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ELI5: How come I fall asleep so easily in a car or on the bus (where there are bright lights, noises, etc.), but I find it difficult to sleep at night in my bed?

I think it has to do with the constant subtle rocking motion created by the movement of the vehicle. It beckons you back to a simpler time of night lights and binkies where sleep is about all you really do other than eat and shit

[Half-life ] why was the combine trying to prevent citizens from leaving doomed city 17?

The combine knew the citadel was going to blow, any citizens that stayed would be killed and probably turned into a zombie that would cause the combine issues later. I can't see any reason for them to dedicate valuable troops to stopping them.

The Combine is a multi-universe empire with vast quantities of disposable assets. At the same time, they KNEW that someone inside the Citadel was responsible for sabotage and its destruction. Their troops were expendable, containing the threat and the individual who destroyed the Citadel was of far greater priority than a few hundred troops, or a thousand civilians.

What type of energy is released during matter/antimatter interactions?

Would it just be light and heat? What particles would be created in this process?

Matter/antimatter collisions can produce all sorts of particles, but the likelihood depends on which quantum numbers need to be conserved and what sort of momentums the particles bring to the table during annihilation. The simplest annihilation event, say for an electron/positron pair would be two gamma photons.

[Star Wars] What was Snoke doing during the galactic civil war? Did Palpatine not sense his presence as a powerful darkside force-user?

We simply don't know enough about Snoke to actually give an answer other than he was around during the Civil War. It could be that he wasn't a powerful force user at the time, potential perhaps but not necessarily strong.

ELI5: How is there no center of the universe?

I've spent the last 10 minutes googling the center of the universe. The consensus is that there isn't a center of the universe, and everyone is raving about this 'balloon' example, where galaxies are like dots on a balloon.. however a balloon has a center so I don't see how this answers the question. If the universe is expanding evenly, I would assume there would logically have to be a static center. If it isn't expanding evenly, I would expect it to have a changing one.. but either way I can't see how there isn't one at all - unless the universe is infinitely large.

The balloon explanation is an analogy. It asks to you imagine the universe as the ***surface*** (and this is key) of a balloon. As the balloon expands, all points on its surface move away from one another. Furthermore, the *surface* of the balloon has no centre. The fact that the 3D balloon has a centre is not relevant to this analogy, because we are only interested in its surface. Additionally, the surface has this property: pick any point P and the further a point is away from P, the faster it moves away from P as the balloon expands. This means that there is no centre that all points are moving away from. Now, the universe is not a 2D surface, but the same idea applies: as it expands, all points move away from all other points. In addition, whichever point P you pick as a centre, points further away from P move away from P faster than points closer to P. Hence, like the balloon, the universe has no centre. EDIT: added explanation of why there is no centre

[Attack on Titan] How frequent does the Survey Corps conduct expeditions beyond the Wall?

I’m currently rewatching some of the AoT OVAs and when Erwin gave the order for the 48th Expedition beyond the Wall to commence, I just realized; **In the entire show as a whole, exactly how frequent are Survey Corps expeditions beyond the Walls to garner only (as of Season 1 of AoT) only 57 expeditions?** I mean, *57* expeditions by the time of Trost within a period of 105 years? Really? This isn’t exactly the Apollo space program. How was it that only 57 expeditions outside of the Wall has been conducted? I get that the Survey Corps isn’t exactly well liked by senior government officials, but I don’t buy that *only* 57 expeditions have been conducted. I’d imagine at least 100.

That's a survey every 1.8 years. That's pretty reasonable for all it entails. That 2 year period between the expeditions gives them time to train new recruits, smooth out plans for once they're outside the wall, and time to get all the supplies they need. This seems like a fairly decent turn around for the tech level that they're at.

ELI5: If cat's and dog's hearing is so much more sensitive than human hearing, why are they not bothered by things such as traffic noise or TV noise?

I was thinking about this the other day when I was watching TV the other night and my dog was happily dozing next to me even though the TV was a bit too loud for me.

Cats and dogs can hear a wider range of sound frequencies. That does not necessarily mean that they will experience noice to be any louder then what we experience it to be. Also, dogs tend to not give a f*ck.

ELI5: Why isn’t Braille just raised letters? Wouldn’t it make more sense if it was?

Not for reading it quickly. It's designed so that each letter is distinctive by touch - Braille readers don't have to feel each letter individually, they can just run their fingers over a row and read it all at once. Another thing is, for someone who's born blind, they might never have learned what "normal" letters looked like - and would not need to. Also, Braille is easy and cheap to produce. You just have a grid of 3x3 or whatever punches, and for each letter, you only activate part of the needles - actually a lot easier to "type" than a regular typewriter where you need dozens of buttons and individual arms.

What is dialectics?

Ive had trouble pinpointing a definition for Dialectics, from what I grasp (which could be totally off base) is that it deals with how things change and half an effect om each other. But im still unsure of what it is. Is it a mode of thinking? Is it an analytical method? Is it a form of logic? Is it a form of argument or rhetoric? Is it something one could put into practice? Are there any easy to grasp resources that give a good explanation?

The word "dialectic" comes from the Ancient Greek *dialektikos*. Originally, a dialectic was a conversation between two people. In Plato's dialogues, one person (usually Socrates) would question another person. The answerer would try to provide a definition of some concept (eg, justice, piety, knowledge, moderation, etc). The questioner would try to show that some of the answers contradicted each other. In this way, dialectic became a method of inquiry directed by a question-and-answer process. In his logical works, Aristotle refers to the dialectic as a standardized method that students at the Academy would use to practice their skills in logic. Plato's and Aristotle's dialectic inspired Hegel's dialectics. However, Hegel thought that that dialectic couldn't provide substantive knowledge. In Plato's dialogues, Socrates may show that some of his interlocutor's propositions are false, but his question-and-answer process doesn't prove that something is true. Hegel wants his dialectic to lead to positive, substantive determinations. To put it very simply, Hegel maintained that things pass through three moments: (1) A moment of understanding. In this moment, the determination seems stable. (2) The "dialectical" moment. A one-sidedness or restrictedness in the determination comes to the fore, and the determination passes into its opposite. The determination is both cancelled and preserved; the determination "sublates" itself. (3) The "speculative" moment. This is the positive result from the unity of the opposite determinations. Most people probably know about dialectics through Marx. Marx was a Young Hegelian who applied a version of Hegel's dialectic to his investigations. However, there is controversy over how Hegelian Marx was during different points in his career. Georgi Plekhanov coined the term "dialectical materialism" to refer to the philosophy that Engels drew the outlines of in the *Anti-Duehring*.

At what point can a mass of cells be considered a living being?

Some time ago I was talking to my brother about abortion, and one thing he said is: at what point can we consider a mass of cells a human and living being? Is there an exact point at an exact time where some cells become a living thing? How can we decide whether or not abortion is moral? Is a living being _living_ if it is conscious? And what about people in coma or vegetative state?

Single cell organisms are a thing. A better question might be: When are these cells considered protected life? When does consciousness actually occur is another great question. What is consciousness, exactly? Is it a will? Or a lens? Or a complex illusion that looks like one of the aforementioned? Does a sphex have consciousness? A dog? An amoeba? Is unconsciousness "dead brain", or "sleep state brain"? Hard to tell if you don't have a definitive answer for what is consciousness. Everything is a moral issue if you frame it as such. How you frame it is pro and con, by definition of morality. Is abortion right or wrong? Probably depends highly on the circumstances. Beliefs about which life is worth protecting and the definition of, or weight given to consciousness, are also major considerations when examining the morality of abortion.

Hypercharismatic people

Has there been any research/writing done on "hypercharismatic" people? The likes of Adolf Hitler and Charles Manson who seemingly had a special kind of charismatic ability to possess and manipulate people, to lead a personality cult even in their personal lives and hence without propaganda tools -- is this a very rare personality trait or merely a combination of narcissism and high intelligence? Or possibly both?

You can't really go wrong starting with Max Weber's *On Charisma and Institution Building* for a sociological perspective on the phenomenon, especially his observation that the 'charisma' of an individual derives from the symbolic needs of a society (or social (sub)grouping thereof), especially when it is threatened. For example, Hitler and Manson were charismatic, sure, but only *for certain 'kinds of people'*, under particular sociohistorical circumstances. According to Weber, a group's need for a charismatic figure precedes his or her appearance and rise to power as such. To put it bluntly, in this sense charisma is highly contextual. Charles Manson may have been charismatic to runaway teens in Southern California of the 1960's, but he was definitely *not* charismatic to lawyers, judges, and juries in subsequent courtroom proceedings.

ELI5: The Watergate Scandal to a Non-American.

President of the United States found out that people working for his re-election, including highly placed members of the White House Staff, were involved in a break-in of the opposition political HQ. After learning about this break-in, the President authorized an attempt to cover it up. Wider issues: President abused the power of his office by directing the CIA to interfere with the FBI, secretly taped conversations in the Oval Office then asserted that he could not be compelled to turn those recordings over to a judicial proceeding, and was responsible for a political operation that broke many laws while engaged in winning an election.

Are all ants in a colony genetically same?

Since all the ants in a colony come from eggs laid by the queen ant, are all of the ants genetically similar? Also who fertilises the queen ant?

Similar, but not the same. Precisely how similar depends on a whole bunch of details. If an ant colony has only one queen, the workers are all sisters. During her youth, before the queen founded the nest, she mated with one or more males. (The ant mating season is when you see winged ants flying around; those are males and fertile females looking for mates. The males die after mating, while mated females shed their wings and become queens.) The queen stores the sperm from these matings, and will use it to fertilize all the eggs she will ever lay. How closely related the workers of a single queen are to one another depends on how many mates the queen had during her mating period. If she only mated with a single male, the workers are all full sisters; if she mated with several, they'll range from full to half sisters depending on whose sperm was used to fertilize a given egg. Many ant species may also form nests with multiple queens, either because the nest was founded by multiple mated females or because additional mated females joined as queens during later mating seasons. If a nest has multiple queens, the queens are often relatives, so in that case one queen's workers are something like cousins to another queen's workers. However, ant relatedness is also complicated by the weirdness of ant genetics. Male ants are born from unfertilized eggs, so they have no fathers, and therefore only one set of genes instead of two. This also means that if two workers share a father, they inherited the exact same DNA from him (unlike the usual situation, where two full-siblings inherit a random 50% from each parent). This increases the amount of genetic variation shared between two sibling workers: two full-sibling worker ants share 75% of their genetic variation, whereas two human full-siblings (for example) share 50%.

ELI5: Since the ISS is moving so fast, does NASA need to account for doppler shift in the radio signal? How do they account for this considering the ISS uses FM?

NASA (and all communications with fast moving satellites) use Dynamic Doppler Compensation, where the frequency of the broadcasts are adjusted progressively through the broadcast to ensure that the receiver maintains a solid signal on the correct frequency.

Are we prepared to handle a direct hit from a CME?

Are there procedures in place for when the Earth is hit by a coronal mass ejection? What are they? What would be the short term effects? Long term? This is coming from a guy who just learned what a CME is an hour ago.

A CME occurs when an explosion on the Sun sends a ball of plasma (and magnetic field) off the surface of the Sun in some direction. If the CME is aimed at Earth it could cause problems when it collides with the Earth's magnetic field, sending showers of high-energy particles through the Earth's atmosphere. The effect depends very strongly on the strength of the CME. An ordinary CME that hits Earth might cause problems for satellites, but would have no really bad effects. But really powerful CMEs like the Carrington Event in 1859 are different. They would be capable of frying all of our satellites (disrupting the Internet), and the giant transformers that are used in our power plants would be ruined. Because these transformers can't be bought off the shelf they would have to be built, and the power outages would last for months. The silver lining would be "Northern lights" visible from the equator. These problems can be avoided by shutting down vulnerable electronics or hardening them against CMEs, but doing either would be enormously costly. Shutting down electronics would require reliable forecasts of dangerous CMEs like those we have today for hurricanes to justify the cost. Right now scientists are working on these forecasts.

How can the universe have a shape? This is mind-boggling to me...

