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When an animal is eaten whole, how does it actually die? Suffocation? Digestive acid? | It varies depending on the species and what their specific eating mechanism is. But generally speaking if the animal is swallowed whole while still alive it will suffocate first and then be broken down by the digestive system. | 8,253 | 9,111 |
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Any tips to not feel dumb during philosophy lectures? | hey guys,
I am a fourth year philosophy major, and I don't know if it is zoom lecture that is throwing me off, my Hard of hearingness, the accent of both of my professors, the fact that I am studying in a different time zone (3am philosophy lectures yay), the fact that I went from Lower division courses, to "medium devision courses", to Upper devision courses but I cannot seem to focus. Every twenty minutes I just kinda zone out and then when it comes time to time to write my paper I get confused. All my classmate seems so smart, like the professor gives a whole monologue and than my classmates are like: "well let me add something, complete analysis with terms I have never heard of". I never had major trouble with my philosophy classes before, sometimes I would not understand a primary text, but my lectures would clear it up.
Any tips? | You are not alone in experiencing this kind of thing. In order of things you can reasonably affect:
1. Try to force yourself into a specific set of note-taking habits
2. Beg the professor for links to lecture recordings (preferably with transcripts) for use later
3. Beg the professor for their lecture notes or, at least, an outline of the lecture prior to the session
4. Beg your professor to take more inter-class breaks (especially if the lecture is for more than an hour)
ETA: If your hard-of-hearingness is documented, then there are lots of ADA protections. It is possible to do CC in Zoom, but professors can't easily do it by themselves (as someone has to live caption). Your college's access office would be responsible for making that happen, but if your access office is having trouble providing this option then you should for sure let your professor know that you need help here. | 16 | 24 |
[Guardians of the Galaxy] Is it ever explained how Groot actually speaks? | The fact that he basically says the same "sentence" over and over again suggests that his language is more tonal, and that the words aren't important. Rocket has no problem understanding what each iteration of "I am Groot" means. | Not in the films, but Rocket might have developed an understanding with time and experience.
It's not impossible for him to use other words (we are groot), but it does seem to imply considerable effort is needed for him to do so. | 175 | 251 |
How long does it take soap to “remove” bacteria? | I’ve seen that the recommended amount of time for washing hands with soap is 20-30 seconds. I know that friction from rubbing is what allows the soap to remove the bacteria from your hands, but is the 20 second rule constant? Is that just to ensure you cover the full surface area of your hands?
If I get my wrist dirty, do I need to rub it with soap for 20 seconds? What about on other materials like ceramic or steel? Does the type of soap impact the amount of time you should spend creating friction (i.e dish soap vs hand soap)? | Soaps/detergents are useful because they make waters surface tension weaker. So when you are washing your hands that are dirty, that "cutting action" of soaps happens because they separate oils and substances from your skin. Same for dishes and also clothes.
I think the 20-30 second rule is mainly used to enforce hygiene in a work place by law, "all employees must wash their hands before returning to work". This general practice is probably used as the standard for washing our hands. | 17 | 16 |
Is there a 3D equivalent to the "Four Color Theorem"? | I know the Four Color Theorem states that 4 colors are enough to fill any planar map. Is there a three-dimensional equivalent?
Intuitively, I think it should need 4^2 colors, but is there a proof?
[Four Color Theorem](https://en.wikipedia.org/wiki/Four_color_theorem) | In 3d you can have situations requiring arbitrarily many colors. Take a cylinder, cut it into N slices like a pizza for any number N, and then on the top of the cylinder attach N concentric rings. Every ring touches every wedge and vice versa, so for each wedge pick one ring to fuse it with, and now you have N different 3D regions that all touch each other. You then need N colors to color them all differently. Since N was arbitrary, we can make it as big as we like. | 49 | 16 |
ELI5: Why is it that you naturally become drowsy when exposed to warm water for an extended period of time? | I've known about this phenomenon for basically all of my life but haven't ever received a proper explanation for why it happens. Any helpful responses are greatly appreciated! :) | The human body naturally gives off heat to keep itself at a comfortable temperature, and gives off even more heat during physical activities. When faced with hot surrounding temperatures like warm water, the body (which is now unable to get rid of its excess heat due to being in an already hot environment) will tell itself to further reduce its own physical activity to prevent from overheating. That’s why you feel sluggish and don’t want to move much when in a hot bath or jacuzzi. | 37 | 32 |
How do marine mammals survive without fresh water to drink? | Marine mammals get their fresh water from the food they eat (ex: fish).
Many dolphins in captivity are "watered", which is basically tubing water into their stomachs (painless and trainable), to make sure they get water that may have been lost in frozen fish during processing. Other methods of ensuring hydration are ice cubes and gelatin.
Gelatin has widespread uses for marine mammals who require lots of hydration.
But marine mammals do have kidneys that are much better than most animals' at filtering out excess salt.
Source: worked with dolphins. | 111 | 215 |
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ELI5: What to people have to gain by claiming climate change isn't happening? | Let me explain. In most issues I'm pretty Republican, but I don't understand why the Republican side is so passionate about climate change not being real. It seems to be pretty cut and dry that it's happening and I don't understand why people believe so strongly that it's not.
So what's the political/economical/whatever upside of claiming it's not happening when there seems to be pretty strong evidence. I can't believe it's solely about greed or protecting corporations. There has to be more to it than just that. | Two really key points that need to be straightened out first before answering you.
* Very few influential people are claiming that climate change isn't happening, there's just too much evidence for it. What a number of people are doing is claiming that climate change (in the form of regional effects of global warming) is not being caused by HUMAN activity. If it's a natural process, we can't be to blame for it.
* Different people have different motivations. Some people honestly do believe that the "truth" is humans aren't causing it, either because their own research leads them to this conclusion or because they believe other people's messages and they're just conveying those opinions onward.
So let's talk about the people who originally create those messages that others might follow, and answer your question.
Many of those people sometimes have very strong interests in disconnecting human activity sources from climate change results. They work for or represent companies that do things like produce lots of greenhouse gas, or produce and sell non-renewal energy sources like coal and gasoline. So their livelihood depends on people not believing that they're causing a potential problem, and they do their best to try and suppress that belief.
Or they're argumentative as a job or as a hobby. A lot of the conspiracy theorists out there don't believe any messages that come from government, and apply less-than-scientific processes to their cherry-picked analysis of what the causes are. They either get their kicks doing it, or get a paycheck from doing it. | 46 | 17 |
ELI5: How would somebody create a new programming language? | You would write a program in another language to make it work.
The two approaches are:
* compiler - reads a file of the new language and changes it to machine code
* interpreter - reads the file line by line and executes each command
Many modern languages, like java, perl, and python take a hybrid approach to various degrees. | 12 | 17 |
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ELI5: What makes haemoglobin toxic to the human body? Isn't it essential for carrying oxygen in our blood? | Haemoglobin is, as you say, essential for carrying oxygen. But technically, we do not have haemoglobin in our blood. Haemoglobin is a protein that is bound in erythrocytes, red blood cells, and that is very important. Another protein is haptoglobin, that forms a complex with free haemoglobin. This happens when a RBC is destroyed, and haemoglobin is released in the bloodstream. This happens all the time, and is mostly no biggie, the haptoglobin-haemoglobin complex will just go to the liver, to be broken down. However, if enough RBCs are destroyed, there won't be enough haptoglibin to bind haemoglobin, and you end up with free haemoglobin in you bloodstream. Free haemoglobin binds very easy to oxygen, that's the intention, but this oxidative property can lead to inflammation and tissue damage if it is not contained in the RBC.
All in all haematology is a very complex subject, but to sum it up: haemoglobin in RBCs is not the same as haemoglobin in blood | 28 | 17 |
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[Iron Man 2] How did Tony Stark get the Mark 5 Suitcase Emergency Suit through customs all the way to Monaco? | How did Tony Stark get the Mark 5 Suitcase Emergency Suit through customs all the way to Monaco? Would he not have had major issues moving it from America to France since it's considered a weapon? | Private aircraft often expedite the customs process with specific customs officers inspecting private jets. Provided he had the details worked out beforehand with higher level officials, those officials would just tell the customs officer inspecting the craft that everything is on the up and up, and all would be good. | 52 | 29 |
Why is it not advisable to give water to burn victims? | The only (verifiable) reason I've found is that ["there is a great potential for burn victims to vomit."](http://uuhsc.utah.edu/burncenter/emergencycare/management.html)
Is there any other reason not to administer water, especially from a physiological standpoint?
| A few hemodynamic changes happen after deep burns or burns covering a large area of the body.
A burn is essentially a breakdown in our barrier to the outside world. Burn patients lose a lot of water, electrolytes and possibly red blood cells for the days following the burn. About 36-48 hours after the burn the patient's ability to maintain volume and fluids is greatly increased as leakage is decreased.
A loss of Sodium is profound in burns and if the fluid you are losing has water and Sodium but you only replace the water you will quickly become hyponatremic. hyponatremia that is brought on abruptly has severe consequences, mostly in the brain that can lead to coma and death. A solution with at least the osmolality of the patients plasma has to be given to maintain proper electrolyte balance.
Also, the kidneys are usually damaged after a burn and inducing a hypo-osmotic, hypervolemic state is a danger for increased kidney injury. The base deficit burn patients show will be accentuated greatly in this state leading to acidotic problems and further acute kidney injury. We try to monitor urine output and content very closely as overfilling the system can lead to rapid edema and the complications that come with that.
Although the metabolic rate is increased immensely following a burn, most patients with severe burns will be glucose intolerant for a little while. Any solution containing glucose is contraindicated early in management (except for children who require glucose). | 100 | 90 |
[Star Wars] How many languages does the average person know? | A lot of people seem to know other languages as well as Galactic Basic | Most people only know one or two: Basic and whatever their own cultural language is. Depending on what they do they may know more. For example, mechanics are sometimes able to understand droid binary, politicians are usually multilingual, and the more unsavory elements can usually at least understand Huttese and Rodian. | 13 | 16 |
ELI5 What is formal logic? I've read the wikipedia page a dozen times and I still feel five. | This is a pretty condensed ELI5 but formal logic is a set of rules you can use to construct valid arguments or prove statements. You can also use it to check whether other people's arguments are valid.
It has heaps of uses. You can check mathematical proofs, make electronic circuits, and solve philosophical problems. You can also use it in debating, law, economics, and many other fields to look at whether people have valid and factually correct arguments. | 20 | 15 |
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[Harry Potter] What laws of physics does magic defy the most? | And by laws of physics I mean science plus the universe as well. | The first law of thermodynamics is that energy cannot be created or destroyed, it can only be transferred from one form to another.
All spells (travelling through time, flying on a broomstick, healing broken bones) would require energy - sometimes huge amounts - but it's never clear where that energy is coming from and it appears to be 'created'. | 100 | 57 |
Number of citations? | In a science field (edit: AGU journals, IEEE journals), I was wondering about the different 'citation scores'. If an author (as lead author) has 5 papers with over 100 citations, is that something that is really good?
