virus could be exponentially different than another person’s, it’s quite amazing.
Much like the flu, the common cold’s virus is always different every year. Although there is no vaccination for a cold, it’s soo important to make sure you are always updated on your most recent flu shot! Every year the strain is different and could be more deadly than the last!
(I am a fellow microbiologist ;-))
|
f2ad1653-7575-4d13-b100-06043beea921
|
c16odj
|
Are we somehow responsible for the weapons our country is selling to other countries ?
|
Government is run by people you elect (democracy of course) but since there is currently no direct democracy anywhere (you are not personally involved in decision making), you cannot be personally responsible for government actions. If you do not agree you can always let your representative know you do not agree to these actions.
|
8bf90047-4608-4972-858d-5e7f1362480c
|
c16pr7
|
How do the pumps at gas stations know when to stop filling the tank?
|
The next time you fill your tank, take a look in the gas nozzle, you will see an object, usually square, near the opening.
This object is a mechanical switch that works off of the vacuum created by your tank. When its low the fuel flows free, but as it fills the pressure changes enough to cause a back flow that triggers this switch, causing the pump to kick off.
|
36d218ab-8e67-4b70-80e7-95c9d0b682fd
|
c16qa4
|
I hate snot. I hate how I have to often blow my nose to keep my nostrils clear. Say there were some surgery that would remove my body's ability to produce snot. Explain to me the negative repercussions that would come with that.
|
I believe mucus keeps the mucus membranes (nose, mouth, etc.) free of contaminate build-up. A toxin removal, so to speak, as well as keeping membranes lubricated. Downside — I’m allergic to dust mites, grasses and several tree pollen. A thing that should help, hurts. Swollen, stuffy yet still runny nose, sneezing.
|
7940768c-b1ba-4373-9c2a-1f6a8e748566
|
c170v6
|
How does your body hold in pee when you’re asleep and when can a toddler do the same?
|
There are two sphincters, or rings of muscles, around the tube coming out of your bladder. One is under unconscious control and the outer one is under conscious control. When you are holding it in, that is you contracting the outer one consciously. It takes time to learn how to control that. Also, it takes time to learn that even the unconscious one shouldn't open automatically when your bladder is full, say like at night. It depends on the the kid, but this is usually achieved by a few years' age.
|
0ad939f3-b0e9-4a80-8d20-a6dd84e67665
|
c174d0
|
what is the difference between Ark, Mig, Tig, and Oxy Acetylene welding. (?Strengh, speed, efficiency?)
|
Hello there!
I want to start off by apologising for how long this post is; I didn’t want to oversimplify it too much.
Both MIG (metal inert gas) and TIG (tungsten inert has) are forms of arc welding. TIG may also be referred to as GTAW (gas tungsten arc welding) and MIG as GMAW (has metal arc welding). Typically when I hear arc welding, I think about SMAW (shielded metal arc welding) or stick welding, which is one of the most common welding processes. However, I have also seen FCAW (flux corded arc welding) referred to as arc welding. All of these processes have a few things in common however; they all use heat generated through electrical resistance and all utilise some form of atmospheric shielding.
MIG and FCAW work almost the exact same, as both utilise a wire feed mechanise that feeds the consumable wire electrode into the weld pool. However, MIG uses an external shielding gas, which is typically either carbon dioxide (CO2) or argon (Ar), which is dispersed through a nozzle over the weld pool. FCAW, however, doesn’t use an external shielding gas. Instead, it uses a hollow wire which inside contains what’s called flux, which burns and creates a shielding atmosphere for the weld pool. Both of these processes are fairly quick to use and easy to learn. However, they cannot weld aluminium and cannot weld very thick metal. My FCAW machine can only weld up to 3/16” metal, however, I surmise there are other, more powerful machines that can weld thicker materials.
TIG welding is a little bit different than GMAW, as unlike these two processes, TIG uses a non-consumable electrode that is made out of tungsten and mostly uses Argon as a shielding gas. This makes TIG a very precise process; it can be used to weld needles together. The TIG process is more difficult than GMAW as the welder not only has to direct the arc, but they also have to manually feed in the filler rod by hand into the weld pool. However, as a result of the precision this process has, it will produce the best looking welds out of all of the processes. The most important aspect of TIG is that it can be used to weld aluminium, and to my knowledge is the best method for welding aluminium. This process isn’t very fast to do, and is difficult to learn.
SMAW was the first arc welding process to be used. SMAW or stick works by having a clamp, which holds a long thick wire, which is why it is called stick welding. This electrode is coated in flux, which makes this process gas free. What the welder does with this process is strike the arc like a match, and pull the electrode across the joint or whatever is being welded. While pulling the electrode, the welder also pushes the electrode down, as it’s consumed during the process. This can made the process difficult to learn, however it is one of the most versatile processes. SMAW can be quick and efficient as its basically a strike and go process.
Oxy/Acetylene or Oxy-fuel welding is the only process here that doesn’t use electricity. Instead, acetylene and pure oxygen are combined and burnt to produce heat and a protective flame envelope. With this process, the welder also has to feed the filler rod by hand. However, Oxy-fuel is a much slower process since you have to wait for the metal to heat up and melt. This makes this process the slowest out of all of the aforementioned processes. That being said, this is the most portable process since it doesn’t require an electric current.
I wanted to wait until the end to touch on the actual strength of all of these processes. Assuming you’re making good, correct welds, all of these processes can produce strong welds. This means that the only real limitation will be the thickness of the metal itself. Because of this, i would say that SMAW is probably the strongest process since it can weld the thickest metal out of all of the other processes.
|
0d8909bd-1087-4dde-a753-ad8309297bcc
|
c176p8
|
Why does the skin get "saggy" when people grow old?
|
As you age, DNA has more and more chances to get damaged by factors such as UV rays and random mutations. Telomeres protect your chromosomes, which are your coiled up DNA inside your cells, and they get damaged each time they replicate. Older age means that you've had more time for them to replicate. Other factors that also protect DNA get damaged. Since DNA is the blueprint to make things in your body (e.g. collagen, elastin, signaling factors), having a damaged blueprint will result in damaged products. So that collagen keeping your skin nice and firm or that elastin keeping your skin elastic aren't being made correctly. These imperfect proteins may now have a structure that causes them to bundle up together. DNA damage will also make it so that your cells can't reproduce or repair themselves as well.
Hormone levels also change as you age, and hormones can also affect your skin.
|
00485af3-e271-412d-b2c4-db05df9b2df3
|
c177xg
|
Hypothetically, what stops California from seceding from the United States?
|
The supreme court ruled that states cannot secede when Texas tried to in the 1800s. Additionally, the US constitution has no procedure in place for a state to secede. Finally, Calofornia's state constitution states that it is inseparable from the United States. So it would be very very difficult and time consuming for California, or any state, to secede from the union.
|
584c0393-a388-47d2-8a25-21bf9ccb2f18
|
c17glz
|
Why does everyone's voice sound different?
|
Everyone's vocal chords are different lengths and the cavities where the sounds bounce are also different sizes.
|
d0d19da6-761a-4794-94eb-69a50b13769a
|
c1805x
|
Why do the add acetaminophen to opioid painkillers?
|
Your body has different pathways to convey pain, opioids work on one of those, acetaminophen on another.
|
58f7f49f-5c3a-4a35-b315-1d787b5b1dba
|
c186th
|
what makes AC less dangerous and easier to carry on long distances than DC current ?
|
It really isn't. The real reason we went with AC for distribution way back when during the days of Thomas Edison and George Westinghouse comes down to the AC of Westinghouse's time could reach higher voltages than the DC of Edison's time, and the higher voltages you can run insures that the less losses you have when transmitting electricity and the longer distance between power stations and substations. Since power loss in a transmission line is R*I^2, and Power delivered is V*I, the higher the voltage the lower the current for the same power delivered, and the lower the current the lower the power losses due to resistance.
