[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why do Lithium Ion batteries lose their ability to maintain charge after many cycles of charging?

Is this due to a chemical reaction? Perhaps Lithium escapes as a gas?

[Assistant]
It is due to several things.

The most important is physical. During charging/discharging lithium atoms move from one electrode to the other. The lithium goes into tiny pores in a sponge like electrode, but when this happens the sponge swells up. Repeated swelling and shrinking eventually causes cracking and fractures in the electrode, degrading it.

The other main effect is chemical reaction in the electrolyte. During charging, tiny amounts of electrolyte material undergo unwanted chemical reactions with the electrode chemicals. Eventually the electrolyte gets polluted with all the byproducts of these reactions degrading it.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5. Maybe a dumb question, but why didn't the Vietnam war produce terrorists, like conflicts in the middle-east?

I mean, the war left the country devastated, and I'm sure there were a lot of people angry at the US.  Why didn't anyone try to strike out at the US?

[Assistant]
Terrorism, particularly international terrorism, doesn't just "happen" and not liking a country is never enough motivation on its own to start. Al Qaeda and other extremest groups of that ilk really have a history of at minimum decades or (depending on where you say it "starts") centuries.

Al Qaeda doesn't just hate the US, they have a vision of a grand pan-Islamic new caliphate. Their strategy has been to find an area with a Muslim population (but not an exclusively Muslim population), destabilize the region and in the chaos come to power using their dedicated and fanatical followers to create an extreme Muslim government. They did this in the former Yugoslavia, they did it in Somalia, they did it in Afghanistan during Soviet occupation, and they tried to do it in the Philippines with a series of attacks most of which we stopped (including the assassination of the pope). "Terrorism" is just a term we have applied to the kind of non-state militias, but they always have a purpose to their actions. It is for the glory of their interpretation of Islam and has the goal of creating a new Muslim caliphate. Al Qaeda litterally means "the base" and that is referencing that it is meant to be the first step in the foundation of a global and unified power.

Vietnam may hate the US, but there is no group like that in Vietnam. The whole war is seen very differently because of the Cold War, but the Vietnam War started the day after the Japanese surrendered in WWII as a war for national independence, not a war against the US.

Ho Chi Minh was not a communist at first but a nationalist. He went to Versailles to plead for independence from France as promised in Wilson's ideal of self-determination, no-one would take a meeting. So when WWII ended, he released a deceleration of independence, declaring Vietnam was no longer a colony but a sovereign nation, invoking Woodrow Wilson, FDR, Thomas Jefferson and the Deceleration of the Rights of Man.

France was not willing to let its colony go and the US sided with it's ally France. Ho Chi Minh started getting aid from the Soviets, but only because the US would not help. Eventually France was defeated (surprise) and the country was divided in two. Ho Chi Minh wanted a unified nation, but the US was willing to defend the south. That's what the Vietnam War was about, we tried to keep Ho Chi Minh isolated to the North, but the Vietnamese people are not really divided north/south.  To them it wasn't a defense against communism for the most part (though that did exist and why many Vietnamese immigrants came to the US in the 70s) but about the unification of the country.

Now the country is unified, it's economy is improving rapidly, it is normalizing relations with the world. The US left scars for sure, but there is no reason for the Vietnamese to keep fighting us. The war is over and there is no reason why it should continue.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5:How does an atom splitting cause an explosion?

Are there other chemical reactions that take place? Alternately, is it a gunpowder type reaction- as in the spark ignites the powder which causes the bullet to launch? Or is it really just as simple as an atom becomes damaged, causes insane destruction? Also, is it any old arbitrary atom that can be split, or a specific type/element's atom that causes this effect?

I am a first year college student taking chemistry for the first time, it's fascinating but I haven't found an answer to this on google that doesn't use terminology that goes over my head.

[Assistant]
Splitting an atom creates two new atoms. If the atoms have an atom number higher than iron, that means the two new atoms (which will have a lower atom number than the original atom) have a lower combined mass than the original atom. The mass that 'disappears' is converted into energy (typically electromagnetic radiation) following the famous equation E=mc^2
This is a very different mechanic than the chemical explosion from for instance gun powder, which converts chemical bonds into chemical bonds with a lower energy, thus releasing (typically thermal) energy.

Note that fusing 2 atoms of lower atom number than iron (famously 2x Deuterium -Hydrogen with 1 neutron- into Helium) actually loses mass, thus creating energy in that way, which is what fusion reactors and the sun do.

Note that splitting atoms in atomic bombs works because the atoms used are unstable, which means they will split (or: fission) by themselves at some point (the half-life time describes how fast this goes, but it is in nature a quantum mechanical probability). To get an actual explosion you'll need (much) more than just 1 atom splitting.
The way this works in a nuclear bomb is as follows: the atom type is chosen such that when it splits, it releases 3 neutrons, next to the 2 new atoms (uranium-235, splitting in to krypton and barium). These neutrons 'fly out' and could 'fly into' a nucleus of another atom. If that happens the atom that 'absorbs' the neutron becomes unstable and will split, releasing 3 neutrons, again. As you can imagine, if all the 3 neutrons are absorbed by a uranium atom every time, the amount of atoms that splits goes up *really* fast (3^n ), which means that it releases a lot of energy in a very short time. In other words: boom.
In order to reach that point you'll need a specific minimum percentage of uranium-235 (which isn't all that common) and a minimum amount of uranium atoms (critical mass). This makes creating a nuclear bomb very complicated.

Obviously this is not a *very* detailed and accurate description of what really happens (ie, I've made some generalizations and errors while explaining), but it should give you a good idea of how it works.
Being a physicist I'd like to add that this is technically not chemistry we're talking about.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Why is nature comprehensible to us?

I went from a physics program straight to a philosophy graduate program and so likely missed out on the relevant literature, but I can't seem to find it on the SEP. So as to make my question more precise, it was motivated by the following two sentiments:

> It is precisely the common features of all experiences, such as characterize everything we encounter, which are the primary and most profound occasion for astonishment; indeed, one might almost say that it is the fact that anything is experienced and encountered at all. (Schrodinger)

and,

> One may say the eternal mystery of the world is its comprehensibility. (Einstein)

That is, we find enough reason to be astonished that, say, abelian gauge theories like quantum electrodynamics offer so precise a framework for predicting and interpreting the time evolution of natural systems. But that we are able to come to this knowledge at all, or even to knowledge of the ordinary objects of experience, seems even stranger. Are there philosophers who approach this question in any manner?

[Assistant]
what is "nature"? what is not nature?

Kant divides our cognition into sensibility (providing access to experiences) and understanding (or intelligence related to those experiences). the phenomenologists and Merleau Ponty particularly collapsed these two, arguing that all comprehension of the world is subject to the perceptual process that creates a "lifeworld" of lived experience for the individual.

"nature" is interesting to consider in that context, because we can ask what is natural and what isn't? philosophy of science (Kuhn and Midgley for instance) has done a lot of work to critique whiggish, objectivist accounts of sciences as providing progressively improving and pure descriptors of nature, and instead argues that the products of science (the sort of sense-experience we get from it) are both convenient and perfectly natural human constructs.

science and technology are constantly redefining what we perceive as "natural," whether in the social sense or the "natural sciences" sense, since they are involved with expanding the scope and nuance of our lifeworld. as we articulate the natural world via science or "conquer" nature via technology, we pacify its raw strangeness, subjectifying what is otherwise incomprehensible. so comprehension also has to do with power. a pheonomenologist like Dylan Trigg might argue that nature in-and-of-itself is a horrifying abstraction beyond our comprehension, so this is why we invent our own means of interpreting it (think Bowker and Star's work on classification or Foucualt's The Order of Things)


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5:Why do ALL big-box stores like target, walmart... have over twice or three times the height needed in shopping space?

[Assistant]
1. The air circulates much better and the experience is far comfier.

2. From a structural perspective a very large but "flat" store would be a very bad idea. Basically if each foot of girder + square foot of wall makes up 1 unit of strength, that means the ability to support the ceiling is directly proportional to the height of the building.

3. From a psychological aspect, a low ceiling makes shoppers feel very "caged in" like mice.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] Does distributed generation (e.g. rooftop solar) on a power grid reduce transmission demand?

[Assistant]
Yes, sort of.
Electricity takes the path of least resistance, from the (rooftop PV) inverter into the service panel, where it will first (try) to power any loads inside the house itself (replacing 'utility' power).

If there is not enough demand in the house then it will leave the premises and (try to) power the neighbour's house, etc, until eventually it will reach a neighbourhood substation and (tries to) power the next street.

The 'electrical' load on the transmission(+distribution) will be lower, but because rooftop PV is not 'dispatchable' (doesn't have a throttle and is subject to clouds) the operators in the grid control room have to work harder to 'balance' the grid at large.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[The Flash] Why doesn't Barry KO his foes with a superspeed punch before they can even react?

