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

[User]
[Batman Begins]- Why didn't the water vaporizer in batman begins vaporize the 60% water in humans?

In the Ship scene you see it vaporizing water everywhere around it, including right beside people running around, but they're only hurt by the steam right beside them and not the weapon itself?

[Assistant]
The ionizer specifically reacted with water in contact with the heavy metals associated with Gotham's sewer system.

It's most effective against water in a pipe, as the rays bounce around in the pipe to vaporize the water quickly, though it works okay on a basin where just the "tub" is metal.

People don't surround themselves in metal, and even if they wore a lot of jewelry or were in a metal building, those materials are not the same ones used for plumbing and pipes, so they were safe.


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

[User]
Does the human eye's depth of field change with iris dilation?

In photography there's a metric called the F-stop that describes how wide the aperture of a lens is, and the narrower the F-stop, the wider the depth of field is (meaning more of a photo will be in focus). Is the same thing true of the human eye? Is more of a person's visual field in focus in brighter light when the iris is narrow (in photography terms, "stopped down") to restrict light coming in?

[Assistant]
Yes.

You won't notice it because your eye flexes your lens to focus on what you are looking at, but the physics still applies: when you are in bright light and your pupil constricts, you get all the benefits of a small aperture. That's why old people like me can read small print at close distances in bright light.


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

[User]
ELI5: Why do hostages of ISIS seem so cooprative if they know they're going to die?

What is the psychology behind a captive acting subdued?

I would think that if it was me and I was going to be beheaded I would be a right asshole. Probably starting with pissing and shitting my pants and attempting to cover myself in that as much as possible.

Depending on circumstances, perhaps run so they kill me fleeing by gunshot... Hopefully.

But who knows how I would act? Not me.

[Assistant]
I heard something along the lines of that they do the speech almost everyday, but arn't killed. Soon they start thinking "it's just another day" and then they get killed.

~~Probably bullshit though.~~


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

[User]
[Call of Duty: Modern Warfare] Didn't Makarov have an entire terrorist cell?

My question comes from the plot of the 3 Modern Warfare games. Spoilers will follow.

Obviously the central antagonist throughout the series is Makarov, and Price's burning desire to kill him all along so the world can be rid of this awful person.

Price's emotional motivations aside, does he, or anyone really, consider the fact that Makarov isn't a lone terrorist? There have been plenty of documented cases where he was seen with many supporters. The two cases that come to mind right now are 1) the group of about the five terrorists that shoot up Zakhaev International Airport and 2) Makarov and his supporters had a house in the mountains where they plotted the attack, complete with expectant living accommodations.

So if Price kills Makarov, does that mean his organization isn't finished? Wouldn't one of the other people that helped him shoot up the airport just take over as head of the terrorist organization he created? I see it sort of as when Bid Laden's death obviously didn't mean the end for al Qaeda.

Thanks guys.

[Assistant]
Not entirely the case. Makarov is a very odd, and unintentionally ironic, reimagining of Bin Laden as a quasi-post-Soviet Russian nationalist. So lots of odd plot holes here and there.

If your comparing it to Bin Laden, then it *did* fall apart, but into splinter groups. When the USN SEAL Team 6 successfully assassinated Bin Laden, al Qaeda collapsed into splinter groups with the largest continuing to call themselves al Qaeda. However, even before the assassination they were slowly falling apart from a combination of funding shortage and low moral.

Makarov wouldn't be any different from his inspiration. He united the separatists under the Ultra-Nationalist banner fueled by the disdain for the ever growing USA Hegemon. Considering they delivered a crippling blow against the USA with their invasion (which for some reason ignores the fact the setting isn't the 1970's), and shattering EU-Russo relations, there wasn't much of a reason for them to stay united anymore. His death would only cement it and they'd implode from infighting for control of Russia.


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

[User]
Chemically speaking, what is "Fishiness?"

A lot of fish and other seafood definitely share this trait, sometimes with smell more than flavor. What causes a fish to be "fishy?"

[Assistant] In order to keep their hydric balance, marine creatures have to have something inside their cells to be isotonic. What most of them have is trimethylamine oxide, a somewhat volatile compound when broken down to trimethylamine. The problem is, trimethylamine happens to smell... bad.


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

[User]
What is the biological reasoning behind the frustration that you can feel in the middle of your chest?

Why do we feel it only at the chest? Does some sort of acid build up?

[Assistant] Stress releases epinephrine increasing heart rate and constricting blood vessels, norepinephrine activating the amygdala and increasing heart rate, and cortisol which will increases stomach acid and blood pressure. It is likely you feel it most in the chest because the heart and esophagus are under increased load and have nerves bundled together.


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

[User] ELI5: Why does protesting work? You see massive nationwide protests when there is civil unrest, but why can't the government just ignore it until the protestors give up?

[Assistant] Protesting isn't about getting the government or entity you are protesting to change because of the protesters. They will always be dismissed as a minority opinion and troublemakers. It is about getting a larger group of constituents (the ones who would never actually go to the protest) interested with the issue.  It is about attention and media coverage and creating a groundswell.  You hope by having 100 people show up you get 5000 to write their congressman.  You hope by staying in place for a month that you get 50,000 to care.  In short you hope to influence a larger group, create pressure.


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

[User]
When research shows some people share 2-4% of their DNA with Neanderthals, what DNA are they talking about?

I read in an article recently that some people share 2-4% of their DNA with Neanderthals. However, we also share loads of DNA (>95% IIRC) with less similar species such as Chimpanzees. So, when we say we share 2-4% of DNA with Neanderthals, is that only some part of our DNA that is measured separately, like repetitive sequences?

[Assistant]
Here's a simple analogy. Suppose almost everyone in your family was Icelandic, except that one of your great-grandparents was Nigerian. Your DNA would be 87.5% Icelandic, 12.5% Nigerian. *Most of the DNA of people in Iceland and Nigeria is identical*. However, those populations have accumulated mutations that make parts of their DNA distinct. So when someone says you are 12.5% Nigerian, what they mean is that 12.5% of your DNA is inherited from a Nigerian ancestor and contains mutations that originated in Nigeria. The actual sequence difference between you and a person of purely Icelandic descent will be much, much smaller than 12.5%: it will be a tiny fraction of one per cent.

Likewise, when someone says your DNA is 3% Neanderthal, they mean that 3% of your DNA consists of chunks that are traceable to Neanderthal ancestors. *Most of the DNA of Neanderthals and mainline Homo sapiens is identical*. The sequence difference between you and a hypothetical person with no Neanderthal ancestry will be much, much smaller than 3%.


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

[User]
ELI5: How sometimes we can go hours without notice a cut or scratch... But as soon as we do notice it, the pain starts and doesn't go away?

You fall you get cut, and hours later you find blood on your leg and go "oh. How'd that happen?!" Then the pain starts all of a sudden... Why?

[Assistant]
Brain is great at selective listening.  After we put on clothes, we no longer feel their weight or texture.  It's very similar with scratches.  The scratch doesn't register to enough nociceptors (pain nerve receptors) and it's dismissed as minor and unworthy of attention, akin to wearing a heavy coat.  Later, with the notice of blood, the brain acknowledges the damage was bigger than originally thought, and starts listening to those nerves more clearly.

Second part is that it takes a while for damaged tissue to implement the histamine response that increases swelling and pain to the region.  Once that gets going it becomes harder to ignore.


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

[User]
[Marvel/DC] What happens if the villains switch universes?

Iron Man swaps villains with Batman
Cap swaps villains with Flash
Spider-Man swaps villains with Aquaman
Thor swaps villains with Superman

Etc etc

Edit - sorry - didn't mean to restrict the 'swaps' - generic universe swap is fine! Thanks for all of the responses!

[Assistant]
Well... Right off the bat, cap gets annihilated by one of the speed force villains, and superman gets murdered by magic. Thor is probably killed by Zod, spiderman drowns, aquaman gets ignored.

Iron man and batman swap pretty well. Iron man's villains are woefully unprepared for the bats planning and sleuthing, and the bats villains can't remotely compete with iron man's armoury. The Joker is completely fucked. Stark would lose patience right quick and end the threat with extreme prejudice.

The flash fares extremely well. None of caps villains would pose any threat to him at all. The moment they came to the flash's attention, they'd get punched into space.


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

[User]
Why did SARS-CoV (Ro of 2-5) not spread to the same levels as SARS CoV-2 (COVID-19) which has an Ro of 1.4-3.9?

SARS had a higher CFR, but also a higher Ro, so why did it not reach pandemic proportions like COVID-19 has?

[Assistant] More lethal, less asymptomatic or pauci-symptomatic carriers. In other words, it would be difficult for people to not know that they are sick, they would automatically isolate themselves (at least stop going to work and go to the hospital), and those who fell sick got very sick and didn't walk around much infecting people. Much easier for an infection to 'burn out' this way.


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

[User]
ELI5: Why does it seem like banks (and most places with cashiers like grocery stores for that matter) are always understaffed?

I get that part of it is related to costs. And maybe someone has worked out that the loss of client base due to unsatisfied customers is less than the cost of hiring more people but it just seems crazy that you wouldn't want a reasonable level of service if you intend to run a business.

[Assistant]
Because odds are that you go there when most other people go as well. You see it as busy and understaffed but had you gone maybe one hour earlier or later the place could be empty.

If these businesses hired more people for busy times, which might only total an hour or two per day, their costs would rise. When the cost of a business rises they either eat the loss pass it on to the consumer or a bit of both.