In fact recently people have been making long distance High Voltage DC lines and there are many 500+ kVDC lines all over the world, and ABB built an 800kVDC power line in China in 2010. The real issue with DC isn't safety, it is converting voltages in DC and converting DC back to AC since houses are wired for AC now. Also, power generation is more typically AC, but that might change if solar power generation becomes more important.
|
8595785b-28e3-4db7-a4f2-884f2f1a4282
|
c18813
|
Ludwig Von Mises' 'Economic Calculation Problem'
|
Prices contain lots of information about 2 key things:
1) How hard it is to make a good or provide a service. If something is hard to make/do, this will increase its price.
2) How much people want a good or service. If people really want something, this will increase its price.
This is important information to have in economy, because economics is all about the question of how we allocate our resources to produce things. We could spend all our time making giant stone monuments, but those things are difficult to make, and people value them less than, for example, food.
In a market economy, which Von Mises supported, this is all worked out by individuals responding to prices in the market. The price of giant stone monuments would be too high for most people to think they were worth buying, so very few would get made.
In a socialist economy, production is instead organized by the state, and there are no real prices. One way to think about it is that the government sets prices. Von Mises argued that the government can never know enough to set prices correctly. Markets are able to aggregate a lot of information about fuzzy stuff like human wants and needs that government agents can't see or incorporate into their economic models. It would be like trying to drive a car while only looking at a map.
There are some criticism of Von Mises' idea - markets are not always perfect, and there's no particular reason why all the information gathering and "calculation" currently done in markets could not be done in bureaucracies instead. However, history has largely borne him out, showing that full-on socialist economies often miss big on very basic stuff. Both the USSR and China suffered catastrophic famines when the government forced workers to farm less and work more in industrialized sectors. This was either a gross miscalculation or a misalignment of incentives between the governments (who like industrialization) and the people (who like eating).
|
c6ec843f-dc09-4be7-a8cf-eff788e23ca0
|
c18d6k
|
666 = Evil, 777 = Good
|
777:
7 is good because God rested on the 7th day, and having three 7's represents the Holy Trinity
666:
AFAIK, the actual definitive answer is not known. The answer I've heard most is this:
In Hebrew, each letter has an associated value that can be used to read any word as a number. When you write Nero Caesar in Hebrew and read it as a number, you get 666.
Another answer I've seen is that, because 7 is associated with completeness and the divine, then 6 is incomplete. So, 666 is "inherently incomplete"^[[cite]](_URL_0_)
|
e40ebee6-f333-40f2-8956-6ea7997ab8c5
|
c18ldh
|
Why dont speakers make the characteristic intereference sound anymore when there is an incoming call?
|
Ha yes, I remember that. You used to be able to hear that even before the phone rang.
The reason why it happened is a bit too complicated for me, but the reason why it doesn't happen anymore is that we don't (or barely) use 2G (GSM) networks anymore. These networks were on the 800-900 MHZ frequencies.
|
93e13617-cfa8-4837-a22d-3fcd7d5fe712
|
c18ndg
|
Why are clouds from above not flat and look „bubbly“?
|
Clouds from below are not flat but bubbly as well.
It may be harder to notice due to two things:
Perspective, whereas when you’re in a plane you have a smaller slope from which you’re viewing (basically viewing the clouds from the side) so those dimensions are far more noticeable.
Secondly, clouds scatter light, which means it’s darker on the underbelly of a cloud, making it harder to see. From the top, you get the full effect.
|
df60c45c-53cc-418c-bb2a-67907250beda
|
c18p1h
|
Where does all the liquid go when you get a drip through an IV?
|
Into your blood veins where it gets blended with the normal blood liquids.
After that it goes through the same things (kidney, liver, heart etc) as that the normal blood liquid goes.
|
39cca35c-77a3-4cfa-8eb4-20a2e3000801
|
c18sdi
|
- How did people ever discover the exact length of a single day? How did they decide on (and keep track of) the exact length of, for example, a single second?
|
Historically, each town would maintain its own time, as marked by its local solar day. A solar day is the time between two consecutive solar noons, which are when the sun at its highest point in the sky.
A second was originally just a subdivision of the day. One full rotation is subdivided into 360 degrees, each of which are divided into 60 minutes, each of which are further divided into 60 seconds.
Because time isn't something that can actually be measured ("The objective reference of a clock is another clock" - [The man from earth](_URL_0_)) a there is no "exact length" of any unit of time. The SI base unit of time is a second, and all other units are defined as multiples of seconds. But, a second is whatever we say it is. For the last few decades since 1967, the official definition of one second is "the duration of 9.192.631.770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom." What that basically means is that there's an atom that emits radiation very quickly, but at a very consistent rate, so one second is how long it takes for that large number of individual peices of radiation to be emitted (this is how atomic clocks work).
|
200f45c6-5bbe-4ffa-976e-0e8c5da446f9
|
c18ylc
|
Why does our skin get injured more easily when we are sweating?
|
This phenomena is likely due to you feeling less pain during physical exertion, so a "light scratch" when resting is far lighter than a "light scratch" when working out. In other words, when you're working out, it takes a lot more force (and damage) before you notice a scratch at all.
|
b45a505a-32d5-49c0-a215-0e96ff57a802
|
c18yux
|
how do new barcodes get made? How do companies make sure their product doesn’t have the same code as a different company when it gets scanned in the shop?
|
Barcodes are actually just a font what represent the numbers that are normally printed just below it. The most common type of barcode is the UPC (Universal Product Code) that is owned and managed by [GS1](_URL_0_). GS1 officially licenses barcodes for products for sale, using a system where the first N numbers of the code represent the manufacturer of the product, and the rest represent the product from the manufacturer.
By sticking to this system, and making sure that their barcodes use the correct manufacturer number, they can know they wont be overlapping with another manufacturer.
Manufacturers can also pay more to get a shorter manufacturer code, so that they can have more digits left over to have more products.
|
cc81c4b0-840e-4165-b396-fe021015c070
|
c19281
|
What causes us to mishear what someone has said but then know a second later what it was?
|
Our brains often work with incomplete information and then attempts to fill in the gaps with likely additional information until it makes sense. This can lead to errors in hearing something that can take a few second to rectify.
|
ece7fc15-f46e-40e8-9890-ec79c626dbba
|
c198p6
|
Why do levels of medications in your blood not increase to the point of overdose after taking them for an extended period.
|
The same reason a drunk person can sober up after a few hours, the liver. The liver acts like a filter to ensure these things don’t stay there forever. It makes use of the things that are useful (nutrients, medicine) and neutralizes the things that aren’t (toxins, alcohol)
|
839409f9-740f-4361-9a3d-a9e0279726fe
|
c19bod
|
Why is preventing swelling important for healing injuries?
|
Swelling/inflammation is how our bodies keep us from using an injured body part. Obviously, we want to avoid using an injured body part so that it can rest during the healing period. Inflammation does \*\*not\*\* help the healing process, and our bodies very frequently go way overboard on the whole matter. We swell too much, for too long, and it can actually cause our muscles to deteriorate. It can become a chronic problem (if untreated), and then affect us for our whole lives, which can atrophy our muscles and/or make them much harder to use, long after the healing is complete.