I cannot understand the concept of [the universe having a shape](http://map.gsfc.nasa.gov/universe/uni_shape.html) If something has a shape than that something "borders" something else. Please read the link above (it's from NASA's official website). It considers three possibilities: 1) The universe is spherical 2) The universe is curved like the surface of a saddle 3) The universe is flat "like a sheet of paper", and infinite in extent In the first scenario, the universe being a sphere, what surrounds that sphere? It does not say that it is infinite, so there must be a "beyond it", right? I could say more or less the same to the second "saddle" hypothesis. In the third case, if the universe looks like an infinite sheet of paper, I understand we couldn't travel to its extremities to reach the end of its extension, but how about traveling "up" or "down" its "height"? Does that make any sense?!? Please help, I'm having an existential crisis... (hopefully the matrix will open up)

Actually, the terminology is somewhat confusing, but they are not talking about the shape of space but its global curvature. The universe could have a global curvature that is like that of a flat sheet of paper, i.e. zero, but it doesn't have to be a flat sheet of paper. Also, the universe could actually have a shape on top of having a curvature. Take a toy universe you are probably familiar with if you have played computer games. If you wander around on the map of an old final fantasy game or an asteroids game, if you keep going in one direction, you'll just pop up on the opposite side of the map at some point. All those maps are flat, but have a toroidal "shape".

Could the force count as a type of magic?

Depending on how you classify magic, then yes. Most of the aspects that we would normally associate with magic are there. Individuals pulling power seemingly out of thin air, techniques which require access to hidden knowledge and arcane writings (i.e. Sith holocrons,) and obfuscation to the point of where force users are the basis of galactic superstition, are all common to the force . There are few limitations to what the force can do. You can talk to the dead, shoot lightning from your hands, make someone see an illusion, absorb a blaster bolt (or a lightsaber strike) with your body. With the proper amount of preparation, the force can even create and extend life through parallels to necromancy (Palaptine is essentially a Lich.) Of course, if you were to sufficiently restrict your definition of magic, then it's easy to disqualify the Force.

ELI5 If cold is the absence of heat, how does our bodies perceive cold?

Our body feels cold as the rate at which you lose heat. That's why materials with high thermal conductivity (like metal) will feel colder than stuff like wood, even if they're at the same temperature.

ELI5: How did we figure out how cold absolute zero is?

From what I understand, it can’t be reached - so how do we know exactly how cold it is? EDIT: people seem to be misunderstanding, I am NOT asking how cold it is. A quick google search reveals it is about -273.15 C, what I am asking is how we know this for a fact, given it is not reachable.

Plot the volume of a gas (constant mass) against it's temperature. As you decrease the temperature the volume will start approaching zero. The temperature where you would expect an ideal gas to have zero volume is very close to -273C. ​ And of course, the more complicated the gas, the more it will deviate from this trend, hence why helium, the most ideal of all real gasses, is the gas we can get closest to absolute zero.

CMV: I don't think the universe has to have a beginning or an end

It's hard to understand the concept of infinity since all that we know has had a beginning and likely will have an end. I understand the pursuit to know what started it all, but why does there have to be a beginning to everything. What if everything always has existed? I guess I'm conflicted. I know that scientific evidence points towards some cataclysmic event in the past that lead to an expanding universe, but I never hear any talk of an infinitesimal existence. Why is this not considered more as a possibility?

> why does there have to be a beginning to everything The Big Bang is the problem. We've got this thing that happened billions of years ago with no explanation to what caused it. All we know is that the universe was some point mass and suddenly decided it wanted to be bigger. So this begs the question, what was before this? Was the universe always just a point mass until something happened? If so, what was that something? What's going to happen in trillions of years if we keep expanding at this rate? Is the universe in a cyclical expansion, contraction, bang, expansion series? If so, what's causing that cycle? And so on. I think infinite existence is still considered in some circles, but the problem is that with the data we have it seems to suggest that there had to be some beginning and will eventually be some end.

ELI5: Why do muscles stiffen and lose flexibility? And why does stretching sometimes feel good and sometimes hurt?

Lots and lots of reasons. But ELI5. Muscles get stiff because they get used to being short and all the fibres get tighter and closer together. It can also be because of literal knots in the muscle. Imagine you cut a piece of string in half, to make it whole you have to tie a knot in it. The string is shorter but it’s whole. These are knots and there can be thousands. Thanks to healing and massage those cuts can be healed to normal. Pain when stretching is normally due to excessive tearing. It’s your body screaming at you to stop. It feels good because of other reasons that I’m not clear on.

[Disney: Snow White and the Seven Dwarfs] Who spread the rumors of Snow White's demise and burial?

Near the end of the movie, the storybook framing device says that Prince Charming heard rumors of the beautiful princess in a glass coffin in the forest. He searches, and this is how he finds and wakes Snow White. But...the Wicked Queen was dead, the animals don't talk, the Huntsman only knew that she had fled to the forest (not that she had died or been interred), and the Dwarfs appear to spend most of their time mourning at her side. So where did the rumors come from? Who knew and spread them?

People who were for whatever reason walking through the forest- travelers, woodcutters, hunters, etc- who stumbled onto it. Indeed, that's why it was rumors. The people who knew enough to give detailed information weren't talking, so everything was coming from "Hey, steve said he saw a dead lady in a glass coffin in the middle of the woods while hunting. Fucked up if true, right?"

ELI5: Why does wrapping a plastic bag around your credit card help it scan?

Sometimes when my credit card begins to go bad the cashier will wrap a plastic bag around it and magically it will begin scanning properly. Why does this help?

Well its not magic, all it does is create an air space between the magnetic strip and the reader. There's an air gap (actually just inert plastic) coated over the magnetic strip in credit cards. With extended use that plastic coating wears away and the strip gets closer to the card reader. Im not 100% on the reason that air gap is important but it has something to do with the reader picking up the right data from the strip.

Is O(1) really constant? Or just theoretically?

Take a database operation where you are looking something up by an index. The lookup is O(1). But doesn't the computer technically have to scan for that index key...which would, practically, take a variable amount of time? What if the entire index grows? Doesn't that make that variable time to find the key longer on aggregate?

An example of a real O(1) operation with no assumptions. Given an an integer N, is N even? You only need to check 1 bit. This however does assume that our model of computation is a random access model. Lots of O(1) operations rely on assuming constant time math operations on arbitrary numbers which is clearly false, but is true if we bound our numbers. So for instance Hash lookups are *amortized* constant time if we assuming hashing keys is constant time.

Was Nietzsche A Liberal On Criminal Justice?

I mean, take passages like this: >66. PUNISHABLE, BUT NEVER PUNISHED.—Our crime against criminals lies in the fact that we treat them like rascals. >70. EXECUTION.—How is it that every execution offends us more than does a murder ? It is the coldness of the judges, the painful preparations, the conviction that a human being is here being used as a warning to scare others. For the guilt is not punished, even if it existed—it lies with educators, parents, surroundings, in ourselves, not in the murderer—I mean the determining circumstances. -F. Nietzsche, *Human All-Too Human* These, and similar statements expressing sympathy with criminals and those who are condemned as "evil" by society, can be found throughout Nietzsche's works. Was Nietzsche an early advocate of rehabilitation? I specifically remember him remarking (perhaps in *The Dawn*) that it would be better for society if criminals were put to work instead of being allowed to rot in prison. Can we safely account this as part of Nietzsche's transvaluation of values?

There's not much to account for, really. This seems to follow from Nietzsche's general skepticism about moral responsibility and free will. Nietzsche argues that it is impossible to be responsible for yourself in any ultimate way, so it seems natural that he would object to the ways in which the justice system pretends like it can hold people responsible for themselves while not holding everyone else to blame.

Would rubbing 2 ice cubes together in a sub-zero temperature environment cause enough friction to melt the ice cubes?

I realize that the ice cubes would be less likely to melt the colder the environment became, so as a setting: rubbing the ice cubes together with your hands in -5°C (but other scenarios and all that are welcome!). A question that came to mind since winter and icy conditions have set in (at least where I am...) :(. I would also add: since water seems to lower the coefficient of friction on ice, would the thin layer of water created on the ice cubes from the friction in turn lower friction to a point that the ice cube would no longer melt?

Ice cubes melt because they absorb enough energy to break the inter molecular forces that make them solid. Cold environments make water freeze because heat flows from higher energy areas (warmer, the water) to lower energy areas (colder, the environment) in an attempt to become equal (2nd law of thermodynamics). Rubbing the ice cubes together, putting your hands on them, or increasing the pressure on them will all cause them to absorb energy, or melt. It's really a battle of how fast you can melt the cubes to how fast the environment absorbs their energy.

Just how specific should my research interests be by the time I apply to grad school?

I've been working in labs with the goal of going to grad school since my freshmen year and since then I have also worked on several independent research projects in psychology. I am applying to social psych programs in the fall and I am just a little concerned that my interests are a little too broad. I have narrowed down my interests to a hand full of topic areas within social psychology and I know generally what I want to be researching. However, if someone asked me point blank "What study would you run if you could do it tomorrow?" I wouldn't know what to tell them. TL;DR Applying to social psych programs in the fall. I've narrowed my interests down to a small set of topic areas but I still don't have a running list of specific project ideas, specific research questions, and study ideas. Is this too broad?

It's good to have a fairly specific idea of what you'd like to do, and even to be able to propose studies you might consider working on, but it's not necessary and in fact it can hurt you in the long run to be too inflexible about that. The reason is that your research will not be solely dictated by your own interests, but by the interests of your advisor, other collaborators, current research questions in the field you work in (which you won't have a good handle on until you read a couple hundred papers, probably), and what you can get funding for. As others have said, focus on finding a professor who works on things that you find interesting, and apply there. Your interests are going to change anyways, you almost certainly will not end up doing your PhD on what you thought you would when applying (although it will probably be related to that to a decent extent).

[Harry Potter] Why is there no Scottish students in Hogwarts when the school is located in Scotland?

I was looking up the locations of the various magical schools in Harry Potter and I realized that Hogwarts is apparently in Scotland, not England like I had thought. I was thinking about it and realized that I couldn't remember a single student with an Scottish accent in the movies, so I looked it up and found out that there was exactly 4 people in Hogwarts that were actually Scottish; Minerva McGonagall, Alastor Moony, Rowena Ravenclaw and Oliver Wood. How is it that there is only 4 people in the entirety of this school from Scotland, when that is where the school is apparently located??

There are Scottish students but the series never made a point of pointing them out unless they had a major focus. For example, Oliver Wood is Scottish and is either a Half- or Pureblood, Cho Chang is Scottish as well... The McGonagall family are also strongly Scottish, they hail from Caithness. The Quintin family are Scottish and they produce the Wizarding Scotch known as Quintin Black... The Ravenclaws were also Scottish as evident that the Sorting Hat described her beauty as "fair Ravenclaw, from glen," glen being a word for a valley in Scotland. There' also Modesty Rabnott and her sister Prudence as an implied example; Modesty was famously appalled by the treatment of the magical bird known as the golden snidget which was released during a Quidditch match so she snatched it out of the air and fled to release it elsewhere; she lost her house after being fined so went to staywith her sister in Aberdeen. Tyere is a national Scottish Quidditch team, but they aren't known to be very good compared to other national teams. There' also the team known as the Banchory Bangers who were both known for their poor skill and excessive post-match parties, but who were also permanently banned from play and dissolved in 1814 after they allowed the bludgers they wrre using to fly off into the night and into Muggle residential areas and for trying to capture a Hebridian Black dragon to use as their mascot, enraging it enough that it flew into a Muggle town. Edit: Damn autocorrect.

What's up with the Normal/Gaussian Distibution? What properties does it have that make it special? Does does one arrive at its probability density function?