So less of a wait in rush hour would make it more expensive for you and they would have people doing nothing in the slower hours.


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

[User] If Noah's Ark were real, and the entire world were reduced to three reproductive couples, how many years could humanity last until the gene mixing made us unviable as species?

[Assistant]
One breeding pair can save a species if and only if you're lucky and deleterious recessive alleles are not present. And they don't end up doing of communicable disease or something due to extremely low genetic diversity.

Larger population helps but ultimately what has to happen at very low populations, whether 2 or 20 or 200, is inbreeding depression needs to be cancelled out by natural selection. Namely, anything that seriously hurts selective fitness that's somewhat rare and recessive needs to do enough damage that it's bred out of the population before the population goes extinct. There are many animal and probably even some small isolated human groups where this has occurred.

The next problem is that with so little population, genetic drift could wipe out most of the existing, already limited genetic diversity for no survival-important reason. This means that in  the post-bottleneck populations, you will have a less diverse genepool which gives everything the sameweaknesses. That's fine if they are in some controlled lab environment where you just make sure they never are exposed to those weaknesses, but in the real world it's quite common that a population bottleneck occurred, causing inbreeding depression, causing a second bottleneck or steepening of the first, removing the dangerous recessives, which allows the population to increase again. Then conditions change and the population goes into yet another bottleneck as they all die to exactly the same thing. So for example a particularly dangerous one is disease because once the population begins booming again it increases the odds of getting a disease, and once the disease strikes it affects every individual organism in the same way. Roll  those dice enough and the population rolls a natural 1.

So you have:

1. Contracting population.

2. Inbreeding depression further contracts population in a vicious cycle.

3. Possible extinction if population can't pull out of the nosedive, or selective elimination of deleterious recessive alleles.

4. Genetic drift causes some alleles to be lost permanently from the population, reducing genetic diversity.

5. The now selectively fit but not diverse population booms to fill it's old niche again.

6. Extremely harsh population crashes occur due to diseases as a result of lack of genetic diversity, kicking the cycle back to stage 5 or driving it extinct.

7. Eventually the population either goes completely extinct or slowly gets new genetic diversity either from outbreeding or mutation. Bottlenecks stop.


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

[User]
[Marvel] How good of a photographer is Peter Parker really?

His pics of Spider-Man May have been huge for the Bugle, but outside of that is Peter that technically skilled as a photographer?

[Assistant]
Outside of his whole "Web a camera to the wall and hope for the best" gimmick?

Yeah, Peter Parker's actually noted for being a very skilled photographer, when he tries. He's not amazing all of the time, at worst he's merely 'average', but he's gotten some spectacular results that've made him stand out. He's taken pictures of public figures, supermodels, and villains and done fairly well for himself. A large part of it, though, is his superior ability to get unique angles and positions, as well as sneak into areas too dangerous or closed off for most normal shutterbugs. He doesn't do it often, but he can easily evade the web of surveillance that keeps his rivals from getting decent shots of various important people and items. Unfortunately, he can't share his secrets, which frustrates some of his peers when they want to hear some of his untold tales. He's not like Phil Sheldon, who was pretty open about "Yeah, that was just a telescopic lens".


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

[User]
ELI5: How does porn still make money?

Is the amount of people who buy porn really enough to support the amount of new professional porn?

[Assistant]
I think the Internet has made the industry even more profitable. The fact that you can stream porn now fulfills impulse buying at an even higher level now.

Basically, men that are horny and are on the Internet are even more likely to purchase membership or a stream when they are in the heat of the moment vs. in the past going to the video store or ordering a DVD. The internet has created less friction and lubed up the purchasing process.


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

[User]
Whats the big deal about HTML5

Also, any sites that use it already?

[Assistant]
[NLY5]

Lots of sites are using it at least a little. You wouldn't necessarily know it to see it though.

In HTML4, if you wanted a video, you had to reach for Flash or Silverlight and embed the video in a site with code (think about the old cut-and-paste stuff to embed content that YouTube would provide). In HTML5, there are audio and video elements integrated into the language - no external plugins required.

There's drag-and-drop capability (like how you can drag and drop a file into SkyDrive in your browser, or the way gmail has integrated drag-and-drop), so there's more interaction programmed in.

There's also a move towards offline stuff. For example, you could write something in Office365 or GoogleDocs even with no internet connection and then it would sync the next time you're online.


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

[User] ELI5: Since STDs like gonnorhea can only be sexually transmitted, how did they get on the genitals in the first place?

[Assistant]
The same way any disease comes to infect a human: A microorganism adapts and evolves in such a way to allow it, and it succeeds enough to further develop into a distinct species.

Considering that there are 10x as many microorganisms in a person's body than there are their own cells, there would be a lot of chance for this to happen.


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

[User] [Pirates of the Caribbean] Why is Blackbeard NOT in the Brethren Court (Pirate council from the third movie)?

[Assistant] To become a member of the Brethren Court you need to get your Piece of 8 from another member of the Brethren Court.  It could just be that no member wanted to give their Piece of 8 to him, or were near him when they were close to dying.


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

[User]
How can I keep my opinion while reading philosophy books?

Ive decided Ive wanted to read all the classics, I just read Meno and loved it. But I have a fear that if I read too much my thoughts will becomes the authors. How can I prevent this. And any recommendations?

[Assistant] If the author is able to convince you that they have a better way of looking at something, why would you want to hold on to your old way of seeing it?  If you don't want your thoughts to be influenced by the authors, what is it you're hoping to get from reading their works?


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

[User]
ELI5: Is all electromagnetic radiation "both a wave and a particle" or is only light considered this way?

I always hear about "light acts like a wave and also a particle" but I never hear about other EM frequencies being described this way ("never" considering my limited exposure). Are light frequencies special? Or does all EM radiation behave both ways?

Edit: thank you for your responses. I was already aware that light is EM radiation; I simply never hear folks talk about "photons" outside of reference to visible light, hence my question  :)

[Assistant] What we call "light" is simply the slice of EM radiation that our eyes can detect as color. As you make the waves longer, you get into WiFi and the various types of radio; as you make the waves shorter, you get X-rays and gamma rays. It's all EM radiation -- all photons -- so it's all the same from the perspective of acting like both a wave and a particle.


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

[User] ELI5: why can little kids watch the same video all day long on repeat, without getting bored?

[Assistant] I feel qualified to answer this as a parent and a teacher. Stories are not so much about the destination as they are about the journey. For young children, new stories contain a lot to assimilate. There may be a great deal of novelty even if they've seen it many times before. They may have learned the meaning of a word, and now some dialogue has a whole new significance that they never understood properly before. They may be in a different mood when they watch it and feel a greater resonance with a less prominent character, giving them a different perspective on events. Even though to an adult the experience of a children's story would seem nearly identical on a repeated viewing, to a child the story appears vastly different each time. They're going on a whole new adventure each time.


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

[User] ELI5: Why do particle accelerators have to be so long? Why can't the same speeds be achieved with a smaller circle?

[Assistant]
Think of it like a NASCAR race.  If they were to hold it in a very small parking lot, they would be constantly turning, and have to go very slow.

You can then move it to a very large parking lot, and now you can go faster.

If you can build a race track, you can go even faster.

The reason you can go faster is because turning takes away energy.  You simply can not go as fast when you are using up energy to constantly turn.  You could build a straight track, and get higher speeds, and that idea has been proposed.  The downside is you send to particles at each other, and they pass each other once.  In a circular track they pass each other thousands of times a second, so you get more collisions.


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

[User]
ELI5:Why is the Rape of Nanking/Nanjing glossed over in US history textbooks?

Or is it? I went to high school in the mid 2000s and I remember being shocked my World History textbook literally had only one sentence on it. Something along the lines of "The Japanese invaded China...something something...now called the Rape of Nanking." End. Finished. And yet, we spent so much time learning about Hitler and the Holocaust. Can someone explain why? Does it have to do with diplomatic relations?

[Assistant]
Wars altogether are glossed over in US history books. There just isn't enough time to put everything interesting or notable in them - the Japanese invasion of China was, you know, the Japanese invasion of China. It didn't significantly involve American efforts or affect the war from our perspective.

The Holocaust and the Nanking Massacre are completely incomparable. Incomparable by a matter of multiple digits.


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

[User]
[Spider-Man] How is Wilson Fisk so absurdly strong and durable? Is he a mutant or something?

In the PS4 game, him and Spider-Man are full-on punching each other through walls and shit. Spider-Man's body was changed by a genetically engineered spider but what's Fisk's excuse? Depending on what media he's appearing in, he looks like he weighs anywhere from 500 lbs to well over 1000 and has the strength of ten men.

Almost every other character like him has some kind of reasoning behind their powers like the X-gene, a symbiote, the venom drug, a science experiment that went wrong, etc. But with Fisk, it just seems like a given. Has this ever been explained or are we to believe that one can naturally achieve those gains in the Marvel universe?

[Assistant]
In universe, you really can get that ripped, or that good with a bow and arrow, or that good with machine guns. "Peak human" (the hypothetical maximum an unmodified human can achieve) includes a lot of feats that border on the inhuman, which in Fisk's case includes turning himself into a walking wall of muscle.

To date, no one has detected evidence of "cheating" on Fisk's part, even when they had means or incentive to do so. A sentinel has never flagged him as a mutant, Tony Stark has never caught him with a pirated Starktech exoskeleton, no one tried to throw him in the Negative Zone for not registering during Civil War, or otherwise. All seen evidence is that he's just an extremely beefy dude.