Because our ability to treat injuries has become so advanced, we want to fix up the injury as best as possible and then reduce the swelling/inflammation so our bodies can go through the natural healing process without having to worry about those problems listed above. A broken bone can be reset and mended far more efficiently in the operating room than in "the wild." We cut down healing time dramatically through modern medicine and surgery.
& #x200B;
tl;dr Swelling isn't a bad thing on its own, but modern healing techniques make it less useful and sometimes harmful. It's better to fix the problem, toss some pain killers down your throat, splint it up, and tell you not to move it.
|
3c408334-adb9-4d7c-80bc-2c806e594651
|
c19nmt
|
Concurrency in programming
|
Concurrency is about a computer system doing more than one thing at the same time. Sometimes the computer is literally doing this by having hardware like multiple “cores”, and sometimes it just flips back and forth between multiple tasks. By analogy, think of two people working on separate tasks compared to one person “multitasking”.
There are lots of advantages to this (speed, apparent responsiveness of a UI, sometimes simplicity for the programmer), but conversely, sometimes more care has to be taken by the programmer. Two particular kinds of error that only happen in concurrent programming are the “race condition” and “deadlock”.
A race condition is when the final result of doing things at the same time depends on the order in which they finish, and is usually a mistake. By analogy, imagine if you bought two things online from two different merchants who then have to process the payment, but the total amount in your bank account was different depending on which merchant processed the payment first.
Deadlock is when tasks are all waiting for each other to do something before they continue. Imagine two people on a date, each secretly waiting for the other to start eating first. They will both just sit there forever until something breaks the deadlock.
Thee are many tools with cute names that programmers use to minimize the problems with concurrency, such as semaphores, locks, latches, promises, signals, and so on. It can still be difficult to write, difficult to test, and error prone, but often worth it compared to other ways of solving the same problem.
|
76a88854-a300-4878-9894-df129e4c1fce
|
c19slh
|
How/why do cars with a start-stop system not use more gas or harm the engine more than regular engines?
|
They don't use more gas because starting an engine doesn't actually require that much energy. Let's do some quick math.
Assuming the car has a 2kW electric starter motor and it takes 5 seconds of cranking to get the engine running it takes (5s / 60 / 60 * 2kW)=0.0027kWh or 2.7Wh of electrical energy to get the engine running.
Again, assuning we have a 60A alternator at 12V will produce 60A*12V=720W, which means in 1h it will produce 0.72kWh of energy. This means it takes the alternator 0.0027/0.72 * 60 * 60=13.5s to produce the electric energy the starter motor removed from the battery.
Of course you still get inefficiencies and your alternator will have to produce more a little more energy than that to charge the battery, but on the other hand your engine probably won't need 5 seconds of cranking to start back up again.
And yes, a start-stop system will put more strain on the starter motor and related components. The starter systems of engines having a start-stop system are usually built more sturdy to account for that.
|
f2a52c1a-e1ec-4f95-99b3-da07edc732b6
|
c19wrm
|
Flying upside down
|
What is important to understand is that two major geometrical factors influence the lift produced by the wings.
The first one is the shape of the wing aka the aerodynamical profile. As you night know, the wings have a specific shape which causes air on the top of the wing to accelerate faster than the air at the bottom, which creates lift through a difference in air pressure between the bottom and top of the wing. Typically, planes that fly upside down have symmetrical profiles, which means that when flying parallel to the ground, air is accelerated equally on both sides of the wing, which results in 0 lift. This is where the second factor comes in.
The 2nd geometrical factor is the angle of the wings called angle of attack. Most if not all planes fly with the nose tilted up a few degrees (between 0 and 15 typically). The plane will still fly parallel to the horizon if you want it to, but the nose will be pointed upwards. It might not be intuitive that the plane doesnt fly in the direction of the nose, but it does. A good example of this that you have probably already seen is when it lands.
In theory, if you fly with an angle of attack of 0 and symmetrical profile wings, you will not generate lift. If you fly with a positive angle of attack (nose up), you will generate lift towards the sky. If you fly with a negative angle of attack (nose down) you will generate lift towards the ground. In the case of the plane flying upside down, you will have the same lift from your wings if you are upright with the nose pointed 5° towards the sky versus upside down with the nose also pointed 5° towards the sky.
|
cb24bd0a-8706-453d-b736-18510e794762
|
c1a6hh
|
If all the power that goes into the electric grid must be consumed and the sum must be 0, how the hell are they able to generate same amount of eletric energy that is consumed?
|
By monitoring grid voltage and frequency we can monitor imbalances between the grid demand and the grid supply. If they are going up then we are making too much power. If they are going down then we are making too little.
Small variations in overall demand are managed by automated systems. Note that while they are pretty much all computer controlled now, this isn’t strictly necessary. We’ve been doing this for a century with analog electrical and even mechanical solutions.
Example of a mechanical solution is a centrifugal governor. Basically, the faster it spins, the higher the centrifugal force is on a spinning weight attached to a turbine- generator. The position of that weight is fed back - mechanically - into the valve that controls how much steam is admitted to the turbine. As the turbine speeds up it closes the valve to reduce steam, and vice versa. By carefully calibrating such a setup, you can make it so it will apply as exactly much steam as necessary to keep the generator spinning at 60Hz (desired grid frequency) to meet demand - and when demand changes, the valve will automatically admit more/less steam to bring the frequency back up or down .
Large changes are predictable based on time of day, time of year, and to a lesser extent the weather. Planners tell generators to turn on and off, or to reduce power, in a coarse way to follow this predicted demand - and then the automated systems manage the second-by-second variation.
|
d6286ac9-eec1-49ed-8540-da1ce8eb332f
|
c1a7e2
|
What can and what cannot travel through a solid wall and why
|
Visible light goes through glass but ultraviolet doesn't. Visible and uv go through water but microwave doesn't.
A substance can either absorb, reflect or transmit light (any electromagnetic (EM) wave from radio to gamma). The ratios are different for each wavelength ('colour' in the visible range), and the sum of the factors for absorbance, reflectance and teansmission are 1 for each specific wavelength.
The question why is a harder one, as many different actions take place. Free electrons like in metals can take almost any EM oscillation and emit them back by doing so. Small wavebands can be absorbed and reemitted in ratios by atoms and molecules (electrons jumping through energy states)
EM waves make molekules wiggle, which is heat, so the photon is absorbed.
It all comes down to quantum mechanics, which is a large topic.
|
6a52c95f-46e7-4ae2-9730-5ad4d4163f86
|
c1aai2
|
Why do all known solar systems have planets that revolve along the same plane?
|
Conservation of momentum. When a dust cloud is collapsing into a star/solar system, the stuff will be moving mostly randomly, but by chance enough of it will be moving in the same direction to impart a spin on the gas and dust. As it continue to collapse, more and more of it will start to move that direction. As more stuff spins faster and faster, the stuff that's not in the center forms into a disk extending from the equator of the star. This stuff forms the planets, so they all end up in the same plane. Smaller stuff that is usually way further out isn't as affected by this gravity and spin, so that's why you have comets and stuff with wacky angles.
|
807a5c02-589a-42b4-aebf-e20533949034
|
c1abiu
|
How are amputees able to control the fingers in their bionic arm ?
|
The company I work at actually exclusively works on this!
