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

[User] ELI5: I've always been told I'm very hot to the touch. All of my past SO's have said that i radiate a lot of heat as well and I've been wondering if there is any specific reason for this?

[Assistant]
Assuming youre a man, men are generally warmer than women. Men biologically have more muscle than women and less fat, and muscle generates more heat than fat.

It also has a lot to do with metabolism. This is usually the culprit for people who run hot as your temperature is a direct reflection of you basal metabolic rate.

However, if you are a woman hormones may be to blame. A womans body temperature varies throughout the month with her menstrual cycle. Thus causing a woman to be warmer when she is the most fertile.


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

[User]
[DC] Has any Batman villain ever been sentenced to death in any comic book storyline?

Youd think with all these villains like Joker, Riddler, Zsasz, Two-Face, etc running around Gotham City causing havoc and murdering innocent people for fun, the city wouldve decided to bring back capital punishment so they can just off some of these fuckers instead of just declaring them insane and shipping their asses back to Arkham for the hundredth time.

[Assistant]
Gotham does have the death penalty, Arkham Asylum basically exists as a conceit to explain why they don't get it.

Joker in a story called Devil's Advocate, but it was notable that it was for a crime he actually didn't commit, and the legal process was fudged for political reason.

Death Man was a silver age villain who actually was executed after being captured by Batman, but his meditation powers effectively allowed him to survive the execution, and resurrect from the grave.

In some incarnations Deadshot was going to be executed at Blackgate Penitentiary in Gotham, but recruited into Task Force X/ the Suicide Squad from there.


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

[User] What happens, phisically, to all the alpha/beta particles and neutrons that are stopped by a radiation shield?

[Assistant]
These are all probabilistic, so not every event will happen in the same way. So I'll just describe the *most likely* for each.

Alpha particles undergo many small-angle scatters off of *many* atomic electrons, eventually slowing down, grabbing onto two electrons, and simply becoming a neutral helium atom. Alternatively, they can induce various nuclear reactions.

Beta-minus particles (electrons) scatter many times off of other electrons, until they slow down and simply become extra electrons in the material.

Beta-plus particles (positrons) also scatter off of many electrons, eventually slowing almost to a stop, and then annihilating with a nearby electron.

Neutrons scatter many times off of *nuclei* (not electrons) in the material until they're thermalized, and probably captured into a nucleus, transmuting it into a different isotope. However they can also induce various nuclear reactions besides capture.


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

[User] ELI5: why is it better to get some diseases when youre a child (chicken pox for instance) because they are less severe in childhood than adulthood? Especially when you consider that children have weaker immune systems than adults.

[Assistant]
it is because adult chicken pox tends to cause complications like pneumonia and encephalitis while childhood chicken pox does not. Adults immune systems are stronger and employ more antibodies (rather than white blood cells) than childrens immune systems do, which is what triggers the immune response and the subsequent symptoms.
Some strains of the flu are like this, too, such as the 1918 pandemic. The Spanish Flu killed young adults instead of the usual flu victims (old people and kids) because that strain triggered a severe immune reaction called a cytokine storm which basically shut down the bodies of infected people. A stronger immune system=stronger immune reaction=worse symptoms.


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

[User]
[ATLA] How does the group make money?

Normally I wouldn't ask, but they keep calling attention to it by needing to buy stuff and make money. They're sometimes struggling, and sometimes Sokka has enough to buy a man purse.

Where does this money keep coming from?

[Assistant] They're often given donations or rewards by people they helped out on the road. During book 1 they were relatively poorly off, but during book 2 they had some money that the chief of the Northern Water Tribe gave them, plus eventually access to Toph's connections and ability to call in favors as a member of the Bei Fong family. During book 3 Toph ran a series of scams in the fire nation that also contributed to their coffers.


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

[User]
[DC] Who looks after the individual cities while the Justice League is on missons?

Like say the League is on another planet for an entire week fighting Darkseid and his minions or something along those lines. Whos looking after Metropolis, Gotham, Central City etc.
Does Robin and/or Nightwing patrol Gotham while Bruce is away? Was this ever explored in the comics?

[Assistant]
Depending on the continuity yes.

The team from young justice

Most versions of the Titans.

Assorted side kicks.

Of course some places won't be covered as thoroughly, but that's the price of super villains in space.

And some villains, like flash's rogues are quieter when the main flash is busy, and Lex Luther isn't that bad of a guy when there aren't aliens around.