There is not a lot of papers, so the h-index and i10 index are not all that impressive. Is there an i100 index? | It is something that is really field dependent, and even community-within-field dependent. There's not really a great way to generalize this! Some fields love conference papers, others journal papers, others books and so on and so forth. | 37 | 21 |
ELI5 - Why aren't the any pictures from rovers of the huge martian landmarks? I understand that Olympus Mons would be quite hard to take a picture of from the surface, but what about Valles Marineris ? | there * sorry lol | They're sent with specific missions, such as taking samples of soil to see if life is viable or every existed on Mars. They're sent to whatever location best suits their mission, and we haven't sent a mission for sightseeing yet. | 59 | 52 |
CMV: Rape would cause much less psychological trauma if it were socially viewed on the same level as violent assault as opposed to being seen as equally bad or worse than murder. | I think that the way western society views rape (sticking to rape of women, here, for reasons I will explain below) blows it out of proportion and causes it to be much more detrimental than it needs to be.
What I mean by this is not that rape isn't a terrible, awful thing, but rather that the way it is viewed as an almost mythologically terrible crime by many causes some victims of rape to impose some or all of the "completely life ruining" aspects of rape upon themselves when it doesn't need to be that way. Among "mythically terrible aspects" I include such things as: years (as in half a decade or more) of vivid nightmares reliving the experience, immediate onset of severe depression, inability to go outside for fear of everyone around oneself, similar severe psychological symptoms.
I say this as a male victim of rape. As I said, I'm trying to keep the discussion to females as victims rape because that is where I perceive most of the "mythically bad" aspects of rape lie, but I include this as a comparison to explain my reasoning: Although I recognized immediately that I had been raped, albeit with relatively little physical harm, I didn't assess it to be all that awful and with support from my partner, I recovered very quickly and very completely.
Maybe if I had been hurt badly, I would see things differently, but I do not personally think that a person who is raped in a manner that does not require immediate medical attention to survive should experience life-shattering negative psychological consequences beyond what a victim of assault should and that many victims of rape only experience such terrible things because they believe they should be experiencing them and so self-impose some of the worst psychological consequences.
CMV.
Edit: In response to the first couple of commenters, all of whom seemed to come away with the impression that I do not think rape should cause any serious effects, please understand that that is not what I am saying.
My view is rather that rape isn't all that different from a violent assault in actual awfulness and shouldn't cause psychological effects that are all that worse than violent assault, but that societal pressures build rape up to be the singularity of evil and thus some victims of rape self impose helplessness and wind up making their symptoms/recovery process worse and longer lasting than it should be or would be if rape were viewed as similar to violent assault rather than as the sole singularity of evil.
TL;DR: Rape is terrible, but I don't think it's literally the worst thing that could possibly happen to anyone ever, and I think that viewing it as such makes people more prone to issues and less able to recover than they really should be.
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> *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[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)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!* | If you think that the trauma experienced by rape victims is partly due to societal pressures, then how do you account for similar reactions across cultures - for example in Asia, and Africa. Don't you think that this implies that rape is inherently traumatizing? | 264 | 855 |
ELI5: Gravitanional Waves | There's a general scientific belief that gravity isn't an instant effect and *something* travels at the speed of light causing the effects of gravity, between 2 objects, in a similar way to how light does.
If something big enough and fast enough moves across the sky, its gravity will sweep along, like a wave. Imagine sweeping your hand through some perfectly calm water .... it will create a wave of water, eminating sideways from and behind your hand. | 12 | 28 |
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ELI5: How or why are people so strong when they do PCP? | I've heard and read a ton of crazy stories about people doing alien-like strong and violent things while they are on PCP. Is this a Hollywood myth or is there a reason? (I have no plans of doing PCP) | Humans are much stronger than our day-to-day activities suggest. Normally our bodies limit themselves to keep us from injury, but when these limits get removed you get seemingly superhuman feats of strength.
Examples of this are when you get thrown across a room from touching a live wire—it's actually your own muscles doing the throwing—or parents under the influences of adrenaline lifting very heavy objects from on top of their children.
PCP is just another way of removing these safety precautions. | 182 | 172 |
Should mathematicians be worried about the implications of Gödel's incompleteness theorems? | From what I understand, Gödel proved that there does not exist any set of axioms, capable of describing arithmetic that are complete. That is, his incompleteness theorems showed that no matter the axioms we choose to base our arithmetic on, in that system, there will always exist truths that cannot be shown to be true.
My understanding of the matter isn't great, but nonetheless it leaves me disturbed. Should mathematicians be concerned about this result? Does this mean that, for example, something like the Riemann Hypothesis could ultimately be impossible to prove due to limitations in the definitions of our axioms? And since it seems we are limited by the way we define our axioms, would it ever be possible to get around this incompleteness by changing the way in which we define mathematics and it's axioms? | This is a subtle question, and there is some room for interpretation:
Goedel showed that for every axiom system that is strong enough to have
some basic reasoning about natural numbers, there exists a formula
that is not provable in this system, but which is true.
This means that we actually know the truth of the formula, it is only the
axiom system that cannot prove it. If you do the obvious thing, which is
adding the unprovable formula as a new axiom to the system, the strenghtened
system will have other formulas that are unprovable.
So, there are always unprovable formulas, and if you add those as axiom,
there will be new unprovable formulas.
The goedel formulas are very specific in nature, very artificial, and
we know that they are true, so they are not a real problem.
If somebody would show that the Riemann hypothesis is equivalent
to a Goedel formula of some system, people would consider the Riemann
hypothesis solved.
It is, however, very unlikely that this will happen, because the Goedel
formulas all have something to do with computation. Natural numbers are strong enough to represent computation. The state of a computer can be expressed
by a natural number, and possible computations can be expressed by relations
between natural numbers. On the other hand, proving can be viewed as form of computation.
Because of this, the system can reason about its own proofs represented
within itself. It is this self referentiality which causes the incompleteness.
So, in order to be potential Goedel formula, the formula must have something
to do with computation. Since the Rieman hypothesis is about continues
functions on the complex numbers, it is very unlikely that it has.
We can still consider the possibility that the Riemann hypothesis is independent
from current formalizations of set theory. There are formulas that
are independent of set theory (continuum hypothesis, axiom of choice),
but these formulas reason about ridiculously big sets.
The Riemann hypothesis doesn't seem to do this. It is just about
complex numbers.
There is no reason to believe that the Riemann hypothesis is unprovable
in our common axiom systems. We are just not smart enough to find a proof.
| 12 | 24 |
Why are viruses so much harder to kill than bacteria? | With the rise of CoVid-19 there are tons of news reports about the fact there are no medications for this virus. Obviously we have tons of antibiotics, but why are antivirals so much harder to develop? | Antibiotics kill bacteria by interfering with the bacteria’s metabolism. They usually sabotage the creation of new bacterial cell wall resulting in the cells to burst, or they mimic nutrients that the bacteria gobble up but ultimately cannot use, so they starve.
Viruses are not bacteria. They barely fit the definition for ‘alive’ and lack any sort of metabolisim that we can exploit. Put a virus in front of you and it will just sit there, completely inactive.
A virus particle only consists of a little bit of genetic information (DNA or RNA) and a protein hull or sheath. That’s it.
Viruses only activate by coming into contact with a living host cell. Their genetic information then enters the cell and reprograms it so that it now produces many more virus particles.
And that’s the difficulty. Since they don’t have their own, discrete metabolism there is next to nothing that can be sabotaged that doesn’t also affect the host.
Basically, if we want to find drugs against viruses we have to find one for each virus type or family separately (and hope that is doesn’t mutate and then drug becomes useless).
That is a VERY long process and we haven’t had much luck yet.
HIV drugs are now around that cannot remove the virus, but can force the virus into a sort of inactive state as long as the drugs are taken. HIV positive patients now have a near normal life expectancy if they adhere to the therapy.
Tamiflu was created for influenza viruses. The idea is that it inhibits an enzyme that new virus particles need to detach from their host cell, so now thy can’t infect new cells. Nice in theory and some countries stockpiled it for severe outbreaks but it turns out that the drug is next to useless.
Acyclovir is used against Herpes (zoster) infections quite effectively.
That’s it. Among the thousands of viruses that we have and that affect us, that’s the best we can do at the moment. | 10 | 15 |
Should laypeople be agnostic about matters that are still debated by experts? | Many laymen hold beliefs which are very controversial in academia and are still debated (one that comes to mind is the theism vs. atheism debate (technically there is a consensus since most philosophers are atheists. However, most of them don't consider the arguments for or against God and debate other issues) another one that comes in mind is Platonism, if you ask some layperson if 2 exists they'll probably say no).
Laypeople don't have sophisticated defences for their positions, they mostly believe what they find intuitive or were taught to believe. And any reason they give for their position probably has been considered and either rebutted or is still being debated.
So in the absence of expert consensus over p, should laymen be agnostic about p? If so would this mean that most of the globe is irrational for not being agnostic over controversial matters in academia?
I also think we can extend this towards philosophers too. Most philosophers don't consider in very detail whether x is true if x is not part of their field, yet they most probably have an opinion on x. | Depends on your views about the domain-specificity of evidence from disagreement (and deference norms, which probably follow similar patterns of domain-specificity). You might think that we should hold pretty tightly to expert opinions in fields such as physics, medicine, and (maybe less so) econ, archaeology, ..., but not very much in philosophy, politics, ethics, ... So you might think that we should be agnostic if experts are undecided in the first type of fields, but not the second.
(An interesting question: should experts themselves follow a similar pattern?) | 11 | 32 |
ELI5: What does it mean when physicists say the Universe is flat? | Currently in an astronomy class i took for fun (not nearly as fun as i thought), but many interesting concepts come up such as this one. How is the universe flat? | Essentially, it means that the universe mostly follows the principles of Euclidean geometry except in localized areas.
That is to say--a triangle light-years across will have internal angles that add up to 180 degrees. If the universe was not flat, this would not be true and what appears to be a straight line would actually be a curved line.
More practically--this means that if you look and see a star off in the distance, you can be reasonably sure that the star is actually in that direction and the light isn't following a curved path to get to us.
Gravity, particularly extreme sources of gravity, can warp space-time into non-flat sections; that's where you get stuff like gravitational lensing. | 347 | 537 |
Explain how 0.999 recurring = 1 (LI5.) | This was explained in class when I was younger. Never got my head around it.
Edit: Well and truly explained. Thanks. | All the numbers can be ordered on a very, very big line, like on a gigantic ruler. Now, if two numbers are different, that just means that there is some space on this ruler between them. That space is full of numbers, too. So, for example, 2 is a different number than 4, because (for example) 3 is between them. In fact, you can find more numbers than you could write a piece of paper between *any* two different numbers. Try it!
Now, 0.99999... = 1 is just another way of saying that there are no other numbers between them. It makes sense once you try to come up with such a number yourself: Obviously it would have to start with 0.99999 as well but then be a little bit higher. But there is no such number that's still smaller than 1. | 28 | 16 |
Gravitational lensing could be used to create a telescope to search for radio signals from intelligent life with 1.3e12 amplification - how? | I read about the work of Claudio Maccone [here](http://www.newyorker.com/online/blogs/elements/2013/06/gravitational-lens-sun-space-exploration-maccone.html). How could gravitational lensing be used to create a telescope like this? How much better would that be than current efforts at looking for radio signals from intelligent life? | >How could gravitational lensing be used to create a telescope like this?