The fundamental reason the normal distribution is so important lies in the *central limit theorem*. Suppose we have many random variables X*_1_*, X*_2_*, ..., X*_n_* that are independent and all drawn from the same distribution. For instance, we could be measuring the heights of a certain population and X*_j_* is the height of the *j*th sample who has been randomly drawn from the population. If we want to estimate the average height of our population, we can use the sample average as an estimate: > S*_n_* = (X*_1_* + X*_2_* + ... + X*_n_*)/n As n --> infinity, S*_n_* --> µ, the true mean of the population (this is the law of large numbers). The central limit theorem says that the sequence of random variables > T*_n_* = √(n)(S*_n_* - µ) "converges in distribution" to a normal variable with mean 0 and variance σ^(2), the true variance of the population. This means roughly that for large enough *n*, T*_n_* is approximately normally distributed. This is remarkable because it does not matter what the distribution of the heights were. The variables X*_j_* can have any distribution whatsoever (as long as it has finite variance). A rough way of understanding the central limit theorem is that, for sufficiently large *n*, the sample averages S*_n_* satisfy > S*_n_* ~ µ + σZ/√[n] where Z is a standard normal variable (mean 0, variance 1). That is, the sample averages are equal to the true population average plus some normally distributed error whose variance gets smaller as the number of samples increases. So we can write roughly > S*_n_* ~ µ + N(0, σ^(2)/n) The sample averages are about equal to the mean plus some normally distributed error with mean 0 and variance σ^(2)/n. It does not matter what distribution the samples follow, as long as the variance is finite. --- Other important properties of the Gaussian function or normal distribution: * The normal distribution has several other properties that make it "nice". * For instance, if two random variables *X* and *Y* are independent, then they are also uncorrelated. The converse, however, does not hold. Uncorrelated random variables need not be independent. However, if you know that *X* and *Y* are jointly normally distributed, then you *can* conclude they are independent given they are uncorrelated. * The normal distribution is stable. Linear combinations of normal variables are also normal. (This is part of the reason why they appear in the central limit theorem to begin with.) * The Gaussian function is also an eigenvector of the Fourier transform (in general, the Hermite polynomials multiplied by a Gaussian are eigenvectors). This makes many calculations involving Gaussian functions and Fourier transforms very easy. * You can also show that this eigenvector property means that the Fourier uncertainty principle (called the Heisenberg uncertainty principle in quantum mechanics) is satisfied precisely for Gaussians. * The velocities of an ideal gas are distributed according to the Maxwell distribution, which is a multivariable Gaussian function.

ELI5: why do human teeth grow so differently and badly? Why are braces almost mandatory for so many?

They're not really mandatory or even almost mandatory. Braces are primarily a cosmetic preference that the U.S. engages in *far* more than just about any other country. Most people could easily live just fine with crooked teeth. Barring severe cases of malocclusion or impacted teeth, crookedness only really makes flossing more difficult but has no significant impacts on health.

CMV: I am an American, and I support Russia's annexation of Crimea.

Hi all, Disclaimer: I am an American, politically active, work in and around politics, center to left-wing, and not a paid Russian shill or any other absurdity. I actually find it quite sad that I have to put this disclaimer here. I just know this is going to be massively controversial, but it seemed relatively topical with the Russian election, all of the stuff going on in the UK regarding the Russian assassinations, in the US with the Trump/Mueller Russia probe spat, and the general flavor of half of the /r/worldnews top posts. So, without further ado, here goes. Due to my reading of history, politics and international relations, I support the Russian annexation of Crimea despite the contentious legal issues surrounding it. I've arrived at this view through trying to understand the Russian, Crimean and Ukrainian perspectives on this, and not simply viewing the issue through the Western lens of 'Russia as an aggressor'; I think that this view is at least lacking nuance and often plain wrong, though of course occasionally borne out. Let's go through the events, as I see them. The situation in 2014 as I see it was this: Euromaidan protests in Kiev and other areas of Ukraine toppled a relatively 'democratic' (though highly corrupt) pro-Russian government, and replaced it with a relatively radical and substantively less democratic (though apparently still corrupt) Ukrainian nationalist government (which was anti-Russian, and pro-Western). All around the country, anti-Russian measures and legislature were enacted, and incidents of Russophobia, sometimes even violent, occurred. At this point, the Crimean local government authority decided to hold a referendum on Crimea's status in Ukraine. The Ukrainian government said they would not recognize any referendum held by Crimea on leaving Ukraine or joining the Russian Federation, and would use force to ensure the territorial integrity of Ukraine. Then, as we all know, a couple of days before the referendum the Russian airborne troops arrived in Crimea, sealed off the peninsula to the Ukrainian military, and the referendum went ahead. The referendum, as well, as we all know, was a bit of a shit show, with the Tatars boycotting the referendum and an outrageously high vote in favor of joining Russia, not to mention a paucity of choices on the referendum ballot itself. Subsequently, Crimea applied to become a federal state of Russia, Russia accepted, and boom, Crimea is now Russia. Etc. These are the facts of the event; I think this is a relatively uncontroversial presentation of what occurred. I'm not claiming the referendum was very legitimate -- just that it almost certainly did represent the will of the people. I'm not claiming the pre-Euromaidan government had a strong, uncorrupt democratic mandate -- just that the post-Euromaidan government had an even worse track-record. I'm not claiming Russia didn't send troops to secure Crimea before the referendum -- only that they did appear to act as peacekeepers and no shots were fired. I'm not trying to present the Russia Today version of this -- I'm just trying to present a neutral view. So here is why I think this was basically the right thing to do: * Crimea has been since 1783 a part of the Russian Empire, and then after the Soviet Union, barring a few of years of foreign occupation in the Crimean War 1853-1856, and the Second World War 1941-1944. So too is true of most of Ukraine, which may be relevant later on. * In 1954, the Russian Soviet Federative Socialist Republic transferred Crimea to the Ukrainian Soviet Socialist Republic, which appears to have been mainly for economic/logistical reasons, as the easiest access to Crimea is through Ukraine. * Looking to the situation today (or in 2014 when the annexation occurred) Crimea is overwhelmingly ethnically Russian and Russian-speaking, with 68% of the population identifying as Russian, and only 15% as Ukrainian. It seems to me that Occam's Razor and countless reports, denounced only as propaganda in most Western media outlets, ring true, given these facts: In the wake of an anti-Russian Ukrainian nationalist revolution, the basically Russian region of Crimea wanted no part of being in Ukraine and held a referendum to join Russia. Russia, for its part, acted as a legitimate peacekeeper in ensuring Crimea was not forcibly reunited with Ukraine by the military, and then accepted Crimea's request for annexation. The whole situation has made me think of a counterfactual to explain it to people who just don't see the 'human' or 'parallel' side of this. Suppose in 1991 it was the United States that fell apart, and not the Soviet Union. Suppose the US split into a bunch of chunks. Suppose that during this process, Texas became a part of Mexico. Then fast forward 25 years. Suppose the United States is resurgent -- Washington DC is once again a credible power, with real influence, and is suddenly no longer being pushed around after a hellish decade in the 90s -- and it is now exerting its influence on other powers around it -- like Mexico. Then suppose in Mexico there's a revolution, and the corrupt but relatively democratic pro-American government is pushed out by nationalist anti-American Mexicans. Suppose the government in Mexico City starts enacting laws that are anti-American, that disadvantage English speakers in Mexico, and there is sporadic anti-American violence. Then suppose that at this point, Texas says 'we want to go back to America' -- and the Mexican government says 'hell no, that's Mexican territory according to international law.' But then suppose the Texans said 'well, we speak English, and we identify as Americans, no matter if we're part of Mexico or not. We're having a referendum.' Then suppose that the United States inserted troops to ensure the Mexican Army didn't force Texas not to hold the referendum -- and then suppose that the referendum, which admittedly the minority Spanish-speaking Texans didn't vote very much in, comes back overwhelmingly that Texas wants to join America. And then suppose at that point that the United States annexes Texas. This would seem to be a directly analogous situation. The right to self-determination would seem to be equally legitimate to territorial sovereignty, and there are a multitude of cases where state sovereignty has been infringed in favor of self-determination (Kosovo comes to mind). **TL;DR Crimea is ethnically and linguistically Russian, and it always has been. It seems they voted to leave Ukraine in the wake of an anti-Russian revolution there, and Russia then annexed Crimea according to the wishes of the people. This was probably in opposition to international law, but was built on a legitimate mandate of self-determination.** So, there it is. A very long post, I know, so thanks and congratulations for reading this far. I really want to reiterate again that I'm trying to be neutral and level-headed about this -- I'm American, and not anti-Western or some The-Donald lunatic or whatever. It just seems Russia was honestly probably right on this one. What will change my mind: * Legitimate reasons Ukraine's territorial integrity ought not to have been violated in favor of self-determination after an anti-Russian revolution * Ways in which I've got the facts of the story wrong * Ways in which this scenario differs from the Texas counterfactual, possibly What will NOT change my mind: * Accusations that I'm a Russian shill or Putin-lover or anti-American or any other ad hominem nonsense * Arguments that Crimea would never want to be part of Russia and it was a hostile Russian takeover (this seems on the face of it obviously untrue -- they're Russians, and every opinion poll, even by Western outlets, has shown they feel Russian and pro-Russia and support the annexation) * Arguments that we ought to oppose Russia even when they're not in the wrong because they're 'generally evil' or our enemies or something like that; I'm not even going to touch this, except to say it's not within the ambit of this CMV, which is just about Crimea's annexation Thanks all! Happy discussing! _____ > *This is a footnote from the CMV moderators. We'd like to remind you of a couple of things. Firstly, please* ***[read through our rules](http://www.reddit.com/r/changemyview/wiki/rules)***. *If you see a comment that has broken one, it is more effective to report it than downvote it. Speaking of which,* ***[downvotes don't change views](http://www.reddit.com/r/changemyview/wiki/guidelines#wiki_upvoting.2Fdownvoting)****! Any questions or concerns? Feel free to* ***[message us](http://www.reddit.com/message/compose?to=/r/changemyview)***. *Happy CMVing!*

>Russia, for its part, acted as a legitimate peacekeeper in ensuring Crimea was not forcibly reunited with Ukraine by the military, and then accepted Crimea's request for annexation. Russia cannot act act true peacekeapers. True peacekeepers are neutral third parties whose presence is to insure that elections are held fairly and that violence is minimal. Russia has a conflict of interest as Crimea would likely join the Russian Federation if it were to leave Ukraine. Presence of Russian military would only serve to passively intimidate Crimean voters who would choose not to join Russia as well as bolster local anti-Ukraine insurgencies who may actively intimidate pro-Ukraine voters. There's also the historical imperialist problem when countries meddle in the self-determination of foreign 'daughter territories' so to speak, such as Nazi Germany's annexation of the Sudetenland.

[Star trek II: The Wrath of Khan] how does the Mutara Nebula disrupt the view screens on both the Reliant and the Enterprise?

The Mutara Nebulas effects the shields and sensors of both the Enterprise and Reliant. But why is the view screen disrupted? Isn't it just getting a live feed from an external camera on the ships hull? Why would a simple visual feed be disrupted?

They're not just external cameras, they can zoom well beyond anything visual from a camera. The nebula contains high levels of static discharge and is comprised largely of ionized gases. It's basically interfering with the what can be detected - the sensors are receiving an overflow of electronic data, and can't process it to filter out the crap. Similar to ECM jamming radar on modern Earth aircraft.

[Avatar: The Last Airbender] How does each nation identify the Avatar?

We know that Air Nomads use the toys of old Avatars, and from Rise of Kyoshi we know that the Earth Kingdom uses a geomancy technique where they narrow the earth kingdom down by a half each time. What are your best guesses for the Water Tribe and Fire Nation techniques?

In the Rise of Kyoshi it explains the Fire Nation method, sort of. All children are tested for bending ability near birth. To avoid firebender children from surprising their parents and burning houses down. Some how they are able to detect the Avatar amongst them. The Fire Sages then notify the Avatar on their 16th Birthday, like we saw with Roku, having known all the while.

If gravity propagates at the speed of light, how does this work on a galactic scale? Since the distances are so vast between galaxies wouldn't the "gravity lag" be quite noticeable?

You wouldn't be able to tell *because* they travel at the same speed. If something happened in another galaxy to cause a change in its gravitational effect on us, the light and gravity from the event would get here at the same time, so you wouldn't know about it either way until both sets of information got here.

ELI5: If you have a small leak from a container full of sand (could be a few tons even) you can shut it by spraying a bit of water on the hole,how does this work? why is the huge mass of sand doesn't push out the wet sand on the hole?