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

[User]
ELI5: How did so many places learn to process and harness Copper to get out of the stone age?

I've been watching heaps of pre-history videos and people replicating how to make tools from copper, iron, etc.
Copper alone seems like such a HUGE jump and complicated process. How would have people have known to mine and heat (put simply) copper ore into all these copper tools?

[Assistant]
Imagine you're using stone all your life to poke and chop things.  You get irritated by the stone always chipping and breaking and you have to go find a new stone to do this... multiple times a day.  But one day you find this neat greenish and shiny stone. You start noticing that the gray bits fall away leaving more of that pretty shiny stuff. But that shiny stuff seems more reliable than the gray stuff.
You show your friends these cool shiny stones and demonstrate their superiority,  so they become the new standard and everyone begins using them.
Then your cousin Ugga, who is also the clan buffoon one day drops his stone in the fire. He panicks and cries,  then goes to bed.  But the next morning,  Ugga comes to retrieve his pretty stone. He sifts through the embers of the fire with a stick for it and finds it completely changed by the fire.  It's now the color of the sun,  shinier,  and deformed relative to how it was when he tossed it in the.
Both excited and upset,  he shows others.  One guy decides to do an experiment and discovers that heat makes the shiny stuff more malleable and devises his own tools to make more shiny rock. Then the first metal spearhead is formed and the first foundry is planned.  And so of your prior now know that metals are weaker with heat and everybody starts spotting metal more frequently.


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

[User]
Is Absurdism an end point in philosophy?

I've done tons of personal research/reading and introspection, and after a lot of thinking I can't seem to see another philosophical path so to speak coming out of absurdism. There only seems to be ways to deal with the idea of the Absurd and figuring out ways to endure. The same seems to be with existentialism and nihilism. They explain the nature of existence and how to deal with that reality, and as far as I can tell absurdism is the most accurate depiction of existence. However, where do you go from there? Is there anywhere *to* go? Is the end point really that one must "rebel" or take some "leap of faith"? Are there any philosophies that stem out of absurdism (or a similar philosophy)? This has been bugging me for a long time, and I appreciate any insight.

[Assistant]
> Is the end point really that one must "rebel" or take some "leap of faith"?

No -- or at least not necessarily, and this is not a point of general consensus. Oodles of philosophers are not absurdists; your thought that absurdism is where philosophy ends up is an idiosyncrasy of your views rather than a recognized result of philosophy.

NB: the absurdist thoroughly denies that a leap of faith is a philosophically acceptable response.


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

[User]
[star wars] Why is the empire so human centric?

You see a ton of aliens in the star wars universe, but none of them are directly employed by the empire. Empire seems to be 100% homo sapien. Sure, they use aliens as bounty hunters and snitches, but Aliens aren't in uniform.

What gives?

[Assistant] The in-universe explanation is that the Confederacy of Independent Systems counted many alien races among their ranks, which bred some animosity (ignoring the fact that there were plenty of humans in the CIS as well). The Empire played up existing tensions between humans and non-humans during the rise of the new order.


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

[User]
[Star Wars: Andor] Why does everyone attribute the Aldhani heist to rebels?

They didn't leave behind any manifesto, they didn't scream "you will always remember this as the day where you were robbed by Saw Gererra partisans!", nobody even was captured alive for interrogation. They just stole 80 million credits and left. Why does no one at the ISB or the Imperial Navy consider the possibility that this was merely a robbery by greed motivate crooks?

[Assistant] The alliance to restore the Republic hasn't been established yet. Blaming the rebels is a catch all term not a specific reference to any group. By this point the different crime syndicates all operated with the tactic permission of the empire or below their radar. No one would be daring enough or dumb enough to try and steal from the empire that much unless they had motivations beyond greed. By treating it as rebellion and insurgency the empire can widen it's oversight beyond that of simple criminal activity.


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

[User] ELI5: Why is it that people make more idiotic mistakes when a boss/supervisor is watching when working any job?

[Assistant] People psych themselves out. Instead of being relaxed and concentrating on the task they are supposed to do, they start to get nervous and distracted. Their thoughts go from focused to divided between what they need to do and what will happen if they screw up, and they're under more pressure to *not* screw up because the boss is there and if they screw up they could get in trouble. But taking away that attention just increases your chances of screwing up more.


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

[User] Why do fluorescent things glow under UV light?

[Assistant]
Fluorescence is the ability of an object, or rather the material it's made of, to absorb light and then re-emit them. They way this works is usually via the absorption of photons by the material to promote electrons into higher energy levels. Then, these electrons relax back to ground state, emitting photons in the process.

In a normal case, one high energy photon will be absorbed and then a lower energy photon will be emitted. This is because when the electron relaxes back to the ground state, some of the energy will be lost as heat. This is why UV light (high energy) is usually used to shine fluorescent objects that will then emit visible light (lower energy) back to us.

There is also another mechanism in which 2 photons are absorbed in order to promote a single electron. In this case, the emitted light can be of a higher energy than the absorbed light. However, not very many photons can be absorbed this way and the absorption is much lower than the typical case above.


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

[User]
What is the currently accepted theory (or theories, if several are competing) for the source of inertia?

I recently watched a Richard Feynman video in which he made the assertion that no one knows why inertia exists. Wikipedia confirms this view. When I did some research, the best I could find was a discussion on the vacuum field theory of inertia, but that was almost 16 years ago and I've never heard anything about it since.

What's our current best guess for where inertia comes from, and what experimental evidence (if any) supports each theory?

----

*Update:* To be clear, what I'm asking is whether inertia a fundamental, irreducible property of matter in our universe (i.e., the "that's just the way it is" explanation), or is it an emergent property that hinges on other fundamental properties (i.e., the "inertia exists because of X, Y, and Z, and X, Y, and Z are fundamental properties of our universe" explanation)? And if it's the latter, what explanations do we have for why it might be an emergent property?

----

Another reason I'm interested is because if inertia _isn't_ a fundamental property, then that suggests it might be theoretically possible to control, amplify, or negate it in some way, which I imagine would be an extremely interesting area of research.

[Assistant]
The trouble with these kinds of questions is that you can say "no one knows why X exists" for absolutely everything.  You just dig down far enough.

E.g.  Why does gravity exist?  Why do electrons exist?  And so on.  Sure you can explain in terms of other things, but then you can just ask why those things exist, and repeat until there's no answer.

For inertia specifically, conservation of inertia is conservation of momentum plus conservation of energy.  So now we just need to explain those two things, and why things have any inertial mass at all.  The second is explained by the higgs particle - the usual colourful explanation being that the massive particle is like an attractive guy.  The more mass, the more attractive he is. And the higgs particles are obese women who crowd around the guy, making his progress hard.

So now you're asking why energy and momentum are conserved.  You can say those are symmetries of nature, but then what?  Why does nature have those symmetries?  Could nature have had different symmetries?


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

[User] [MCU] As an expert marksman, why doesn't Hawkeye ever use other types of firearms or projectiles? Why always a bow?

[Assistant] Because a sniper rifle doesn't have grappling hook bullets, electric bullets, hacking bullets, etc. Bows are a true test of skill, any psychopath with a dead family and a hero complex can shoot a gun.


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

[User] How exactly are cockroaches able to survive the radiation of a nuclear bomb?

[Assistant]
Cockroaches probably wouldn't survive that well actually. The adults can withstand radiation pretty well and not die, but 1,000 rads and they will lose the ability to reproduce. So the cockroach is still dead.

Fruitflies on the other hand can withstand around 64,000 rads and flour beetles will live through 100,000 rads. Most cockroaches are dead at around 10,000. So the cockroach would not fare well in a nuclear war. The kitchen pests that will inherit the earth are the flies and the beetles.


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

[User] ELI5: When you're swimming, why doesn't the water flood your ears and kill you?

[Assistant]
Lucky for you, your ear has a protective barrier called your tympanic membrane (eardrum). This keeps the middle and inner ear separated from the outside environment.

Even if your eardrum gets torn, your body has a connection from the ear to the throat known as your Eustachian tube so if you were to go swimming with a perforated eardrum (a bad idea since the risk for infection skyrockets), you'd still be alright.


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

[User] ELI5: Why do pre-cooked chickens cost less than the raw chickens at the grocery store?

[Assistant] The rotisserie chicken you see in the front of stores is a loss leader. The store loses money on each chicken sold. However, when you put it in your cart and walk around with it, you smell the chicken and get hungry, thus buying more.


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

[User]
Why is oil lighter than water?

I've gotten this question from oil spills. Since octane is a hydrocarbon with eight carbon atoms and 18 hydrogen atoms, basically C8H18. Water on the other hand only has two hydrogen atoms and one oxygen atom to make up H2O.

Since from this it's obvious that octane would have a higher molecular mass than water, yet it floats on water. I've also googled their molar masses only to find that octane has 114 g-mol^-1 while water has 18 g-mol^-1

As such by logic, an oil spill would result in water being displaced on top with oil settling on the bottom; yet the reverse happens. Why?

[Assistant]
Molar mass does not determine whether something sinks or floats, but rather the relative densities of the two substances.

Think of it this way, water and ice are both H2O, therefore they have the same molar mass.  But ice floats in water.  This is because ice has a lower density than water.