Because mass warps spacetime and thus bends the path of light, so light passing near a mass such as the sun gets lensed around that object. The Sun would essentially behave as a gigantic lens, hence the considerable amplification.
This idea is very far from implementation however. For one thing you have to get a working telescope 90 billion miles (!) from the Sun, which is an order of magnitude farther than Voyager 1 is from the Sun. For another, the Sun emits its own radiation which would have to be corrected out somehow. | 12 | 69 |
Why is black and white vision more adventageous for predators than color vision? | Your eyes have two receptors - - rods and cones. One dealswith color, but the picture is not very 'sharp'.
The other sees black and white but is very sharp.
So black and white vision tends to be sharper accurate than color vision.
Also black and white receptors work better in low light. Which is obviously good for predators hunting at night.
This is why you can sometimes see stars in the sky better by looking through your peripheral vision than dead on. | 16 | 18 |
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How does electricity know the path of least resistance before it gets to its destination? | I have a very basic knowledge of electricity, but I'm puzzled by how and why a current takes the path of least resistance. Why does lightning differentiate between striking a metal tower versus the ground 20 feet away? | Others have addressed your second question (about lightning). Let me address your first question: electrical flow in a conductor.
> a current takes the path of least resistance
That's an over-simplification that us electrical engineers make, and state as fact, when that's not actually what happens.
Current flows through all conductive paths between two points with a voltage differential, in varying amounts. The question is not "where does the current flow?" but "how much current flows in each path"?
Once you ask the right question, then the answer becomes clear: a lot of current flows more easily along the path of least resistance, a bit less in the adjacent path, and so forth, until you get to the extreme edges, where, yes, some current does flow, but not enough for us to consider in our analysis.
For an analogy, think of the classic image of metal filings between the two poles of a magnet; they are not lined up in a thin line between the poles ("the path of least reluctance"), but instead are spread out in a ellipsoidal area between and even around the poles.
For another analogy, think of a stream. It's not that all the water flows in the top and middle of the stream. Yes, more water flows there, but water flows in the entire cross section of the stream, just less so along the edges, because of higher resistance there.
You don't ask "how does a water molecule know where the flow is easiest?". The water molecule doesn't "decide" where to flow. It just flows slower or faster based on the resistance to the flow it happens to encounter where it happens to have ended up.
By the way, the path of highest current flow is not necessarily the one of least resistance: with AC, most current flows in the path of least impedance, which may have more resistance, but less inductance.
Search also for "skin effect".
| 62 | 50 |
How does glue work at an molecular level? | Does it bond with the contact material or is there a more simple 'sticky' explanation? If the glue does not bond with the contact (as I assume is does not because of the relative ease of separation) then how does it stick in the first place while losing it's initial stickiness when hardening? | Two main words: Adsorption and Chemisorption.
Adsorption is kinda like the surface tension of water. Molecules spread over the surface of an object and adhere to it through a bunch of small magnetic attractions (van der Waals forces). This surface will now adhere (stick together with) another surface using this same van der Waals force. No chemical bond, it's just acting like a bunch of tiny, weak magnets that add together to make a relatively strong attraction between the two surfaces.
Chemisorption is a bit different. This is when the substance that causes this adhesion actually chemically reacts with the surface and forms a new compound, joining the two surfaces together into (almost) a single thing. | 371 | 1,203 |
ELI5: why is vomiting an early sign of pregnancy? | Note: thanks to everyone | At the beginning of a pregnancy, the woman's entire endocrine system (which regulates hormones and the body's ability to process energy and food) is going through massive shifts as it prepares to build an entire second human. These shifts can easily cause nausea and other symptoms. | 12 | 19 |
ELI5: How is it all breeds of dogs are the same species? | How is it that the tiny, white fluffy poodle is the same scientific species as the massive black great dane? Why is there is such a wide range of dog types and how can they all be considered the same species? | Because they can successfully interbreed. A species is a group of individuals who can successfully interbreed with each other.
There is a wide range of breeds because people keep breeding new breeds. A lot of this is accomplished through inbreeding. This is why a lot of breeds have a lot of genetic problems. | 12 | 16 |
How is a mirror both silver AND able to reflect everything at the same time? | I don't understand. Is it actually not silver and there's some crazy cultural mind trick convincing me to think it's silver when there's actually no silver there in the first place? | I believe your question is asking how can a mirror be colored silver, and at the same time show a reflection.
The way vision works is that light hits an object, bounces off, and then hits our eyes. When this happens some of the colors of light get absorbed, and what is left gets reflected. A green leaf will absorb every color except for green, which then bounces off for us to see.
A mirror is a very very smoothly polished surface, so that light bouncing off does not go in random directions. Instead all of the light rays bounce in the same way, so the light we see is almost exactly the same as what originally bounced off the object. A mirror also does not absorb very much light, so most of it bounces off unchanged.
If the silver part of a mirror was roughed up it would start to appear more "silver" because the light would be bouncing around randomly instead of all reflecting the same way.
TLDR Mirrors don't absorb colors of light, so their color is whatever hits them. | 40 | 61 |
ELI5: How do DNA/Ancestry kits work, and how accurate are they? (Like the ones from "23 and me" and "ancestry.com") | There are common genetic findings that frequently occur due to descent from a specific set of ancestors. Researchers have identified specific sets of findings that typically indicate where groups of ancestors lived previously.
If you'd like to read more, look up haplogroups and subclades | 50 | 308 |
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CMV: The soccer/football time keeping method (counting up to 90 + injury time) is inferior to the counting down and time-stop methods used in other major sports. | Watching the world cup, their time keeping method is a glaringly inferior system. There is no reason the fans shouldn't be able to see the same time that the time-keeper sees. Some of my main gripes with it:
- It creates an unnecessary barrier to new viewers of the sport. I've heard countless people ask how long the game is, and why they are still playing after the 90 minutes, and how long injury time is.
- It takes away from the suspense of the last few minutes, when for all the players/fans know, they could throw another 10 minutes onto the time.
Using counting down/time stop just seems like such an obvious and easy fix that they could do, and the only reason I see for keeping it this way is because of tradition (which is a poor reason).
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> *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[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)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!* | In response, there are several good things about the current system:
* It's flexible and allows the referee discretion as to how best manage the clock
* There's nothing more frustrating than a sport in which the clock stops every 10 seconds. At most, the "final" 2 minutes of a soccer game will take ~6 minutes, while the final 2 minutes of a basketball game can take 20 real life minutes. | 88 | 126 |
Is Double-Slit Experiment about measurement limitations or nature of the light? | Hi,
I was reading about Double-Slit experiment lately and Complementarity. Can we say that:
The act of "**observing**” affects the electrons/photos but this doesn’t mean that the reality was not there. We don’t have a way to measure our system without changing the information in it. This is still more a **measurement limitation** for me than explaining the nature of the light.
Is Double-Slit Experiment and Complementarity about measurement limitations or nature of the light? | "Observing" mean the the light interacts with macroscopic objects, such as the slit, barrier, and the screen. The experiment is about the nature of reality. It's not a technological limit on our human measurements. A full discussion would include the concepts of local hidden-variables, and Bell's theorem (look them up). | 53 | 69 |
ELI5 What is Doughnut economics and how does it work? | It’s an economic model that takes 12 social necessities and 9 ecological ceilings into a single model. Basically we want to fulfill the necessities without damaging the ecosystem. If a society manages to do so it’s considered economically prosperous.
Simplier put it’s a model that measures economical prosperity by aiming to fulfill social needs (water, housing, education, justice etc.) without damaging the eco-system. If a society could provide enough water for everyone but the water will run out in a few hundred years than it is not considered economically prosperous. | 98 | 119 |
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I know everybody hates "This is what belongs in ----" posts, but i think I can actually be constructive. | Obviously I can only give my opinions, I can't say "This is what it's for!" with an iron fist, but I think I have some sound reasoning. From the title "explainlikeimfive", I think everyone can gather that questions are asked and answers are given either literally as if to a five year old, or the title is taken as an exaggeration and an answer is merely simplified.
Why though? The important implication here is that this format is essential for questions with answers so complicated, or so intricate, or so ambiguous and hard to grasp, that in order for the average redditor or individual to understand, it would likely REQUIRE an explanation a five year would also understand. This often includes, but is certianly not limited to: philosophy, economic theories, entire political systems, crazy ass science, and complicated historical events. To give an example, I think I first thought ELI5 kicked ass when I learned about [the casimir effect](http://www.reddit.com/r/explainlikeimfive/comments/jn7qg/eli5_the_casimir_effect/). If you want more mostly "good" examples according to this reasoning, just look at [The Five-Year-Old's Guide to the Galaxy](http://www.reddit.com/r/explainlikeimfive/comments/j86h2/the_fiveyearolds_guide_to_the_galaxy/). Things like "How does Youtube 'partnership' work", "Why are monitors wider, and not taller?", "How is fish not considered a meat?"... jesus christ. I don't have the answers to these, but I guarantee they can be answered in about three sentences and probably any five year would understand.
**Conclusion/TL;DR:**
What could be a loose guiding rule:
ELI5 is for questions that you could probably find the answers to, but the answer is so far over your head that you need it broken down to the level of a five year old. Example: The Reimann Hypothesis. Unless you're a math major, I don't think [this answer](http://en.wikipedia.org/wiki/Riemann_hypothesis) is going to help you much.
I know this has all been said before, even in one of the top posts of all time, but clearly it needs reiterating. Thanks for listening, and sorry if it sounded too wordy, I was trying to making a defensible argument instead of an opinion. | Adding to this, ELI5 gets answers wrong plenty of times. Take for example the question about why we sneeze when we look into light. ELI5's top answer was "because you tilt your head back".
So next time people have a scientific question that doesn't involve complicated shit like quantum mechanics or something, please *ask a scientist* on r/askscience. *That is what they are for!*
Tell them you're a layman and to keep it simple. It's not like they only have moonspeak mode or some shit. | 81 | 289 |
What happens to veins after they are injected with a needle? | Not sure what you mean... so hopefully the following helps;
First, IDK if you can say they're injected with a needle; they're punctured/pierced by the needle - you then inject the contents of the syringe into the vein.