This is something that happens often: The flash arrives to the place where the bad guys are and, instead of handcuffing them before they can even react or knocking them out in less than a second, he stops to talk or fights in the most inneficient way possible, which gives his enemies the chance to escape. Because of that, he loses a lot of fights that he should win. Like, It was comprehensible when he was just a beginner, in his first week of fighting crime, but after all this time he should have realised that there are better ways to use his powers.

[Assistant]
Depending what Flash we are talking about, but to make it simple, lets use Barry and Wally as they are the two most noticeable. Both of them are known for being compassionate and yes, they talk to their opponents because they rather resolve the issue with the least amount of violence and fighting as possible. They know that most that they face are in terrible or hopeless situations that lead them to where they are facing the Flash and they rather not make it worst.

Plus, using that punch (The White Dwarf Star Punch) would kill most people and that wont look good for the Flashes.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why did film have to start out black and white? What part of the technology was missing that there couldn't be color?

Thanks so much for all the answers, guys. I really appreciate it.

[Assistant]
Color film was EXTREMELY high tech, actually.  It took a lot of care, trial and error, and investment to get it to work right.

B&W film is a sheet sandwiching a layer of gelatin full of silver crystals.  These crystals darken very quickly in a similar fashion to sunburn.  Just like sunburns, you don't get a variety of colors, just different levels of "darker than your normal skin".

Color film is actually the same process, but with several layers of emulsions for each color.  So you now have a sandwich that is like quadruple layered, but in order for it to work it still has to be thin enough to go through the camera.  All those layers and protective interlayers are thinner than a human hair.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: Why is the immune system so fast to respond to allergens, but take days to fight off a legitimate infection?

[Assistant]
Your immune system fights off most germs as quickly as it responds to allergens.

Our bodies are invaded by germs constantly. Every breath you take. Every bite of food. Every cut in your skin brings germs into your body. Nearly all of these germs are killed within minutes or hours by immune cells that respond instantly.

It appears to us that infections take days to fight off because we only notice the ones that get out of control, but the overwhelming majority are so quick and painless we never even know the germs were there.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Doctor Who] What kind of political system do the Daleks use? Do they have an infrastructure? Do they trade with other races?

We see that the Daleks have both an Emperor *and* a Prime Minister, and that they have a ship-based Parliament but *also* a governing body on Skaro (where Davros and the Supreme Dalek seem to rule). How exactly are Dalek politics managed? And if all are equal, how are some Daleks promoted to Supreme Dalek or Emperor? Is the Prime Minister voted for?

How are construction projects and other vital public sector tasks managed by the Daleks, do they just scavenge supplies and carry them out themselves? Or do they trade with other races and use slave labour to complete necessary projects? Of course trade seems incredibly unlikely for a hostile race like the Daleks, but it seems it might prove more useful to have *some* alliances here and there rather than going planet to planet killing people and stealing shit, as that's *bound* to piss off every other race in the universe. Do the Daleks have any money with which to trade if necessary?

[Assistant] The daleks don't trade, they conquer. There was only one race to rival them in power and they actually won that war. They have noone to fear and no reason for any allies. They outclass everyone else. Also they are super space racists that kill everyone that is not a dalek (or is a genetic impure dalek)


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why did it take so much time to introduce dark theme on the most common platforms? And why do companies act like it was such a difficult task to realize it?

I mean, when they add dark theme it seems to be the biggest revolution in history, instead of saying "we are sorry it took 10 years to accomplish this pathetic color change"

[Assistant]
Software developer here.

TL;DR: Realistically dark mode is just much more complicated than it seems on the surface, and there are many reasons why.

First is your design and how easy it is to translate to dark mode. Sure, you can go ahead and ctrl+f all whites to blacks and vice versa, but the result will be much like a negative photograph - it just looks and feels weird. Shadows meant for a light app will feel out of place on a dark background. You may find your brand colours do not fit at all in a dark theme. The list goes on, but to build a usable dark mode many things need to be slightly "redesigned" to fit a dark theme. And this is not a one-time task: having dark mode available also means that any new features will need to also be designed to work in it, which increases design work needed to ship new things.

From a software development perspective, implementing dark mode requires the overall theming of your app to be setup well, ideally such that you can change a single line of code to e.g. change the accent or background color across your entire app. This is pretty much a prerequisite for being able to have dark mode (the user clicks a button and the theme changes). Traditionally it has been quite rare that you would need to change your theme colors, which also means that many apps and websites are built without any such fancy theming system in place - colors are just hardcoded and other more important features have been prioritised. Or perhaps development of the app was started some time ago, when the entire idea of users being able to change the colors according to their preferences was not very trendy. In any case, if your app has not been built with a theming system in place, the effort required to implement such a system now  in a large project  might be many weeks of work and involves slightly editing almost every single file in your project.

Often development/design resources are limited and implementing dark mode would then mean that some other work will be delayed for however long it takes. In the end, dark mode is a purely quality-of-life update for an arguably niche user group and it can be very hard to convince your sales team that the value of adding dark mode is higher than all of the other things waiting on your roadmap.

EDITs for clarity.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] Why does putting a hole in a balloon cause it to pop instead of leaking air from that hole?

[Assistant]
The "pop" is really just a fast leak. It's happening so fast because of the balloon material is under stress after expanding during inflation. The hole allows the material to relax while reducing internal gas volume.

Fun fact: the pressure inside a balloon is about equal to the atmospheric pressure on the outside. It expands because you are increasing the number of gas molecules inside (according to the ideal gas law PV=nRT; where P is pressure, V is volume, n is moles of gas, R is the ideal gas constant, and T is temperature).


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
is there a reason our map is the direction it is?

i saw a pic of a map of florida that was upside down to help tourists or something. i started to wonder if there is any reason that north america is on the top of the map and south america is below it. is there a scientific reason or did they just have to pick a direction?

[Assistant] North being up is simply a product of Greek and Roman cartography revival during the Renassaince in  Europe.  Many maps used to be East is up as it was named Orient and therefore used to 'orient' the map.  But North=up is completely arbitrary, we are just in space, and space does not have an 'up'.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Kilanova explosion timing

So, I just learned about kilanovas (yes, I seem to be a bit behind) anyways, if the kilanova on 2017 was 130 million lightyears away, wouldnt that mean it happened roughly 130 million years ago because the light from it all had to travel to earth? Or is there some other magic I dont know at play?

[Assistant]
Nope, you got it right.

If you look at the sky, the moon you see is not actually the moon. Its the light that was reflected from the moon some time ago - 1.12 seconds approximately. Which means if an explosion happened on the moon, you wouldn't see it until 1.12 seconds later.

But moon is close. Other stuff is futher away. Yes, if you were looking at the telescope and saw the Kilanova, that means the light from that had to have reached you already, meaning it happened previously. If the Kilanova is 130 m.l.e. away, then if you JUST saw it right now, that would mean it happened 130 M years ago. If you are seeing it in progress, then it means it could have happened even earlier than that. But never later.

If something happened in that same area now, you wouldn't know about it until 130million years later.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Is my finance professor misleading me?

Hello, my new finance professor has been teaching us about how the Federal Reserve is screwing the government by forcing the government to pay interest on the money the government borrows. He believes the government should print money, therefore they wouldn't have to take on so much debt.

Is this true?

[Assistant]
The government does pay interest to the fed, but this ignores the fact that the fed remits all its profits to the treasury. So the government pays say 500 million USD to the fed in interest (no idea the real number), and then the fed turns around and reports that as profit and gives it back to the government through the treasury.

We could have the fed not charge the government any interest but this would merely change some numbers on a spreadsheet somewhere and wouldn't change anything about the government budget.

EDIT: What your prof. might be saying is that the fed should lower its interest rate target to 0% so that the government doesn't have to pay interest to other (non-fed) bond holders. This is correct in the sense that it would actually affect the government budget but is wrong in the sense that it would often lead to runaway inflation.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
They say that a photon takes a million years to make it out of the Sun. But what does it even mean? How do we define that a particular photon now is the "same" photon that was there then?

When I'm doing photons-in-a-box problem with large enough number of photons, and I add a photon in, and later I let a photon out, there isn't really a sense in which I can say which one of the photons got out, any more that when I add 1+1=2, and then subtract 2-1=1, can I tell which one did I subtract (quite literally, this is how Fourier transform seems to work). They just blend into one wave until I decide to unblend them.

I'm imagining the interior of the Sun to be a giant soup of photons, constantly absorbed, reemitted, bouncing around. Sometimes new photons are created by fusion, and sometimes some photons get out into the interstellar space, but how do we "track" them?

[Assistant]
It would be more accurate to say: "The energy from a photon released by a fusion reaction in the core takes about 1 million years to reach the surface." They start as gamma ray photons. Due to the density they only travel a short distance before colliding with a particle and being absorbed. That energy is re-emitted (sometimes as multiple photons with less energy each) then re-absorbed by something else. That random process continues until an energy-excited particle near the surface finally releases a photon that escapes into space.

Consider the game "Plinko" as an analogy for this. The million year figure is a statistical approximation, not a measurement.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [MCU] Have car insurance rates gone up due to the rampant destruction of vehicles by heroes and villains?