Red robin, night wing, or dick Grayson as batman usually deal with Gotham specifically, and it depends on when in the continuity it is.
Heck, Damian has worked with dick Grayson batman almost as much as Bruce.


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

[User]
Is it realistic to want to be interdisciplinary?

My favorite Wikipedia pages are the ones that say John/Jane Doe was a philosopher, scientist, historian, sociologist, mathematician, and artist. Those are the kinds of people I look up to. Those are my role models.

But theres a lot of information out there. More than there was 100 or 200 years ago. Which means it takes longer to become an expert in a discipline than it once did.

Are there still polymaths in the 21st-century?

[Assistant] Being a 16th or 17th century style polymath is difficult to impossible, but interdisciplinary studies are basically required at this point. Where do you draw the line between compsci, biology, and chemistry in genetics? Where is the line between biology, chemistry, and psychology when you're working in neuroscience? Toss in some physics for flavoring when you're talking about acoustics, or fMRI, or...


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

[User] ELI5: Why is the ocean salty and rivers fresh water?

[Assistant]
Rain has no salt in it.

The land has some salt in it.

When rain falls on the land, it runs downhill into the river and then into the ocean. As it goes, it picks up some salt from the land.

Water leaves the ocean when it evaporates and becomes clouds. Clouds don't have salt in them. And clouds are where the rain comes from.

If we drew a picture of how the water goes through all these places, we would see that the water picks up salt on the land, but does not bring salt with it from the ocean into the clouds.

Which means the salt is getting left behind in the ocean.

Slowly, over a long long time, salt is moving from the land to the ocean.


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

[User] ELI5: Why does a lake of ice cracking sound like laser beams shooting "Pew Pews"??

[Assistant] The way something sounds is determined by the way it vibrates.  and when you have big chunks of ice like that, they don't have much room to vibrate so they vibrate in high frequencies that sound a little bit like stereotypical laser sounds.


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

[User]
ELI5: Why do so many people have a primal fear of spiders when only like 1% of them are dangerous?

Personally I am terrified of spiders but I have no issue with snakes, which I rationally know are much more dangerous.  What's up with my brain?

[Assistant]
Because 1% is actually a pretty high number. Would you get into a cab if you knew that 1% of them exploded before reaching their destination?

Yes, most spiders aren't dangerous. But the ones that are? They can be dangerous enough that we evolved this reaction to spiders -- especially since there's no evolutionary downside to avoiding all spiders.


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

[User]
ELI5: Why do airplane cabins need to be pressurised?

So, when the cabin is sealed, the interior pressure is equal to the atmospheric pressure at sea level. When the plane lands, the exterior pressure is equal to the interior pressure. So why does the plane need to be pressurised for the duration of the trip?

[Assistant]
Because the air pressure is extremely low at typical cruising altitudes. You'd lose consciousness from lack of oxygen in less than a minute, and would die not long after. That's why planes have oxygen masks that drop down in case the plane loses pressure. It's also cold. Like, really cold. Upwards of -60C cold.

As an aside, plane cabins are pressurized, but not to sea level. Usually they're pressurized to somewhere between 6,000ft - 8,000ft. This is enough to be comfortable for people while also reducing stress on the aircraft from the pressure differential.


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

[User] [Elder Scrolls] Why is Tiber Septim's ascension to godhood accepted while the AlmSiVi are considered false gods?

[Assistant] Because ALMSIVI were not inherently gods, they obtained their godhood directly from the Heart of Lorkhan, which was destroyed during the events of Morrowind. And with the heart destroyed they no longer had access to the power that made them gods in the first place.


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

[User]
Can animals from the same species communicate if they are from different parts of the world?

If two chimpanzees from different parts of the world were to meet, would they be able to communicate immediately or would they not understand what the other chimpanzee was trying to communicate?

[Assistant]
We can ask the same question about humans and we already know the answer. It's possible, but it takes time to learn another language. But facial expressions are universal. A person from Asia and a person from Europe will immediately recognize one another's emotions without any verbal communication.
Most animals "converse" in a similar way, through body language. So a dog from Asia, and a dog from Europe will immediately recognize one another's emotions as well. And the same applies to captive chimps around the world, their facial expressions and body language are universally recognized among chimps.
(Edit: Wording.)


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

[User]
How do you find articles talking about specific things when writing essays?