So first thing to mention is that sand isn't a liquid, it's a particulate solid. If it were water in that container, and you tried to plug it with sand, then it would absolutely be forced out. That's because water is far more fluid than sand. Sand will naturally compress down to form what almost resembles a solid, even when completely dry. Sand particles aren't perfectly smooth, and have friction, which means the particles don't easily move past each other when compressed. The particles need space around them to move. If you take some sand and "pour" it from one container to another, there's a lot of air in there that allows the particles to move around each other and "flow" as though it's a liquid. In your example, the tons of sand in the container are compressed under their own weight. The hole at the bottom is not under great pressure, because the sand has, for all intents and purposes, "solidified" and won't flow easily, so there's very little pressure at the hole.

CMV: We should have a land value tax which would replace as much of other forms of taxation as possible

Today, most developed countries derive a majority of their revenue from the income tax (and payroll tax) which is a tax on labor. There's also sales tax and VAT which tax consumption, capital gains tax which taxes interest (gains from capital), and the wealth and estate taxes which tax idle wealth. I tend to be a centrist on the issue of taxation. According to republicans, taxes are evil. According to democrats, taxes are necessary. Both are correct. Just about every tax incurs a deadweight loss upon the economy (not including pigovian taxes). This is because of opportunity cost. Money handed over to the government isn't spent on consumption or investment. But what if it didn't have to be that way? ​ There are three factors of production: land, labor, and capital. Labor refers to effort by man to create. Land is anything made by mother nature like natural resources and land itself. Capital is anything manmade, especially to create goods and services. Profit is also split into three categories: wages (labor), interest (capital), and rent (land). Of the three factors of production, land appears to be the odd one out. This is because while labor and capital have a potentially unlimited capacity, land is in fixed supply. Although land specifically refers to natural resources, the namesake is fitting because the primary use for nature in most developed countries is real estate. Land has a fixed supply, meaning that any increase in demand will increase land prices. Furthermore, increases in the value of land benefit no one except the landowners, unlike increases in capital and labor. This is because, as mentioned before, land has a fixed supply. If the price is up, that means there's more economic demand for that land. The saying goes that there is no such thing as a free lunch. This isn't necessarily true, there is a way to get a free lunch. Typical investment involves putting money into something in the hopes of getting more out. When you put money into a business, you are feeding it capital. At some point in the future, assuming the business grows, you will eventually get more out than you put in. Speculation is a form of investing which does not contribute to the investment itself. An example would be buying something for $10 and selling it for $2000 as a rare collectible. This isn't to say that all forms of speculation are bad. In a volatile commodity market, speculation can help serve to stabilize the price. But it's in the real estate market that we see the pernicious effects of speculation because land retained by speculators is not contributing to the economy, at least not as much as it could. This is why an economist by the name of Henry George proposed a land value tax (LVT). The LVT differs from a property tax in that it only taxes the land itself rather than anything on it. This means that decay and improvements won't affect the amount taxed. This is important because more efficiently used land tends to be taxed more. What may affect it is everything happening around it. Another problem that the LVT may solve (at least if it's implemented at the state or federal level) is the inefficient use of land encouraged by governments. I'm mainly referring to byzantine zoning codes and subsidies to roads. Bad zoning is often the result of local nimbys opposed to new development. What the LVT would do is tax homeowners on very valuable land. Of course, land zoned for single-family housing is worth less than land where highrises can get built but if there's a shortage of housing, land values will go up. An LVT would make the same people who push against projects reconsider, lest they pay significant taxes. Furthermore, an LVT would tax roads subsidized by lower levels of government. One concern is that it will hit rural america like a trainwreck, devastating agriculture. My response to this is that this tax would actually be a tax on suburbia, let me explain. Landowners in downtown areas will be paying the highest taxes but property there, after enough time, will derive a very high percentage of their value from the improvements rather than just land (Is the land in Manhattan worth more or are the skyscrapers worth more). Rural property will derive a minimal percent of value from improvements but land value will likewise be low. It will be suburbia which gets hit the hardest. This is because suburban land is used the least efficiently. Property taxes encourage suburban sprawl because property encouraging a higher density is typically taxed more. An LVT would encourage efficient use of the urban core, decreasing demand for suburban housing. This would actually be good for farmers because it would slow down suburban sprawl. It would also be good for small farmers because big farms tend to be more land-intensive (small farms have more buildings per unit of land, subjecting them to property taxes). The LVT would also curb gentrification, or at the very least slow it down. This is because of the way that development would go. Currently, development is incentivized to push toward low income areas because going there means lower property taxes and land is easier to purchase. To illustrate how this would change, take Chicago as an example. You have the north side and south side, the former is home to affluent white communities while the latter is home to poverty stricken black communities with high crime rates. The LVT would incentivize more development in the north side because land values there are higher.

There's a homeowner tax, and its derived from the area and location your property is located in. But there's a huge flaw if the tax is derived from the land value. If you buy a property, invest in it, and the property value rises significantly. You may end up having to sell it because you cant afford to pay that much. This means, you could drive out people by driving prices up, and make them face the government when they cant pay their taxes.

ELI5: Why does the bullet go where the sight of the gun is even tho the barrel is lower than the sight?

I don’t understand how on a rifle or any gun the sight of the gun is often above the barrel yet the bullet goes where the sight is. Does the bullet always go where the sight is or is there always going to be some inaccuracy?

You set the sights up so they “zero” at a certain distance. The barrel will be angled very slightly up compared to the sights. Imagine you draw a line straight down the sights and another straight down the barrel - they’ll intersect at some distance away. You set up the sights so the bullet lands on the bullseye at a known distance (eg 100 yards). (The actual process also compensates for “bullet drop” as the bullet is continually being pulled down by gravity just as one you drop out of your hand would be. Then if you want to shoot further - say 200 yards you adjust the sights by a configured amount (“clicks”) on the adjustment wheel to compensate for the bullet falling over the second 100 yards of the shot. The “misalignment” is actually essential to being able to shoot any significant distance. If the sights somehow were completely aligned with the barrel then you couldn’t make the required adjustments to compensate for the bullet falling during its flight.

ELI5:Is there a limit on how many different metals can be mixed into an alloy, and what would the results of alloying many different metals together be?

Well there’s a hard limit on the periodic table - there’s only so many different metallic elements. More practically, you’ll want some chemical/structural synergy between the elements you’re alloying to produce a final product that has superior properties than the components. This means you’re looking specifically for another metal that is soluble in the major component and will modify or gap fill the crystal structure just right. Not all metals are soluble or stable in eachother, and some will separate out like oil and water or corrode if you try to blend them. But if you just wanted a messy and useless slag of all the stable metallic elements cooled into a crispy oxidized lump of jumbled phases and crystals, sure you could do that.

[Star Wars] R2D2: Why doesn't he fly from ANH onward (would have been useful in RotJ instead of falling head-first into the sand), and why doesn't he remember Yoda in ESB?

The blaster shot from Vader's TIE fighter fried most of his relevant memories and third party software. The post battle of Yavin R2 was basically the old droid's personality grafted onto a new brain.

Can our brain know what time it is while we're asleep?

Is our biological clock aware of the solar clock?

Yes! Each cell has a set of specific genes which are transcribed and/or translated rhythmically. For most people, each cycle takes about ~24.3 hours. This coincides with day length and is known as your body's circadian period. As it's slightly longer than 24 hours your body needs to keep re-adjusting to changing day length (if you kept cycling at 24.3 hours you would eventually be waking up naturally later and later until you are out of sync with everything around you). To keep in sync with the external environment your body clocks entrain to the solar clock as you said. To prevent too much information, you have a master circadian clock in the suprachiasmatic nucleus (the SCN) which is a structure in your hypothalamus coordinating all of your peripheral body clocks in each cell. The action of the SCN is directly controlled by light. Thus, for a quick answer, your body cells are an orchestra and the SCN is a conductor keeping them in check. Each cell knows what time they think it is and runs accordingly, but the solar clock is used to keep re-adjusting the actions of each cell to match the changing external environment.

ELI5: how does a blender, with fixed blades, perform different types of mixing by just varying the blade speed?

The only difference between frappe, mix, etc is just how fast the blades spin? Is there any other physics going on here?

As well as the speed of the blades, the machine can also pulse - a quick burst of high speed, followed by a pause to allow the mix to rest and to settle. This requires a small computer to run it, but micros are cheap these days - much cheaper than the triac required to change the motor speed. More expensive blenders have higher speed motors. A cheap blender might have a motor similar to that used in an old-style multi-speed fan - which has 3 or 5 different speeds depending on how the coils are connected via a multi-way switch. Or it might have a motor like a modern fan, which is speed controlled using a circuit like a light dimmer. A better blender will be controlled with a synchronous motor, driven by an inverter circuit as used by modern air conditioners. This allows the motor to be driven at any speed, even backwards, or to stop dead. This allows the makers to design all sorts of drive patterns to do anything. It's all bells and whistles, made possible by a slightly more complex circuit, with a few more expensive components, and a more expensive motor.

CMV: Jar Jar Binks is a good character for the Star Wars series and the hate he get from the fandom is unfair.

Jar Jar blinks is one of my favorite characters from the star wars series as a whole. He is a clumsy Gungan from Naboo who has spent his entire life living at the bottom a a lake. A lot of the explanations I have seen revolve around the fact the he is incompetent, silly, and just gets in the way of the main characters. So far as incompetent during the clone war he was raised to a respected senator, which I do not believe an incompetent being could do. Silly is a wrong term to ascribe to him as well. His speaking and mannerisms are nothing more than the norm in Gungan society. He is clumsy and was mainly seen as a slap stick character but I believe he was more. He showed that even a dejected and unlucky person who has a positive attitude can make something of themselves. He shows that even though he is reluctant and afraid that he is also bold and brave. He risks his life to do what's right and is a great addition to the Star Wars universe. _____ > *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!*

Assuming this isn't just a bad attempt at an April Fools' joke: You're conflating diegetic (i.e., "in-story") details with the writing of the character itself. It doesn't matter that he becomes a senator (which you admit is not a very believable turn), nor does it matter that he is a good person. He is a badly written and executed character, for the following reasons: * His dialogue is difficult to understand. * The Gungans' dialogue and accent sounds vaguely like Caribbean pidgin. This, combined with Jar Jar's oafish demeanor and the way the Gungans are portrayed as simpletons, comes across as appealing to racial stereotypes of black people. * At best, Jar Jar's antics are extraneous to the plot of the story and serve to distract from it. At worst, they introduce plot holes. * Other characters' reactions to Jar Jar are not believable.

ELI5: Why do people who have college loans seem shocked by or unable to pay their loan amounts?

I understand that the cost of a college education these days is egregious, the textbook racket should be brought under control, and that sometimes people's circumstances in life change. That notwithstanding, it seems like students who have their loans coming due are asking in various forums how they can pay for it, get out of it, or find some other way to reduce their financial burden. Is this a case of kids not reading the fine print when they agree to a loan? Surely the interest rate, how much they will owe in the end, and the due date are no surprise. I'm not trying to surreptitiously promote my own feelings on the matter. I genuinely don't understand why I see so many instances of this and would like a better understanding. Edit: Thank you all for such great answers!

Because people have been told their entire life "Go get your degree and you'll be guaranteed a good job" or "If you don't get a degree, you'll never get a good job." Many students are exiting from university to find, even with their degree, they can't find a job. Many accept jobs paying minimum wage and part time, jobs they could have acquired with their high school degree. During college, they were told "Just take out loans, you'll be able to pay for them with that nice job we told you about" or "your employer will help you pay them back." Well, when they take the job at a supermarket that barely supports them, they find themselves unable to pay because they kind not find the quality of job they were promised when they signed up for college.

ELI5: If the northern white rhinoceros is on the verge of extinction (~5 still alive), why isn't in vitro fertilization used to facilitate breeding? Could the southern white rhinocerous be used as a host? Are the two subspecies compatible enough for this plan to work?

Because the population is so low that inbreeding would be a problem almost instantly, secondly large mammals normally don't breed more than a few times in their lives. The ability for the species to recover is pretty much lost at this point.