[Assistant]
Not really, no.

Despite the large scale very visible damage caused by superhero events, they are still few and far between.  That means it's unlikely in the extreme that your car will get hulk smashed or something similar.  It's far enough down the actuarial tables that they haven't had to raise premiums over it.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: If our body is trying to conserve energy by losing muscle mass we're not using, why does being sedentary ultimately end up being more harmful?

[Assistant]
Humans evolved in an environment where conserving energy was a definite survival advantage as food availability wasn't guaranteed - so the human body developed a 'use it or lose it' system.

But humans also evolved in an environment where survival involved constant physical activity whether that was hunting, searching, foraging, fleeing, etc.

So the 'use it or lose it' system never needed to develop a safety net, because humans tended to maintain a minimum level of physical activity, especially when food was scarce.

So these days, the 'use it or lose it' still functions, except people don't tend to starve if they're not active. So the musculoskeletal system - bones, tendons, ligaments, joints and muscles - will slowly degrade to the point where your skeleton will struggle to just support your own weight.

The cardiovascular system and your aerobic capacity undergo similar atrophy, and there's also the fact that people who live sedentary lifestyles rarely tend to adjust their calorie intake accordingly which leads to weight gain that exacerbates all the other issues.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: why do people get sleepy from 2-5PM but wide awake from 2-5AM sometimes? Why isnt it the opposite always?

[Assistant]
When you eat, your body has to do work to digest the food. This is why you sometimes feel tired after lunch.

Most people don't eat in the middle of the night, so this isn't going to be a problem then, but when it's dark and quiet, lots of people get worried about things that they are too distracted to think about in the daytime, so they feel awake thinking about them because worry makes you alert to look out for danger.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5 Why do we not bleed out during a surgery?

Myself, having gone through a surgery, I wonder why we do not lose huge quantities of blood during a surgery.

[Assistant]
That is one of the things about learning to be a surgeon that makes it more difficult than butchery. Anesthesia can be used to lower blood pressure, medicines applied to reduce bleeding, and as the surgeon cuts they will try to avoid major blood vessels and clamp shut those they must cut. Smaller ones may even be cauterized, burned closed by a heated tool.

Most of the time (~94%) blood transfusions are not given during surgery because they are not necessary. Keeping your own blood inside you while making holes for them to work is part of why they need so much training.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [Dragon Ball Z] Why did Dr. Gero turn himself into an energy absorbing Android when the 17 and 18 models were demonstrably superior?

[Assistant] Gero's model literally had no limit to the amount of energy he could absorb and utilize. Even though 17 and 18 were strong, their power never changed, and Gero was convinced he would surpass that power using his newer models. And as far as he was aware his base power was more than enough to handle the z fighters, PLUS he had backup with his other android. It was a great plan but he just had bad information.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [Game of Thrones] Besides high Valyrian, what languages do the noble kids have to learn as part of their formal education?

[Assistant]
Probably just High Valyrian. If you know Common Tongue you can communicate with anyone in Westeros, even with most of the Wildlings, and if you know High Valyrian you can communicate with anyone in the Free Cities and Slaver's Bay you just need to be aware of the regional dialects.

Those two languages cover basically everywhere west of the Dothraki Sea.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Can the Doppler effect make sounds inaudible by shifting frequencies out of human hearing range? Or vice versa?

Say a speaker playing a song travels away from you fast enough, would the bass part become silent?

Say you were traveling towards a whale making low frequency sounds out of hearing range, would you be able to hear them if you were traveling towards each other fast enough?

[Assistant] Absolutely, although in practice, the frequency of the sounds would need to be fairly close to the limit of human hearing so that you wouldn't need to be going very fast.  At very high speeds required for very high doppler shifts, wind noise would likely drown out what you were trying to hear.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Does friction exist on a subatomic scale?

As I understand it, friction is the result of electrostatic forces between different objects interacting (electrons and protons attracting and repelling each other). So if you were to take two neutrons and rub them together, would there be any friction?

[Assistant] Friction is a macroscopic effect. There are no meaningful analogs at the atomic or sub-atomic scale. At the atomic scale there are interaction cross-sections and various types of forces somewhat generalized as bonds and weak interactions such as van-der-waals forces and things like fermi-level interactions, cooper pairs other inter-molecular forces. At the subatomic scale its entirely different. The strong and weak nuclear force dominate. Friction is the result of many small forces combined. Atomic is the opposite of that.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why are metals like gold, silver or copper not as reactive as sodium or potassium even though all have only one electron in their outer shell?

 I have learnt that since sodium has only one electron in it's outer shell, the atom becomes highly unstable and reactive, and in order to become stable, it often reacts with other elements to form compounds. But, even less reactive and stable metals like gold and silver have only one electron in the outer shell, why aren't they as reactive as sodium or potassium. Why aren't they unstable and react with other elements commonly?

[Assistant]
Reactivity isn't just about how many electrons are in the outer shell, it's also about how tightly bound those electrons are and which shell they're in. The farther out you go, the less energy involved. Gold is a much much larger atom than something like sodium, so the outer electron shell is much farther out, and more sparse, the energy change involved in the outer shell electrons is much lower, and hence the reactivity is much less.

Filling the 2nd electron in the 1s (first) orbital, like with hydrogen, is very energetic. That's why hydrogen reacts with basically everything.

Gold is far larger; there are 79 electrons, filling parts of 14 orbitals. Pulling an electron off the 6s orbital (gold) is a lot easier, hence doesn't involve nearly as much energy and isn't so strongly favoured.

Gold is also big enough that the orbital filling order gets weird, it's lower total energy to fill higher orbitals than to try to overstuff some of the lower ones. In addition...gold "should" have a full outer shell 6s orbital if you're just counting electrons but you end up in an lower energy state if one of those outer electrons drops down to complete a lower orbital (5d for gold). Copper and silver are the same way, they have an electron count that corresponds to having a full outer shell but the electrons are reconfigured to a lower energy state within the orbitals that results in the outer shell having just one.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: Why does a slightly hot shower feel like you are burning when it touches your skin, while a hot tub set at 102F feels comfortable when you get into it?

[Assistant]
In addition, a hot tub has its water somewhat static. When you enter, the hot water transfers its heat to you but stays roughly where it is, so it kind of forms a shield of slightly colder water around you. You notice, when you move inside the tub it gets hotter briefly.

In a shower, there's new hot water constantly touching your body, its gonna be hotter.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
How are natural instincts explained on a fundamental level? Where do they originate and how are they inheritable?

How are instinctual behaviors inherited? Would they survive in an animal raised in isolation from others of its same species? I find complex behaviors like intricate web, hive, and nest creation particularly fascinating.

[Assistant] you can think of instincts as neurological patterns that have been selected for and evolved over millions of years. The ones that adapt to react to certain stimuli caused them to survive better in certain situations. very gradual.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
CMV: Children should not be punished for bad grades.

With the holiday season coming up, I have seen several tweets spark joking about kids/teens knowing theyre no longer going to get anything on their Christmas wishlist due to bad grades. When I was younger, I also got grounded for bad grades, sometimes even spanked. I do not believe in this method of discipline (for non-rebellious bad/failing grades). Heres why:

1. I believe it projects a message of poor problem-solving skills as a parent: grounding or punishing your child for poor academic performance is an easy cop-out rather than dealing with the problem at hand.

2. I believe children (who arent being lazy, skipping school, etc.) who are producing subpar grades in school may simply not understand the content. Even if I cant personally help my (future) child with his or her homework, I would ask other relatives, contact the teacher, or reach out to a tutor/friend who could assist.

3. Revoking toys, games, etc. from children dont really teach them the importance of making good grades. Children should know the content not only for the benefit of passing the class, but to prepare them for future classes, as well as knowing basic skills once college comes around. If nothing else, they should be able to help their own kids with these same problems later in life!

4. Lastly, I believe punishing children for something they do not understand is merely torture, not fair, and counterproductive. Let them bump their heads & mess up a little. Put them on the spot and teach them the importance of consequences. Furthermore, your children should never be afraid to show you a report card out of fear or embarrassment. Parents should be of help and support.

*I am not a parent, I am 20-years-old. Maybe my mindset will change later in life. Id love to hear from both parents and non-parents!

[Assistant]
Is the child getting poor grades because of a lack of understanding, or because they actively choose to not complete work / study?

Those are two different scenarios, and should be treated different.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why doesn't earth have nearly as big craters or nearly as much craters as other planets?

Edit: OH MY GOD, I LEFT FOR TWO HOURS AND THE POST BLEW UP. Thanks, I really appreciate the answers!
Edit 2: Guys thank you for all of your answers, I really appreciate it.

[Assistant] The Earth has erosion and large oceans which other planets do not have. Erosion erases craters. So does deposit of sediments. Oceans cover craters and tectonic plate movements erase them eventually. Geologists have become better at identifying craters which have become obscured. The Atlantic Ocean is 250 million years old which means no craters from before that time are visible.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Since the adventures of Scooby Doo and his gang have pretty conclusively proven to us that there's no such thing as ghosts, why do a few periods of their life seem to contradict this?