Second, the needle breaks the wall of the vessel, but since it's sharp and small it does fairly little damage... and when removed the body's response quickly closes the hole. Any leakage turns into a small bruise/blood under the skin, which then gets re-absorbed over the next few days. | 2,483 | 3,188 |
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How long would it actually take to learn programming from zero? | I'm a synthetic biology PhD student and I have recently realised the strong need for dry lab skills! Ive always had an interest for modeling biological systems, but the thought of learning programming seems overwhelming. Also knowing that it probably will take so much time to only achieve average coding skills makes me feel like I will never be able to achieve novelty/ publication standard understanding. Do you think I'm just being scared or should I concentrate on what I'm good at? | I’m going to disagree with others’ advice here and say that it would be most effective for you to take an intro to programming course. This is because although you can learn most coding by working on a project and googling, even knowing what to google (keywords etc) is challenging for complete beginners. Taking an intro course gives you the mental representation and vocabulary to become self-sustainable and helps you progress much faster. There are many free ones offered on Edx/Coursera etc, and since Python is probably the most useful and beginner-friendly language, perhaps start with that. It’s going to take a while. For me it took around a year of frequent coding to become comfortable and two years to become relatively fluent for research purpose. | 114 | 67 |
ELI5:Why use / should I use Docker? | For programming projects, i've tend to seen a lot of students using docker as container service, where they have like a db container, frontend container etc..
why would you even do that? instead of installing the dependencies (database) local on your pc.
one thing that i can come up with is, not using your own local pc storage for database etc | There are a lot of benefits to Docker. Since everything is packaged it’s easy to launch anywhere with consistent results. You can scale up for more users by launching new containers. You can scale down by killing them off to save money when your app is not seeing much traffic. Scaling should be done with no side effects from leaky configs. Deployment pipelines are rapid and easy to set up.
_Edit:_ also, to answer the question in the scenario you discussed, it’s probably just good practice to get used to packaging/deploying code to a real environment. A lot of companies use Docker/Kubernetes these days (regardless of whether or not it _really_ benefits them). It shouldn’t add too much extra dev time and sets you up with a lot of knowledge for “the way things are” in real work environments. | 26 | 46 |
ELI5: If you go to sleep hungry, why do you wake up significantly less hungry than you were before? | The amount of sugar in your blood stream has a big impact on how hungry you are. When you eat something with sugar your blood sugar immediately rises. As time passes your body uses that sugar for energy and your blood sugar levels get low. This causes you to feel hungry, however if you wait long enough your liver will process stored fat to increase your blood sugar levels. That's why if you ignore your hunger(or sleep through it) you will feel less hungry.
Edit:
Unless you're diabetic. Then you should probably not go to bed hungry. | 575 | 714 |
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Student researcher lied to regarding publication and recognition | For context, everyone I mention (including myself) are student researchers at a very prestigious research university. I’m going to try and omit genders, ages, our field of study, etc. to try and keep this post from potentially biting me back. I can try and share more details in PMs or comments if it’ll help.
Earlier this year, as we were preparing to submit our research paper to a conference (on par with NIPS), our paper’s lead author lied to me about how we were going to be recognized in our work, literally seconds before s/he submitted our final draft to our journal. It was clear that my colleague lied in order to try to gain more recognition for himself/herself in our work. (I’m sorry for being vague as this situation is highly-specific to us. Happy to talk more in PMs.)
I thought it was an extremely egregious lie so I asked other more senior colleagues in my group about it. They all agreed it was extremely sketchy. One even remarked that it should be grounds to no longer work in our group. Yeah, it was that serious.
I approached our advisor (a full professor, highly-respected/admired, etc.) about the lie. S/he told me s/he noted the lie and my objection and told me to let it go. I trust my advisor to do the right thing and s/he’s been highly supportive. However, it irks me beyond belief that my advisor has trusted my colleague with even more work involving leadership of other students. And, nothing's been done to rectify the situation, either by correcting the error or disciplinarily.
I don’t know what to do and I’m frustrated beyond belief that I was cheated out of something I was clearly promised earlier on. I don’t know how to approach the situation anymore. I really just want to leave our group now but I don’t want to throw away the rapport I built with my professor.
I'm usually an extremely chill and composed person who has never lied in a professional context. However, being outright lied to by a colleague is beyond reproach for me, especially in academia. I don't know what to do... :( | Are you a grad student or an undergrad? Is the lead author a grad student, postdoc, or other professor? What was the type of contribution you made to the project (experimental design, data collection, analysis)? What percent of the total work in the project does that equate to? How much of your data is actually in the paper submitted for publication? | 23 | 38 |
Can electrons experience the Doppler effect? | In the sense that they will appear to have more or less kinetic energy depending on which reference frame they are viewed in. It's an analogous to the Doppler effect of light, which itself is analogous in a different way to the Doppler effect in sound, if that makes sense. | 105 | 297 |
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Is Mathematics a 'Social Constructed'? | Is mathematics fundamentally existent within 'reality, the universe, or whatever'? And we as humans are simply in a process of 'discovering' it? I.e If isolated cultures and peoples exist for long enough, they will all inevitably come to create mathematics as we have today (granting that on the surface it may seem different with symbols and such, but the core principles being the same)?
Or is mathematics a grand and glorified 'inductive opinion' held by society. Of which our current interpretation of it has stood the test of time, on account of the tremendous utility it provides?
​
My own views (which are not concrete) are that it IS possibly a social construct (or at least has elements of 'social construction' on a fundamental level). And my reasons for this is the 'concept of zero'.
When looking this question up online, I found the following comment (answering 'no') interesting. It stated '' The symbols used to describe mathematics is a social construct, but what those symbols describe is a real entity. '' (this was quite representative of mostly everyone who answered ''no'').
Of course, the concept of 1, 2, 3 etc CAN (and do) pertain to some manner of 'real entity'. I.e I hold a single Apple in my hand, and mathematics contains the concept of 1. Ergo, the mathematical concept of 1, corresponds to the 1 Apple I hold in my hand... Success!!
BUT... Zero does NOT pertain to any 'real entity' in the same way (as the other number do). Yet the 'concept of zero' is incredibly important to the field of mathematics. This, combined with the fact that the 'concept of zero' steadily spread among the ancient world, and slowly over time became adopted into mainstream Mathematics (short, but interesting article about it here [https://www.scientificamerican.com/article/what-is-the-origin-of-zer/](https://www.scientificamerican.com/article/what-is-the-origin-of-zer/) ), suggests to me that 'zero' is somewhat of a 'smoking gun' in showing that Mathematics is INDEED a Social Construct (at a fundamental level).
But I'm super interested in hearing your thoughts. | You seem to be presenting two main arguments for the idea that mathematics is socially constructed. One is that there are mathematical ideas we talk about even though they do not plausibly correspond to particular things in the physical world. It seems to me that this is an argument against empiricism, but not against Platonism.
Your other argument is about diversity and change in the way that people talk about mathematics. But note that one could say the same about, say, whether the Earth revolves around the Sun, but this does not imply that there is not really a right answer to the question. | 13 | 27 |
ELI5: what is the equivalent for cardinal points North, south, east, and weast in space? | As others have said, you have to have a reference point.
Now, in orbit, there are some directions that are used for navigation, but they're dependent on your particular orbit.
Still, they're handy to have if you ever find yourself in an orbiting space hotel and want to impress that cute tourist :)
They are:
* Prograde: Your direction of motion relative to the thing you're orbiting. If you think of the orbit as a roller coaster track, you're looking directly forward. This is the direction you want to accelerate to raise your orbit.
* Retrograde: The opposite - looking directly backward. This is the direction you want to accelerate if you want to lower your orbit or re-enter the atmosphere.
* Normal: In an equatorial west-to-east orbit, this would point north. In an inclined orbit, it'd be north-ish. It's 90 degrees from the prograde/retrograde line, parallel to the planet surface. If you could move in this direction without disturbing your imaginary roller coaster track, the track would seem to curve to the left, with your orbital path going counterclockwise. This stuff's hard to describe without pictures :) If you look in this direction, you'll see the horizon of the earth, with the ground moving from right to left beneath you.
* Antinormal: 180 degrees away in the other direction. Again, if you're in a perfectly un-inclined orbit at the equator, this would point "south." You'd be looking at the southern horizon and the earth would seem to be moving left to right beneath you.
* Zenith: Straight away from the planet surface. Closest thing to "up".
* Nadir: Directly toward the planet surface. "Down". | 46 | 43 |
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ELI5: Why is it ok to watch a sunrise/sunset but its not okay to look directly at the sun? | During the sunrise and sunset, less of the sun's rays are shining on your location, and they travel through more air to reach you. This causes the beams into change to a less harmful intensity, and allows you to look properly at the sun. | 25 | 30 |
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CMV: Digging up Mummies and displaying them in museums in barbaric and disrespectful | I am a lover of history and museums, but this one I just really don't understand. It's one thing if someone agreed to be mummified and put on display before they died (this is the case with some mummies in the Vatican). But if some Egyptian king thought he was being laid to rest forever in his tomb, we ought to have left him there. We're not better than grave robbers to put his body on display now.
I think it's fine to study the artifacts in there with the body and maybe put those on display, because they tell us a lot about those cultures. I understand their value to history. But I don't understand the disrespect of displaying someone's actual body without their permission. Am I crazy? | Consider the purpose of mummification:
> In order to live for all eternity and be presented in front of Osiris, the body of the deceased had to be preserved by mummification, so that the soul could reunite with it, and take pleasure in the afterlife.
Now consider what happened to *other* mummies that weren't placed in museums:
> In the Middle Ages, based on a mistranslation from the Arabic term for bitumen, it was thought that mummies possessed healing properties. As a result, it became common practice to grind Egyptian mummies into a powder to be sold and used as medicine.
This (and similar practices) continued up until the late 19th century. Now considering that whoever was mummified wanted their body to remain intact - where do you think they might prefer to be? Left in a tomb at the mercy of grave robbers, or kept in a climate-controlled museum, their body attended by groups of workers whose sole interest is in seeing it preserved? | 1,054 | 2,641 |
ELI5: NASA's latest announcement about Mars' atmosphere | EDIT: More ELI5 answer:
A long time ago Mars had plenty of water flowing on its surface. Shortly after the flowing water was there Mars lost its magnetic field. The magnetic field is caused by melted metal inside of Mars moving around; the same way Earth gets its magnetic field. The metal cooled and became solid faster than Earth's because Mars is smaller and Earth has more radioactive rocks inside of it heating it like a nuclear reactor.
This magnetic field was like a shield for Mars. This "shield" protected Mars from the Sun. When Mars lost its shield so long ago it was exposed to the Sun's winds which blew the air off of Mars and evaporated all the water on Mars too! The water was blown off of Mars and lost to space as well.
Mars is still losing its atomosphere at a rate of 100 grams a second (that's about as much as a cheeseburger!).
Original post: Mars' lost its magnetic field about 4.2 billion years ago which then allowed solar winds to, over the 500 million years, "blow" away Mars' atmosphere. Before that time water had been "abundant and active" on Mars.
Currently, from rough estimates, Mars' atmosphere is being lost at a rate of 100 grams, or 1/4 pound, per second. | 27 | 89 |
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Academics what are different research tools or programs that you wish people knew how to work? | I'm looking for jobs and I want to become better versed in research tools that are regularly used in labs and academia. What are tools that you find indispensable to work? (the field is biochemistry focusing on genetic and epigenetic research) | Super generally...