The density of ice is 917 kg/m^3
The density of water is 1000 kg/m^3

Ice floats in water.

The density of octane is 698.6 kg/m^3.
The density of liquid water is 1000 kg/m^3.

Oil (octane in your example) floats on water as well.


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

[User]
[Friday the 13th series] How did Jason survive his apparent drowning?

Kid drowned. Dozens of witnesses claim to have seen it (the other Chrystal Lake campers) and it was a known fact the kid couldn't swim.

Furthermore, how did he make it to adulthood? I mean, twelve year old water head Jason, couldn't even swim, finds a reliable food source, figures out rudimentary carpentry to build that shed, and just kind of hangs out?

Just seems ridiculous.

[Assistant]
There is a fan theory that covers it fairly well:

Look closely through the first or second movie and in his mom's place you'll see a familiar prop.  Necronomicron Ex Mortis - the book of the dead - from the Evil Dead series.  And it is the same prop (recycled into another movie)

It has spells that being dead people back as messed up deadites, which is a fair description of adult Jason.  Mom just bought him back and raised him up.


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

[User]
[Eve Online/Mass Effect] Reaper invasion

The Reapers have begun an invasion of the eve galaxy starting in the Eve Gate system with them heading for the Amarr system. Word spreads to everyone including the alliances in 0.0 causing them to form an alliance together. How does the war go, who wins.

[Assistant]
The Reapers smash the shit out of the first empire they run into. They come from nowhere, the biggest of them have Titan-equivalent beam weaponry, their mass-effect shields are tougher than anything in Eve, and due to the way they bend physics, they maneuver *way* better than anything their size has a right to. Their reactionless mass-effect drives are comparable to top-tier Microwarp drives, without any of the signature drawbacks.

But Eve has an incredible industrial capacity. They don't outclass the Reapers, ship for ship, but a hundred or more fully industrialized solar systems can churn out a *shitload* of ships. They quickly learn what works okay and what doesn't against Reaper shields (bad: kinetic, good: thermal). The remaining three empires, recognizing a huge external threat, form a working treaty to push out the Reapers. The independent corporations, recognizing a gold rush of salvaging Reaper hulls, chip in with enthusiasm. The allied Capsuleers can reincarnate in cloned bodies, and do not need to fear death as they send wave after wave of moderately effective cruisers to blast away at the Reapers.

The human losses (and *expenses*) are horrific, but it's a great time to be a manufacturer or salvager. The Reapers retreat after suffering moderate losses with no gains. Eve space celebrates for a week, and then goes back to political in-fighting over disputes about Reaper salvage, insurance, and who gets to reclaim and rebuild which Reaper-wrecked territory. Corporations fill the power vacuum next to the few Amarr territories left, Eve space settles back into a dynamic equilibrium. CONCORD keeps a Reaper watch running, to sound the alarm and call the alliance back together if they rear their space heads again.

All that salvaged Reaper stuff? It's still alive. All of the top researchers and trophy-taking CEO's analyzing the leftovers are gradually subjected to the Reapers' Indoctrination effects. People successfully reverse-engineer the mass-effect FTL drive, and in the process, top empire & corporate figures are turned into Reaper sleeper agents. Lots of people realize what's happening and/or notice active Reaper nanomachines, but they're up against sleeper agents and perfectly rational competitors who think it's a BS conspiracy theory. Some null-sec corporations fold into cult-like sects and disappear from the galactic scene, flying their new ME FTL drives into dark space in search of their gods.

There are a lot of shrewd, un-corrupted people who isolate themselves from Indoctrination, but hardly any organization gets by without *any* sleeper agents.

Months later, the Jita port authority shuts down its automated defenses and enforces a hard blockade on its warp gates. Atomics go off on every station moments before the Reapers come back for their second attack. The defense is disorganized, sensor-jammed, sabotaged, and at least one capsuleer out of every twenty turns against humanity. Billions die, against two Reapers destroyed.

When someone in a pod is killed, their clone is still indoctrinated wherever it wakes up. Reincarnation policy has to be seriously re-evaluated. Some organizations begin outright prohibiting clones that have had extensive Reaper contact, others quarantine them. And, of course, sleeper agents in positions of authority abuse those quarantine procedures to lock out hundreds of un-indoctrinated pilots.

Coming right behind a massive wave of industrial sabotage, terrorism and intentional dereliction, the Reapers tear apart the empires. It takes a while, and there are losses, but Eve can't fight them back without a very organized defense, and the fear of Indoctrinated authorities or allies, where it is real and where it is imagined, makes that impossible. All the manufacturing capacity in Empire space is either destroyed or appropriated, and once the Reapers have space superiority, the trillions of people planet-side are processed.

The last survivors of humanity, months later, are distant null-sec corporations, in far systems and hiding in wormholes. All it takes is one indoctrinated member - or brief contact with some indoctrinated transient - to call out their location and bring a hundred Reaper capitals in a minute later. Fully-indoctrinated groups roam the far systems pretending to be refugees, and bringing hot laser death on anyone who doesn't shoot on sight. Unable to trust each other (with good reason) the surviving organizations are not able to fight back in any meaningful way. It might take years for the Reapers to track down the very last nomadic outpost jumping through wormhole space, but humanity loses.


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

[User] ELI5: What was Watergate all about?

[Assistant]
A bunch of ex-CIA spys working for President Nixon's reelection campaign got arrested trying to bug the phones of the Democratic Headquarters (at the Watergate Hotel).

Nixon said he knew nothing about it. Everyone belived him.

Over the next two years, two reporters with the help of an informant in the FBI who had secret knowledge of the actual events, showed that this wasn't just ONE break in. That Nixon's campaign was using secret money to fund all sorts of dirty and illegal political tricks.

So a bunch of Nixon's staff got called into congress to testitfy who knew what about the illegal campaign stuff. That's when one guy accidentally let the world know that Nixon tapes every conversation he had in the oval office.

So after a long legal battle, the Supreme Court forced Nixon to release the tapes. And they show that not only did Nixon know about the break in, but personally directed the efforts to cover it up. So he got caught with irrefutable proof he lied about Watergate a lot.

Soon after the Democrats in congress began to try and impeach him but he quit before he could be fired.


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

[User] When SETI detects a radio signal and states that it came from the region of a certain star many light-years away, how do they determine that considering that the signal has taken so long to reach Earth?

[Assistant]
The thing you have to take into consideration is that visible light and radio waves both travel at the speed of light, due to them both being light. When you point a radio telescope at a star, you're receiving signals sent at exactly the same time as the visible image of the star when you point an optical telescope at it.

The distance, in light-years, between us and any star is equal to the age of the visible image we see when we look in that star's direction, so we are technically unable to view any distant objects in "real time".


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

[User] ELI5: Why hasn't Caitlyn Jenner been punished for killing someone in the car wreck that happened a few months ago?

[Assistant]
It's not a crime to kill someone in a car wreck if it was genuinely an accident. According to wikipedia:

>In July 2015, Los Angeles investigators determined that while Jenner was inattentive, "she was not intoxicated or texting" before the crash, and would not face felony charges.[77]


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

[User]
Does a fish see clearly when out of the water?

Anytime I open my eyes underwater, everything is blurry, but I can see fine otherwise. Is it the same way for a fish? Can they see fine underwater and then have trouble seeing out of the water? Is there even any way to test this?

[Assistant]
When light moves from one medium to another, it refracts (distorts). The eye evolved underwater, so it evolved to have fluid inside it so light would move from the water into the eye without refraction. Your eyes have adapted to compensate for the refraction that happens when light goes from the air to the fluid inside your eyes. Underwater that refraction doesn't occur so the compensation ends up distorting the image. Fish would have a similar problem out of water. Since they aren't compensating for the refraction, they would also see a distorted image.

Interestingly, since the eye developed underwater it's believed that fish generally have better eyesight than we do, since our eyes are basically underwater eyes that have had to be adjusted (imperfectly) to work on land.


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

[User]
[LOTR] What does no man can kill me actually mean? Does it refer only to adult human males?

Technically, Merry is a Hobbit and Eowyn is an adult human female. Neither fit that definition of man. But did the prophecy use a looser definition, where any male would qualify, or any human?

[Assistant]
I feel there are a few misconceptions regarding the Witch King's battle with Eowyn.

First, he technically does not say "No man can kill me" but rather **Hinder me? Thou fool. No living man may hinder me!"** as a response to Eowyn's demands that he cease his attempts to desecrate the body of King Theoden. The Witch King is the chief of the Nazghul and a powerful wraith who straddles the world between the living and the dead.

He is essentially saying "I am the chief of a powerful group of wraiths, kept alive through dark powers beyond mortal understanding. Who the hell are YOU, peasant?"

As for the prophecy regarding his defeat, Glorfindel says:

**"Do not pursue him, he will not return to this land. Far off yet is his doom, and not by the hand of man will he fall."**

Our favorite balrog-slaying elf isn't saying that the Witch King is magically impervious to male warriors, but rather he is foreseeing the Nazgul's downfal in the distant future. He is delivering this prophecy to King Ernur who tried to destroy the fiend at the Batte of Fornost but failed due to the Witch King's dark aura frightening his horse.

Basically Glorfindel is telling King Ernur he is in over his head, not because he's male but because his warrior's pride is no match for the Witch King's dark magic.

I would further argue that the Witch King's arrogance against mortal men (whom he has far surpassed through the power of his ring) is what sets him up to fail.  He's overlooked the Daggers of the Westernese, forged by men long dead. Daggers which were deliberately enchanted to do harm to his kind.