I remember back when Scooby and some of the gang were tracking down thirteen actual ghosts, or more recently, encountered some actual zombies and cat-creatures.  Just what is the nature of magic in Scooby Doo's universe?  Sometimes logic can be used reliably, "ruling out the impossible", as Sherlock would say, but sometimes it can't.

[Assistant] Why do you think Shaggy and Scooby would be scared shitless of every disaffected carnival operator in a glow-in-the-dark costume if they didn't have real experience of the supernatural? This also explains why attempting to disguise fairly petty crimes as the activity of ghosts is so incredibly common in their world. In fact, the gang, though skeptical, tend to approach each event they investigate as if it could be supernatural, ruling that out once they find clues that point to a mundane origin. This suggests a setting where supernatural events do occur, but are rare. As the gang picks up a reputation, they eventually start to become more and more involved with higher profile cases involving genuine supernatural powers.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[X-Men] Could Wolverine really teach an art class?

What other surprising things could he teach?

[Assistant]
He is like civil war old.  He has had time to learn all sorts of things.  Almost certainly has hidden depths.   He has lived in other countries.   Hes lived in Japan enough to absorb the whole "code of the Samurai" thing.  Pretty sure that means understanding more than the arts than just the martial ones.

Maybe he knows flower arranging.

Betcha he knows all the lumberjack arts.

Almost has to know enough to be in the merchant marine with all the travelling he does.

Equestrian skills - lived plenty of years before cars.

Survival (duh) - Huntin n Fishing and other homesteading skillz.

How to get through a long Canadian winter alone with yourself.

Self-taught hair stylist would explain the consistently unique do - does it himself.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [MCU] What purpose does Hela's spiky head thing serve?

[Assistant] It's a crown. Its purpose is mostly symbolic, to show her authority and power to the world, and to make her easier to pick out of a crowd (which was an advantage in the style of warfare she was used to).


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Star Trek: TNG] How does the Holodeck simulate large spaces, particularly when two people are far apart from eachother?

I understand that it creates an artificial environment and can sort of move like a treadmill to make you think you are traveling long distances,

BuT...

I watched the episode last night where this pre-industrial planet is dying so Warf's foster brother transports them into the holodeck, into a simulation of the cave they were in. He then tells them they have to go on a long journey to a new home, at which point they would be transported back down.

At one point however, somebody says he forgot something and has to go back. Warf lets him go back . How is this accomplished? Isn't the small cube shaped room already changed to a different environment? (where the core group of people currently are). How is he then able to walk away from them such a large distance, back to the starting point?

Jeff

edit: i started a new office job recently and was so used to ending all my emails with "-Jeff" that i just instinctively did it with this post... but I'm gonna leave it because i kind of like it.

[Assistant] I've always pictured it putting up a holographic wall between the groups and displaying the appropriate images on each "side" depending on either groups point of view. One would show the person who left walking towards the horizon while the walkers side would show whatever he left shrinking as his perspective changes. Essentially it would treat the different groups as scenery for the others.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
How do T cells recognize the S protein as an antigen on MHC-1 for the mRNA covid vaccine if it is foreign?

I've scoured the internet to find this, and a lot of answers are along the lines of "yeah your body just know that the S protein = bad when presented on MHC-1." As you can expect, this isn't very informative.

From my understanding, the mRNA vaccine doesn't secrete the S protein extracellularly either, so they aren't phagocytized by an antigen-presenting cell.

I was thinking maybe there's a specific T cell that binds to MHC-1 and somehow has a receptor for that S protein? Is this the case? Because there is a huge variation of T-cells made with different receptors right?

 1. If this is the case, isn't it quite ineffective to wait for a T-cell to come along with maybe a 1 in a million chance of having a receptor that binds to the S protein (Covid spike protein)?

 2. Is there another way that our body recognizes the S protein as an antigen?

[Assistant]
So the MHC doesn't present the whole S Protein,  but various fragments of it. But yes,  then it is necessary if a pre existing immune cell with the right receptor to recognise one of these fragments, this occurs because the innate immune system sends out triggers for circulating immune cells to enter the area.

That first cell (or more likely various cells) doesn't need to have perfect recognition, just enough to trigger binding, because after the initial recognition that cell will undergo massive expansion and hypermutation to produce variants of itself hunting for the best fit.  The immune cells produced with the best receptor get the strongest proliferation signals and end up being the majority cell type in the immune response.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Harry Potter] Why didn't Dumbledore just cut off his hand to stop the curse form spreading to the rest of his body?

Surely losing a hand is better than losing one's life.

[Assistant] The damage was done, the hand was just the physical representation of what was happening to the rest of him. That poison was going to kill him lose a hand, everything below the neck, it wouldn't matter.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
I don't understand how someone else's happiness compensates for my pain in utilitarianism

There should be nothing wrong with utilitarianism here if 10 people rape a woman and there is great pleasure, and then the woman is killed and no one knows about it. But I don't see how their pleasure can compensate for my pain. We are different people. How can their happiness affect my pain?

[Assistant] This is essentially Rawls' objection to utilitarianism. He objects that utilitarianism fails to respect the separateness of persons. Just as we usually think that pain suffered by me now can be compensated by the experience of pleasure by me in the future, the utilitarian assumes that the pain suffered by one individual can be compensated by the pleasure experienced by other individuals. But, according to Rawls, this neglects the fact that in the latter sort of case, the pleasure and pain are experienced by different people. Parfit famously tries to respond by challenging the moral significance of the fact that two individuals are separate people.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] In a plant seed, has the metabolism completely stopped until germination or is there still very very very slow "life" happening? In other words, is it "paused", or is it consuming energy very slowly?

[Assistant]
Seeds have inhibitors in place to prevent wasting Large amounts of energy and germinating In conditions that do not have adequate: water, oxygen, temperatures, or soil. Some seeds do use small amounts of energy while dormant to fuel cellular respiration.

So, to answer your question, seeds that havent germinated yet use small amounts of energy for basic processes to stay alive and wait for good germinating conditions.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Fight club] would they let women join?

 It would help project mayhem to have access to women in housekeeping and janitorial.

Would they fight men or have their own division?

[Assistant] No. Tyler's ideology was that Fight Club and Project Mayhem were a way for men to reclaim their masculinity through violence. The entire point is to reinforce premodern gender roles, therefore he would have no place for women in the fight.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] What happens during near-death experiences?

[Assistant]
First off: there isn't all that much known about NDE's apart from anecdotal experience.
Chemically, it is often said that during an NDE, there is a release of certain neurotransmitters in your brain, including the powerful psychedelic compound DMT. This is often used as the explanation of the NDE, and the effects of DMT do often correlate with those reported to happen during NDE's.
The 'typical' experience often involves floating above your body and looking at yourself from above; possibly flying around and visiting relatives etc. If you want to experience similar things, try lucid dreaming, meditation and even DMT itself.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
"If the assumptions imposed in an economic theory are unrealistic, then the theory may nonetheless predict better than any alternative theory."

I don't quite understand this statement, I was wondering if someone could provide an example of what an "unrealistic assumption" might be within a given economic theory/model.

[Assistant]
common sense and classical economic theory predicts that if two people are similar (same gender, age, schooling, skills, etc), they should be paid similarly. However, that is not the case when we look at real data.

People like Mortensen and Pissarides showed that in their economic setting, one of the major causes of this was what they called search frictions, that is, people wanting jobs and firms wanting people don't meet efficiently. This causes wage dispersion and unemployment.

If you look at their models' assumptions, we have standard stuff like utility maximizing agents, to some more out there assumptions like Nash bargaining behaviour, random job destruction, exogenous wage determination etc that makes the models more tractable. Obviously none of these assumptions actually happen in the real world. People are not thinking about Nash equilibria, wage determination is very complex, etc. However, (some of) the predictions of the model are on point and consistent with what happens in life. How come such an 'absurd' and simple model can make predictions so consistent and reasonable? That speaks to the value of abstraction and mathematical modeling.

If you tried to come up with an unemployment model that tried to have no assumptions and tried to have every feature of the real world in it, it probably would be of no more value than a much simple one, and at a much higher cost.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
What is a mathematical proof? How is something "proven"?

Can someone also give me an example of a mathematical proof that I can, as an arts major, understand?

**Edit**: I *am* going to read all of this! Not tonight, though. Thanks for the answers, and for any more answers to come.

Also, I thought I'd put this question up here since it generated a lot of discussion:

**Follow up question**: How are the basic laws of mathematics proven?

[Assistant]
Here's an explanation for the layman. In practice a proof is just an explanation of the truth of a statement that is sufficiently convincing to other mathematicians because giving all the details is usually prohibitively time consuming and unnecessary.