* A reference manager (mendeley, zotero, bibtex, sente, pick your fave)
* A programming language (python, java, c++, R, again take your pick)
* LaTeX
There's others but they're department/discipline specific. | 15 | 15 |
How do lasers measure the temperature of stuff? | Usually they're used to just align an IR sensor, but in principle you could shine a laser on something and determine the ratio of Stokes to anti-Stokes scattering, which would be an indirect measure of the temperature. | 2,049 | 6,112 |
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ELI5: why does metal fire up in the microwave? | Microwave radiation is a form of radio waves. The microwaves radiation induces electric currents and voltages in the metal, just like a radio signal induces an electric current in an antenna. This electricity causes arcing. | 11 | 19 |
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Do children who speak different languages all start speaking around the same time, or do different languages take longer/shorter to learn? | Are some languages, especially tonal languages harder for children to learn? | Basically, all the languages in the world have approximately the same difficulty level, so you'll see that child language development happens at the same rate regardless of the language being learned. It just seems to us that some languages are harder because of how different they are from the language we grew up with.
A child under six months has the ability to distinguish between phonemes that an adult would not be able to. After that six month mark (approximately. It varies from person to person) the brain starts to recognize the specific phonemes it needs to learn the language it's exposed to. Simply put, it cuts out the phonemes it doesn't need, which is why as an adult, it's much harder to learn a language with a lot of phonemic differences from your own. | 1,150 | 2,542 |
ELI5: When I shoot somebody in a video game, is there an actual bullet flying through the air? Or is that just added light effects I'm seeing. | I always imagined it as when your sights line up on someone, there's an invisible "laser beam" that attacks people when you shoot the gun.
Edit: The amount of dense people in this thread who seem to think I'm retarded, and that I believe there to be real bullets flying out of my TV screen is ridiculous. Obviously I'm referring to virtual bullets. But other than that, thanks for the awesome replies everyone! | It depends on the game or weapon. Some use what's called "hitscan," which is similar to your laser beam example: when the weapon is fired, the bullet is treated as a straight line that appears instantaneously. A hit is registered when that line intersects with the target.
Bullets can also be programmed as actual projectiles although it's more complex. Basically, a hit is registered when the hitbox of the bullet collides with the hitbox of a target. | 2,753 | 3,248 |
ELI5: How does blood interact with organs/skin if it stays inside veins/capillaries? | Do you understand what I mean? I understand that blood is pumped through the veins to all parts of the body, bringing with it oxygen and other goodies and is then recycled back through the heart. But... how exactly do those goodies get from the blood to the skin, for example? Wouldn't the blood have to leave the tubes (veins, capillaries, etc) in order to make contact with the skin? How does this work? Does this make sense? | the blood cell doesn't have to directly interact with our structures. our capillaries have several capabilities that allows blood to exchange stuff with our cells. capillaries are very, very thin. so thin, in fact, that some stuff on red blood cell such as oxygen can just diffuse through the capillary and go to the cell (while dissolved). other stuff can also diffuse if they're small enough, but some capillaries also have little holes called fenestrations. these holes allow larger stuff to pass through them. for example, in your intestines, when you eat food, the capillaries there are extra hole-ridden to allow carbs and proteins to be absorbed (fats are a different story). these nutrients are carried not by the red blood cell, but rather dissolved in the serum (the watery portion of blood), which allows them to be distributed all across the body | 36 | 43 |
eli5 How can life insurance be used before death? | How can life insurance be used when you’re alive? I saw people comment that they used it to purchase rental properties. How? | There are two types of life insurance, Term and Whole Life.
Term is just like car insurance. If you keep paying the payments you’ll get cash when you die. If you stop paying you get nothing.
Whole Life is like term except it has an investment component. The money accumulates over time. If you die you get the full payout, if you stop paying you get a partial payout (which could be significant if you’ve been contributing for decades).
Like any other investments, you can borrow money against the savings. | 19 | 16 |
Why are bugs drawn to light? | Is it because it resembles the sun in some way? Do they derive energy from it? Do they just like shiny things? | In many cases, the insect uses either the sun or the moon for navigation by keeping it at a constant angle relative to another reference point (such as the honeybee "waggle dance," for instance). Issues arise, however, when they find themselves actually getting close to the light source. That angle is constantly changing as they get closer, so they begin to turn in order to compensate. This results in the insect flying in circles around the light. | 16 | 18 |
ELI5: Why do websites such as Facebook and YouTube constantly update their layouts when nothing is wrong with them? | Facebook has gone through almost one layout change every year for the past 4 or 5 and YouTube is constantly changing.
Why do they keep changing Where a website like Google is constant? | They make changes to make money. Product teams inside of these companies are responsible for KPIs, or Key Performance Indicators. They often have very specific goals that feed into broader business goals.
Facebook is extremely data driven. They might have a metric that tells them that people who post photos at least twice a month spend 10% more time on the sight than other users. So they will devise some UI changes to encourage the posting of pictures and then measure the impact against their large user base.
These companies aren't just bored or trying to 'stay fresh'...they have very specific business goals and have the data to back up the changes that they make. | 830 | 1,011 |
Leaving academia with no idea where to go? | I’m a TT professor at an R1 in the US, about halfway into my tenure clock. In brief, I kind of suck at research and am very unlikely to get tenure (I’ll probably pass mid tenure review, because to fail that here you need to have almost literally nothing to show for yourself).I’ve considered quitting but haven’t because I have no idea what I would transition *to*. I’m taking an accounting course this semester, which I’m really enjoying, and I could go back for that full-time (to be CPA eligible), but financially that doesn’t make a lot of sense, as I’m in my 30s and need to save for retirement. I’ve also considered just running out the tenure clock and trying to check off the requirements of a career change, but honestly even trying to half-ass this job is a 40-hour workweek at least.
Thoughts?
Thanks! | Do you like teaching enough where it's worth considering going to a "lower tier" university or college where teaching tends to be more important and research requirements much less?
You could start applying for those kinds of jobs.
Unless you don't like to teach. Then maybe start leaning on some contacts from grad school who went non-academic? Could you do research for government where publication isn't always the goal?
You can also see if your alumni association from your grad school has networking events and whatnot. A lot of that stuff has gone online in this COVID era.
Just some thoughts. | 18 | 27 |
ELI5: What happened that led to the downfall of Myspace and the quick transition to Facebook? | Consistent clean design, the feeling of exclusivity (initially only Harvard students could use it, then other universities, finally everyone), and the expectation that people would use their real names.
Myspace permitted all kinds of awful design choices and aliases to the point where nobody took it seriously, with Facebook you didn't have to worry about XXx_Sn1p3M4St€r_xXX's page to load and blast Jimmy Eat World at you. | 90 | 61 |
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What is the role of reactive power in transmission networks? | I've studied electrical engineering for some years, but honestly I'm still struggling with understanding complex AC concepts, especially reactive power. What's its role in transmission networks since reactive power can't do real work? Why is it important for large alternators on the grid? | Reactive power is the flow of energy contained in the electric and magnetic fields of capacitors and inductors during AC operation.
For example, the magnetic field around an inductor gets filled up with magnetic field energy as current passes through it, thus part of the energy and power going through the system gets stored in that field, but when the current alternates through this inductor, that energy in the magnetic field moves back towards the source. Thus, effective power is the amount of power that actually gets to your load, while reactive power is the power required to maintain the fields of the transmission lines passive components (capacitors and inductors) and the fields in the transmission line itself.
Now, although the current associated with reactive power does no work at the load, it still must be supplied by the generator, thus reactive power is important to define when designing a circuit so the right power source can be used, or the right capacitive bank can be used to store that reflected energy and resupply it to the inductors. A higher reactive power means more power must be supplied by the generator to dissipate the same power at the load, something power companies do not like :).
Tl;dr: Some of the input energy to a circuit is stored in the electric and magnetic fields, and then returned to the source during the next current cycle. This means not all of your power gets dissipated in the load, which we call effective power, thus we call the power that returns to the source "reactive power".
Reactive power is the imaginary component. Effective power is the real component.
Edit: So many great explanations in this thread! Edited various parts to include other peoples superior additions. Thank you u/helios210! | 184 | 470 |
ELI5:Why does the air seem "fresher" in the morning? | Are you referring to outside air or your perception upon waking in general? Speaking to outside air, generally speaking (noting that each climate is different) humidity raises in the morning as the air is being warmed by the sun. As humidity increases, our perception of smell increases which would be one contributing factor for a fresher smell.
Also as the ground and air warms, more insects that interact with the plants (bees, flies, etc..) are moving around, stirring up sent particles which also can contribute. Wind invariably still moves regardless of the time of day however insects move inside of folds and cavities of plants where a more dense consultation of sent particles are contained.
tl;dr Humidity increases in the morning, heightening our sense of smell. Same reason your farts smell worse in the shower. | 16 | 25 |
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In Earth travel, we use North, South, East, and West, plus altitude for three-dimensional travel. Since those are all relative to the Earth, what do they use for space travel? | Pretty much on every planet or moon it is possible to define North, South, East and West based on the body's rotation. Alternatively, they can be defined based on the Solar System's North and South (as the IAU did with Uranus, whose extreme axial tilt makes the rotational North opposite to the Solar System's North, but for all the other planets it's the same).
However this isn't very precise to plan spacecraft trajectories. There are more precise reference frames based on longitude and latitude, so a prime meridian is defined pretty much arbitrarily as they did on Earth. It's also quite common to use Cartesian reference frames centered on a planet but with the axes based on far away celestial objects because they don't rotate with the planet, so you have an inertial reference frame.
In deep space, far away from any planet, we use a reference frame centered on the Sun, with the X axis pointing along the ecliptic plane parallel to the vernal equinox (the intersection between Earth's equatorial plane and the ecliptic plane), the Z axis pointing North from the Sun, and the Y axis pointing 90° ahead of the X axis following the right hand rule.
It is possible to define others, it depends on each particular trajectory. Basically you need a center (a planet, the Sun, etc), a fundamental plane (the ecliptic plane, the planet's equatorial plane, etc) and a direction for the X axis.
| 3,273 | 8,809 |
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[Jetsons] What does the button that George presses do? | The Referential Universal Digital Indexer requires input from an external source, be it a Human, a Robot, or a Mechanical Mechanism, to approve a queue of automated functions. Think of it as a failsafe to prevent Artificial Intelligences from doing things we wouldn't want them to.
Largely it means that George spends most of his time hitting 'Ok' to proceed with the queue, for a few hours until the queue is empty. | 31 | 26 |
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ELI5: What is overclocking and how does it help/hurt your computer? | A computer program is basically a step-by-step recipe for your processor to follow. However, there are many different parts of a processor, and many of them have to work together for the program to correctly execute. Therefore, everything in your computer has to be synchronized, so that you don't accidentally start the next step in the recipe before the previous one is finished.
The way this is achieved in a computer is through something called a **clock signal**. This is basically an electronic oscillator that sends out a regular pulse. Each individual pulse signals to the rest of the computer that it is time to move on to the next step.
So now we get to overclocking. Usually, on a retail computer, the clock timing is very conservative. This basically means that the clock cycle is longer than it needs to be, just to make sure that all of the parts have the time they need to finish their instructions before moving on to the next step. So often, you can just make the clock cycle shorter, which will make your computer run correspondingly faster because it spends less time waiting.