The reason Merry and Eowyn are able to triumph in their fight with the Witch King is because Merry's dagger is able to nullify the Witch King's dark magic. Eowyn, empowered by her desire to avenge her fallen Uncle, is able to soldier through the lingering Black Breath to deliver the coup de grace. Even weakened, the Witch King was still an unholy abomination of dark magic.

So in short, the Witch King isn't magically protected from human males but rather is too powerful for the average man to slay on account of his dark magic. His death at Eowyn's hands is just delicious irony because, hey, technically a man DIDN'T kill him in the end.


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

[User]
[Harry Potter] What if a muggle born Hogwarts graduate tried to enlist in her Majesty's armed forces?

Would the ministry allow it? How could they use their powers to covertly help their unit?

[Assistant] "I see here that you dropped out of school at age 11. And it seems you don't understand math very well. Or the sciences. Or English. Or any other subject taught in school. You also don't seem to be overly fit, save for being really good at walking up staircases."


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

[User]
[MCU/Antman and the Wasp] Question on the Sokovia accords.

In the movie. Hank and Hope are on the run because they violated the sokovia accords. But all Hank and hope did was develop the technology while Scott went to help Cap without their consent. Given this loophole, would the accords give the government control over emerging technologies being developed by private technology companies by claiming that someone could use said tech to violate any laws?

[Assistant]
Congratulations. You just figured out the alterior motives of the US government.

These are the same people who virtually enslaved mutates and superpowered beings like Ghost and wanted to nuke Manhattan despite criticizing the Avengers for falling rocks. They don't give a shit about people, they want conto over the mightiest heroes.


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

[User] [Interstellar] How tall is the wave on the water planet that's near the black hole? Could it be concieved that there IS land somewhere on that planet, even with these waves?

[Assistant]
I was always puzzled how they don't notice the planet was all water. Same goes for the planet Damon landed on. They traveled all that way, and never once thought to reconnoitre thier destination.

I always wondered if the combination of gravity and water managed to erode whatever landmass that used to poke above the water.


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

[User] [Star Wars] Do Jedi/Sith feel any impact when deflecting blaster bolts with their lightsabers?

[Assistant]
A blaster fires by a small amount of gas (often Tibanna) being energised and transformed into a beam of energy particles which is focussed and fired. A bolt would have fairly little mass, but due to the high energy it would still potentially cause some small impact on the deflection as it would hold kinetic energy.

When deflecting the bolt a Jedi would probably feel enough impact to let them know they had successfully hit the bolt, but not enough to knock the lightsaber back.

Materials which were hit by bolts would fare worse than a lightsaber (which, after all is deflecting and not absorbing the energy) as the energy could be transferred to the material and would do great damage to both organic and inorganic matter.

*****

EDIT: There have been some more detailed explanations below about how the bolts damage materials and throw people back that are all v interesting, mine is rather over simple!


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

[User] Eli5 Why do we find 'things' beautiful. Not people, I get the logic behind finding a person, a 'mate' attractive. But a sunset, a pretty flower, a super car... Why? What is the logic / reasoning for finding these 'things' beautiful...

[Assistant]
This is an area of active research so we cant give you a definitive why. One thought is that when we see images that are easily scannable we find them pleasing.

Symmetry and landscape orientation are key.

Its thought to provide an evolutionary advantage if we can easily scan scenes or objects when looking for food, predators, prey, etc. It really doesnt matter whether its an object or a landscape, both are images on the back of our eyes.


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

[User]
(Star Trek) What are the implications of transporter technology being able to transport not just matter, but also consciousness?

When a person is teleported, somehow his reassembled body is not an empty shell, but a fully conscious human. The crew member remembers everything about his life, and has an apparently continuous stream of thought from the moment he was on the Enterprise to the moment he is not. There is no noticeable break in his perceptions. Does this mean a teleporter is able to read and reassemble a person's thoughts, feelings and memories along with everything else? And if so, does this imply we also have the potential to store the essence of an intelligent lifeform?

[Assistant] Your consciousness is the electrochemical state of your brain. That's why brain damage impairs cognitive function. Transporters, especially transporter clones from the pattern buffer (Scotty, duplicate Riker) prove this.


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

[User]
ELI5: Why do some lights glow after being turned off?

Sometimes when you turn a light off it glows quite dimly, but it only happens with some lights, can anyone explain why this is?

[Assistant]
There are multiple reasons.  Many lights have capacitors in them that store a charge.  Once it's turned off that charge will slowly discharge through the electronics resulting in it being lit dimly for a while.

Good quality lights should have a resistor in the circuit that will quickly drain this charge so it goes out immediately.

Another way is that sometimes the current through the wiring induces a slight current in nearby wires.  This can be enough to slightly power lights even when the switch is off.

Another reason is that some lights like fluorescent bulbs, use phospors, a chemical that absorbs UV and then re emits it as visible light.  These phosphors slowly discharge that light once the UV light is turned off.  It's basically the same process as glow in the dark materials, but not as strong.


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

[User]
Continental metaphysics

Hello. It's my understanding that Nietzsche and Heidegger both saw themselves as working against metaphysics as they understood it and called for an end to metaphysics. How has more recent continental philosophy discussed metaphysics? What texts would you recommend where the author thematizes metaphysics explicitly? I'm wondering if recent continental philosophy still sees itself as working towards the end of metaphysics or if this orientation has shifted.

Thanks!

[Assistant] Deleuze could be of some interest to you. He embraced metaphysics even when they alerte extremely unpopular. Even going as far as to call himself a pure metaphysician. Plus, he engages heavily with Nietzsche and Heidegger to a certain extent as well.


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

[User] [Harry Potter] Could a Dementor destroy a Horcrux by sucking the soul out of it?

[Assistant]
No.

As Hermione said, horcruxes are the opposite of human beings. In humans, the soul and the body are distinct entities, and it is possible to separate them. Furthermore, you can damage the body while not hurting the soul, and you can damage the soul while leaving the body intact. For a horcrux, the opposite is true: the soul fragment and its vessel are bound together inseparably. Thus, you cannot physically damage a horcrux unless you simultaneously damage the soul fragment inside through magical means. This means that, to attack a horcrux, you need something that is highly destructive both physically and magically, and there are only a tiny number of things in the world capable of this. For example, magical fire that can incinerate the vessel while hurting the soul fragment, or a really sharp sword that's been imbued with magical venom.

Dementors do not physically destroy the target of their kiss. Therefore a Dementor could suck on a horcrux all day long if it wanted, but it wouldn't accomplish anything except look rather silly, and, depending on the shape of the horcrux, possibly slightly perverted.


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

[User] eli5: how does it work that for every pound of weight you lose, there is a 4 pound stress reduction in your knees?

[Assistant]
Place a rock on your foot. That's how much it weighs. Now drop the rock on your foot. Different experience?

Walking or especially running requires your knees to not just support your body weight but stopping your falling body weight.


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

[User] [Star Wars] The Senate will decide your fate..." Suppose Palpatine is taken into custody, what does a trial look like for the man who "is the Senate"?

[Assistant]
*Hilariously*. All the judges/militant senators keep slipping on tea and breaking their necks. Evidence keeps getting lost. Terminals containing the relevant information keep losing files. Witnesses quickly recant their stories and claim having been under duress by the Jedi. Pretty soon it will be about how badly the Jedi tried to indict an innocent politician.

So, it will eventually lead to Order 66 by whomever is Palpatine's designated successor.


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

[User]
What do blind people see?

Is it pitch black, or dark spot like when you close your eyes or something else?

[Assistant]
The people who are blind from birth do not have a visual sense at all. Hard for us to understand, but that's how it is. They don't see black - they don't SEE anything at all.

People who lose their vision later in life also say that it's an absence of vision rather than blackness.


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

[User]
[Marvel] Why did Magneto believe that Cyclopes deserved to be the leader of the mutants?

Ok lets get one thing straight, I actually like Cyke, hes a compelling character to me. I feel like theres a lot of readers who dislike him due to one reason or another and while I do understand some of those reasons, I find a lot of them to be too over exaggerated and based on inconsistent writing, more than anything else. Cyclopes is allowed to be a complex character and I think some writers try too hard to find an excuse for people to disagree with him. So this isnt me bashing on him.

But anyway, why did Magneto proclaim him the Savior of mutants? Magneto himself is no slouch. Hes someone whos championed mutant kind before and hes proven to be a competent leader as well. Hes also way more powerful. So what did he see in Scott? What qualities did Magneto see in him that made him think Scott was more fit to lead the mutants than him. This was during the time when the X men were more divided than ever too and Magneto does have history of leading mutants while towing the line with the X-men. So what made him decide he was gonna support Scott rather than the other way around?

[Assistant]
At the time when Magneto conceded to Scott, mutantkind was at a low ebb. Almost all of the survivors were concentrated on Utopia, with Cyclops as their uncontested leader. Scott had rejected and ejected Professor X and embraced a form of mutant separatism - in effect, he had come round to Magneto's way of thinking. An alliance was the natural choice at that stage.

Meanwhile, Magneto was also at a low ebb. He had been depowered by Wanda and, although some of his powers had returned, they were far weaker than before - just a short time before his arrival in Utopia he had allied with the High Evolutionary in order to get a temporary power boost that would let him challenge the X-Men. He was no longer the god-like being that could subjugate armies; he was just a powerful and charismatic mutant. He had tried attacking the X-Men just a few issues earlier, and been roundly defeated; he clearly could not conquer them. So if he was going to ally with them, he would need to treat with them as equals at best, and possibly even superiors.