More precisely, a mathematical proof is a series of logical deductions and inferences that reduce a proposition to a logical combination of axioms or previously proven propositions, or to a contradiction of such, thereby establishing that the statement is as true as the assumptions and axioms. Technically, a valid proof is reducible to a series of statements in set theory (or some other foundational theory of mathematics and logic) that could in principle be verified directly or by an automated proof checking program.

Axioms -- basic laws of math -- are never proven; they are assumed and generally simple enough that most mathematicians accept them without issue. Some people study the axioms and whether they are consistent, and there are many deep results (Godel's theorem's) and controversies (e.g. the axiom of choice). There are many difficult issues that arise that are not initially obvious, such as the fact that some statements can not be proven true or false in a given system of axioms (they are "undecidable"), though they may be true or false given another set of axioms. Just deciding if a set of axioms is consistent turns out to be extremely difficult.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: Why do some people lose their appetite when they're upset or depressed, while others consume more food??

I'm the type that absolutely cannot eat when I am upset or depressed. I know this is common, but so is eating more when depressed. What determines how a person's hunger will be affected by their emotions?

[Assistant]
People who eat more food when depressed generally do so because it's comforting to them (hence the name "comfort food"). Food high in carbs and sugar also help increase levels of serotonin in the brain (a neurotransmitter that elevates mood), thus helping to calm their nerves. So basically they use food as a drug to self-medicate their depression.

People who eat less food generally do so because they feel a lack of motivation or energy to eat food. Then there is also the fact that your stomach can have a hard time accepting food when you are extremely stressed (which is why some people throw up when stressed). Sometimes their bodies are just too riled up to be able to process food, so it doesn't seem as appealing.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] Why does alcohol dissolve ice faster than water?

[Assistant]
In any ice / liquid bath, the ice will stop melting when the whole system reaches the melting point of the system. That is to say that when you mix water and ice together, ice will melt until the water reaches zero degrees Celsius, at which point the rate at which water freezes is equal to the rate at which ice melts - there is no net change in phase. The only reason we observe ice melting continuous is due to incoming heat from the environment.

Alcohol has a lower melting point than water. This means that more ice must melt before equilibrium is reached.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
I believe that salaries in sports are insanely too high and pros don't deserve this amount of money. CMV.

In my eyes, pro players of any sports don't deserve to be paid in the millions for practicing their sport. Yes, they are the best at it in the country/world, but even 500k/year during 10 years in plenty of money to go on with your life after being a pro.

I don't get why the governement don't tax the shit (talking about 80-85% for huge contracts) out of the money they don't need. After all they are just there for entertaining the public. Without us, they would be nothing.

As you can tell, Im sitting on the very left wing in terms of politicals views.
For context, I live in Canada so hockey is more relevant here.

CMV. I'll read every comment.

[Assistant]
Alright, so lets say you work for a company that manufactures hammers. Each hammer sells for a fixed price, and you're paid more for each hammer you're able to assemble.

The people Who are able to assemble more hammers make more money. Why? Because each hammer represents a certain amount of money, and after the cost of materials and everything else, a part of the profit is given to the worker. Of course, this depends on how hammer sales are doing. If nobody was buying any hammers then it wouldn't matter how many you're able to assemble.

Pro-sports are basically the same thing. Athletes provide a service to a team, that team makes oodles of money as a result of the service athletes provide. A cut of the profit made by these teams is given to the athletes both as an incentive to play well and because its just fair to pay a worker something for the services they provide.

Think about it like this, if we paid athletes less than we do now - the only change would be in the bottom lines for the teams. It isn't like that money would magically be used to fund education.

In short, athletes are paid so much because the market has a demand for their unique services.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5 Why does bread "sweat" in the microwave?

[Assistant] No doubt this will illicit many answers about microwaves and water molecules, but bear in mind bread also "sweats" when placed in a normal grill on low heat. Water is one of the ingredients in bread, and heating the bread by any means just steams out the water.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [Frozen/Avatar] If Elsa was in the Avatar universe would she be viewed as just a particularly powerful water bender or something else entirely based on her feats?

[Assistant]
The main sticking point would be the ability to alter the climate: while water benders can freeze water, they can't simply make it cold, and certainly can't affect things on a national level. Likewise, while benders can animate stuff by moving it, creating living beings is something there is absolutely no precedent for in the ATLA verse.

There'd be more then enough evidence for people to realize that there's something going on here beyond merely a water-bending prodigy.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
If photons are massless, why does gravity have an effect on them?

I was thinking that something without mass should not be affected by gravity.  Maybe my google skills are lacking or I just didn't understand what I read but I would appreciate any insight.

Thank you.

[Assistant]
Because when you hear "Gravity causes objects with mass to attract objects with mass" that is wrong. It's a simplified view before Einstein.

It is better to say that "Mass-energy causes space-time to curve, a curved spacetime causes particles that travel through spacetime even though particles travel in a straight line, they would have their overall direction changed, the particle moved straight through bent spacetime. This is why mass tends to gather, as more mass warps spacetime more, allowing more particles to be directed or bent towards said object and have a higher gravitational field.

Everything causes gravity, even energy. Thus a massless photon even though it doesn't contribute to gravity by it's rest mass it still has energy to contribute curvature. Normally we assume mass = rest mass, and through E=Mc^2 talks about rest mass only, it's the shortened formula, you need to include a particles energy as well especially since some particles are massless. This includes their motion, since mass and motion contribute to overall energy.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5 The colour and birth of wizards (LOTR)

Can anyone explain the colour sequence (if there is one) for the wizards of the third age on Middle Earth? Also, I know Treebeard said the wizards first came from over the seas, but are the wizards born, or created fully grown?

[Assistant]
They came from Valinor (the land "in the West" where the elves go.) Men cannot go there anymore. The land of Valinor is ruled by the Valar. These are ancient beings that were basically angels that entered into creation to hang out until the end of time. The Ainur were the same, but were basically servants to the Valar. The Valar selected 5 Ainur and sent them to middle earth as Wizards. They were called the Istari. They were to have the appearance of old men.

As far as the colors go, White was the one in charge, but the other colors had no real hierarchy. So Saruman was in charge until he went batshit crazy (corrupted by Sauron) and was replaced by Gandalf the White.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[John Carter of Mars] What's going on in 2019?

Is there still life on Mars today? Green Martians, Red Martians, etc? Evidence of their society?

If so, Earth must know about them by now. How is that going?

[Assistant]
A running theme of the John Carter books is that Mars is a dying world. In the first story (iirc) Carter saves Mars from loosing its atmosphere by sacrificing himself to repair the atmosphere factory. While Burroughs wrote plenty more books in the series after that, it is reasonable to assume that eventually Carter eventually failed to save Martian life from annihilation, resulting in a total extinction event that rendered the planet a cold, barren desert like it is today.

Sandstorms came to covert the lost cities of Martian civilization in the century following life's extinction, leaving the planet appearing, from orbit, to be nothing more than a lifeless rock. Our probes failed to land in the right spots, or dig deep enough, to uncover the planet's history. However, once humanity puts its boots on Mars and gets digging, her secret history and the adventures of one Earthling will come to light once more.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Avatar: The Last Airbender] What makes Zuko so sure that the last Airbender must *be* the Avatar?

In the beginning of the show, Zuko is attempting to track down and capture the Avatar by looking for evidence of Airbending. In the first episode, he spots Aang from a distance through a telescope, wearing his Airbender garb and jumping a great height. "Quite agile for his age," he remarks. Zuko spots an Airbender and immediately decides he's *certain* that Airbender is the Avatar.

This got me thinking. IIRC, this isn't the only time someone in the Fire Nation mentions searching for the "Last Airbender." They all seem very sure the Avatar *is* an Airbender. How do they know? Clearly at the start of the show they're unaware of Aang's long sleep in the iceberg, so they're assuming the Avatar is actually over 100 years old.

What makes them so sure that the Avatar didn't simply die of old age and get reborn as a Waterbender 40 years prior? How does Zuko know he hasn't just found... the last Airbender? Who has no particularly significant role? I mean, at that point doesn't even know any other elements, so he's *just* an Airbender.

[Assistant]
Because every other airbender was wiped out, but the Avatar was never found among them. It can't be another tribe or nation because that nation would've absolutely used the Avatar in the last 100 years to help either them or the world in the war.

So it *had* to be the very last member of the race that was completely and totally wiped out previously, because that's the only thread they can go by.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Star Trek] Did Kirk fail the Kobayashi Meru?

I understand it's meant to test you are your ability to keep a cool head and make decisions when all the options are bad ones. So when Kirk rigged it so he would win, did he actually fail the intended rubric?

[Assistant] Yes he failed the purpose of the test. It's not supposed to be winnable. To pass all you need to do is react decisively and adjust to the situation. Accept that winning is impossible and instead find the least tragic outcome in the situation while under pressure. Panicking or surrender or going for a hail Mary are fails. Kirk both ethically and morally failed the test. He created a scenario he controlled and one that required little to no input to win. Instead of cheating or even just giving up he chose instead to give himself an impossible to fail test that wasn't the kobayshi test and pretend it was.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Letter for a professor.