However, if you keep pushing the clock cycle shorter and shorter, eventually there won't be enough time for the computer to finish its instructions before the next cycle starts. This is when you will start getting errors. There is a way around this, however.
It turns out that increasing the voltage that your computer runs at will also increase the speed that the components in your CPU executes instructions. So if you want to push your computer even further, you can crank up the operating voltage, and continue to decrease the clock cycle time. However, increasing the voltage also means that your computer will be outputting more heat, so if you're severely overclocking a computer, you will probably need to find a better way of cooling it.
So the advantages of overclocking are basically that it makes your computer faster, without changing the hardware at all. The disadvantages are that you can start getting errors if you're setting your clock cycle too fast, and that if you're running it at a higher voltage, your computer will run hotter, which could lead to a shorter lifetime for your computer. | 111 | 52 |
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CMV: Parents who have no custody over their children should not be required to pay child support. | So this comparison came up in another thread and I thought it was apt.
If a parent or parents decide they do not wish to keep their child they can relinquish it to the state and not be involved in its life. The adoptive parents, assuming there are some, don't receive monthly child support checks from the biological parents. We recognize that a biological parent who has no involvement in their spawn's life is not financially responsible for that child if they don't want to be.
This changes if only one parent wants responsibility but the other does not. If Parent A says they have no interest in a child, but Parent B says they do, Parent A ends up paying Child Support to Parent B.
My argument is that for Parent A the decision is the same in both cases. She or he is not involved in the child's life and has no custody. The decision is the same on their part and therefore the result should be the same from that decision: they aren't financially liable.
The onus of raising a child should be on the parent(s) raising it, and not on the biological parent(s) who have no hand in raising the child.
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> *Hello, users of CMV! This is a footnote from your moderators. We'd just like to remind you of a couple of things. Firstly, please remember to* ***[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)****! If you are thinking about submitting a CMV yourself, please have a look through our* ***[popular topics wiki](http://www.reddit.com/r/changemyview/wiki/populartopics)*** *first. Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!* | Both parents are responsible for the creation of the child. Why should the one who took on the burden of taking care of the child with their time and effort, also have to solely bear the financial burden as well, since they are both equally responsible for its creation? | 30 | 36 |
If the atmosphere of Mars is less than 1% the density of Earth, why are there large dust devils and sand dunes? | Two factors are involved there. First, windblown sand is not like beach sand, it's much finer, almost like talcum powder. Desert sand dunes are not much like beach sand dunes, which is a very common mistake people make, as most people are more familiar with the latter rather than the former.
Second, since the grains of sand are very small, they don't take very much wind to get aloft. The faint whisper of the winds of Mars is sufficient to shift its very fine sands. | 37 | 125 |
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[Star Wars] How major are the power differences between the main characters? | Seriously, like I see titles of "best swordsman" or "gifted force user" on just about everyone. Just how big are the power gaps between the big names like Sidious, Dooku, Obi Wan, Yoda, etc.? | I think the best way to conceive of the different skill levels is to think of a pyriamid. Lots of Force Sensatives at the bottom - a few skilled users higher up - with a few rare masters at the top.
The difference in the top and bottom is such that they probably can’t be compared.
At the top - it seems the defining difference to be slight - think light saber duels that last a significant amount of time with 99% non-destructive strikes but when one makes a mistake - the other is there to exploit. | 52 | 77 |
[Independence day] Was Russel casse actually abducted by Aliens? Or was he just a nut? | The novelisation might be informative. When Russell first sees one of the city destroyers, he is convinced that the same aliens that abducted him are in there, and the novelisation describes Russell's experience in substantial detail.
However, there is also a scene that isn't in the movie: when Steven Hiller comes across the convoy of trailers and recreational vehicles, he shows several people the alien he was dragging in his parachute, and Russell was horrified because the alien was totally different to what he remembered. He suddenly finds himself questioning whether his abduction actually happened at all. | 40 | 43 |
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Why did Homo sapiens become the dominant species on Earth rather than other ancient hominids? | Do we know what developed in our brain that allowed *Homo sapiens* to become dominant rather than other ancient hominids such as the Neanderthals who were either absorbed into the gene pool of *Homo sapiens* or simply died off? | You're making a very large assumption by concluding that difference in brain size/physiology/whatever was responsible for a competitive advantage in homo sapiens vs other hominids.
There are a variety of factors *not* related to the brain that resulted in a competitive advantage for homo sapiens. One of the most ignored is that homo sapiens were capable of speech. Neanderthal anatomy, for example, lacked a descended larynx. This prevented neanderthals from being able to produce the variety and complexity of sounds that homo sapiens are capable of and use in speech. In other words, neanderthals were much more limited in their ability to verbally communicate than homo sapiens. This could easily impact the ability to transfer new skills, resulting in homo sapiens being able to much more rapidly disseminate information as they could talk about instead of having to show someone. This type of adaptation could *definitely* create a competitive advantage for the species and has *nothing* to do with the brain. | 35 | 28 |
Do you have an example of something you can prove is immoral? | https://www.reddit.com/r/DebateAChristian/comments/336j4b/what_evidence_is_there_that_god_exists/cqix184
So I was challenged on this, and I'm a philosophy laymen. Are there any examples?
Now my understanding is you can make a deductive argument for an objective standard on multiple things, then show that doing something can be immoral, and not doing it is thus moral, right?
Again, total layman, just felt the arrogance in the linked comment with the presupposition that it can't possibly be answered is absurd, but I can't quite answer it myself.
Not looking to have the debating done for me, but I'm also genuinely curious. | It seems that most ethicists think that something like how you describe the matter is correct. The PhilPapers survey suggests that 56% of philosophers (or 56-63% of philosophers working in one of the major fields of ethics) are moral realists and 67% (71-82%) are moral cognitivists--though these are terms of art, and not quite getting at what we want here, but it's at least a rough indication of where considered opinions are falling on such matters. Certainly, formative figures throughout the history of the discipline have defended a view like the one you suggest--we can think, for instance, of Aristotle, Aquinas, Hutcheson, Kant, and Bentham.
There are two sorts of questions implied by what you have asked. The first is the "meta-ethical" question regarding the nature of moral judgments--for instance, are they just subjective opinions, or do they report facts? The second is the "normative ethical" question regarding what specific basis there is for judging a certain case moral or immoral--for instance, are the morally relevant factors the consequences or the intentions? In many of the classical positions, such as those listed above, it seems to me that these two questions are interconnected, though ethicists recently have been more inclined to treating them separately.
So it's possible to have a dispute on either of these issues. Thus, while two people might agree that there are objective moral distinctions reporting moral facts, they might still disagree about what those facts are.
In any case, if one wished to argue, as /u/brojangles does in that thread, that there cannot be an objective moral distinctions, since morality is just an expression of opinion, they would be defending a position that is relatively unpopular among people who study these issues, but it's still an argument which one may wish to make, and it's still a position that has some significant defenders, if they are in the minority. The obvious problem here is that /u/brojangles never gives any meaningful argument for this position: he just insists that it's correct, and, having taken it as correct, thereby dismisses any alternative as nonsense. This is, of course, straight-forwardly begging the question. Since it's straight-forwardly fallacious, one needn't defer to any authorities to see why this isn't a compelling argument.
Or, perhaps /u/brojangles means to imply that there isn't any dispute on this matter, that the considered view on the matter is unanimously in his favor, that no significant alternative is on offer, and this is why he needn't give any substantial defense of his opinion. If this is the case, referring him to a relevant scholarly resource--as you have already done, and which I've added to in this comment--should suffice to remedy him of this misunderstanding. | 19 | 19 |
Eli5: What is the difference between shampoo, shower gel, 2in1 and conditioner? | Title basically says it all. Specifically, though, what makes 2in1 able to do the job of both shampoo and conditioner? | Shampoo basically reacts with the natural oils and binds so when you rinse, the shampoo takes the oil with it.
Conditioner helps to repair hair damage and basically adds a protective coat to the hair.
AFAIK, two in one doesn't really work at moisturizing the hair. | 15 | 26 |
ELI5: How the US came to be a current world superpower | As others mentioned, the USA has had a wealth of land mass and thus natural resources that helped propel its growth and progress since its founding. The influx of African slaves and Chinese railroad workers also played a significant part in this.
It was a series of events starting after the First World War and the ensuing Great Depression and culminating in the end of the Second World War and the dawn of the Nuclear Age. USA's isolationist policies from 1918 up until their entry into WWII helped focus all efforts to post-Depression recovery internally.
After being forced into participating in WWII following the attack on Pearl Harbor, the industrial machine of USA was a huge asset to their war efforts. Not only that but winning the race to become the first nuclear nation meant not only militarily, politically and symbolically a resounding global victory, but also a big boost for USA's scientific progress. Of the world's most powerful nations preceding the War - Germany, Japan, Great Britain, USSR & USA - only USA emerged from it unscathed, since they were the only nation of the 5 who did not fight any battles on home soil (apart from Pearl Harbor, of course).
The League of Nations - set up after WWI by the USA - now became the United Nations and under its resolutions, both the German and Japanese military forces were prevented from rebuilding and their economies were crippled in such a way to ensure this. USSR, belonging to the "winning" side of WWII also profited from the victory and annexed huge swaths of territory reclaimed from the Nazis' spread throughout eastern Europe, and set up the Iron Curtain.
The entry of USSR into the exclusive group of nuclear nations meant that they and USA dictated not only military but also economic policies around the globe for decades to come. | 15 | 20 |
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Why do we still have daylight savings time? | Wasn't it created for farmers? Can't farmers just set their alarm clocks to match the sunrise? | As society became more industrialized, things like the beginning of school, work (for those with non-agrarian jobs), and public transportation were all synchronized by times, which were constant year round. For farmers who traditionally worked based upon sunrise and sunset, this caused their schedules to become mismatched with everyone else's at certain times of the year, so DST was proposed to alleviate that
That's only one of the reasons originally proposed for DST, though. Another was that adjusting the clocks so that it stayed light into the later hours of the day would reduce the need for artificial lighting and save electricity. This may have been true initially, but with the introduction of air conditioning into housing, more recent studies have shown that any electricity saved by reducing the need for lights is offset by needing to run the air conditioning later into the evening.
Finally, some people just argued that it made sense to have an extra hour of sunlight in the evening, after people had finished working, rather than to sleep through that hour in the morning. | 11 | 25 |
How does smell work? | At an interested engineer, totally not a biologist level, I can smell things. When I try to understand how smell works, though, I get confused. I've heard a couple of answers which I'm not convinced by, so thought I'd get some clarity.
* Resonating bonds between atoms in molecules. This sounds semi plausible, but it doesn't account for handedness, where (AIUI) for instance a left hand identical arrangement of atoms smells of lemon and the same atoms arranged right-handed smell of mint.
* That suggests shape is the driver, which seems compelling, but then why do brand new molecules we never evolved for have a smell? Not perfume blends, that's obvious, but molecularly. If we don't have a receptor for a molecule shape, how could we smell it, and how could we evolve a receptor for something that doesn't exist?