/u/WashingtonFierce post is incorrect, we do not yet have commercial technology designed specifically to physically interact with the brain and detect limb movement. The amount of time, money, and risk is prohibitively monumental. Imagine being an ethics review board member having to review an experiment about splitting a subject's head open to insert a sensor that you may or may not know will work effectively and reliably unless you try.
/u/TheLazyD0G has more or less explained it correctly, and I can add some additional info.
* Your brain sends signals to nerves in the arm, and the nerves are connected to the arm muscles. What actually happens when your arm muscle contracts is a bunch of sodium and Potassium ions moving about the cell walls of your muscles. Since these ions have positive charges to them, their movement generates a very very tiny voltage. The two sensors that sit in the prosthetic socket and touch the forearm are sensitive enough to pick up this change in voltage. This concept is called [EMG](_URL_1_).
* [So depending on the voltage change, the sensors can detect how hard you're flexing, or even at all.](_URL_2_)
* [The way the hands are programmed are in that they cycle through different pre-set grip modes, and the patient can only open and close them in the different modes.](_URL_0_) The bebionic3, for example, you start out in Tripod grip (so you only close index, middle, and thumb) and can only close and open in that formation. You have to press the button on the back to change to Power grasp, and then you can only open and close them in a fist. You then have to press the button, AGAIN, to go into another grip, say Precision grasp, and then you can only open and close the thumb and index finger together. In a sense, they're just hand-shaped swiss army knives.
* The patient opens and closes them by flexing their limb in one direction or another. Imagine flexing your wrist towards your chest. That's close. Now flex your wrist away from you. That's open.
* This can get tedious (how many times did I have to press the button?) and can get frustrating if you make a mistake in a high-pressure situation (e.g. getting change into your wallet after the cashier hands it to you)
* The pattern recognition that /u/TheLazyD0G mentions attempts to use multiple (3+) sensors and machine learning to have the arm change the grip based on which hand gesture you trained it to do earlier. However, this concept is still bogged down by the hand's programming of only changing between different pre-set gestures.
* We have not yet achieved the level of fineness in detecting individual finger movements, largely to the concept of "Crosstalk". With the current size of these skin sensors, the region of muscle they observe can't distinguish whether a movement was for one finger versus another. Implantable sensors can theoretically solve this issue, but research into them so far have been very preliminary.
Let me know if you have other questions!
|
224fff74-6158-4174-9052-a9f9e7d079c0
|
c1ad07
|
What is turbulence and how do pilots see it coming?
|
Turbulent air (in regards to weather) is just a region where two layers of air are exchanging places, ie. hot air moving up, and cold air moving down to take its place.
& #x200B;
Some areas may be continuously turbulent, like where the gulf stream meets colder northern air. And sometimes you can predict that an area will be turbulent due to changes in weather, or cold fronts moving in.
& #x200B;
Planes flying in close proximity to each other can also experience turbulence due to the air that has been displaced by wings and engines.
|
62b8527a-1c4b-4363-836a-f722c5465ae2
|
c1adph
|
what causes your ears to randomly start ringing?
|
As another poster has said, tinnitus is partially your brain filling in a sensory gap. The nasty, long term tinnitus is damage of some sort, and your brain fills it in with static. The sudden onset limited ringing is usually sudden onset hearing loss from eustachian tube dysfunction.
This is where the tube that connects your middle ear to your nasal passages, which is used to equalise pressure, gets closed off with mucous or swelling or any other thing. This causes a relative vacuum to be formed, decreasing perception of sound and causing or enhancing ringing!
|
30a31d82-858f-4004-87dc-45f4e0684c07
|
c1anyw
|
How come acid can't dissolve ceramic or glass vials but it can go through metal?
|
It's about how chemically reactive the materials are, not how strong they are. Metals are fairly reactive, in some cases they form oxide layers on top that block further reactions, but acids can strip away the oxide layer, making the base metal weaker to further reactions. Ceramic is much less chemically reactive
Note that aluminium is so easily destroyed by acid that cans of carbonated drink have a layer of plastic inside to stop the acidic pop/soda/juice from actually touching the aluminum
|
6cb152e9-7a24-4ac7-b346-234b415a61ba
|
c1b1ax
|
What is happening in Hong Kong? What is the protest about?
|
This is a very brief explanation but
HONG Kong was a formerly controlled by Britain until 1997 as a result of the opium wars. As such under this 99 year British rule, the people of Hong essentially enjoyed a very westernized style of government and were sovereign from China. This is no longer the case as the treaty which provided the brits control ended and China now controls HK. HK does have it's own ruling body and judicial system and what not and are still a semi autonomous body. But China is trying to implement an extradition bill which would give main land China the power to extradite any ppl from hk for basically no reason, obviously the people still want their freedom they they are protesting the bill.
|
d7281580-6231-4cc3-b057-ec5f9012d2af
|
c1b4sj
|
why is all this happening in hongkong right now
|
A bad man from Taiwan fled to Hong Kong. Hong Kong said let's pass a law to send this man back to Taiwan to face justice! Then China said yes and don't stop there; also send back everyone who criticizes the communist party back to China to face justice as well!
Hong Kong said no! But then the executive leader of Hong Kong (who was chosen by China) said let's do it anyway.
Now Hong Kong is saying NO by protesting.
By the way currently China sends their secret police to Hong Kong to kidnap people who criticize China. That has sparked protests in the past. If the proposed law is passed they won't have to be secretive anymore.
|
fce3538d-03a4-4b2b-a048-81021e16c89c
|
c1b99f
|
The differences and processes of ROM and RAM
|
Rom - read only memory. The chip is programmed once, usually by using a writing voltage that is high enough to “burn” the bits in.
Ram - random access memory. You can read and write to it. Writing doesn’t burn bits in, each bit is just basically a capacitor that temporarily stores a charge.
|
00dddfe8-99ad-475d-bc11-b9c2cbac15d5
|
c1bisv
|
Why are there millions of protesters in Hong Kong?
|
Extradition Law. China wants to be able to extradite "criminals" from Hong Kong. This is in quotes because everyone believes China would abuse this power to imprison political rivals and other social dissidents, who are not even on Chinese soil.
Hong Kong has a long complicated history with Chinese control/interference, so that is also at play.
|
b9a832de-acd2-407d-8dde-92196774f3bd
|
c1bjg0
|
What is happening in Hong Kong right now?
|
China utilizes an ultra strong central government, combined with strict draconian laws and applies unethical implementation and enforcement of those laws to deter anyone that would question said laws (“political dissenters”).
Hong Kong was, for nearly 100 years, the opposite (in comparison), and has largely been left to its own devices....until now (edit: now really means 1997, but imo China has done an ok job of leaving them alone ever since, until this law).
The new proposed law would allow Hong Kong nationals to be extradited (moved) from HK to China, where presumably, they would be charged with whatever “crime” China can come up with, and subsequently no one would ever hear from them again (presumably killed, imprisoned, etc).
The issue, aside from the obvious, is that HK is quite open in comparison to China, with regard to political dissent. So the new law would basically result in HK nationals living in fear, they - like most Chinese nationals - would never be able to speak freely about their dissent of China, ever again.