I had an English professor last fall whose class I really enjoyed, and I ran into him waiting for a bus. We started talking and I told him how much I enjoyed his class, and he asked if I could write a letter to the department head telling them that he is a good professor so he can keep his job, it's his first year teaching. I've never written anything like that before, but I would really like to. Has anyone ever written a letter like this that could share some pointers on maybe what to say and what not to say? The last thing I want to do is come off the wrong way in a letter when I just want to help him. Any advice is greatly appreciated.

[Assistant]
Perhaps you should email the head of the department, tell them that you so enjoyed the class (and be specific about things that the instructor did to make your experience so great) that you would like to recommend the instructor for a teaching award but you don't know how or even if the department has such an award (though many do). You'll either be sent in the right direction, or you will be told there is no such award. If it's the latter, reiterate that the instructor was so great, and lament that it's a shame he cannot be formally recognized but that you do hope his excellence in the class is rewarded in some way.

ETA: Also, consider writing a nice note on something like stationary and sending it to the instructor. He is (or ought to be) collecting these things for purposes of career advancement.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Clarification about the Pauli exclusion principle

This is something that has been bugging me for a while. The Pauli exclusion principle claims "no two fermions can be in exactly the same quantum state." Most qm books I have encountered describe this equivalently as "no two fermions can have exactly the same set of quantum numbers" and then proceed to list a finite set of them that describe the complete state: J, L, S, ml, ms, N, etc (I might be forgetting some). But an electron in the ground state of hydrogen will always have L = 0, S = 1/2, J = 1/2, ml = 0, ms = 1/2, N = 1 by definition. So if a state can be completely characterized by this set of quantum numbers, and an electron in the ground state of hydrogen will only take these values, this seems to imply that there can only be ONE electron in the ground state of hydrogen in the entire universe. Clearly, this is not true, but I'm having a hard time seeing how it is not implied by the Pauli exclusion principle. Can someone clarify the Pauli exclusion principle for me to help me resolve my misunderstanding? Thanks!

[Assistant]
To answer your immediate question, an electron in the ground state of hydrogen can have ms = +1/2 or -1/2.

Slightly more interesting, perhaps, is that the PEP you know is a bit simplified.  The actual statement of the PEP says that when you put two identical fermions together, their combined wavefunction must be antisymmetric with respect to exchanging the two particles.  You can get the simplified version from the complete statement by seeing that if both fermions have the same quantum numbers, exchanging them won't change the sign of the wavefunction, so this configuration is symmetric and not allowed.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: how can a PC game be developed for years? don't the constantly emerging new hardware capabilities far outrun what the game (engine) started out with?

[Assistant]
There is a lot to a game besides it's interaction with hardware, essentially everything about game design is independent of hardware, save for things like user interface or graphics.

But you can write an entire game which outputs with blocky models and low resolution textures in a boring 3D world, but then relatively easily replace all those with better models/textures/lighting later in development without a huge cost.  Add to that the fact that most development machines are very powerful and you have a situation where it's not hard to develop with the expectation that hardware will be able to do more in 2-3 years.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Help! Any way to change mentors in an F32?

Hi, I am an NIH F32 fellow stuck in an abysmal mentorship situation. My mentor has bullied me, and has asked me to do unethical research practices, and has not fulfilled any of their mentorship commitments. After years with good mentors and colleagues, I still can't believe this is happening. The tolls on me have been extreme. Has anyone had experience switching F32 mentors? Any thoughts on whether it is possible to switch mentors either within an institution or outside of it, and what the consequences are of doing so (in terms of academic job prospects as well as future funding from the NIH)? I am almost one year into a two-year fellowship, and am unsure whether I should just tough it out for the remainder of the fellowship, or it is worth trying to find a better situation.

For various reasons going to the NIH or filing a formal complaint is not an option - the risks of retribution are simply too big given my position.

[Assistant]
Grant administrator here! Yes, you can change mentors, although your exact steps will depend on which IC (NHLBI, NIDDK, etc) is funding the F32. Essentially you will submit a request to NIH for prior approval to change mentors at your current institution, or your current institution will need to relinquish the award and the new institution will submit a transfer application. **This process should be handled entirely though your sponsored programs office, NOT through your current mentor.**

You don't need to provide any negative information about your current mentor - you would focus on the new mentor and why they are a better fit for you to complete the research project that was awarded.

This varies between ICs, so if you have more specific questions DM me.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] What happens to the dust and other particles we inhale?

[Assistant] The particulate matter we inhale is filtered in a way by the mucous membranes of the airways, which is then expelled in either snot or phlegm. Anything that reaches the lungs is processed by macrophages and either destroyed or stored. Which is why smokers lungs are black - captured soot can't be destroyed so it's stored in tissue resident macrophages.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [40k] What if Sanguinius didn't die above Terra? During the Horus Heresy?

[Assistant] Basically the same thing that would of happened if any loyalist Primarch were to survive. They would become the defacto new EoM and would either intentionally or unintentionally prevent the rise of the Ecclesiarchy because there would be no power vacuum to fill . They would still be reeling from the death of the big E and the loyalist Primarchs but it would have a single point of clear undisputed leadership and as a result would get its feet back under it much quicker.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: Why did religions like Norse, Greek, and Egyptian die out but religions of Jewish decent (Jewish, Christian, Islamic) thrived?

[Assistant]
The basic answer here is that Christianity and Islam became the official religions of empires that ended up conquering most of Europe and the Middle East.  And, since they were monotheistic religions, they tended to replace rather than exist alongside the local religions in those places.

Judaism is the odd man out since it survived less as a result of its own conquests, but because it is in a sense a prequel to Christianity and Islam, and so ended up being more like a "sect" of those two faiths in terms of how it was treated, rather than being absorbed or displaced.

There are, of course, other more specific factors as well, like the nature of the faiths, their own resistance to being co-opted, the displaced faiths being tied into political or social structures that were also outlawed, and particularities of history and culture.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Zoey 101] How much is PCA's tuition?

My kid keeps asking me if he can go to Pacific Coast Academy. How much is the tuition there? How expensive is room and board?

[Assistant]
I've never seen actual numbers, but I've heard it stated that tuition is about what the average college tuition is. Average college tuition is $33,000, so it would be right around there.

Considering that it is essentially a high school, however, that is pretty expensive.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
In an SSD drive, how is the data persistent, even if the power is off?

I'm a CS student and I know the ins and outs of data storage in RAM. But RAM needs electricity to save data. Since an SSD (I assume) uses the same basic technology, how is it possible that we can take it off the grid and the data is still saved?

[Assistant]
RAM and flash memory are actually less similar than you might think.  They have a similar structure allowing individual bits to be addressed, read from, and written to but the bits themselves are vastly different.

In RAM it uses a logic gate with two possible stable states, basically being two not gates wired together in such a way that one side is powered at any one time and applying power to the unpowered side will flip the state of the circuit.  These logic gates require a power source to work, when power is turned off and on again the circuits will revert back to a single default state.

In solid state memory the data is stored in the form of a static charge.  The component that makes this possible is a special kind of transistor with an added electrically isolated part that can hold a static charge.  The presence of a negative charge prevents the transistor from working which is how the data is read.  To write new data the part holding the charge is electrically connected to another circuit and either grounded or given a charge to give it a 1 or 0 state.  Since a constant current is not needed to maintain a static charge it will still be there even after power is disconnected.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Guardians of the Galaxy] Is it ever explained how Groot actually speaks?

The fact that he basically says the same "sentence" over and over again suggests that his language is more tonal, and that the words aren't important. Rocket has no problem understanding what each iteration of "I am Groot" means.

[Assistant]
Not in the films, but Rocket might have developed an understanding with time and experience.

It's not impossible for him to use other words (we are groot), but it does seem to imply considerable effort is needed for him to do so.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
What did Camus mean by "Become so very free that your whole existence is an act of rebellion?

 What did the famous Philosopher Albert Camus mean by his quote "Become so very free that your whole existence is an act of rebellion."? What sort of rebellion did he mean? Can someone explain this quote to me?

Thanks.

[Assistant]
The kind of rebellion exemplified in Sisyphus - whose continued existence is an act of rebellion (in his case against the gods and his fate).

Camus says we have no gods, of course, but we do have a sort of fate - the fate of being fellow sufferers in, as he sees it, a fundamentally absurd situation.  Camus calls on us to embrace our situation - the absurdity, contingency, ambiguity, responsibility, etc., *and also* the possibility for joy and passion *but without* hope or sentimentality.

Just doing this is an act of rebellion.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
(LOTR: ROTK) Question about the Beacons.

So do those guys live at their posts, or is it a six month posting, or what? One of the beacons is just sitting on top of a mountain, it must take an enormous amount of resources/money to keep those things manned.

[Assistant] Sentries likely spend a few weeks at a time stationed. It's not that expensive to maintain actually, since it only requires that the wood for the fires stays relatively dry and some food for the sentries. There is trade between nations, so fresh guards can simply ride along with a caravan and head up the mountain when their shift is due.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
Can water, if shaken violently for long enough, come to a boil?