[Star wars] What would have happened if Darth Maul had died in the original encounter in the dessert?

The largest change would be Qui-Gon staying around around to train Anakin. A more relaxed morally grey Jedi may have been able to temper Anakin's frustration with the Jedi Council. Hearing less " you must trust in the councils wisdom!" and more "well, that's just like their opinion man" may have kept him off the deep end.

[Star Trek] How is Starfleet able to regulate dress/grooming for officers without being discriminatory?

Starfleet generally can be perceived to have fairly open minded and receptive standards, culturally sensitive to differences. However I’m not sure how they can enforce any standards at all. Starfleet dress/grooming standards in my opinion would have to be soft guidelines rather than hard rules in the interest of maintaining it’s open minded non-discriminatory approach to dress and grooming. 1. We know that at the very least Starfleet has allowances for facial hair (Worf, La Forge, Riker, Sisko etc all had beards at various points). The previous examples were mostly due to personal choice but we also know that Starfleet makes allowances for facial hair based on cultural practices or religious traditions. With so many technicalities it seems like it would be simpler to simply allow facial hair of any length for any anyone simply due to personal choice. 2. Physical restrictions to hair length or grooming seem to be in place but once again these are also given allowances to cultural or religious practices. It would also have to have bodily allowances for alien species that must physically maintain long hair or horns etc for physical health. Further still it would be difficult to have one set of rules for every distinct species because there are also species interbreeding that could combine any number of factors involving physical requirements, religious beliefs, or cultural traditions. 3. For dress regulations most Starfleet officers generally seem to wear the uniform in the same way with rare exception. Those exceptions being an available skirt option regardless of gender (as seen on an officer during Picards’ command) and cultural regalia (Worf). We also see that Counselor Troi briefly wears a unique variation of a Starfleet uniform briefly. This is all assuming the officer in question has a body type completely compatible with the humanoid silhouette of the uniform. If an officer had shoulder spikes or a head in an unusual location, additional arms or legs etc. So many exceptions would have to be made it would make the standard uniform more of a suggestion if anything Curious to hear other opinions or thoughts

- Grooming requirements: barring cultural/religious exemption, all hair (facial or otherwise) must be neatly groomed and caref for. - Uniform requirements: Specific uniform requirements are dictated by your ship or station's command; refer to your command regulations for specific uniform requirements. Uniforms are to be be adjusted to fit nonstandard or unusual bodyplans, should they be required. Non-regulation accessories are prohibited outside of items that are of cultural or religious significance. Uniforms are not required if it inhibits one's health or duties (such as acting as a councilor). - A ship's Captain has final say on grooming requirements, non-regulation accessories, or when a uniform must be worn (outside of health reasons). It's entirely possible to enforce standards, even after accounting for issues that might pop up in trying to apply them.

Honest thought when analyzing fed funds rate cycles: Why doesn’t the Fed just become an algorithm and they fuck off??

This isn't as flippant as you think. Central banks have been debating discretionary vs rules-based monetary policy since the 70s. There are many problems with rules based policy such as credibility and stabilisation bias, but most Central Banks today can be located somewhere on the spectrum of how rules-based their policy is. Under a classic Taylor rule, the Central Bank sets a fixed target inflation rate, and then raises the interest rate by x amount everytime the inflation rate differs from the target. This can be calibrated for just about any number of variables or sensitivity, but reduces the Central Bank to a data gathering function. The benefit of this is predictability and expectations formation. If people know that the Central Bank would always act to minimise inflation, then they will not change prices, and so inflation would be stable. This occurs because changing prices comes with costs and rigidities - which we call menu costs - part of it is you have to reprint menus, but it's mostly the cost involved in changing contractual terms. This is beneficial because it means we can keep inflation low even with an adverse economic shock without any adjustment periods. A large problem is credibility. Namely that since the Central Bank knows people would always keep their price stable regardless of any positive or negative economic shock, the optimal policy it should do is different from the rule it has just committed to following. Imagine a one off demand shock threatens to create inflation and growth at the same time - people expect the CB to raise rate according to the rule, and so they don't change prices. The optimal action that the CB should do at that point is to not raise rates, allowing the higher growth without the inflation - and so there is a time inconsistency between what it should do and what it has committed to doing.

Why don't I get an infection when I shit so hard that I bleed? Serious question.

Your body has natural protection against bacteria called White Blood Cells, these help protect your body from harmful buildup of bacteria in the body. The veins and arteries in your rectum are small, not like the large ones in your gut or in your legs/arms. This means it is not an open freeway so much as a dirt road that the bacteria must travel through. This helps the White Blood Cells target and destroy that bacteria before it becomes too harmful. Lastly, recently expelled feces does not have as many harmful bacteria as feces that has been out in the open for long periods, this reduces the chance of infection.

How do deer survive the winter in New England?

When it's really cold they will herd up in areas with thick undergrowth, especially evergreens with low branches which shelter as a tent might. They also move to areas with better foraging opportunities or less snow.

ELI5: Why do we still use X-Rays when ultrasound machines exist?

My wife is pregnant, so I've been seeing a lot of ultrasounds lately. These things are amazing; I know what my daughter looks like before she's born. I also know what her kidneys look like, which is weird. X-rays are relatively safe in small doses, but why bother with even a small risk if we can use an ultrasound machine, which is safe enough for a baby in the womb? I'm sure an ultrasound machine is expensive, but X-ray machines probably are, too. And you don't have to line the walls of your office with lead. Is there something X-rays can do that ultrasounds can't?

Yes. X-rays provide higher resolution than ultrasound can. And X-rays are better at imaging things like bones, which ultrasound has trouble penetrating. Both types of imaging are valuable. There are other imaging tools (MRI etc.) that can do other things that X-ray and ultrasound can't. Doctors try to use the best tool for the job, minimizing risk to the patient while maximizing their ability to see what they need.

[The Santa Clause] Why didn't Santa give Laura and Neil the specific gifts that they wanted when they were little?

Laura wanted a Mystery Date game, and Neil wanted an Oscar Meyer Weenie Whistle. Laura said that she at least got many other gifts, so it's safe to say she was nice, but they didn't get what they wanted the most. So...why not?

Maybe that Santa wasn’t as great. In The Santa Clause 2, the Elf Bernard says that Scott is the best Santa they’ve ever had and productivity and satisfaction had never been higher. It stands to reason that not all Santas were good at the job and seeing how there are so many ways to lose the Santa gig (fall off a roof, not get married, and evil Jack Frosts) I’d imagine that there is a new santa in training fairly often.

[LOTR] What would the Valar do if someone brought the One Ring to Valinor?

Elrond says "And they who dwell beyond the Sea would not receive it" at the Council of Elrond. Would the Valar prevent the boat from docking, violently if necessary? Will one of the Valar drop it off back in Middle Earth?

It would never make to to Valinor in the first place, the way there would be barred to anyone attempting the voyage. >For Ilúvatar cast back the Great Seas west of Middle-earth, and the Empty Lands east of it, and new lands and new seas were made; and the world was diminished, for Valinor and Eressëa were taken from it into the realm of hidden things. The Silmarillion >the Eldar were permitted still to depart and to come to the Ancient West and to Avallónë, if they would. Therefore the loremasters of Men said that a Straight Road must still be, for those that were permitted to find it. And they taught that, while the new world fell away, the old road and the path of the memory of the West still went on, as it were a mighty bridge invisible that passed through the air of breath and of flight (which were bent now as the world was bent), and traversed Ilmen which flesh unaided cannot endure, until it came to Tol Eressëa, the Lonely Isle, and maybe even beyond, to Valinor, where the Valar still dwell and watch the unfolding of the story of the world.  The Silmarillion When Nùmenor attempted to invade the Undying Lands, Eru litteraly changed the shape of the world into a shpere and men were unable to take the Straight Path to Valinor unless given permission. The Maia like Gandalf were allowed to pass as were the Elves, but even then it was at the blessing of the Valar. Someone like Sauron who was corrupted, even if he had someway to access the Straight Path, would find his way blocked and the full might of the Valar against him. Even so, it is unlikely that he would even be allowed to depart Middle-earth, notice that it is said that the Elves were "permitted" not that they automatically gained entry. The same would be true of Sauron, Ring or no.

ELI5 why people in older pictures/movies (black and white) look "different" than modern day people?

As in: Why can't picture what they would look like in real life, whereas if if you showed me a 5 year old picture made black and white in photoshop I could definitely do that. I don't know if anyone else can relate or if this makes sense, but I hope so!

**15 year old version:** Oldschool photos are in that style as it maximises the technology they had at the time. Technology advanced, the style of posed photography changed, and we got really good at capturing more detail and greater light intensity. Digital cameras do not resemble old-school film cameras in the slightest - they compensate for light, colour balance, levels, contrast etc. If you're to take a 2011 photo in Photoshop, you'd easily be able to make it look old if you reduced levels, added a sepia filter, added 'noise' or film grain, added a vignette, added dust & scratches, darkened the midtones and blurred the whole thing. There are a number of Photoshop actions which automate this - search for 'vintage photoshop actions'. But...the way we pose for photos and the way action photos are shot has changed. Because we don't have to stand stock still for 2 minutes waiting for the film to be exposed, pics are often more candid or less formal, which effects the 'mood' of the photo. **True LI5: ** A long time ago, taking photographs cost a lot of money and needed very special cameras. These cameras were not very good, so the photographer had to play around with the photos and the camera to make the photos look good. Over time, we learn how to do things better. We learnt how to make better cameras, and the cameras took better pictures. The cameras were able to take photos using less light and much clearer photos. Today, digital cameras are very good and take good photos. In order to make them look the same as old photos, we have to mess them up a bit.

[Star Wars:TPM] What is the cannon reason for the Trade Federation blockade of Naboo?

Why is the trade federation blockading the Naboo planet? 2.What is the Trade Federation gaining for helping the Sith Lords blockade Naboo? 3.Why dose the Trade Federation have such a large army?

Space taxes on space trade routes. The Trade Federation handled the movement of goods all across the Republic so those taxes would cut into their bottom line. The Trade Federation has a large army to protect their ships and planetary interests.

Is the "observable universe" limited by our current telescopic technology, or can we see that far and there's nothing behind it?

When we look farther away, we're looking farther back in time. If we look far enough, we're looking at a time when the universe was much hotter and denser. Beyond a certain point, the universe was so hot and dense that it was full of ionized plasma, and light couldn't propagate. The plasma cooled and formed hyrogen about 400,000 years after the big bang, and that is the farthest we can see (which appears as the cosmic microwave background). If we can drastically improve our neutrino detection capabilities we could see farther back, because neutrinos travel unimpeded through basically everything.

CMV: Edward Rooney was not in the wrong and should not be viewed as the antagonist in "Ferris Bueller's Day Off".

For those who are unaware/too young to know who I'm talking about, *Ferris Bueller's Day Off* follows high school senior Ferris Bueller, who decides to skip school and spend the day in downtown Chicago. Accompanied by his girlfriend Sloane and his best friend Cameron, he creatively avoids his school's Dean of Students Edward Rooney. Now don't get me wrong, as a kid I was totally on Team Ferris. Objectively speaking though, Bueller was a dick and Rooney was the good guy. This is based on two points: * Rooney is the Dean of Students for Shermer High School (let's assume it's the same high school John Hughes frequently used). This means his job, quite literally, is to prevent students from doing precisely what Ferris Bueller is doing. All Rooney is doing is what he gets paid, through taxpayer's dollars, to do for the school district. In fact, he goes above and beyond to do his job. Shit, that's pretty admirable for a public school employee. * Rooney was right. He wasn't going on a wild goose chase for nothing. Ferris wasn't sick. Sloane's grandmother wasn't dead (or at least didn't die that day). Bueller lied to his parents about being sick. Bueller lied to the school about a beloved family member dying. Bueller stole, and then destroyed, Mr. Frye's car. Bueller is nothing more than a snobby rich kid who gets away with and thinks he's owed everything because he's awesome and special. Rooney knows this too, and all he wanted was, for once, to have Bueller suffer the consequences for his narcissistic actions, which in my opinion is well-deserved. At the end of the day, Edward Rooney was just doing his job, and by no means whatsoever is he the "bad guy." **EDIT**: Change "protagonist/antagonist" to "good guy or hero/bad guy or villain." _____ > *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!*

School is not prison, and students are not prisoners. One small portion of the job of a Dean of Students is indeed to promote attendance. But if a Dean is to act in the students' interests rather than as their jailer, he must promote attendance by making school desirable rather than by punishing students for choosing to use their time in other ways. Dean Rooney appears to be putting minimal effort into improving the school and making it a better place. He appears to be "after" Bueller, squandering his on-the-clock time on a personal vendetta aimed at punishing Bueller specifically. This is bad not only because he's wasting too much time on one student but also because he doesn't seem as interested in helping that student as in punishing him. Beyond this complete waste of his time and taxpayer money, Rooney commits trespassing and poisons Bueller's dog. This exposes the school district to significant liability risk. The potential legal damages far exceed any possible benefits even if the home invasion really were motivated by some (off-camera) concern with his student's best interests.