Beyond that, kneeling makes a powerful gesture - not just to encourage the alliance he was seeking, but also to ram home to Scott the fact that he had gone from Xavier's disciple to Magneto's heir. It was a way to not just get the alliance he wanted, but to make it clear *why* he was seeking that alliance.


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

[User]
[Warcraft] If Bolvar is the new Lich King and there must always be a Lich King...

Why doesn't he order the Scourge to jump into a volcano or something?

[Assistant] It's a battle of wills, Arthas wasn't the only willpower behind the Lich King, although it turned out he was the strongest. Bolvar doesn't want anyone else to become the Lich King but at the same time he's going to be fighting with himself non stop from this point on to keep from turning evil. That's why he was saying to leave and never return, if he can isolate himself he can fight unhindered. Essentially he can't die and he can't give up his fight for control, making the Scourge kill themselves would be great but it would take all his strength to make them do it which would lead to him losing the mental fight, turning evil and the whole thing starts again. The most he can hope for is a "happy" medium and hope the other heroes can stop the rest of the Scourge.


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

[User]
Why do we perceive octaves to be the "same" note?

Is it cultural, psychological, or physics? I've always wondered this. Is it a feature of the waves? And if so, why does our brain interpret that feature to be the "same". Is it possible for a sentient being to perceive different "octaves" than ours, say a 15 step octave?

For that matter, is there any significance to what is considered a half/whole step in music? Or is it all cultural/psychological?

[Assistant]
We perceive pitches that are an octave apart to be the same pitch class because there's a unique mathematical relationship between the two pitches - 1:2.  For example, the A the orchestra tunes to is 440 hz and the A above that is 880 hz.  The octave is not universal per se, but it is very, very common in different world musics.
Tones and semitones are somewhat less clear-cut, but they're based on the same principle.  Collectively, the pitches of a scale embody the pitches that have relatively simple ratios to the tonic pitch.  If you take the first 12ish notes of the harmonic series, you'll get the chromatic scale.  This is less universal than octave equivalence.


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

[User]
[Star Wars] You are in command now, Admiral Piett. Are there no ranks betweeen Captain and Admiral, or does Vader just not care?

Title pretty much says it all.

Did Vader have a reason for skipping these ranks, or were there none?

[Assistant] There aren't ranks between Captain and Admiral (of some type, Rear, vice, lower but Admiral in short form) in most navies. A Navy Captain is much a much higher rank than an Army Captain. A Navy Captain is the equivalent of Colonel. An Army Captain is the equivalent of a Navy Lieutenant.


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

[User]
Another day of writing (grind)

Hi yall just wanted to leave a note for those who are struggling like me, I am feeling burned out from research. I get super motivated and work like nuts and then at some point it fizzles. I think the reason is because progress is slow despite the amount of effort I put in. It is the nature of academic work but it is soooo hard!!!! Aside I realized I have no joy outside this pushing urge to publishother than making different pasta dishes?! Basically no life, maybe. Any tips?! Empathy welcome.

Note: I am a postdoc.

[Assistant]
The best way to wrote is to combine it with reading: read a paper and immediately take notes or write a sentence/paragraph. If you wait to finish reading everything first, and only then start writing, the work seems much bigger and you will also have forgotten things that were in the first paper you read.

In general, we all like to get. big project done and think we can do that through focused work. Instead it is better to divide it in small chunks that you can easily accomplish. Completing a small section every day and ticking it off will feel more satisfying than checking of one big box after a month.


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

[User] ELI5:If a virus works by injecting its DNA into healthy cells, why dont we Re-program the virus to inject our own healthy young DNA into our cells to prevent us from aging?

[Assistant]
They are working on things like that.

Aging is more complicated than that. But it does include the fact that the Chromosomes in cells show aging.  Cancer is a result of uncorrected genetic damage.

Generally a virus is much smaller than our own DNA. So it is like wanting to use a back pack for a shipping container. The sizes do not match up.

Our tissues are specialized. The cells in our organs are specialized. They function the way they do because their genes have been turned off and turned on specially for what they do. You cannot just inject even your DNA into a specialized cell and expect it to work.

There is a lot of research which needs to be done before what we want can be done. Study to go into the field. Support research. Tell your congressional delegation that you want more Federal money for research instead of for bombs, and guns, and drones which make others hate us and want to destroy us.


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

[User] ELI5: Why do public projects always seem to go overbudget? Often by up to 3 to 10 times? Eg IT systems, civil engineering projects?

[Assistant]
To get funded there's intense pressure to quote the lowest possible figure for costs.  Politicians want a low cost estimate because it makes the sale of bonds or the raising of taxes more palatable to voters.  Most projects are awarded based on a bidding process and the lowest bid is usually the winning bid.  Once a project is underway it is commonplace for changes to be requested by the owner of the project (some layer of government) and when those changes are made the project managers figure out how to gross-up the costs of those changes to wring more profit out of the deal they usually underbid to win in the first place.  It is often well understood by everyone involved that the profit of the whole project will come from such change orders - and jobs are often put out to bid even when everyone knows that substantial changes will be required after the bidding is complete and during the project.

The "lowest bidder wins" contract award system has proven to be the worst possible option -- except all the others.  Not using a cost-based bid tends to unlock endless corruption since it's worth just about anything to influence the selection. And spending a couple hundred grand on bribes to win a billion dollar project is totally always worth it.


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

[User]
ELI5: Why do they keep buying new burner phones on tv shows?

I was watching Burn Notice (amongst other similar shows)  and they go through dozens of cheap phones just binning them after they're done... Why not keep the handset and just use a new sim card which would have a different number etc? Sure the hand sets are individually cheap but if you had to keep buying them it'll add up...

[Assistant]
The SIM card, which has its own unique serial #, stores your phone # and a bunch of other stuff that is unique to your carrier and/or you as a unique subscriber.

The cell phone however has its _own_ unique serial # (several in fact) the most important which is the IMEI number. Think of this as a globally unique serial # for the cell phone.

Police and intelligence agencies that can track and trace cell phones can latch onto a phone's IMEI just as easily as the SIM card data.
In order to trace and track your IMEI, you need to make either a long enough call, or several calls before they can nail you down.

While it may be possible to spoof or change an IMEI #, Im pretty sure they're burned into silicon similar to a MAC address for ethernet devices.


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

[User]
ELI5: How was Chris Hanson's show, To Catch A Predator, legal?

I'm in full support of exposing child predators and putting them behind bars. What they do is despicable. I am curious, however, how the premise for the show is legal. Seems sketchy, legally speaking, since the child in question isn't actually a child but a fake online profile controlled by an adult with the sole purpose of incriminating someone else.

[Assistant] What you're probably thinking of is entrapment. Entrapment is when the police convince someone to commit a crime that they wouldn't otherwise commit. The suspects have to be the ones to do thing like start a sexual conversation, suggest a meeting, etc. The person behind the child's profile just plays along.


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

[User]
ELI5: Why do some non carbonated, sealed drinks increase in pressure when you shake them?

For example, shaken coffee or milk. When you open the container, it releases pressure. Where does the increase come from? It doesnt happen with water. It seems to be more likely if the liquid can produce bubbles when shaken. The gas in the container is the same as before shaking, why does the pressure increase?

[Assistant] Gases dissolve into liquids at varying amounts depending on the liquid and gas. Gases also escape liquids based on the pressure of gas above the liquid. A bottle of juice at rest has a volume of gas on top, a volume of liquid on bottom, and a surface area of interface in the middle, all at equilibrium. When you shake a bottle, you produce more surface area which allows dissolved gas to partition from the liquid into the bulk gas phase. When you stop shaking there is exists a greater amount of gas in the bulk gas phase, which results in a greater pressure. That pressure of gas either escapes when you open the bottle, or is forced back into the liquid to establish the initial equilibrium.


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

[User]
[Marvel] What would happen if Ant-Man shrunk himself, ate enough food (relative to his size) to get him full and then grew back to normal? Will he still be full?

Does the food grow as well as him? Does he stay full? I need to know.

[Assistant]
In the MCU, I'd say probably, but he wouldn't be getting much energy from the food.

Pym explicitly states at least twice in the movie that the technology works by decreasing the **space between atoms**. That means that tiny Ant-Man has the same *number* of atoms as regular sized Ant-Man. Our bodies need food so that our mitochondria can respire and make ATP.

The amount of energy you need is proportional to the number of cells you have. And because tiny Ant-Man has the same number of atoms as regular Ant-Man, he has the same number of cells, and therefore has the same energy requirement.

Now, if Ant-Man ate a crumb while small, his stomach would get full. And when he increased back to regular size, that crumb would also *probably* increase in size proportionally; therefore Ant-Man would still have a full stomach. **But** by the same logic of Pym particles stated in the movie, making an object larger would not increase the number of atoms, it just increases the **space between atoms**. Therefore a crumb would not provide any extra nutrition after being expanded.

If an item of food could be expanded and the process increased nutritional value proportional to size, wouldn't Pym have tried to exploit that trick to solve world hunger? The answer is no, because that trick would violate the first law of thermodynamics (conservation of energy), and so it does not happen. Expanding food does not increase the *number* of atoms, therefore it does not increase the nutritional value of an item of food. If a regular-sized person ate an expanded food, they would feel full without having consumed as many calories - probably a great idea for a line of diet foods.