I understand that a microwave excites and vibrates water molecules causing them to heat up, thus heating your food, but that's not what I'm talking about.

If what causes heat is molecules rubbing together (is friction what causes the heat?) at a very fast rate, then could you take some water and shake it up long enough to make it boil? Shaking the water would cause the molecules to rub against each other faster than if it were still, so it stands to reason (in my head anyway) that the water would begin to warm up.

So if we took a jar of water and put it into something like one of those paint shaker machines at Home Depot for long enough, would the water eventually get hot? Could it get hot enough to boil? How long would something like that take?

**Edit:** When I said, "come to a boil," I meant heat to around 100C/212F.

[Assistant] I don't know if you can add enough energy through a paint shaker, but if we sonificate something (basically hit the solution with a jackhammer a few thousand times per second to mix it really well), then we have to use an ice bath to make sure the solution doesn't start to boil. So yes, it's very possible.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [HALO] How long would it take the average man to walk the length of The Ark (Installation 00), accounting for time needed to rest, eat, drink and perform other vital biological functions?

[Assistant]
The Ark created rings of 10,000 km in diameter.

So let's assume the ark is bigger since it has to make them. If Master Chief could walk at 8km/h then it would take him a minimum of 1250 hours. If we say he can walk for 16 hours straight at a constant pace, no running, then it would take him nearly 80 days. Minimum.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Warhammer 40000] What is the life like for a solar Admiral in the Imperial Navy?

The wiki gives some info but it's very limited. Quoting some passages from the wiki for officers and Solar Admiral alike:

1. Solar Admirals are often prospective sector commanders waiting for assignment to a sector. As such opportunities are rare, it is far more common for Solar Admirals to be dispatched to warzones in command of a reinforcing fleet or kept busy on "special duties" with their own independent flotilla

2. For the Imperial Navy officer class (admirals, captains, commanders, first lieutenants, etc.) on board, an entire section of a large Battleship's command deck may be divided into huge, luxurious staterooms, with vast bedrooms, offices and wardrobes, bathrooms and toilets mirroring those of an Imperial Planetary Governor's palace, and even harems of concubines and handmaidens.

So basically what I'm trying to ask is the following in greater detail:

* What is the day to day life of a Solar Admiral?

* What do they do precisely?

* Is there any limits one can expect for such a person with such power?

*  How would such person be treated should they dock on say a hive, forge or civilized world?

* What are their equipment, perks and responsibilities?

* How are they're children treated and how would they be raised precisely?

Thanks for answers all my questions or as much as you could.

[Assistant]
A Solar Admiral would be a very powerful individual. They would be either a well respected veteran of multiple engagements (or one with enough political clout and wealth to compensate for a lack of real combat experience)

Along with experience, they would be highly intelligent, well connected, and above all ambitious. These are men and women who have changed the course of battles and entire wars by the decisions they have made. They would certainly be given a few iotas of respect.

As for their family life. Providing they actually were married (instead of just having a courtesan(s) or mistress/lover) they would be exceptionally wealthy and likely own a large estate on their homeworld/currently posted world. They may even have multiple holdings over many worlds and across several systems.

They might be the ruler of a vast family of a military dynasty, or the first child to ever achieve such a high office.

Anything goes at this level of political and military power in the Imperium. Suffice to say, only those worthy of the title would make it this far in the Imperial hierarchy.

The level of politics and intrigue that occurs this high up the totem pole would be immense. One wrong step could end ones career prematurely. You might anger the wrong High Lord and find an assassin breathing down your neck. Or maybe you might find your reinforcements arrive too late to save you. That sort of thing.

On the other hand, if you play the game well, then you could find yourself in a very favourable position and want for nothing. Glory and honours aplenty could be yours.

In time, you might just get that coveted position of Lord Segmentum. Maybe even make your way all the way to the top as Lord High Admiral of the Imperial Navy and a seat on the Senatorum Imperialis as one of the High Twelve.

The stars are the limit when your playing at they top.

Now as for your duties. They could range from a mundane staff position at Segmentum Command. Maybe a tour now and they to inspect critical facilities and positions. Fancy dinners and staff meetings aplenty.

Or, you could filter from crisis to crisis. Trying to put out every fire before it burns out of control. Whatever the Emperor requires of you, for you serve at His pleasure.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Spider-Man] (2002) [NWH] So, what's the deal with Green Goblin?

In No Way Home we assume Green Goblin gets taken before being impaled by his glider. This is moments after his confrontation with Spider-Man after he rejected his offer in which he made him choose. Then he gets taken to a completely new reality in which he meets a boy who is also named Peter Parker who also happens to be Spider-Man, so he makes the rash decission to take him out of his comfort zone and weaken him. But, why? The reason he made spider-man pay in his reality in the first place, is because he saw Peter as the son he always wanted, so he thought it was necessary for him to be his ally, once he rejected him he saw that as a betrayal. This kid is a complete stranger to him, he doesn't know him, what does he get out of knocking him down. Doesn't he crave power, and want Peter to accept him as a mentor, so, what's the use?

[Assistant]
To start, we dont know exactly when Goblin was pulled aside from the clean condition of his suit, putting it anywhere from Thanksgiving to right after Peter saved MJ and the kids. SecondlyPeter was trying to cure Norman, which would kill the Goblin-an outcome he doesnt exactly approve of as he explicitly states.

So right off the bat he already wants to rip the kids spine out and strangle him with it. Then theres what really pisses him off. Strong enough to have it all, too weak to take it. Goblin despises weakness and he hates morality, and he think Spider-Man is a pathetic fool for using his power to *help others*. And hes smart enough to know Peter wont be more willing to listen, and probably doesnt even care. MCU Spider-Mans very existence offends him, and he wants to kill him to boot. Goblin has killed for less.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] What would happen if I looked at Medusa through contacts or glasses?

[Assistant]
It depends on whether you could see her clearly or not.

If they aren't your prescription, and they make everything blurry enough, you won't be able to see anything but a blob and be fine.

If you can see through them fine, you'll gaze upon her legendary visage and be turned to stone.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: The difference between a university and a college?

Is there a difference at all? I've always wondered this.

[Assistant]
Traditionally a college teaches one thing or a set of related things.  A University is a collection of colleges. A University is made up of many colleges.

The words aren't that specific anymore.  Some schools are still called colleges for historical reasons even though they have a bunch of colleges. A good example is the College of William and Mary. There is no reason that William and Mary isn't a University; it has many schools in it.  We just call it a College because that has been it's name for a long time.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: How was an eclipse used to show that Einstein's theories were correct?

[Assistant] The eclipse blocks out the light from the sun allowing us to see the stars around it that are normal invisible because the sun is too bright. This allowed us to show that the gravity of the sun was bending the light of the stars behind it and to the degree general relativity predicts.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [Pacific Rim] Why didn't Gipsy Danger lead with it's blades?

[Assistant]
Kaiju Blue. Kaiju blood is incredibly acidic, and requires special containment to stop from poisoning the surrounding air and water. The general rules of engagement begin with concussive attacks (that is, generally fists), then moves on to attacks designed to cauterize (the plasma cannon, or Striker Eureka's "anti-Kaiju" missiles -- these are imperfect, but better than nothing), and only uses actual cutting attacks as a last resort. It's a containment measure. Buildings can be rebuilt, roads re-laid, but Kaiju Blue takes a long fuckin' time and a lot of very expensive resources to clean up. That they'd rather knock down a few buildings than deal with it up-front should tell you exactly *how* expensive the cleanup process is.

Crimson Typhoon's use of sawblades as a first-line attack was considered highly controversial, but the Chinese government was willing to do the cleanup, so nobody really questioned it. Other governments were more sensitive to the long-term environmental damage.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Harry Potter] Is the Patronus spell really the only thing that can take down a dementor?

Surely if a bunch of people do Bombarda Maxima or Sectumsempra on a dementor, it would scurry away instead of continuing to try to suck somebody. I know that they're living creatures so surely they must have an urge to retreat when blasted with spells they can't respond back to

Also, if you focused on a spell that was pure hatred/sadness would they be repelled by it? They enjoy happiness so, wouldn't hatred "taste bad" to them?

[Assistant]
>I know that they're living creatures

Not exactly. Dementors are what wizards call amortal. They're not alive and can't die. Ghosts are also amortal, for another example, as are poltergeists.

Dementors don't fear destructive spells because they know they can't be harmed by them.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] France and Germany have agreed to boycott Facebooks Libra cryptocurrency. Whats the threat they want to prevent?

[Assistant]
The cited reason that they want to preserve the sovereignty of money.

Its pretty overblown. imo libra will neither be a successful substitute for money in the developed world nor is that even their goal.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: why humans seem particularly bad at understanding devastating news, such as the death of a loved one. Why is our first reaction usually to not being able to process the information? Is it not psychologically disadvantageous to not be able to understand and respond to such news?