ELI5: Where does wind come from?

pressure differences caused by temperature differences. the best eli5 answer would be to just open your freezer about 4 inches and put your hand over the gap. You will feel the cold air come out of the freezer pretty quickly because the difference in room temperature and the freezer temperature cause the air to 'even out', moving the cold air in to the warmer air and thus, wind (on a very small scale :) )

ELI5: Could someone tell me why inflation happens? I've been told inflation happens when oil prices go up. Oil has gone down recently, no? Why don't the prices of goods go down if oil goes down?

Inflation is related to the amount of currency in circulation. The more money that is in circulation, the less value an individual unit (1 dollar, etc) of that money has. The effect is that prices go up. What once cost you $10 might now cost you $12 because the value of your money has gone down. It has absolutely nothing to do with the price of oil.

ELI5: why do soap operas all have the same ‘look’ to them?

You can tell something is a soap opera by just looking at a scene. What causes this?

The nature of their rapid and cheap production forces them to have a very homogenous style. The game of soap operas is to produce as much content as possible as what you are really doing is making the bare minimum that justifies the ad-breaks (hence being called soap operas, because their early radio-play form were dominated by soap commercials). So they are produced cheaply and quickly, meaning there isn't time or budget to do much more than write the script then stick the actor in an existing set to deliver them. Those sets need to be made ready for production very quickly so the lighting setups for them are just left in place. You rock up, hit the switch and the set is lit. That lighting is done so that the actors can stand anywhere inside them and still be well lit for the multiple cameras pointing at them. You want multiple cameras because doing multiple takes for different angles takes time and time is money. So everyone is just homogenously lit in the scene and every scene is lit like every other scene.

ELI5: If Blood Plasma is 95% water, why is it so precious?

I donate blood plasma bi-monthly. and one of the things that has bugged me is the high water content. around 19/20's of it is just plain water. It seems like it that would leave a relatively minor part of it to synthesize.. so why is blood plasma so precious that encouraging people to sign up for having needles stuck in them is the most efficient way of obtaining it?

The minority component of plasma that is so precious is the variety of proteins in it. Proteins are very long, complex molecules that your body makes to take care of all sorts of things, including carrying different types of nutrients, mediating cell reproduction, and making other molecules your body needs. Proteins are extremely difficult to synthesize in a lab, so it's more than worth it to ask people to donate blood plasma.

[Looney Tunes] What happened to Lola Bunny that changed her personality so drastically before the events of the 2011 "The Looney Tunes Show" TV show?

Much like the Muppets, the Looney Tunes are a company of actors whose main roles are usually more-or-less based on themselves. Lola was playing a different character in Space Jam than she was in TLTS.

ELI5: What power does the UK have over its overseas territories that are being used as tax havens (British Virgin Islands, Bermuda)?

Ordinarily, the overseas territories are self-governing and the UK government is only responsible for their defence and international relations. However, the UK does have sovereignty over the overseas territories and could overrule the local government or remove it entirely and impose direct rule. They did this in the Turks and Caicos Islands in 2008 in response to serious corruption in the local government, so it's not a hypothetical "technically they have that power but it's a historical oddity that they could never really use", but it would still be a last resort.

Could the "big bang" have been a result of the universe being ejected from a black hole?

Sorry if that's a common theory/explanation. I just thought of it and, rather than Google it, I figured I'd ask on here because the discussion it provokes inevitably leads to me learning something I probably wouldn't elsewhere. I feel like this theory would also explain the universe eventually collapsing back in on itself and going through cycles.

The big bang's cause, if such a description can ever be deduced, is unknown. While the idea "the universe came from a black hole's formation" sounds poetic, as it stands, it is just vague speculation. >the universe eventually collapsing back in on itself and going through cycles Unfortunately the universe has been measured to be accelerating which essentially rules out any simple collapse prediction. According to the current model, the universe will simply expand forever and never collapse back on itself, we have no idea why this acceleration is occurring so we call it dark energy.

ELI5:Why do some people vomit when they see a corpse and/or witness a homicide?

Is it simply because it's gross? Sorry in advance if this is a stupid question.

We essentially vomit at the sight of gory or bloody death as a defense mechanism. In the face of corpses or death, we are often at risk ourselves, and therefore vomit to remove possible biohazards from our system that may have been spread by the dead, as blood and gore are often good at transmitting biohazards. It also prevents us from possibly ingesting any biohazards by forcing everything out of the mouth that may have been headed for the stomach (i.e. blood).

ELI5 Why do factories require such high chimneys?

Factory chimneys are tall so that the pollution they generate can rise higher in the atmosphere and, more importantly, various volatile compounds can have adequate space to break down. If the chimney was shorter, the exhaust from the factory would spread faster over a smaller area around the factory itself and "smoke out" the workers and adjacent businesses. Making the chimney, or smoke stack, really tall doesn't eliminate the pollution or render all the released compounds inert (or even broken down completely) but it does help dilute the compounds in the atmosphere and minimize the immediate localized damage. Not only does making the chimney tall help get those gases up high to begin with (because the structure itself is tall) but the hot exhaust in a tall chimney flue uses physics to your advantage to eject the gases higher into the air. It's literally called the "chimney effect" or "stack effect" --- the bigger the chimney and the hotter the air exhausted into it, the higher and further the gas will be ejected away from the top of the stack.

[Star Wars] Do all non-sentient animals have the ability to use the Force?

We’ve seen plenty of sentient species using the Force, but are there any animals capable of using it too? Is it just specific species or can any type of animal use it, like a Bantha?

Animals which can use the Force: Loth-wolves Purrgil Convorees have a connection to the Force, but no reports of them actually using it. Ysalamiri are canon, their force-use is still only Legend, has yet to be shown Vornskr in Legends

I don't think "slut shaming" is a big deal or is worth putting much effort into stopping. CMV

I think people should be able to sleep with who ever they want as long as both partners are of age and consent to said sexual activity. However, if you choose to participate in these activity you need to be an adult about it and accept whatever consequence comes with it. Continuing in that vein, the recent movement about "anti-slut shaming" and subsequent "slut walks" just cause me to sigh and roll my eyes. Yes, there are double standards regarding women and their sexuality , but there are double standards for male sexuality as well. No one talks or cares about "virgin shaming" for men (which exists, would the movie "The 40 year old virgin" have existed if it was a female protagonist?). I realize it's anecdotal, but I am a male who lost my virginity as soon as I could to the first girl who would take it because I was told my whole life if i was a virgin past 18 I was a worthless failure. Many other young men I know feel the same. I acknowledge the double standard is unfair but I just can't bring myself to care on any level that would cause me to take action against it. I am all on board for women's rights- reproductive rights, equal pay, equal treatment and safety. This just seems like first world feminism to me. I consider myself a liberal, open minded person. So please, CMV and open my eyes to why you think this is an important issue.

Using your logic it seems like "slut shaming" could be substituted for anything that people get bullied for. Why do you believe that harassing other common bully targets (homosexuals, transgender, obese, etc.) is unacceptable while harassing people with a larger than average number of sexual partners is OK? Couldn't we use your logic to say that homosexuals should realize that their orientation may cause people to harass them and they should "be an adult about it"? Wouldn't "being an adult" mean not harassing someone for their life choices?

CMV: Rappers Shouldn’t Be Obsessed With Diamonds Considering Where Most Diamonds Come From

First, I’d like to say I am a huge rap fan so I’m not coming at this idea as an outsider. I like flashy chains and designer clothes as well and I don’t think that materialism is the issue here, just the fact that most diamonds are mined by enslaved Africans. However, I think it’s interesting how rappers seem to be obsessed with diamonds and those same diamonds potentially come from their distant enslaved African relatives. Everyone knows how disgusting the diamond trade is in African and unless rappers like the Migos (who have, no exaggeration, probably 10 millions worth of diamonds between them) specifically source non slave trade diamonds, I don’t get how this doesn’t impact them morally. If I can afford them one day, I’ll probably have a nice classy diamond necklace or something because I like jewelry too but I’m going to ensure those diamonds didn’t come from African slaves. I hope nothing I said was offensive and I’m interested in what you guys have to say about it. I feel like this is something that has’t been posted on here before. Edit: I don’t mean to make it seem like all rappers are African American. More so, Rap was originated by very conscious African Americans and I would expect any race rapper to respect African and African American culture and not want to partake in anything negatively contributing to Africa, or anywhere a historically oppressed people come from. Conclusion: I thank everyone who responded with thought out and educated responses. I did learn a bunch and awarded deltas to those with good comments. However, to the PC easily triggered white people, the racist accusations are pathetic. This was simply a post to discuss a thought, I’m not a racist, I don’t think Africans and American Black people are the same, I feel like anyone with a brain would have realized that. Just had to give a big FU to PC wannabe racist reddit vigilantes. Thanks again to those with good comments. My view on this has been changed. Peace!

You're assuming a lot here. One, not everyone truly knows or understands the diamond industry or its atrocities. And two, African doesn't equal African American. In fact, there's a history of contention between the two groups as they don't necessarily see themselves as the same thing. Sure, they may look similar to non blacks, but the two groups have significantly different cultures, history, and at this point different phenotypic make ups that become quite glaring when discussing societal issues. Hell, the diamond business doesn't even affect all Africans the same. Remember that Africa is a continent with 54 different countries, roughly 2000 known languages and an infinite number of ethnic groups. What affects the Nigerian might not bother the Ethiopian.

ELI5: Why does audio feedback always sound like a high squealing noice?

As far as I know audio feedback is when the input of your microphone gets amplified and caught up again by the mic, causing a loop of amplifying the input. How come that whatever this imput is, it always almost immediately becomes a high squeeling noice and not just an amplified voice or something?

There are 2 things happening here. In a feedback loop, the microphone is picking up some of the amplified sound (because it "hears" it from the speaker) and sends it back around. This is why it gets very loud, very fast. The high-pitched squeal happens for a different reason. If the microphone and the speaker are at a certain distance and orientation with each other, such that the sound coming out of the speaker hits the microphone at a certain point in time, certain parts of the sound are amplified slightly differently. Microphones, amplifiers and speakers are not perfect...they work better with some frequencies better than others. If the alignment is such that a certain "high sound" gets amplified better than the other sounds, this results in the squeal you hear. This looping happens very fast, which is why the sound starts a fairly low volume and pitch, then gets very loud and high pitched. If all microphones, amplifiers and speakers (and room acoustics!) were perfect, this would not happen. For you techies: One trick that used to be used before modern DSPs (digital signal processors) was to place 2 microphones at every performer. One mic was actually used by the performer, while a second mic was a few inches away, but connect 180 degrees out-of-phase ("reverse the wires"). The performer's mic would capture both the performer's voice AND whatever else (instruments, crowd, etc) was near by. The second mic had the same, but no vocal. Since it was 180 out of phase, you could add this to the other mic (with a special amp...) and almost perfectly cancel out everything but the vocal. A pain in the ass to set up, but you could get some great sound that way. Edit: Added some cool microphone info

[Sleeping Beauty] If Maleficent HAD been invited to the christening, would she have just attended as a proper guest and not caused any trouble?