I don't know what the Marvel comics explanation of Pym particles is, but in the movie universe, the answer is - **yes**, grown Ant-Man would *feel* full, but as the growth process does not provide any extra nutrition, his body would only absorb the amount of energy that was present in the original tiny piece of food.


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

[User] ELI5: If I shine a flashlight towards the night sky, how far does the light travel?

[Assistant]
It just keeps on going until it hits something.

That could be a bird, a plane, a cloud, the ISS, another planet, a distant galaxy...

The torch is a pretty weak light source, and the light intensity follows an inverse square law (IE if you're "X" times the distance away from the torch, the light is only 1/X^2 times as intense).

This means that fairly quickly the light your torch produces is lost to the human eye. But the actualy photons/waves (however you want to think about light) will just keep going.


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

[User] ELI5: Why is the Middle East so torn apart by war?

[Assistant]
Because religions hate one another.
Because after being gone for 2000 years, the Jewish people returned and took Israel from the native Palestinians somewhat by force.  A world that felt guilty about the Holocaust let it happen.
Because the world has a frightening amount of latent anti - semitism.
Because the Soviet Union and the US fought a war by proxy through the middle east.
Because at the end of WWI the victors drew lines on a map to make silly borders irrelevant to the people living there and handed out control of the area like prizes for winning the war.  They also installed royal families invented out of thin air from collaborators etc.
Because the US fights wars against terrorism and Iran by proxy.
Because Oil = money = the US, China and Russia cannot mind their own business.
Because oil = money = huge divide between rich and poor = instability.


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

[User]
[Papers, Please] How do citations work?

I am immigration inspector on border of great country Arstotzka.
Every day after I walk to work, I see people who want to enter Arstotzka and inspect papers.
Is very important job.
Sometimes I make mistake and citation printed with mistake I make.
Citations always accurate and come seconds after I stamp passport.
I only person in border. I only person looking at papers.
Who send citations? Who check papers? Why not stop man not supposed to enter Arstotzka? Why need inspector if know if papers correct?

[Assistant] Glorious Nation must employ the hardworking proletariat! How will workers control means of production if machines are control of the workers? Would be of violation of Arstotzkan Dream. Remember to pay asking-questions fine by sundown, ok comrade?


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

[User] ELI5: Why are conflicts going on in the world right now not a world war? And when will it become one?

[Assistant]
Never before has world has been in a state of peace such as this. There are almost no active wars going on now, which is unprecedented.

World War is a hazy term, but generally speaking you'd want large nations wage active war against each other. Proxy war does not quite suffice, for example, Cold War was fought as a proxy war between US and Russia, never did the two nations troops directly clash, they merely supported different sides of various conflicts.

Syria is sort of a proxy war, for example, with plenty of conflicting interests, but the ones actually doing the fighting are locals for the most part.


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

[User]
ELI5: How do streaming services, like Spotify, make a profit?

The majority of users are on free plans so I was wondering as to how a profit was generated. Also, why do artists give their music to such services where their music can be streamed for free?

[Assistant]
Advertisements for the free users and the rest pay a montly subscription fee.

Artists gets payed based on how many people listen to their songs on spotify and they also reach a lot more people with their music. This increases their chances of more people coming to their conserts and buying albums.


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

[User]
[jojo] How does killing DIO save Holly?

DIO gives himself a stand and because he has Jonathans body, the members of the Joestar Bloodline manifest stands too. Holly isnt strong enough to handle a stand so its slowly killing her. How does killing DIO save her? If his death will weaken her stand, why doesnt it weaken Star Platinum, Hermit Purple, or Crazy Diamond (who was also killing a young Josuke before DIO was killed)?

[Assistant]
Joseph Joestar explains this near the beginning. When Dio was inert and not fed they were fine. He's recovering, trying to regain/get more power. And that was having a side-effect of manifesting stands in Joestars, all of them we know of at the time which included Jotaro, Joseph, and Holly. DIO himself mentioned this was an unintended and unfortunate side effect since he didn't want anyone fucking with him while he recovered/gained power. Joseph presumed if they put him down, that the stand that Holly hadn't tried to harness and control would calm down since it was only manifesting in response to DIO.

He was right.


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

[User] ELI5: Why do people have crazy dreams when they fall asleep again after waking up in the morning?

[Assistant]
First, this happens because you stimulate your conscious brain at a time you would normally be experiencing REM sleep. This leads to consciousness in dreams. Second, when you do return to sleep, you will dive straight into REM sleep from a conscious state, also inducing multiple dreams one after another.

You also have a far greater chance of becoming lucid after waking up then going back to sleep.


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

[User]
eli5: What are those little bumps at the floor of your mouth? (in the area at the base of your frenulum)

The title says it all. They almost feel like mini bumps that that are near fluid-like if you mess with them, throughout the floor of your mouth. I've noticed them for years now and never thought anything of it. What are they exactly?

[Assistant]
ELI5 answer: Those bumps are the openings of tubes coming from your salivary glands. They deliver saliva to your mouth to aid in chewing and digestion. You have another opening on your cheeks coming from another salivary gland that you can probably feel as well.

ELI15 answer: That is the sublingual caruncle where the submandibular gland and the sublingual gland empty into the oral cavity via Wharton's ducts and Bartholin's excretory ducts.


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

[User]
Why don't humans have a mating season?

Most mammals have a mating season. Why not humans (not that i'm complaining) ;) ? Was there any such thing at any point in human history.

[Assistant]
Many mammals breed opportunistically. The basic rule seems to be, if a breeding g season results in the survival of more offspring, the there will be a breeding season. If not, then not.

Humans, other apes, rodents, domestic dogs and cats and many others don't have a season.

The animals that do tend to "plan" their births around the arrival of plentiful food and/or good weather.


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

[User]
Why do biologists distinguish between odd-toed and even-toed ungulates?

What makes this distinction useful? If it has to do with ancestry, why did these animals keep odd or even numbers of toes? Is there an evolutionary pressure to lose/gain toes in pairs?

[Assistant]
It has to do with ancestry.  The odd-toed ungulates are a clade called Perissodactyla, while the even-toed ungulates are the clade Artiodactyla.  These two groups diverged in the Palaeocene, over 60 million years ago.

The perissodactyls have a stance that centers their weight on their middle (third) toe.  In equids (horse relatives) all four of the other toes were eventually lost, while in most other perissodactyls only digits 1 and 5 were lost.  Very early perissodactyls had 4 or 5 digits.

Artiodactyls have a stance that centers their weight on digits 3 and 4.  Many artiodactyls today still have digits 2 and 5.

So to answer your question, if the digit isn't being used for primary weight-bearing there's a possibility of it becoming vestigial or disappearing.  Since the animals' weight is more or less centered on the limb, this reduction of digits tends to happen from the outside (digit 1 for artiodactyls, or 1 and 5 for perissodactyls) and move inward.


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

[User] What measurable effects has the Panama Canal had on the ecosystem around it? Between migratory routes, aquatic wildlife moving from one body of water to the other, etc?

[Assistant]
The canal inside the locks is mostly fresh water and so most sea creatures cannot traverse it.

However, loads of organisms travel in ship's ballast tanks, not only through the Panama Canal, but all around the world. That has created many instances of species turning up from the other side of the globe and creating an invasive problem.


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

[User]
[Destiny] Why is there a lot of 20th-21st century junk in the cosmodrome?

So, if I've got my timeline right. Humanity is just chilling, doing it's thing. Then traveller appears, gives everyone superpowers and shit. Humanity starts becoming ber advanced under traveller's guidance and protection, has a golden age, spreads across the stars, colonised planets, builds super cool space ships, etc. Then, darkness comes along, begins to pwn traveller, humanity collapses and retreats to the tower (last city).

Therefore, we should be looking at the wreckage of a super-advanced humanity with sleek spaceships and flying cars, etc. So why do a lot of the burnt out cars and planes in Russia look more late 1990s than 2290s? Was the traveller anti-Russian and didn't let them advance as much?

[Assistant] We can only presume it was used as an Aircraft Graveyard during the Golden Age. As for cars, flying cars aren't really practical in large numbers.. you have an issue of not clearly defined lanes etc. The only advances in cars would probably have been cleaner and more efficient engines plus a few other safety features.


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

[User]
[The Matrix] Why does everyone wear black clothes?

I saw the trailer for the newest matrix movie that is coming out and it got me thinking about the other movies.

Why does everyone who is part of the resistance wear only black clothes and such when in the matrix? Wouldnt you want to blend in with ordinary humans in the matrix to prevent agents from noticing you. Like a guy in a group of people who is wearing a black shirt, black pants, a black overcoat, and black glasses isnt that covert compared to say a guy in jeans and a shirt in the same group.

Like was it explained in the movies or is it just a style choice the creators chose?

[Assistant]
Its not addressed in the movies afaik but its probably out of rebellion and nonconformity.

The citizens of the Matrix are under the control of machines where theyre forced to live dull lives, conforming to the world the machines engineered for them. When they get liberated they obviously have more freedom but their clothes are little more than scavenged rags. When they go back into the matrix they are given much more control over their appearance and clothing and such, so they wear what they consider to be super cool clothes (their concept of which is almost certainly shaped by the fact that they all grew up in a society that is designed to perpetually emulate 1999 earth culture).