* Smell buds, and every aroma is a unique combination of the nose equivalent of bitter/sweet/salt/acid/umami. This seems pretty unconvincing to me as with shape alone - how could novel molecules smell?
* Nose as a diffraction column. Doesn't seem intuitive, but unique graphs for aromas at least includes the possibility of novel molecules having a smell, but we return to the handedness question.
What am I missing? Am I overthinking it all, missing something obvious? I mean it seems like something we should know, but I'm not seeing consensus.
Thanks for your ideas about this, it's troubled me a while! | **Shape is the driver.** This is a core concept of biology. Biology is just physics due to shape due to chemistry.
There are tons of chemicals we can’t smell.
The ones we can smell are easy enough to explain. There is not simply one receptor per smell just as there is not just one taste receptor per compound in your food. Each smell is a composite signal of all the signals from different receptors that got triggered to specific degrees and your brain turns it all into a perception. You have receptors with specific shapes, and many different molecules will have a close-enough fit for that receptor to trigger it to some degree. Some of these signals may be time-modulated, as a receptor with a molecule that fits half the time will send half the overall signal as better-fitting molecule might.
You only need a toolkit of a certain number of receptors to generate unique signals for an arbitrary number of chemicals. Each combination of receptor-response “fingerprint” is unique; each scent need not have its own unique receptor.
Your immune system also works or you’d be too dead to type this, which suggests that a limited toolkit is quite sufficient for recognizing arbitrarily many new shapes. Instead, your infant body prepared a limited set of shapes ahead of time, and they’ve worked to keep you alive since. | 33 | 46 |
How do two particles "become" entangled? | I've been trying to understand entanglement but I fail to realize if the link between two particles is locked at random or if the particles need to originate from the same source (i.e:sub-particles of the same particle) to be entangled. | usually, it's in the "creation" of the particles. A spin zero particle decays into two spin 1/2 particles, and conservation of angular momentum tells you their spins must be opposite, for instance. Or a photon passing through a crystal that splits it into two photons, one will be polarized one way and the other polarized the other way. | 18 | 36 |
What would Milton Friedman say about a planned economy where the monetary policy was to increase the overall money supply more or less in line with global norms? | I guess this is a rangey type what if question, but Ive been watching some Milton Friedman on youtube because I realised I had no idea what he thought about anything. My loosest of loose grasps is the following:
Keynes|Friedman
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Government spends to stimulate the economy in key areas|Government backs off to give the economy space to stimulate on its own
Government prescribes policy (minimum wage, inheritance tax etc) to establish norms with reasonable limits|Let the market set its own limits - there are all sorts of circumstances Government can't account for
Communism failed because the government relentlessly targeted the wrong sectors for growth and investment while neglecting others|Communism failed because the economy was planned and closed, and the overall money supply was closed and fixed. Printing extra money just spiked inflation, like post-Versailles Germany
Could a Planned Economy with an independent Monetary policy and Reserve Bankwith a gradually increasing money supply, have been able to have sustained for instance the Soviet Union's economy in the 70s/80s/90s?
Or would a Planned Economy always be doomed to hyperinflate or deflate because the economy isn't diversified enough? Is Keynes really Fiscal where Friedman is Monetary?
Weird questions, and no shortage of misconceptions, I'm sure! Any answers would be helpful | The typical issue with a planned economy is known as "the knowledge problem": how do people coordinate their plans given the inherently linked nature of supply chains? E.g. how many cars are made depends in part on how much steel is available, but how much steel should be made depends in part on how many cars will be made. And it gets more complicated from there on. E.g. there are different types of steel, with different properties and some uses need very particular types of steel, while for other uses there's some ability to substitute one type of steel for another. And it's not like uses are easily defined, different climates, e.g. Siberia versus Ukraine can mean different trade offs.
In a market economy with market determined prices, this coordination is done through prices: if demand for a product is high then its price will rise, encouraging producers to supply more and people who can use substitutes to do so, reducing demand. This happens because of the profit motive.
The idea of a centrally planned economy is to do away with prices. Instead the central planner would send instructions to the steel makers about how much of each type of steel to make, and how much should go to the car makers. This would require not only solving a massive set of simultaneous equations, which just wasn't doable with the computing power available for most of the 20th century, but collecting and processing ridiculous amounts of data about what is made and what could be made, which still isn't doable.
Therefore the Soviet Union used broad brush plans, e.g. so many tonnes of steel, and gave the managers of firms some control over their production and purchases, there was a complicated system of inter-firm currency and credit, and then there was the rubble for personal purchases, along with government provision of things like housing.
The fundamental problems of the Soviet Union were driven by the information problems of central planning, monetary policy couldn't change that. | 11 | 71 |
What would our color spectrum look like if we had four (or two!) cones rather than three? | I had already asked this question on asksciencefiction, but was told it probably belonged here.
FWIW, I'm asking mostly from a writing perspective, as in I want to have a species that varies in number of cones, or the specific wavelengths of cones than humans, but I'm having trouble wrapping my head around the idea. I'm currently learning about visual sensation and perception in one of my courses this semester, if that helps at all with answers either | Imagine the specrum that your species can see is redshifted. They can't tell purple and blue appart, but can see infrared, and we can't.
You visit his ship, and asks you to press the 'infrared button.' You see four buttons, blue, yellow, red, and red. One of the red ones is actually infrared, but it's beyond your specrum so you can't tell.
Later, you are showing off some nice flowers and tell him about how you arrainged them into a rainbow of sorts. Since he can't perceive purple, he asks why there are two blue ones at the end.
I don't really know how cones would play into this, but from a writing perspective it would go something like that. | 23 | 40 |
ELI5 why do the touch screens of some mobile phones only work with the finger. They dont work with a pen or anything else. Why so? | URL or Text Here | Most touch screens with a hard surface, like on phones etc, use an effect known as 'capacitive coupling' (hence the name capacitive touch screen) to sense a press. The surface of the panel forms a capacitor with your body and the circuitry senses this.
It requires a slightly conductive pointer, hence why a hotdog will work but an insulating pen wont.
A resistive touchscreen (they are *slightly* squishy to press) relies on physical pressure, so any pointer will work with them.
Then there's infra red touchscreens too, which line up a row of sensors and IR transmitters (like a row of tiny versions of your TV remote) along the edges of the screen and sense your finger blocking the light from travelling from one side to another. They can use anything that isn't transparent to work. | 1,267 | 925 |
ELI5: Why I see a glorious and massive moon sometimes, with my eyes, but when I go to take a picture, it just looks like a tiny minuscule dissapointment? | One's perception of the size of the moon is heavily influenced by 'context clues', or other nearby structures. It's a bit of an optical illusion to say that the moon ever looks significantly larger or smaller.
When you take a picture, you lose many of these context clues and your brain interprets the picture differently than looking out over the horizon, so the effect is different inside your brain. | 16 | 19 |
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How does raising the interest rate help inflation? | It certainly appears that it only removes lower wage people from accessing loans, lowering the overall spending for the economy.
What am I missing? | Raising interest rates raises lending interest rates from banks, once rates rise this discourages taking loans including credit cards, this slows spending, when spending slows demand drops, when demand drops prices drop. It also encourages people to save money because interest rates are high so people will put money away into savings rather than spending on expensive stuff, and paying down debt to avoid higher interest rates from banks. | 30 | 34 |
Eli5: How does it come we notice when we get direct eye contact with another person? | There is something that makes you know when you have that direct eye contact with a person, even though they might stand meters away from you and you are surrounded by other people too.
What makes you know when you have that eye contact? Because even if there is someone that is standing almost right behind me I know when someone that is standing let’s say 6 meters away is looking at the other person or when they are looking at me. | Eye contact was very important for our ancestors, to find potential mates or threats. Because of this our brains developed a "super power" when it comes to eye contact, reading the miniscule changes in the eyes that indicate we've made contact. Note that this system is hyper sensitive so it can trigger a lot of false positives (thinking there's eye contact when there's not). | 69 | 72 |
Why are so many materials opaque? What's special about transparent materials like glass that sets them apart? | Also, why do other EM frequencies outside of visible light go through so many materials so much more easily? | There are two requirements for transparency:
1. No absorption in the visible EM spectrum. Absorption in the visible spectrum is usually associated with electronic transitions in the material. Some of the most common materials we use like plants and metal happen to have absorption in this region but most organic compounds actually have none. They are opaque due to reason two.
2. None or very few interfaces. Most materials like paper or cloth are white because unlike glass they don't have one homogenous shape, but instead consist of countless little strands of material. In this instance, the light gets scattered instead of passing through like through glass. Essentially it bounces around inside the material due to reflection and refraction. This gives it a white but intransparent appearance. Take a transparent crystal and crush it into powder and it stops being transparent. Naturally occurring materials have tons of little defects, rough surfaces, inclusions and so on that transparency would be extraordinarily rare.
Combining the two just doesn't happen a lot with natural materials, since being crushed into tiny bits or being a messy combination of several materials is kind of the default state of most matter in nature.
​
edit: Minor corrections: Saying that transparency is rare is actually kinda wrong. Water is transparent since its shape is defined by its container and always forms a homogeneous transparent body (unless heavily contaminated).
Regarding absorption: Metals (or conductors in general) are also a bit of a special case since they can also reflect light instead of absorbing it. No interactions with the visible EM spectrum would be more physically correct if a bit unspecific. | 1,081 | 2,157 |
ELI5:How does Antivirus work? | I expect others will chime in with more detailed answers but for an ELI5 it works in a few ways.
Firstly it scans for programs people have identified as viruses/malware. A virus may be a file on your computer or it may be just a part of a file on your computer the virus has modified. These are scanned everytime a file is opened from the hard disk. Because a new virus may be found and added to the database your computer also needs to be scanned periodically to make sure nothing slipped through the net.
Secondly it detects suspicious behaviour. For instance one program editing an existing program on your machine is rather dodgy. There are a few applications that would do this (think AppStore or Updates) so if you exclude those anything else attempting to do that is likely dodgy.
In order for virus scanners to detect viruses it needs to make sure it gets priority over everything else which is why they usually get a bad rep as this low level tinkering/invasive scanning slows machines down and can do rather annoying thing like giving false warnings.
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How does the body keep itself warm? How does it raise it's own temperature when you're ill? | The main mechanisms to conserve/produce heat are (1) vasoconstriction to decrease blood flow to extremities and skin surface, (2) shivering, (3) decreasing sweating and (4) increased energy production via metabolism.
When you're ill, this normal homeostasis is dysregulated, and, as an example, you can have shivering even when you are already very hot (e.g. chills). | 14 | 36 |
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ELI5: Why is it that waterdrops can't be bigger? What's stoping water from forming like the size of a golfball or even bigger? | Water drops are held together by surface tensions, and the hydrogen bridges that create it.
Whichever force is applied to the drop will "battle" with surface tension. If the force is bigger than the tension, the water drop breaks. If not, the water drop stays together.
Here on earth gravity is the most common force, when the drop is somewhere on the ground, or dripping off something.