So they’re literally protesting this new proposed law because the law would result in censure.
Edit: it would result in much worse things than just censure, but the long term and most damaging impact would be censure, because everyone - and I do mean everyone - would be afraid that anything could be interpreted as some kind of political dissent, so it would essentially be the end of the current “two system” policy that allows HK the freedom it enjoys. It’s highly dangerous to HK’s long term law-making ability.
Edit 2:
To clarify, the law would permit the “chief executive of HK” to extradite without judicial review or oversight. The chief executive of HK is essentially appointed by China. The law would mean that extradition would occur, without review from HK courts, and would be initiated by a Chinese appointed official (the chief executive).
|
a07d9fac-26e1-4c2a-8829-e8e8182cc623
|
c1bo6h
|
How do people crack databases of big comapnies?
|
Often times they dont. If a smaller company has a breach and usernames / passwords get leaked they use bots to try them across many providers as most people use the same password everywhere.
Google / bing / duckduckgo search your password from time to time to see if your password is posted on a list somewhere
|
5536d678-0198-4627-86b2-ab0ec2c55191
|
c1bvp3
|
What kind of techniques are best for counting the number of protestors in Hong Kong? Or any crowd for that matter?
|
Draw an imaginary square and count how many people fit inside, then count how many squares are in the crowd and you a pretty good guess
|
9802fa27-9914-402d-887d-d8dc7c7bb1aa
|
c1c2u4
|
How does prosthetic arms know how/when to move its fingers?
|
That's an entire 300-level college course, right there, but the basic answer is electronics and black sorcery in coding.
The prosthetic uses special sensors that read electrical signals from nerves or brain neurons, and turns them into signals that run the prosthetic limb. The brain doesn't get feedback from the arm, but it does eventually adapt to moving it. Kinda like moving your hand if it's completely numb.
|
ac216a23-f970-4ea1-8220-9688119565d4
|
c1c8y2
|
Why do lots of mobile video game advertisers just show random fragments of out of context gameplay, without showing us the name of the game or even trying to make an ad that is nice to watch? Does that strategy even work?
|
ads are designed to capture as much attention in as short a time as possible. and these ads you're talking about do exactly that. after some time you might realize the ad doesn't represent the thing very well, but there're tons of people who haven't seen the ad yet. and the more exposure you're given the more likely hood of you doing it. so even bad ads can be effective.
|
51f88c36-880f-494d-a438-0bd8a5b65d81
|
c1cejg
|
What causes a "cough"
|
A cough is a involuntary reaction to try and get mucus out of your respiratory system. Your lungs are meant for air so when non air gets in your lungs or trachea your body is trying to get it back out.
|
49fbeeaf-a394-4369-81fb-fc492b36559d
|
c1chaq
|
How on earth does the power supply to an entire Country fail?
|
There is a problem with turning the power back on again that makes it difficult to do it:
Many appliances in a normal home are consuming a lot more electricity for a while when you start them up. Fridge? Needs more electricity. Freezer? Needs more electricity. Some tv start up, realise that they are not supposed to do anything and hibernate again. And so on.
Not to mention that a fridge that has been turned off for a day will have a pretty rough time cooling down the food in it again. It will consume a lot more electricity in the upcoming day than it usually does during a day, just because it has to catch up.
Now, imagine that a whole bloody country does this at the same time. It'll demand so much from the producers that you literally can't turn it all on at the same time. You have to turn on a section at a time. And pay attention to the load you get, and then carefully pick a section to turn on after an hour or two. And still pay close attention to the load.
And at the same time you run into other problems. When you turn on power, it's a really large circuit breaker that has to be moved. I'm gonna bet you that if you open 20 really large circuit breakers that haven't moved in a decade, then one or two of them will probably fail. Or at least be bit cranky.
And some of the large breakers are fully manual. How...how do you manage to get personell out to that breaker, when gas stations can't sell gas to the company vans and cellphone towers are knocked out for lack of electricity?
There is a lot of practical problems that...are not necessarily solved in advance. Not all the line workers have satellite phones. Not all the depots got their own fuel depots with a hand-cranked pump for emergency refuelling. And...
Well. Yeah. Once it's blacked out, you face a lot of practical problems with the restarting procedure, if you wait for too long before you get started.
As for the question on how things fail... that is a good question. But it literally only takes that a very, very, very large power line gets disconnected before there is a fault on it. Or that a large producer has a failure. I haven't read up on what the problem actually is, but it's usually one of those two. There is a problem with production or there is a problem with transmission.
EDIT: I browsed a news article or two about it.
The problem appears to be that the consumption is so large that the producers can't meet demand. Producers can't maintain the goal frequency on the production. Voltage goes down. Voltage goes up and down violently when the producers try to meet demand and can't.
Eventually, lots of equipment will start to disconnect, because when the voltage does that, it's...an obvious problem. In a perfect world, it means that the production units will have a less rough time keeping up. In a real world, it can mean that the producers loose *too much* consumption, and force them to do an emergency shut down because of that instead. And once a large producer shuts down, it'll give too much load to all the others. And the vicious circle continues.
It's all a matter of failed load balancing. Production can't meet demands. And whoever it is that has balancing as their job failed at it. Or reacted a hint too slow. And now they have to start up slowly. From scratch. One consumer area at a time. one production unit at a time. Probably for days.
|
9741dae4-9fbf-4d0a-8260-3cc385f25b29
|
c1cipf
|
Why does Germany retain a budget surplus, when most countries agree that incurring debt to fund economic growth is a better strategy?
|
What’s supposed to happen is the Government is supposed to accrue the budget surplus in good years and put that money back into the economy in leaner years this averaging everything out . That’s the principle of Keynesian economics
Debt is not a good way to prop up your Government if it’s done year after year
|
3ba58f62-6b92-4e3f-8b33-721985bff2c8
|
c1ckun
|
How do wasps build nests?
|
They find exposed wood (generally from dead trees or fallen branches AFAIK), chew it off and mix it with saliva to make a pulp. Then they spit that up at the nest and mold it into the shape they want.
There are also some species of solitary wasps that build little hollow domes out of mud on the ground near water, like a river bank.
|
0ce819cc-b3a8-4fe5-9c69-379363ac3506
|
c1cl9o
|
How come there are still $15T in assets in mutual funds, when ETFs seem better in every conceivable way?
|
When you sell a security you've held for a long time you have to pay a ton of taxes. The tax hit is not worth the small advantages of a nearly identical ETF.
So say you have $100,000 long term profit in an S & P 500 mutual fund. If you sell, you'd have to pay 20% of that money to the government meaning you'd lose $20,000 right away. Then you'd just reinvest that money back in a S & P 500 ETF. Even if the ETF has slightly lower fees, there's no way that's worth it.
Furthermore, ETFs are easier to day trade, usually have very slightly lower fees, and have a slight tax advantage. But most money is saved in long term tax free or tax deferred retirement accounts. The advantages of an ETF are minimal in these cases.
For example, mutual funds are easier to set up for an automatic buy. You can automatically withdraw $100 from your bank account as soon as you get your paycheck and have it automatically invest the money for you in a mutual fund. Meanwhile ETFs require more manual work. You can't buy $100 evenly. You buy a share for $77 and have $23 leftover.
Note, this is for talking about passive mutual funds vs identical passive ETFs. Some people (i.e., idiots) like active funds because they think that the money manager they've hired is a genius and worth the high fees they charge. Those were traditionally structured as active mutual funds (but is starting to change with the advent of active ETFs).