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

[User]
[WH40K] Are Psykers able to teleport long distances?

Just wondering. Would a human Alpha level Psyker with decades of training and experience be able to teleport say, himself and 6-7 people with him a distance of a thousand miles or more? What about an Eldar Farseer?

[Assistant] Yes. It is possible. It is exceedingly difficult to do, however, and causes passing through the Warp, without the protection of something like a Gellar Field. I'd be surprised if the chances of survival are better than one in a million.


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

[User]
ELI5: how can a sitting US president create "permanent" legislation?

It seems the only good news coming out of DC as of late has been a series of actions in relation to environmental protection, such as the setting aside of marine preserves and the banning of offshore drilling in many areas.

In all of these circumstances, it is said that these ocean preserves are to be "permanently" off-limits to fishing and mining.  Likewise, the bans on offshore drilling are supposed to be "permanent."

How can they be "permanent" bans?  What is preventing the next president from just going in and reversing those permanent bans with the stroke of a pen?

Is it just another "norm" that subsequent presidents respect such legislation? Or are they required to?

I guess my questions is: how can a temporary head of state enact a law that is permanent and untouchable?

[Assistant]
They are permanent in the sense that if left as-is, they have not expiration date. They can still be modified by congressional action.

From what I've read on the subject, another sitting president cannot undo the action because it is based on powers deligated to the President by law, and those deligated powers only provide for establishing these regions, not removing them.


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

[User] ELI5:Why can't I take home my organs after having my appendix or tonsils taken out? I mean, isn't it mine technically?

[Assistant] When you have an appendix or tonsils removed, it's due to appendicitis or tonsillitis, meaning they're infected, heavily, with bacteria.  Taking it home and not disposing of it properly allows many harmful bacteria an opportunity to hurt you or others again.  In short, that organ is now a biohazard.


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

[User]
Where did Angela Davis say "radical simply means grasping things at the root?"

To start off, if this is the wrong place, please let me know where the right place and I am aware that this is a rewording of an earlier Marx quote. With that out of the way, I am trying to cite the place where this quote started but I am having a hell of a time finding it. It doesn't help that it appears on a million random quote sites without any attribution. Can anyone let me know a place where Davis wrote these words? Thanks in advance!

[Assistant]
It's in her book *Women, Culture, & Politics*. The quote is from her address "Let Us All Rise Together: Radical Perspectives on Empowerment for Afro-American Women:"

> In the aftermath of the Reagan era, it should be clear that there are forces in our society that reap enormous benefits from the persistent, deepening oppression of women. Members of the Reagan administration include advocates for the most racist, antiworking class, and sexist circles of contemporary monopoly capitalism. These corporations continue to prop up apartheid in South Africa and to profit from the spiraling arms race while they propose the most vulgar and irrational forms of anti-Sovietisminvoking, for example, the evil empire image popularized by Ronald Reaganas justifications for their omnicidal ventures. If we are not afraid to adopt a revolutionary stanceif, indeed, we wish to be radical in our quest for changethen we must get to the root of our oppression. **After all, radical simply means grasping things at the root.** Our agenda for womens empowerment must thus be unequivocal in our challenge to monopoly capitalism as a major obstacle to the achievement of equality.


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

[User] [Star Wars] Are there any Sith that prefer to use other weapons over a light saber?

[Assistant]
Well, Lumiya was trained by Darth Vader, and was known as the Dark Lady of the Sith.  However, whether she counts as a "true" Sith Lord is a matter of debate.  In any case, Lumiya favored a lightwhip, which was similar to a lightsaber, except the "blade" part was long and flexible, instead of simply being a straight, rigid shaft of glowing plasma.

Lumiya was not the only wielder of a lightwhip, as she found the schematics for it in an ancient Sith tome.  Therefore, it is likely that there were some earlier Sith who also used lightwhips.


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

[User]
ELI5: How do big companies/colleges maintain high internet speeds across hundreds of people's devices?

It was a random thought that occurred to me. I've heard about how connecting a ton of active devices to a home network can cause congestion (and slow it down?). I'm a university student and I am always able to have a fast internet connection even when there's hundreds of people in the same building as me using the network.

[Assistant]
Your building has lots and lots of access points all connected to many, many switches. Each switch is likely to be able to handle a Gbit of traffic *on each port*  so for a 24 port switch that's a 24+ GBit back plane.

Your college also has an industrial level internet connection. And if its a large research institution it likely is a node on Internet2 which is an all fiber network that connects lots of colleges and other institutions. When you data needs to get to one of those institutions, it gets automatically routed over the super fast fiber connection.


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

[User]
[General Fiction] What is the closest fantasy/magic equivalent to the Culture society?

The Culture, from the Culture series by Iain Banks, is possibly one of the most utopic and powerful sci-fi civilizations ever conceived. I'm looking for the closest civilizations to it that exists in the fantasy genre. A civilization that started with wizards instead of scientists, that runs on magic instead of sufficiently advanced technology.

[Assistant] The Tippyverse, which was a thought experiment from the Third-and-a-Half Age of Dungeons and Dragons. Basic needs could be met with repurposed magical traps, infrastructure could be handled with magic and a variety of constructed, hired, or enslaved magical creatures. Non-mages would contribute to the society by giving or selling their experiences to the artificers responsible for maintaining this hypothetical society's infrastructure.


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

[User]
ELI5: How does MVC programming work?

Hi! I just started using codeigniter and I love it! I have programmed in php for a long time, but simple things. Now I am tasked with a big project and CI will help... Only I can't seem to wrap my head around MVC programming. I know what code to write, but I usually don't know where to put it.

[Assistant]
The M stands for model. This is where you create a data 'model' of the problem you are working on. You might have a user and that user has certain data related to it like a name and an address and a password. That user might have a 'shopping cart'. There might be many 'items' for sale. You want all of this code to reflect something about reality, but it isn't involved with how to interact with the user.

The V stands for view. This is how the data from the model gets presented to the user. There might be many different views for the same underlying data. All the view needs to know is that it will get model data somehow and then turn that into a data structure which will be delivered to the user. This might be a web page, a JSON object, calls to a graphics API, or something else completely.

The C stands for controller. It's involved with taking input from the user, interacting with the model to get some data, managing delivering that model data to a view, then handing the view back to the user.

MVC is about separating concerns, in this case it separates persistent data (model), creating data for the user (data), and responding to user input (controller).


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

[User]
ELI5: solving old cases like Jack the Ripper

I remember how i would hear, from time to time, that some new information about, lets say Jack the Ripper, appeared and the case about him changed on some way. Same thing on John Wilkes Booth, Napoleon and other people from way more than 100 years ago. How can something from so much time in the past still change? Wich kind of evidence is this and how people get it? Investigations are still happening? Can we trust the new information?

[Assistant] To put it simply, we have better tools to analyze the historical records now and communicate things that seem strange in them. Or records previously undiscovered turn up. Or new general knowledge happens that explains anomalies that people at the time couldn't (like scientific advances). Also, in the case of criminals specifically, the subject being analyzed is no longer able to fight back and destroy evidence.


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

[User] ELI5: If a magnet is 'hovering' by being repelled by another magnet, is it's weight placed on the bottom magnet?

[Assistant]
Yup. They will follow Newton's Third Law, for equal and opposite forces.

Although I'd be careful about saying "weight placed"- the force applied is via the magnetic force interacting between the two, it just happens to be equal to the weight in this particular set up.


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

[User]
ELI5: when pouring soda into a cup of ice, why does the ice sometimes trigger massive amounts of bubbles, while other times hardly any?

It seems to happen with no rhyme or reason and wondering which variable is the cause ... cup material? ice shape/size? soda temperature? something else? I can't say I've found any common denominator in the many years this has confounded me.

[Assistant] I think it is the same effect as mentos. Nucleation (the bubbling) occurs with a hard surface. So fresh frozen, very dry ice will fizz more than say, ice thats had the opportunity to melt a little and the surface smooths out.


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

[User]
ELI5: Why anyone would be opposed to the Iran nuclear deal?

I have been watching the news and I have yet to see/hear one person provide a legitimate reason as to why they believe the nuclear deal with Iran is not a good deal. Every "reason" to oppose the deal I've heard has been some variation of, "This deal is a fast-track to Iran getting a nuclear weapon." Given my (possibly flawed) understanding of the deal, that argument doesn't seem to hold water.  Are there legitimate (non-partisan) reasons that this deal is as "terrible" as  many Republicans are saying?

[Assistant] It gives Iran back their money and opens revenue opportunities for them to sell oil and make even more money.  Money they will likely use to expand all their weapons programs, thus threatening their neighbors.  Threatened neighbors feel they have no choice but to use a first-strike strategy, leading to a war in the Middle East = bad.


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

[User]
ELI5: Why is height the only biometric used to determine if you can ride a ride.

Carnivals and theme parks will often say "you have to be this tall to ride". Why is height the only important factor when riding a ride safely? Wouldn't many other metrics also be important?

*EDIT* So it appears that the other biometrics are considered when allowing someone to ride. The height metric is more visible due to lack of offense. Others have pointed out that too tall, too heavy, too wide of a waist, and more are all factors that can prevent a rider from riding.

[Assistant]
Height varies a lot and very short people - children, usually - won't be properly held in by the ride's restraints.

Very tall people and very fat people also might not be able to ride, but they will be a lot less common. But theme parks are full of children who might not be tall enough for some of the rides.