In space, for example on the ISS drops of water can be huge because gravity doesn't apply anymore. | 21 | 19 |
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Does philosophy arise due to the limitations in our language? | It occurs to me that most philosophical enquiries revolve around the question “what is XXX?”. For example, in Republic, Plato discusses what Justice is; in Being and Time, Heidegger explores what “being” is. The branch Aesthetics ask questions about what beauty is.Hence i would like to ask to what extent is philosophy about defining words that we use in an everyday sense that we are not conscious of the real meaning most of the time? And this leads to the second question, does philosophy arise due to a limitation in our own language? | Wittgenstein would say it’s not limitations in our language, but it’s a temptation growing out of language itself. In *Philosophical Investigations*, he says this:
>Philosophy is a struggle against the bewitchment of our understanding by the resources of our language [paragraph 109].
For him, a lot of philosophy is driven by our tendency to suspend our everyday use of words and to try find some pure, abstract meaning of them that would lurk behind all their uses. Wittgenstein urges against doing philosophy in this way. He sees the job of philosophy not as the search for new fundamental explanations about the world, but rather as describing what we in some sense already know but distort in our effort to get past the ordinary:
>Philosophy just puts everything before us, and neither explains nor deduces anything. [paragraph 126]
But again, he denies any notion that we are constrained or limited by our language, as though there could be some beyond language we could access that would somehow satisfy a craving for the abstract. | 75 | 73 |
Why are there hydrating creams, gels etc for the skin of the face and the body? Doesn't water get to every skin tissue to hydrate it? | There are three main types of moisturiser:
Occlusives: create a barrier to “seal” moisture in
Emollients: usually contain a high level of fatty/oil ingredients and aim to repair the skins barrier
Humectants: attract water to the skin
The type you use depends on the issue. If you’ve got chapped lips or broken skin any where, your skin won’t do it’s job very well of holding in moisture but it also leaves the skin open to bacteria. This is where occlusives like Vaseline help, it creates a complete film over the skin.
Emollients are good for dry and flaky skin. Dry skin usually has a disrupted lipid bilayer and emollients contain ingredients which try and act as a replacement to our natural oils and fatty acids. This helps “heal” the skins barrier and allows it to retain moisture.
Humectants are hydrophillic* and attract water to the skin. Hyaluronic acid is a good one. This creates a “plumping” affect and is good if you have wrinkles or fine lines. These types of products shouldn’t be used if the air is dry as it can actually cause trans epidermal water loss.
The products are less used to actually hydrate your skin but more to help your skin retain its own moisture better
*edit for error | 4,724 | 4,017 |
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ELI5: What's the relation of video resolution to screen resolution? | I mean if I have HD display and can still run 4K videos ... Even if there are not enough pixels
I may have wrong preconceptions | Screen resolution is the maximum number of pixels a screen can display, whereas video/image resolution is the number of pixels that particular piece of media has. It's of course possible to display any image on any screen, but there are some drawbacks if the two resolutions don't match.
If your image resolution is larger than your screen, it has to be scaled down in order to fit on the screen. By reducing the resolution you lose some of the detail in the image, so a high-resolution video scaled down to fit on a low-resolution screen looks pretty much the same as a low-resolution video that matches the screen.
If your video is smaller than your screen, displaying it 1:1 would cause it to only take up a portion of the screen. In order to make it fit it has to be scaled up, increasing the resolution to match that of the screen. However, because it's not possible to generate new detail in an image by just scaling it up, doing this causes the resulting image to be blurry and/or blocky. | 21 | 55 |
how would you explain x^-1 and x^1/y? | How would you explain taking a number to the negative power?
I don't understand how that would be the reciprocal of x!!
I also don't get taking a number to the reciprocal of something like 4^1/2 how is that the square root of 4?
| Well, for the first one think about it this way. If you multiply two numbers with the same base raised to an exponent, you simply add the exponents: a^x * a^y = a^x+y. Now what happens if you divide by a? Lets say a^3 / a = a^2. But that's exactly the same thing as saying a^3 * a^-1 = a^2. So by comparison a^-1 must be the reciprocal of a , if we follow the rules of multiplying two numbers with the same base.
It's the same kind of idea with raising something to the fraction of a power. See if you can prove it to yourself. | 68 | 23 |
Why can influenza infect a person multiple times, but once a person is infected with measles, they gain lifelong immunity? | Primarily because there are multiple strains of influenza that circulate differentially depending on a variety of factors. Influenza also has a high rate of mutation, which the means the prevalent strains circulating at in given season have changed enough that your immune system doesn't recognize them. Also, immunity to pathogens varies significantly depending on the antigen molecules (usually) on the surface of the virus or bacteria: Some are more easily recognized by the immune system than others. | 108 | 135 |
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ELI5: What makes the value of a stock go up or down? | Supply and demand.
There is a limited quantity of each stock. When there are a lot of people selling but only a few buying, the buyers have more control of the price, so it goes down. Conversely, when there are a few people selling and a lot buying, the buyers control the price so it goes up. | 12 | 30 |
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ELI5: What's the difference between a subsidiary of a company and a division of that company? | Imagine you own a big supermarket with many departments, meat, sea food, produce, paper goods, etc. Each department would be a 'division' of the company. Everything gets sold at the same registers, and the stock crew fills up all the shelves regardless of what the product is.
Now you buy a deli across town. You own it, and have someone else running it for you. If someone buys a loaf of bread at the deli, they pay for it there, not at your supermarket. The deli and the supermarket might have different insurance companies, sell different brands of soda, etc.
If you're the 'corporation' the deli and the supermarket are both subsidiaries. | 418 | 274 |
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ELI5: Why are some people seemingly born with good time and money management skills while others need actual training to become decent at it? | People have different life experiences. If you had parents who discussed money in front of you, gave you an allowance and encouraged you to save to get things you wanted - you would likely grow up to manage money well. Likewise, if you grew up and had to beg your parents for money, needed to spend it right away before a sibling stole it - you would probably suck as money management as you grew older. | 36 | 39 |
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Why can you eat meats like beef and seafood raw/undercooked but not chicken? | Essentially different meats are subjected to different bacteria throughout their life, as well as during their slaughter and processing. Because of this, different legislation and regulatory levels are applied differently to meats. Chicken is of particular concern due to salmonella being present throughout the meat itself instead of just a surface contaminant which it is in beef. Therefore cooking beef, even just searing the outside ensures the bacteria will be killed, chicken however must be cooked entirely through. In the EU if salmonella is present on beef steak for example it is still fit for human consumption because it is assumed proper cooking will be performed to eliminate the surface contamination. If the beef is minced however and a positive result for salmonella is found, the meat will be reject because the salmonella will be present throughout the minced meat, not just the surface. Seafood contains different bacteria but are often very dangerous as well because they tend to concentrate bacteria present within dirty water. Therefore they are often placed in fresh clean water to filter themselves before being sent for human production. Fish are a concern because they tend to eat other fish resulting in bioaccumulation of bacteria and chemicals dangerous to humans. No meat is 100% safe for consumption, it's all about risk reduction and trying to ensure proper management from the farm level, the hygienic slaughter, cold chain refrigeration from slaughter to customer to ensure conditions which do not favour bacterial growth. | 174 | 251 |
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ELI5 How do civil engineers determine if a building is structurally sound after an earthquake? | They would assess the structural components for signs of failure or serviceability issues.
If they were looking at steel they could check and see if members or connections had yielded or worse. This might be evident through several different methods such as bolt holes being larger than they should be or members having localized sections with a reduced cross-sectional area and elongation.
If they were looking at concrete they could check for unusual cracks, spalling, exposed rebar, or again a multitude of other things.
They could also check member deflection. Typical floor members are generally limited to a serviceability deflection of L/240 under dead + live load. For example, if a floor beam was 20 feet long (240 inches) that beam would be limited to 1" of deflection over the span length under this condition. If the beam is sagging 6 inches something is probably off. | 10 | 23 |
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How can same volume engines have different HP/torque/etc.? | The displacement of an engine is not the only factor contributing to work done by the engine. The compression ratio for one will change the power output (the more you squeeze the air and fuel the more power you get out). Intake and exhaust manifolds will affect how effectively air can enter and exit the combustion chamber (less pressure loss on the intake will help get more air into the engine, less back pressure on the exhaust will help clear the chamber to allow cleaner air in). How well the engine is tuned as well will play into the performance of the engine (igniting the air/fuel at the right time to make sure the mixture ignites when it is compressed the most). There is much that plays into HP/torque than just volume | 70 | 156 |
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ELI5: If there's actually an advantage to using foam, solid or liquid soap over the other 2 | I've heard people talk about how one is better than the other but never really specify why.
There may be nothing better, but if there is which is the most advantageous to use and why? | A recent study has suggested that solid soap can retain germs on its surface. You can dislodge a lot of them by simply rinsing it off, but it does provide a minor benefit in that a dispenser type soap can help sidestep that problem. However, if reusing the bottle one needs to clean it thoroughly or else you're potentially just in the same boat, getting germs inside of it.
So a bar of soap may be less desirable in a social setting like a public restroom, where it can pass through many hands and not be subjected to the tightest level of cleanliness. | 22 | 60 |
ELI5: What gives different people's houses their unique scent? | I think I could be blindfolded and know whose house it is just from smell, and objects from there also carry the scent. Is it just perfumes and air freshener or something else? | It's usually based upon what kind of pets you have, what kind of laundry detergent one is using, what you eat/cook. And a ton of other factors like how well your house is kept/having no moldy foods, what temperature it is, etc... | 10 | 16 |
[Journey to the Center of the Earth] In 1880, Sir Oliver Lindenbrook leads a successful expedition to the center of the Earth. How does this alter human history? | [Here's the Journey to the Center of the Earth IMDb Page, for reference.](https://www.imdb.com/title/tt0052948/) | Minimal amount of change as it'd be a curiosity more than a resource until post ww1. As African colonies destabilize and become independent from their respective empires the major nations would seek to colonize and exploit the inner world. Wars fought over any access to the inner world and proxy wars for territory within the inner. Without a stabilizing force in Germany ww2 would happen and much how the remaining colonies were split up after ww2 in our time the same would happen but would include the inner world colonies. Unless vital resources like oil uranium or similar modern valued mineral wealth or lumber is available the inner world would become largely ignored by the surface world and develop itself similar to South America or central Africa with minimal beneficial aid from the surface beyond exploitative practices and shake and bake operations. At best by 1990s the inner world would resemble a politically stable but distinct world like South America at. Worst it turns against itself like subsaharan Africa attempting to unify but divided over regional and ideological lines. | 10 | 15 |
ELI5: What does "open source" mean when people are referring to software and programs? | When a programmer works on an application, the file or files they produce are usually called "source code", and those files are used by a compiler to build an executable program.
"Open source" means that a project team has intentionally posted their source code publicly, so that anyone can inspect it. Other programmers can read the code to see exactly how the program was built and what it does, which allows others to learn from the code, audit it for bugs or security issues, and potentially contribute patches back to the project.
Many open source programs are free to use, and people tend to associate the two ideas, but it's not necessarily a requirement.
You can find many open source projects on websites like GitHub or BitBucket, which provide free hosting for those projects. | 66 | 119 |
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