Generally, being unpredictable is kinda a main feature of the fey. Usually, not associating with them at all is the safest course of action - if that's not possible, then treating them with the utmost politeness while still being permanently on your guard is the next best option. If Maleficent had been invited, she probably wouldn't have used such crass methods as directly cursing the princess. She might have very well caused trouble in a more removed fashion - giving a valueable, but dangerous gift, for example, or baiting people into breaking the rules of hospitality first so they don't bind her anymore.

Is there a connection between the age of newborns mother and the life expectancy of the baby?

For example will a baby born to a mother who is 20 have a longer life expectancy of a baby born to a mother who is 50 or vice versa?

I looked into this about 3 years ago, and could find no scientific study on the topic in humans. In some species of birds, there is an inverse u shaped longevity curve, where offspring of young mothers die early due to inexperience and offspring of very old mothers die early due to a physically less capable provider.

[Avengers Infinity Wars]Did Dr. Strange know this all along?

Throughout the film, there were multiple events that could have prevented the snap like: like Star Lord not losing his mind, Thor going for the head, Wanda destroying the mind stone before Thanos gets the Time stone; yet Doctor Strange didn't prevent any of it. What if Doctor Strange thought Thanos's plan made sense after all and he intended half the universe to stay dead for five years so that the remaining half learnt the value of conserving the finite resources in the universe? What if he ONLY intended the snap to be undone after humanity [and other sentient life in general] had learnt it's lesson? In the 14,000,605 outcomes he saw, could it be possible that he saw the Avengers winning several times but leading to a future where all resources are consumed and life slowly and painfully ceases to exist?

Strange had no way of telling Thor to go for the head. He also had no way of telling Wanda to destroy the Mind Stone faster. If he had delayed Thanos getting the Time Stone Thanos would have probably killed Iron Man. Then Thanos can just go to Earth and reverse the Mind Stone’s destruction. Not to mention Strange had to plan out the events to make sure Scott Lang was in the Quantum Realm when Thanos snapped. A couple minutes too early or late and Scott would have been outside and unable to help the Avengers discover time travel in the future. As for Star Lord, we never see the future that would have come from Star Lord staying calm. But I’m guessing it’s worse than the current MCU (things seem to nearly have returned to normal by the time of Far From Home)

[DC] Why is Martian Manhunter called like that? Did he hunted humans at some point?

Manhunter was his occupation and title in martian society. There's no direct translation to human languages, so Manhunter is the closest we got. But he was basically a mix of police officer, detective, judge and soldier. The manhunters would travel around the planet capturing criminals, solving crimes, judging disputes between civilians and protecting the planet from exterior threats. For that, one needs to be an expert fighter and possess a strong moral code, and for that they were very respected and looked up to.

ELI5: Why is it that most of the time when an organ hurts, the pain isn’t where the organ is located?

For instance a lot of people say they have pains in their shoulder and it turns out to be a liver issue, or sometimes kidney pains are closer to the bladder.

This is called "referential pain" and it's a result of the way our nervous system is wired throughout our bodies. We don't always have direct pain receptors on all of our organs and the electrical pathways that our nervous system utilizes are quite complex. If you've ever done any electrical work on a car or house, you can appreciate how seemingly mind-boggling and frustrating this lack of direct correlation can be. However, with a bit of studying, there are many common signs and symptoms that are indicative of organ damage/dysfunction which may seem random to the untrained eye

[LOTR] How does the plumbing work in an underground Dwarven Kingdom?

Following on from thinkaboutfun's relatively sensible question regarding smells: Regards the renouned underground caverns in which Dwarves live, it seems that they'd be skilled at creating vehtinilation, but not everything can be carried away on the wind. Where does Dwarven excrement go? Is there just a massive cesspit at the bottom of their home, and as they go deeper, do they have to dig another, or do they - urgh - extend the original by digging beneath and letting the previous accumulations drain through? Do they make use of these chambers? Are they like ants, and use their waste as an agricultural based recycling? After a hundred years are the upper levels then renovated into living spaces? Or do they have a disgusting pulley system of dwarven shit and piss to be deposited outside of their homes in some sort of sloppy fecal volcano? Have these fecal volcano holes, these orifices of dwarven cities, these oozing shitholes of the collective Dwarven residents, ever been used as an entry point for goblin infiltrators? DID BILBO ENTER EREBOR THROUGH THE SHITTER?

Have you ever noticed that, whenever dwarves "delve too deep", the creatures that emerge from the black caverns beneath the world are always in a seriously grumpy mood? Yeah, this is pretty much why.

ELI5: How does touching the glass of a headlight bulb make it burn out faster?

You leave oils behind on the surface of the bulb, which causes the surface of the bulb to heat unevenly as those oils/contaminants are heated up. Certain bulb types, like halogens, output enormous amounts of heat while they're operating. At these high temperatures, that uneven heating can compromise the structure of the bulb and eventually destroy it.

eli5: Why would someone be unaware they’re on top of a large mountain when at the summit of Olympus Mons?

“Similarly, an observer near the summit would be unaware of standing on a very high mountain, as the slope of the volcano would extend far beyond the horizon”

Because the slope of Olympus mons is so shallow it wouldn't look like you're standing on a mountain. You can only see you're on a mountain or hill by seeing how high you are above the valleys. On Olympus mons you literally can't see any Valleys, so there's nothing you can gauge your height by

The fovea is so small compared to the size of the visual field, so why does the world not appear to be of terribly low fidelity?

By fidelity I mean blurred and generally degraded.

To add to what /u/monory said, you don't *experience* the world in low resolution because of generally speaking if you are actually paying attention to an object or landscape - in other words actively trying to process, understand and commit it to memory - you will point your fovea at it. Additionally, ALL of your senses are shaped by previous experience. It's called top down processing and it is basically your brain filling in gaps in sensory information. For example, generally all of the grass you've ever seen is a certain shade of green. Therefore, even though your peripheral vision lacks detail and color, your brain will experience that *whole* meadow as green, not just the part landing on your fovea. That's just one example of many that keeps you from being totally disoriented by objects outside of where your eyes are focused.

[Classic Doctor Who] was the TARDIS ever depicted as actually flying the way it sometimes is in modern Doctor Who?

I'm well-versed in the modern episodes, but have only seen a handful of the classics. In the current series the TARDIS is always described as disappearing one place and appearing somewhere else instantaneously, but we randomly have images of it actually flying in spacing or flying through the time vortex. Was it ever depicted this way in the past? Does anyone have an in-universe explanation why sometimes it flies and sometimes it instantly changes places?

A few factors in play. Timeframe perspective - When the TARDIS appears to vanish or appear from nowhere it's actually the TARDIS translating to/from the Time vortex. The view you see is locked to your (the camera's) timeframe, which the TARDIS is entering or leaving. Being 'part of events' - When we see the TARDIS 'in flight' like a more "conventional" spacecraft its not changing its position in time, only in space. As the Doctor remarks once "short hops are difficult" so if he doesn't need to move through time it's usually easier to just fly the TARDIS from point A to point B instead of accessing the Time vortex, assuming he landed in the open to begin with and not in a structure.

[Wheel of Time] What did Elayne Trakand see during her Accepted test?

All she says about it is "I could not be that awful, Egwene. I just couldn't!" Any guesses as to what Elayne saw during her [Accepted test](https://library.tarvalon.net/index.php?title=Accepted_Test)?

The three tests loosely follow the pattern of past, present and future. The first test would show Elayne's commitment to the White Tower measured against her history. Gawyn and Morgase would be in danger, perhaps with Caemlyn under siege from the False Dragon Logain. Elayne must leave them to their unknown fate to proceed. The second test would measure her commitment versus her current life. Her new friends Nynaeve and Egwene are under attack in the White Tower from the Black Ajah, she must leave them to face possible torture and Turning to proceed. The final test sets her against the future. Queen Elayne of Andor and the Dragon Reborn, Rand al'Thor stand against the Shadow at the Last Battle, joint leaders of the free world. The tide of battle turns and Rand is wounded and trapped, causing the morale of the Andoran army to break. Elayne must leave the fight when Andor most needs her, when Rand most needs her.

ELI5: What makes a tire rotation necessary? Do they switch sides when rotated?

front and rear tires wear differently because different loads are placed on them. front wheel drive cars wear the front tires quicker. rear wheel drive cars wear the rear tires quicker. left and right tires wear differently because you turn right alot more aggressively than you turn left. and if you're driving solo, there's an extra 150-200 pounds on the left side of the car.

ELI5: Where does my bellybutton go?

ELI5:I know that it was my source of nourishment in the womb but now that I’ve been out of there for a few decades, where does it go? Is it still connected to something inside my abdomen or have the muscles )and I use that word loosely) separated it from my “insides”?

Medical student here Your belly button is the artifact left behind of your umbilical cord. Once you are birthed, they snip the cord a few inches off the base. After a few days it drys up and falls off because no nutrients are being received. The inside part of the cord is connected to the bladder, the gut, and the main vein that goes to the heart called the Vena Cava. Since your body has no need for those structures, they just get broken down by the body. Sometimes, they aren’t fully broken down and can cause a cyst or a full on opening such as a Meckel’s diverticulum or Patent Urachus. Usually these need to be closed or removed surgically.

Is it ethical for me to abandon vegetarianism?

Recently, a study came out suggesting microdeficiencies of things like omega-3 (found exclusively in fish) and Vitamin B12 (found in red meat) are tied to mental health issues, specifically depression. The chance of a false positive was calculated at less than .1%, so it would seem these things are definitely tied. However, correlation is not causation. It could be that people likely to develop depression are also likely to become vegetarians due to feelings of guilt over causing animal suffering. Furthermore, these is young research, so there are only a few studies on it. I have been a vegetarian for just under eleven years. When I began, I was a mere eleven years old, feeling guilty after watching *Chicken Run*, if you can believe that. Over the years, I developed my ethical code into one based around reducing death and suffering. So clearly, it’s unethical for me to eat meat - i don’t *need* to to survive thanks to the growth of alternative proteins like fake meats, and I’d be causing suffering, meaning I’d be causing suffering for my own pleasure. However, a few years ago, I developed depression. It’s been with me on and off since, despite medications and psychotherapy (they help, mind, but they just reduce it rather than kill it). Now it’s looking like it *might* be due to such microdeficiencies mentioned above. I could test this by eating meat. However, I feel dread over the possibility of doing so and finding it doesn’t help. Naturally this isn’t so ethically related, but I also feel extremely apprehensive about changing my diet of half my life. I realize that to some extent I can reduce the suffering I’d cause by eating meat by seeking out only meats I can assure were dealt with humanely, eg being fished or hunted rather than farmed. However, the central concern of whether or not it is ethical to cause suffering because it *might* reduce my own suffering is really causing me some difficulties. Any input is accepted. I don’t necessarily need an answer; I realize you won’t just tell me what to do. I just want some more ways to think about this and hopefully deal with the dread and guilt. EDIT: thank you all for your input. Here’s the study, if that helps: https://www.medscape.org/viewarticle/887603

You might want to ask your doctor, mental health professional or even a dietitian before you worry about ethical issues; there are alternate sources for most vitamins so you may be able to get away with a diet adjustment if that's the cause of your depression. Something else to consider: can you use supplements to make up the vitamins you're short of? B12 in particular can be gotten from bacterial sources and omega-3 from plant sources. Vegan supplements are a growing business, just be careful in your sourcing.

[General] What exactly does "Selling Your Soul" to a particular deity entale?

so I sold me soul to a deity. What does this mean? Do I have to do everything they say? Do I go to their domain when I die? Bonus question: what can one usually get in return from selling their soul?

For good, firm detail on the contractual ins & outs of the negotiation process, read Christopher Marlowe's play *Doctor Faustus* or, if you've got the intellectual stamina for it, Goethe's novel *Faust*. Preferably while listening to the incredible krautrock band Faust.

[The Simpsons] How much does Homer make?