[Assistant]
Humans are very much learning creatures, we don't do a whole lot on instinct. Because of this we aren't particularly good at doing anything very well the first time we try it, this includes emotional things like grief.

The people who have trouble grasping devastating news are usually having to handle something like that for the first time and aren't very well equipped to do so. People who have had the misfortune to have already handled significant tragedy do better with devastating news.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[the Enigma of Amigara fault] why didn't they just simply drilled the human holes or blow them up with explosives ?

l mean why didn't the Japanese rescue team just simply drilled the human holes until they found the people inside them ?

[Assistant]
Those holes were pretty deep....

Also this is clearly some kind of archeological wet dream, aside from the supernatural aspect.

Imagine telling the Abenaki you have to blow up or destroy their holy site because Billy fell in the well.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] [MCU] Considering Tony's carrying the nano-armor around on his chest, does the whole thing only weigh like 10lbs at most?

[Assistant] Even with the most advanced composite alloys, a suit of armor is still a suit of armor. Tony was always one to find time to hit the gym, even if only to maintain his looks, and carrying around the Suitcase Armor didn't hurt in terms of building muscle, either. The only conclusion is that Tony is low-key pretty jacked underneath his dress shirts and Iron Man suits. Not at superhuman or even peak human levels, obviously, but definitely pretty above average by human standards.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5 why does childhood traumas affect you as an adult, and why a lot of people can never get over them?

[Assistant] As a child, your mind is completely malleable and youre learning how the world works and how people operate, and if your initial worldview is skewed because of trauma, thats built into you right from the beginning and its incredibly difficult to reverse the effects after theyve had a chance to grow there for years before youre aware of them.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[Dune] How come no one seemed to care that much about Arrakis until the events of Dune

It seems like in Dune, no body cares that much about Arrakis, despite it being the source of the most important substance in the universe.

The Harkonnens send some nephew to oversee it. In like 10,000 years no one bothers to explore the southern regions.

The Spacing Guild doesn't seem to care that much about who is in charge on Arrakis, otherwise they might refuse to transport troops, or whatever.

The Emperor is willing to swap governors around as a power ploy unrelated to spice-- although the same ploy could have been done with any planet.

Yet at any time the Spacing guild could have demanded control of the planet or withhold space travel. The emperor could have moved operations there to oversee the extraction of the substance that keeps him in power.

The Harkonnens could have used the same ploy that Paul does at the end of Dune-- threatening to destroy spice production-- to secure a seat as emperor.

In real life people go to war all the time over resources that are less important. Access to waterways, oil, opium. Why isn't anyone angling to get control of Arrakis before Dune?

[Assistant]
Maybe you should re-read the book, this is all explained in Book 1.

>The Harkonnens send some nephew to oversee it.

That's a ploy:  The Beast Rabban is meant to torment the Arrakeen people so that the gentler Feyd Ruatha can then come in and look like a savior.  And Feyd is the heir to House Harkonnen.

>In like 10,000 years no one bothers to explore the southern regions

The Fremen pay the Spacing Guild to keep the skies in the deep deserts empty.

>The Spacing Guild doesn't seem to care that much about who is in charge on Arrakis

Because they *don't need to care* who's in charge:  No matter which side wins, they will need access to space travel, which ONLY the Spacing Guild provides.

>The Emperor is willing to swap governors around as a power ploy unrelated to spice

Because Leto Atreides was a threat to his power and needed to be eliminated without setting the entire Laandsraad against the Emperor.

>The Harkonnens could have used the same ploy that Paul does at the end of Dune-- threatening to destroy spice production

Impossible, because the Harkonnens weren't Fremen:  They couldn't control the desert and Spice production.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
What about water puts out a fire?

Is it blocking off the fuel from making contact with air? Stealing away the activation energy? Something else? All of the above?

[Assistant]
Mostly, it steals away the energy from the area. The evaporation of the water requires a lot of energy, and thereby results in reducing the temperature. Hopefully below the ignition point of the fuel, so the fire is contained or even put out. Most everyday things will only burn if the heat is concentrated. Like a single log will not burn on its own, since it radiates too much heat away. You need to build a fire that concentrates the heat at the center to sustain the fire. Robbing it of just a little bit of that heat, and the fire is no longer sustainable.

But the steam produced also lower the oxygen density of the air around the fire. And the water no doubt also simply washes some of the combustible gasses out of the air, before it can reach any free oxygen.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
[MCU/FATWS] How exactly big is Sokovia?

Weve seen Sokovia in 3 Marvel properties now (AoU, WandaVision, and FATWS), and Im still puzzled at the size of it. It seems, to me anyway, that the size of Sokovia is just the city sized asteroid we saw destroyed in AoU, and would thus be a city-state. Was the city destroyed just the capital or the whole country? If Sokovia is a city-state, how does it have any armed forces outside of a police force, let alone Spec Ops soldiers like Zeno?

[Assistant]
Sokovia is the name of both the capital and also the country (akin to Mexico city).

Although, as an aside, city states have armed forces. That's one of the things that makes them city *states* rather then simply powerful and influential cities. They're nations in their own right, with all that entails.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
CMV: If a woman has a unilateral right over deciding if she wants to abort or not, a man should not be forced to pay child support if he doesn't want a child.

A strong argument can be made that no one else should have a say over a woman's choice to get an abortion or not. But that considered, then if a woman decides to keep a child against the wishes of the father, then the father should not be forced to financially support that decision.

1. A common argument i hear is, if a man is given a say over a woman's right to choose, then he has rights over her. Thats an argument i completely agree with. But a lot of people (at least in my circles) disagree with this argument when applied in reverse. If a woman decides to keep a child against the wishes of the father, then doesn't she have a right over him, if he is forced to support her choice financially?
2. Abortion gives women the ability to opt out of parentage. But any ability to opt out of parentage for men is completely in the hands of the mother. This isn't equal treatment of the sexes.

Caveat:- The ability for men to opt out of parentage should only be available as long as a women is legally allowed to abort a child, i.e, a man cant deny a child once its born or its too late to abort.

EDIT:- I quite foolishly assumed the following information was a given. I am making this argument from the context that conception has already taken place (accidentally), due to unforeseen circumstances, such as a condom break.

[Assistant]
Child support is not for the woman, child support is for the child.

He is only forced to support his choice financially- if the child exists, it has a right to financial support from both its biological parents. If the child exists it exists because of the choices and actions of BOTH it's biological parents and BOTH of it's biological parents are held legally, financially responsible for it.

Child support is not for the mother or her choices. It's for the child due to the choices of both the parents, and is a duty of both the parents.

Edited to add:

>But any ability to opt out of parentage for men is completely in the hands of the mother.

Vasectomies, withdrawal, making sure to use a condom, discussing things with the woman before having sex, not having sex with people you don't trust, etc. are all in the hands of the mother?


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: If I steal a game/music from a store and am caught there's up to a $500 fine, but if I download it instead then the fine is up to $250,000.

[Assistant]
If you steal a game/music from a store then you are accused of Theft. That has either a fine or jail time as a punishment.

Now when you download a game or a song, then you are also uploading that song. That means that you not only downloaded a copyrighted work without paying for it, you also made it available for others to copy it from you. Now the company can sue you for the loss in revenue because of your actions. Thats mostly what the big fines are for. But for the most part, its a way for them to scare people from downloading stuff online which they haven't paid for.


[System] Given the following post, respond as if you're commenting on Reddit:

[User]
ELI5: How does a horn amplify sound without adding any energy to it?

I was watching a tuba player the other day.  The buzz of a guy's lips can be amplified to the point where it shakes you.  Horns seem to defeat the first law of thermodynamics.  What is going on here?

[Assistant] Your lips, instead of just vibrating nearby air, vibrate the horn which in return vibrate the air inside the horn, thus making the amount of air originally vibrated much larger, and the sound stronger. In addition, the shape of the horn focuses the sound wave in a certain direction.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: I keep reading all these recreational drugs increase dopamine - the 'feel good' drug in the brain. So why is just injecting dopamine itself not a thing?

[Assistant] Dopamine cannot cross the blood/brain barrier. Injecting it into your bloodstream wouldn't work. Injecting it directly into your brain would create all sorts of other problems. Starting with the fact that you just stuck a NEEDLE into your BRAIN.


[System] Given the following post, respond as if you're commenting on Reddit:

[User] ELI5: When defusing a bomb, why cant you just cut all wires at once?

[Assistant]
Most bombs are simple and cutting the power or detonator wires would disarm it.  But it's trivial to design bombs with failsafes so that if it were tampered with, it would explode.  Of course, there is no standardization of such design, and certainly no standard colors (i.e. "cut the green wire" is ridiculous)

There have been bombs specifically designed to fool the disposal people with the actual trigger mechanism obscured.  Cutting the "obvious" wire being what causes the detonation.

Sometimes X-ray machines are used to examine the bomb, but in reality, if it's not clear how to defuse it, they will just evacuate and blow the bomb up "in place".