As a final point, Vanguard is the largest money manager, and they have a patent on a hybrid mutual fund/ETF system that allows their mutual funds to have the same tax advantages of the ETF. So at Vanguard it makes no difference. Once that patent expires, it'll make less of a difference at other firms too.
|
6a06744b-22aa-4dd8-8dd6-5e5100e43b39
|
c1cmyz
|
Why can our arms get tired of moving if our heart never gets tired of beating?
|
The short answer comes down to good old fact that mitochondria are the powerhouse of the cells. Normal skeletal muscles (e.g. your arm muscles) contain about 1-2% mitochondria where your heart contains \~35%. This (combined with the fact that your heart has a consistent supply of oxygen - i.e. blood) means your heart has an excellent supply of energy reducing the chances it will ever get fatigued.
& #x200B;
Your heart also spends a lot of it's time resting. The average cycle of a heartbeat is 0.8 seconds which is 0.1 seconds to contract and the remaining 0.7 second to relax (for the atria - it's takes slightly longer for the ventricles to contract) - so the heart is actually spending a lot of it's time relaxing and being able to recover. It just does so rapidly.
& #x200B;
The heart can become fatigued with exertion though - it just takes a long time to get there. And it will usually do so when you are engaged in physical exertion. So what tends to happen is that your other muscles will become fatigued before your heart does forcing you to slow down.
|
8e955737-2ee9-44fc-8df5-a0350e556aa7
|
c1crje
|
What are the white semi-circles on a person’s nails?
|
I'm no expert, but according to my own research for curiosity purposes:
There are a lot of complicated names for a lot of different bits of the nail structure. The white semi-circle you're talking about is called the **lunula**, and it's actually just the visible portion of a larger structure called the **matrix** under the root end of your nails, underneath your skin. The matrix is the tissue that actually builds new nail cells, which is what causes your nails to get longer.
The shape of the matrix - and therefore the shape of nail that it grows - is mostly determined by stuff like bone structure. Some people just have more of their nail matrix visible i.e. a larger lunula.
Source: wikipedia, _URL_0_, [_URL_2_](_URL_1_), etc
|
c5699646-918a-4830-a133-a2bc768898ad
|
c1czpg
|
Why are there protests in Hong Kong?
|
Extradition Bill --- > Moves wanted criminals or persons of interest to China.
& #x200B;
China is known to have unfair trials --- > usually death penalty or the person goes missing for 15 years and then resurface into a completely different person.
& #x200B;
HK's younger generation feels like democracy is falling apart, China is slowly regripping their hands around the island and HKer's do not want that. They had 150+ years of Bristish rule which flourish with "democracy" and "freedom".
& #x200B;
China bans stuff. HK does not.
|
2c789150-d097-4c69-bb20-4a5cdddb1b36
|
c1d1r0
|
How do we know for sure that there's a recession coming, and why can't we stop it?
|
Recessions are natural. We know its coming because they come in a cycle, and its been a while since the last. There are also a number of indicators that suggest a shock will come soon. The difficulty is in predicting the exact time and severity of the recession.
We can't stop it because recessions are a natural product of our economic system. We rely on unproductive businesses going bust. Stopping recessions would require unproductive businesses to be kept afloat (since we have no effective way of knowing which are productive if we subsidise them) which would slow productivity growth in the long run. The USSR avoided recessions because all firms were state run, but perpetually low productivity growth meant that in the long run it was poorer than market capitalist economies.
What we can do is mitigate recessions, by preventing downward spirals and using various methods to prevent recessions causing poverty, like lowering interest rates or launching public works.
|
99b41411-17b6-4c0b-bd7d-7756e58b74ea
|
c1d4qh
|
Why does sneezing feel good?
|
Sneezing and orgasm work off the same brain mechanism, I believe I read somewhere it is a lower order function (from our reptilian part of the brain) that comes from our instinctual past and is coded I to our DNA
|
9fb36575-3924-4cd6-bfe5-ac0bfdbd53cf
|
c1d936
|
Why do things like coffee, tobacco, spicy foods, etc. speed up the digestive process?
|
Since this has been ignored I'll give you my understanding which is based on experience in the boutique liquor industry rather than any scientific or academic background.
The concept of aperitifs and digestifs may be helpful. These are, respectively, a drink you take before the meal, and a drink you take after the meal.
Traditionally aperitifs are bitter drinks like Campari. While aperitif can just mean having a drink before a meal, ostensibly the drink should stimulate your appetite or make the meal more pleasurable. Bitter herbs supposedly stimulate the digestive system - they start the juices flowing. The touch of alcohol should relax you, making your senses more receptive. That's the ideal anyway.
A digestif, again, can just be a drink after the meal, but as the name suggests it is traditionally thought of as aiding digestion. While brandies and sweet liqueurs are often offered as digestifs, if you really want to help digestion you should have some more bitters, for the same reason as an aperitif. It will stimulate the digestive system.
Coffee is both a diuretic and full of bitter tannins. It will make you want to piss and also stimulate digestion, moving everything along.
Tobacco's mechanism relating to the bowels I do not know about other than that I intimately know about it. Nicotine for me is directly tied to my defecatory processes.
I'm not sure how capsaicin directly effects digestion, but I imagine it's a similar but more extreme reaction to the bitterness. As bitterness could be a poison, the digestive system activates, ready to purge. Capsaicin could be interpreted by the body as poison, so maybe it acts similarly.
But if you had enough bitterness to provide a similar *painful* sensation in your mouth to chilli, it is entirely possible that your body would attempt to reject the bitterness like it does the spiciness.
TL;DR Don't drink too much red wine at a Mexican restaurant.
|
a312339a-82fa-43ae-9c32-f751b96f7cf4
|
c1digd
|
How does a large radiation source cause surrounding objects to become radioactive too?
|
The clothes themselves aren't radioactive, per se, but they are contaminated with radioactive material. Particles, dust, even individual atoms of radioactive material can cling to the surface of things they come into contact with. As those contaminants decay they release radiation, but they can also be dislodged or transferred to people who come into contact with them, so they pose both a direct and indirect risk of harm from radiation.
|
15b59a08-9e5b-452c-a3b0-edd88b021d13
|
c1dn52
|
Freezer Burn
|
Freezer burn is a condition that occurs when frozen food has been damaged by dehydration and oxidation, due to air reaching the food. It is generally caused by food not being securely wrapped in air-tight packaging.
It makes you food taste weird because it damages it, changes the texture, and allow "contaminants" into the food
|
552ed83e-9bbf-4819-95e5-7f4f72c97381
|
c1dsvg
|
How are you able to keep bandages/dressings on post surgery for an extended amount of time before it can be washed/changed without getting an infection?
|
Right now that bandage is a shield. It’s acting like your skin in the sense that it’s keeping all the gross things outside.
Medical bandages are woven tighter, and have a denser glue that holds it together. This prevents dirt and bacteria from being absorbed. They’ll also usually have a layer of antibiotics underneath, so they’re not accidentally trapping anything when it’s first put on.
As soon as they’re wet though, that can introduce bacteria. That’s why it’s important not to wash it.