He supports a 3 kid family as the sole earner, has a huge house in a nice neighborhood, two cars, 2 pets, drinks all he wants, eats what ever he wants including enough hot dogs to put two+ kids through college, etc, etc

He self-describes as being "Upper lower middle class" meaning on the upper end of lower middle class. According to Homer's paycheck in *Much Apu About Nothing*, Homer makes $479.60 before taxes each week. Discounting bonuses, and assuming he's paid every week, he makes $24,939.20 annually. However, that's in 1996 dollars. Adjusted for inflation, that's about $49K today. With three kids and a mortgage, it's not outrageous to call that "upper lower middle class." It's way above current "actual median" (which is about $31K) and below "real median" (which is about $62K) and closer to the latter than the former. It's low for an urban income but approximately normal for a 5-person household in rural America. Springfield is just super cheap to live in, it's kind of a shitty town. It's not rural but it's also not really a suburb of a major city either.

ELI5: How does Toxic Shock Syndrome happen and why does it occur so quickly?

To put it simply, some bacteria can produce toxins that result in toxic shock syndrome. Normally, you have these immune cells that take in a pathogen, break it down and present its pieces on the surface. Then another immune cell type called a T cell can come by and recognize the present antigen thereby getting activated. Usually way less than 1 percent of T cells get activated. But when you have these special toxins, they behave as super antigens. They don't need to be processed by an immune cell and presented, they just bind to the protein that usually presents them on the surface of these cells, directly from the outside. And they can activate a huge number of T cells (up to 30 percent). These cells then cause a cytokine storm (a gigantic number of inflammatory and other signals get released). This causes the body to react so dramatically and so quickly and usually so little T cells induce a whole immune response, so a huge number will be ultra fast and ultra dramatic.

[Blade Runner] Spoiler

I was born in 1981, and as long as I can remember Blade Runner was my dads movie, he loved it. As a kid , I just knew it was sci-fi and futuristic , but I had no clue how deep the movie was. I just recently saw an old interview where Ridley Scott says , " yes Deckard is a Replicant" How many others did not know this like me.(I found out last year) My question is, are Deckard and the other Replicants ancient versions of Bishop from aliens or David from Prometheus. Another question I have is, could Bishop and David be the Replicants that are going crazy in deep space ?

. /' // . // |\//7 /' " \ . . . | ( \ '._ | '._ ' '. ' / \'-'_---. ) ) . :.' | \ | . . . . ' . | | | \^ /_-': / / | | '\ .' / /| | \\ | \ \( ) // / \ | | // / L! ! // / [_] L[_| It's too bad she won't live. But then again, who does?

[WH40K] How common are regular troops using personal energy shields, power armor, power weapons, mechanical exoskeletons, and genetic modifications after the Imperial army was reformed into the Imperial guard?

It seems that during the great crusade and Horus heresy, there were many regiments using equipment far superior to what we commonly see guardsmen using now, like energy shields that can stop bolter rounds or exoskeletons that allow troops to carry heavy crew served weapons like assault rifles. Do these kind of regiments still exist in the modern guard?

Most of the rare, high value equipment was rolled into the Storm Stroopers. The Heresy wreaked havoc with the Imperiums production, and caused the Adeptus Mechanicus to become even more insular and protective of knowlege than it was before. This in turn caused high-tech equipment to become exceptionally rare. This was caused partly because of the Emperor not being around to tell them what to do, and partly because the Dark Mechanicum stole a great deal of knowlege when they fled. In the centuries following the Heresy, you could probably have bought yourself a planet with a single Personal Field Generator. Especially if the Adeptus Mechanicus had lost the design in the Heresy. The further you go, through, the more rare these technologies become. As it stands, i don't know of any Planetary Regiment that can still deploy large numbers of Shields, Power Armour or exo-suits. Genetic modification seems to be common, though illegal, on Hive Worlds mind you.

[DnD] Why do they have cemeteries in cities, when they inevitably attract necromancers? And why isn't cremation more popular to prevent this?

Here are a few reasons - communication, closeness, faith and resurrections and security of the grave. First, not all necromancers are grave robbers seeking to raise up the undead. Necromancers can be an asset to a community. When someone dies, a necromancer gives family a last chance to say goodbye or say things they need to say to them. The necromancer could allow an actual conversation to help both the living and the recently deceased. If a crime were involved, or secrets buried, all that could come out too. Secondly, people like to bury family close by, maybe even visit. Having a body cremated or carted away in a 'bring out your dead' scenario is pretty permanent. Third, cremation may also be against the faith of many, since it destroys the body that may be important to their faith. The body may be a vessel for the spirit, or may be resurrected someday. Resurrections are more common than you think. Finally, a close by cemetary guards the dead from grave robbers, body snatchers and other ghouls. A boothill outside of town is just an invitation to come and rob the graves of body and loot.

CMV: Helen of Troy should be referred to as Helen of Sparta

This is a pretty straight-forward one. Helen was born of the Spartan queen Tyndareus and the Zeus Swan. She is seduced by Paris of Troy and take to Troy. But that doesn't make her "of Troy." She is still "of Sparta." The standard naming convention is to say where people are "from," not where they move. Leonardo da Vinci is from Vinci, even if he made his name in Florence. Isabella of Portugal keeps the moniker "of Portugal" when she becomes Queen of Spain. Saying "Helen of Troy" gives the false impression that Helen was a native Trojan. ​ Edit: My view has been changed. I didn't really expect that to happen so quickly. A number of people have pointed out that the point of adding the location moniker is to distinguish the person from others with the same name. Isabella of Portugal is called that so she isn't confused with Isbaella of Castille (or other Isabellas). Helen is a Greek name, so there are likely many Helens from Sparta, if none as famous, but likely no other Helens in Troy. It's also been pointed out that naming conventions are really inconsistent, so there's no formula for names. I still think calling her "Helen of Troy" misleads people into thinking she was from Troy. I'm also not convinced of arguments of "we've always called her Helen of Troy," because (1) I don't know how long that tradition has been around and (2) if it were sufficient, I wouldn't have had posted this CMV in the first place. I do agree now that the name is appropriate, though.

Isabella of Portugal has that name because there were several famous women with that name but only one from Portugal. Leonardo da Vinci has that name because he's the only famous Leonardo from Vinci. Helen of Troy is only famous because of Troy. She's a key part of the story of the fall of Troy. The fact that she's from Sparta is immaterial; Sparta isn't really an important part of the story. Troy also doesn't have any other famous Helens so it keeps her distinct. Remember, the whole point of the monikers is to differentiate between people with the same name. By saying Helen of Troy we immediately know who she is; "Helen of Sparta" doesn't have the same impact.

Do the more extreme phases of matter like Bose-Einstein Condensate and Quark-Gluon Plasma still exist in nature?

Or are they only attainable under laboratory conditions currently? Or are there other, more exotic phases of matter that I'm unaware of that fit the bill?

Neutron and white dwarf stars are made of degenerate matter that could be described as a Fermi-Dirac rather than a Bose-Einstein condensate (although not the same as a fermionic condensate). Neutron star interiors are believed to be superfluid, which is a form of Bose-Einstein condensation. Also inside neutron stars it is possible that something like a quark-gluon plasma exists, but this is unknown for sure.

[Star Trek] Why was Earth of all places chosen as the capitol of the federation?

Because humanity was no one'e enemy, is the short answer. The long answer is that, when humanity began exploring the stars, the other founding members of the Federation (the Vulcans, Andorians, and Tellarites) had longstanding rivalries, occasionally breaking out into shooting wars. Humanity was allied with the Vulcans, but officially neutral in their longstanding conflict with the Andorians. After a number of incidents in which the Enterprise NX-01 aided the Andorians, humanity earned enough respect from both the Vulcans and Andorians that those two races asked humanity to mediate negotiations to end their disputes. Eventually the Tellarites were brought into the negotiations, and the end result was the formation of the Federation.

(Marvel) Who can She Hulk have sex with?

Strictly speaking, She Hulk roughly has the same strength as the Hulk in non enraged form. Who in the Marvel Universe would have the strength, or endurance to take her?

I mean technically she could have sex with anyone she wants to. How would you stop from taking what she wants...? It shouldnt be that hard for a regular dude to have sex with her, its not like she is going to be fighting you. Weve seen her open doors just fine without ripping them off their hinges. As long as she isnt on top or you have a spanking fetish you should be fine. Also, use a condom, every time.

[Asimov] Some questions about the 3 laws.

In "Lost Little Robot," one of the Susan Calvin stories, there's a situation where the 1st law has to be truncated to allow robots who work closely with humans in high-radiation environments to do let the humans do their jobs while taking an acceptable risk. We learn that the 1st law kept kicking in and that robots kept "rescuing" the humans from the radiation, even though the humans were taking reasonable precautions to negate the danger. Why wouldn't this have been a problem before? We do a lot of things, including a lot of things depicted in Asimov's Robot stories, that have an inherent, if small risk of harm. Things like spaceflight, or even navigating the expressways could all bring harm, and we don't see robots intervening in any of these cases. Why not? Why is it gamma radiation specific? Further, as our own culture gets closer to using machines that are capable of "thought," how realistic is implementation of the 3 laws? Would they work IRL? Would it be useful to build robots this way?

There are several factors in play here: 1. First and foremost is actual versus potential harm. The robots were protecting the humans from actual (albeit low levels) of harm. Gamma radiation physically and actively destroys your cells as you are exposed to it and the robots knew this. Compare this to risky behavior that merely invites the chance (however high) of harm that has not yet occurred. 2. Second is awareness. The robots in this story had to be specifically programmed with knowledge of radiation. Sans that specific knowledge, they wouldn't understand that harm would be occurring. 3. Lastly, robots at this time were not commonplace. A common theme was humanity's bigotry toward robots. They were only in use on Earth in limited and specific areas, and quickly banished from Earth altogether.

eli5 What is the difference between a proverb, aphorism, epigram, and adage?

Math major here haha. Are they not the same thing?

A proverb is typically a memorable, commonplace piece of advice: "Never wake a sleeping bear." An aphorism is more an observation: "A bear in spring is always hungry." An epigram is made to be clever or funny: "Always respect mother nature. Especially when she weighs 400 pounds and is guarding her baby." An adage is similar to a proverb, but tends to be less poetic and more of a definition: "The best way to be kind to bears is not to be very close to them."

[Dr. Who] What is the difference between a Time Lord and a time agent like Jack Harkness? I'm currently on season 4 episode 7, please keep things spoiler-free!

If it is explained more in-depth in later episodes just say so.

Time Lords are essentially Gallifreyans mutated by the Time Vortex. They are the ruling elite of Gallifrey. They police time based on their own authority. Time Agents are government agents from the 49th-52nd century that police time. They're not immortal, they don't regenerate, they're just guys with time-travel wristwatches that bip in and out of time to prevent alterations and the like.

ELI5: Why is the record on voyager plated in gold?

To add, the record is copper, plated in gold, and then plated in U-238. The reason to make it all metal is that vinyl couldn't possibly survive the harsh environment of space without quickly decaying, and the uranium, with a half-life of 4.468 *BILLION years*, is there so optimistically, a civilization who discovers the record can date it's age.

ELI5: why do people say today's education system is suited well for girls over boys?

Iv heard multiple times (no particular sources just general talk from online articles and in person) that today's educational system favors girls. What is the basis for this and is there truth behind it? I know that in my highschool there were more girls than guys on honor roll, and when I went to college there was a higher percentage of females as opposed to males.

Girls generally mature faster neurologically (the female brain is more or less developed by 19-21 while the male brain may be as late as late 20's), girls are generally also more compliant and follow orders better (whether that's due to biology or social conditioning or some of both is up for debate). Generally boys may tend to learn better through "active" learning techniques and competition than the current passive learning techniques used in institutions currently.

Why does strong coffee make me uncomfortably tired sometimes?

You are dehydrated. If you were properly hydrated caffeine would not make you sleepy. The more water you've drank before cup of coffee the better your body handles the restricted blood flow from shrunken blood vessels. I'll be searching for references. This is the answer I've seen from a similar post.

ELI5: How are hills made? For example, how are there hills in central Texas if there is no seismic activity?

There is a fault line that runs along I35 between Dallas and San Antonio. If you stop at Wonder World you can tour the fault line and they do a good job showing the different topography on each side of the fault. So the answer is that the hills were formed due to seismic activity that formed the hills and Balcones Fault long ago.