Source- have had multiple surgeries, dad’s a doctor, this is how it was explained to me. Call me out if any of this is wrong.
|
8b493350-0837-4d78-b4df-faf6a0c43977
|
c1dx8n
|
Why is it that space travel takes so long? If space is (nearly) a vacuum and by Newton's laws, the acceleration of a spacecraft would be incredibly high, wouldn't it allow the spacecraft to reach nearby celestial bodies quickly?
|
Acceleration it according to F=m\*a is a=f/m. So the accelerate quickly you need a powerful engine compared to the mass of the spacecraft. But a powerful engine require more fuel and you have a more mass in the spacecraft.
So it is limitation it not the max speed but the amount of fule (more exact propellant) you can carry and for how long you can use the engine that is the problem.
The amount fuel you need increase a exponentially way because initially you also need to accelerate that fuel that you have in the spacecraft. The result in the [rocket\_equation](_URL_0_) where the limitation is the "efficiency" (specific impulse) of the rocket engine.
You can look at [_URL_1_](_URL_1_) for a video with a beter explanation in simple terms.
The problem is often called "tyranny of the rocket equation"
|
d81663ff-bb6a-4409-975a-fa6f91a6b0a2
|
c1dxi2
|
How do doorbells work?
|
So traditional wired doorbells are normally simply a complete wired circuit involving:
- a bell
- a transformer to lower the voltage so that if the button gets compromised people won’t get a high voltage shock by pressing the button
- a button outside
- and wiring connecting it all
When you press the button outside it completes the circuit by allowing electricity to pass through and ring the bell.
|
b1e51ae1-97f5-4816-b1e7-add1fcd80ad4
|
c1e150
|
What are API's, and how do they work between software or applications?
|
An API is like a menu at a restaurant. You don’t need to know how the chef works and how the kitchen runs; you just need to know what to ask for.
Likewise, an API for a program tells you what you can ask for, without needing to know how the program works. A game, for example, won’t let people see its code because that could lead to exploits, but there may be an API that lets people request character information from the game so that they can use it on a fan site.
|
e7c78db5-250f-4e36-ba30-eafc22ad0781
|
c1e4t5
|
what is spectral efficiency in telecommunications and what is it used for?
|
Whether you broadcast over wires or wireless, you will be limited by the medium to an amount of bandwidth. Bandwidth is the distance across band of frequencies, so from 99MegaHertz to 101 MHz is 2MHz bandwidth. Spectral efficiency is just a measure of how much actual information you can pack in that bandwidth. Channels, whether radio or TV or other telecommunications each occupy certain bands that have certain bandwidths.
So, The higher the Spectral efficiency, the more information you can transmit over a channel.
|
8f2665ed-ab08-4347-83cb-719f2c4e5bc5
|
c1e6wq
|
why do sheep, snakes and some other animals have slit pupils? How does this change the image created on the retina?
|
Sheep, goats, and a few other mammals have rectangular pupils. It gives them a relatively poor depth perception, but allows them a roughly 300 degree field of vision.
Slit style eyes (seen in cats and reptiles) construct to allow for a much greater range of lighting conditions.
|
fdba18df-cad7-48d7-bd28-db0b48a1dd6d
|
c1ec5r
|
All insects have 6 legs, but their larvae often has more. So is a caterpillar an insect?
|
Yes, caterpillars are insects. The many "legs" that you see on caterpillars and other similar ("eruciform", which literally means "caterpillar-shaped") types of larvae aren't actually real legs, they're what's called "prolegs": basically, stubby leg-esque appendages that don't have the same structure as a real leg but get used to move around. A caterpillar's six real legs, called its "thoracic" legs, are the six spindly little appendages you see near its mouth. If you look really closely, you can see that the thoracic legs are segmented like the legs that it will have when it grows into a butterfly. The prolegs are not segmented; they're basically hydraulically-powered little tubes (with a little bit of muscle) with hooks on the end to hang onto stuff.
Note: This information is apparently under some scientific dispute, so I might not be completely right. This is what I'm given to understand is the most currently accepted information.
|
e2c608b8-1318-4f5b-8283-81cd67023b02
|
c1ehj3
|
Why do some tail lights appear to flicker in dashcam videos?
|
Old filament lights won't do this, modern LED lights will, the brightness of the light is varied by switching the supply on and off rapidly the on time and off time can be varied, the longer it's on the brighter the light, this switching happens at something like a thousand times a second, the human eye can't detect that flicker but the dash cam has a frame rate that, although different from the LED flashing speed, will occasionally syncronise and capture several frames when the LED is off. It won't capture the same off event but just a series of different ones but it allows you to see the flashing, it is called aliasing, and it happens with digital sampling of many different types of signals.
|
76587941-8d5c-4e2b-8c31-ce569c29601a
|
c1eo92
|
what is the plank length? What do they mean when they say it’s the “shortest length”?
|
The Planck length is a unit of length in a set of natural units called Planck units. Natural units are units that are defined in such a way so that certain physical constants are 1. For instance, in Planck units the speed of light in a vacuum (\~300,000 km/s), the gravitational constant (a measure for the strength of gravity, \~6\*10^(-11) Nm²/kg²), the reduced Planck constant (a constant that relates the wavelength of light to its energy, \~6\*10^(-34) Js), the Coulomb constant (a measure for the strength of electromagnetism, \~9\*10^(9) Nm²/C²), and the Boltzmann constant (a constant that relates the average kinetic energy of the particles in a gas with the gas' temperature, \~10^(-23) J/K) are all normalized to be 1.
By now manipulating these constants, until you get something that only has metres as its units, you get the Planck length. Similarly, you can get the Planck mass, Planck time, Planck charge and Planck temperature. In this set of units, a Planck length is about 10^(-35) m, which is tiny. In fact, even smaller than anything we've ever observed. Similarly, a Planck time is incredibly tiny, and conversely the Planck temperature is really massive (\~10^(32) K, as a comparison, the Sun's core is about 15\*10^(6)K). The Planck charge and Planck mass aren't really special, besides being derived from the same normalized constants.
But, at the scale of the Planck units that *do* matter (Planck length, time, temperature and energy), our known models stop making sense. That means that we can't apply our known laws of nature, but there are a whole set of new ones. Ones we don't know (yet). This is similar to quantum theory. When you go small enough, we can't use regular Newtonian physics to predict stuff. We needed a new theory, which was quantum theory. And if you go big and fast enough, we can't use Newtonian physics either, but have to resort to relativity. So in that sense, the Planck length is 'the smallest length', with the caveat that it's the smallest length at which our current knowledge of physics stops working. But this doesn't mean it's the smallest length period. It's just a really really tiny length, where things get even weirder than with quantum mechanics.
|
ab566a6a-91aa-484b-a6ad-91e42e0a6b68
|
c1eomx
|
How do flight computers in planes know how high above the ground they are.
|
So there are a few ways.
- Barometric altimeters measure the atmospheric pressure outside the plane and use that to (fairly accurately) estimate the height above sea level. This works because atmospheric pressure drops at a predictable rate as you increase your altitude, but because air pressure in a region can fluctuate you may need to adjust for local conditions. This gives you your elevation above sea level, so you have to calculate your height above ground based on your exact location.
- Radar altimeters bounce radio waves off the ground beneath the plane and measure the time it takes for the waves to return. Since radio waves travel at a constant, known speed, you can measure your height above the ground this way.
- GPS altimeters use satellites orbiting Earth to pinpoint your exact location, in three dimensions. They work on a similar principle as radar, but instead of measuring your distance to the ground, they measure your distance from three (or more) satellites. If you know the location of the satellites and you know your distance from them, then you know your location. This, obviously, gives you your altitude.
Different planes may use one, two, or a combination of all three of these to give an accurate and reliable measurement of altitude.
|
f2646ff5-7b82-440a-9450-bcf2218cef75
|
c1eyg3
|
What are the protests in Hong Kong about?
|
They are protesting a new law that allows Chinese government to arrest residents inside Hong Kong and bring them back to China.
You see, Hong Kong used to be a British colony, and was ruled like a western, free country. It was turned over to China a few decades back but China has *promised* not to enforce Chinese rule in Hong Kong for the next few decades.
People of Hong Kong of course do not want authoritarian rule from China, are protesting against encroachment of Chinese rule in this new law.
|
5927718a-a31e-4a11-8a62-2cad8148343f
|
c1eykt
|
How does composting work? How is it beneficial? What does it do?
|
By composting food scraps, you are giving the food to bacteria to eat
Bacteria poops out all sorts of stuff that plants love eating.
The process however also creates a lot of heat and temporary nasty stuff that could kill plants.
So you wait until composting process is done and take the remaining stuff, now compost, and give it to plants to eat.
When plants grow up, you can now eat the plants.
Tldr: Composting is good because it turns stuff we throw away into useful food for plants.
|
4585541d-a4eb-473b-ac71-b3f2bf22669f
|
c1f1iv
|
How does Air Conditioning work?
|
A compressor takes electrical or mechanical power and uses that to compress a refrigerant gas. That gas is then released into a series of coils where it can expand in volume. That expansion causes the gas to become very cold, which makes the coils very cold. Air is blown over the cold coils, which cools the air. The cool air is then blown through ducts to cool the building/car/whatever.
|
b7835d44-2f82-41ac-82cd-7bd39e2a1df8
|
c1f26l
|
What makes things funny?
|
Obviously there is no single answer to this because different people find different things funny in different ways. However the general theory of why we find things funny is found in Peter McGraw and Caleb Warren's "Theory of Benign Violation". The general principle is that when an event violates the natural expectation of how we expect an event to play out and the violation does not have consequences severe enough to be considered abhorrent then we find the event humorous because it subverts our expectations in an unpredictable way.
|
2b27bf87-2d5d-4379-b2e0-6cafbc387c68
|
c1f4cd
|
- What do people mean when they say that Hong Kong is “semi-autonomous” from China and how is this autonomy affected by the new extradition laws China are trying to push through?
|
Taiwan is a totally independent country. HK and Macau control some of their own affairs but are under Chinese sovereignty and therefore the Chinese government and military call the final shots there. Taiwan has their own military, whose entire purpose is to stop China being able to invade and annex them, which China has threatened to do many times.
|
5a948d9a-b034-4801-9523-c9297caafa43
|
c1f71m
|
If flu is seasonal, what happens to it in between seasons and how does it come back?
|
It's always around, to an extent. People are always catching the flu, all year round. Most of the time, it doesn't spread that quickly, so only a few people are catching it. Very few. But when the the whether is cold, something happens that suddenly causes it to spread much faster. Doctors aren't entirely sure why, although there are a number of possible explanations. It's somewhere we don't know yet and hence cannot be explained.
Whatever the explanation, once whatever causes to flu to spread much faster than usual ends, sick people get better and it goes back to spreading at it's much smaller rate. It doesn't "go" anywhere, it's just spreading much slower, so you don't notice it.
|
b0b7bd54-3230-4e2c-a22c-9d1e550c9f00
|
c1fbg2
|
How do geiger counters work?
|
They are chambers filled with a special gas (Boron Triflouride) that interacts with high energy photons and neutrons by releasing electrons. These electrons are attracted to a positively charged center rod in the chamber, and as they accelerate towards this rod, they create secondary reactions in the gas, releasing more electrons. When this large group of electrons hit the center charged rod, it created a momentary difference in voltage which is interpreted in the circuitry as a count and moves the needle on the Geiger counter a bit.
|
e0e4c6a4-44a3-43ba-bb6b-bd8f0ad48d2e
|
c1fixw
|
how did people used to keep their teeth clean before toothpaste?
|
Primitive toothbrushes, aka chewing and rubbing with soft sticks.
Or just dying before dental issues could really be a problem, depending on how far back you want to go.
Also they didn't have a bunch of shit and sugar in everything so teeth lasted longer.
|
1547e4e6-4f60-42d9-9017-9e8af5431c8c
|
c1gi1r
|
How did higher education work in the Soviet Union?
|
Generally, college was free and job placement was 100% since it was government centralized and there was a huge focus on preparing students for the workforce, and education was a priority. You picked a job before you graduated and had to work there for a certain number of years to sort of ‘repay’ the education.
Unfortunately degrees gained in the ussr weren’t transferable (in at least some cases). I know a few professors here who had to redo their PHDs because they weren’t accepted in the us.
|
035f40dd-a238-4a67-ac31-2426535ceb96
|
c1gj9s
|
Epsom Salt, how does it work to help relieve pain on sore joints?
|
Epsom salt is Magnesium Sulfate. Your muscles use magnesium to relax. Soaking in it causes the magnesium to get absorbed through the skin and helps your muscles relax. You can also spray magnesium oil on your skin or take a magnesium supplement internally for the same type of effect.
|
8db79646-2487-4017-bcfd-d4394614bceb
|
c1gqbp
|
Why do photos of stripes/patters get all messed up on computer screens?
|
Do you mean moire patterns?
_URL_0_
In television and digital photography, a pattern on an object being photographed can interfere with the shape of the light sensors to generate unwanted artifacts.
|
e760d174-eb3a-4675-af07-e39f6e3d1788
|
c1gro3
|
The mass of what I eat compared to the waste that comes out isn't even close to balanced. Where does it all go?!
|
The largest amount comes out in the form of urine. The moisture in your food is extracted.
A lot also comes out in your breath, in the form of H2O and in the form of CO2 (carbon waste).
|
dec0bb8d-89f7-412f-b6f9-a49f81e4e73c
|
c1gwrr
|
How can scientist determine what things are made of on different planets or moons?
|
imagine you drop a ball. ball 1 hits wood, ball 2 hits carpet, ball 3 hits metal.
you'll notice when you do this, each ball bounces to a different height. If you couldnt see the floor but only know the height the ball bounces you could reasonably guess what kind of floor it hit.
Now instead of a ball, they use light. We know how light bounces off different elements and using that, we can tell whats there.
|
b3738c0e-82fc-41f0-a0a3-cbc46c3063fc
|
c1hbuq
|
. Why do bugs like me?
|
Factors such as blood type (particularly Blood type O) is more attractive to mosquitos, studies show. Also things like your metabolic rate, weight, and even what color clothing you’re wearing can be a factor. Dark clothing tends to be more attractive to flying insects.
|
625e6b11-3573-43bd-a6a2-37c71c2dde22
|
c1hlsl
|
We have goat milk and cow milk to consume, but why is it merely impossible to find pig milk in a grocery store?
|
Firstly, it just doiesn't taste very good. Pig's milk is watery, and quite gamey.
The real reason though is that pigs simply don't produce very much milk, and don't like being milked. Cows have been domesticated for thousands of years, and selectively bred for milk production and docility. Pigs, on the other hand, will put up a hell of a fight.
|
febddbf3-25b3-40ee-80f8-b80fd574182f
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.