I've always had difficulty when writing papers because of the fact that most of my knowledge is built on the reading we are given, so when it comes to write an essay for a class, I am at a loss to write about besides just reiterating what the reading says in my own words. This seems sophomoric at best.

I want to broaden my horizons when I write papers, look at things in a way the readings for my class have not considered. For example, I am writing a paper on Confucianism and Guanxi, our reading that dealt with that specific topic was few and far between. Hence, I don't have very much to talk about, even though it is a topic that interests me very much.

I figure will be many papers on this topic, but I wouldn't know where to start. Any advice?

[Assistant]
So there is the direct method: go to your library's website, under "databases" you'll find The Philosopher's Index. Put your search terms in there.

The other method is to look at your readings / relevant SEP articles and examine the citations found there. This is probably your best place to start: the stuff cited in SEP articles / the articles you're reading are those most likely to be relevant to your subject.


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

[User]
[Dragon Ball] Why is it that Chichi and Bulma can't fly or otherwise utilize Ki on even a basic level, when they've been around Goku and the others almost their entire lives, but yet someone like Videl can pick it up in a matter of days?

Granted Videl was only able to fly and would never have stood up to any threat in combat, but she managed to grasp the concept of manipulating Ki for flight in a very short time frame.

Meanwhile, Chichi and Bulma have known Goku and the others since forever but I've never seen them even attempt to fly. It's also somewhat of a running gag that Bulma always slows everyone else down because she needs to use a flying vehicle when everyone else can just fly with Ki.

In fact, now that I think about it... Now, I never saw the original Dragon Ball in it's entirety, but... can't Master Roshi not fly either? I don't think I've ever seen him fly. What's up with that?

[Assistant]
Bulma's not a fighter, and Chichi gave up serious training after she married Goku. As for why Master Roshi can't fly, maybe the technique (among humans) might not have been around in his youth or more likely he just didn't learn how, the technique may not have been in the subset of martial arts he was studying.

As for Videl, she trains. Not on the level of the other human Z fighters, bu she's got a reputation to uphold, you know? She's the daughter of the world's greatest fighter, married to the son of the world's second greatest fighter. She's gotta keep her chops up.


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

[User]
[War for the Planet of the Apes] Why are the human attackers in the trailer being tactically stupid?

In the trailer, you see an army of humans attacking an ape fortress, running across an open field, with terrible spacing, with no cover, and with helicopters flying just barely above.

Why are they being so stupid? Where is the artillery preparation? Why are they attacking across an open field? Why are the helicopters flying in so low and close and exposing themselves to danger? Those are Apaches. They could sit back a kilometer and hit the walls with their 30mm cannons, with rockets, and with Hellfire missiles.

Earlier in the trailer it's shown that the humans do have rocket artillery. Why aren't they using that to soften the defenses, first? Why aren't they using it to provide concealment for their push (in the form of laying down a smoke screen)? Why are they just rushing the front gate with no semblance of proper spacing, without any regard for anything like proper military behavior? I mean, with this retardation, it's no surprise that a bunch of apes with bow and arrow and not much else are winning the war.

[Assistant]
We dont know what they were up against or why.

Without knowing that we cant really establish how dumb this actually was. What if they were forced to move right now? What if they were a distraction for whatever reason? What if they had no ammo for the helicopters? What if they had no artillery? What if the apes were weak but only immediately? What if those helicopters were on the verge of breaking down and barely functioning?

Too many what ifs to know how tactically inept this was.


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

[User] ELI5: When a stock price goes down, is it that many people have sold and now have that value in cash OR is it that the market just decides the stock price is now worth less collectively?

[Assistant]
It's closer to the latter of the two, but it's both.

The key thing to understand is that when you see a stock quote or stock price, that is *the price at which shares changed hands most recently.* In other words, a few seconds ago someone sold a few shares to someone else at that price.

Importantly, a stock quote is *not an offer to buy or sell at that price.* So if you see a stock quote and you go sell your shares at "market price", you will get slightly higher or lower than the quote based on various factors. (The "bid" and "ask" prices in the quote are the current offers to buy and sell, respectively.)

A stock going down means that there are more sellers than buyers, "the market" is collectively pessimistic about the stock's value, and so the sellers are dropping their "ask" prices to get the few buyers to bite. Each successive trade is for a slightly lower price than the one before. This continues until the price hits a level where potential buyers start getting more excited and jumping in.


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

[User] ELI5:Why do some scientists believe that we are living in a simulation?

[Assistant]
We think it should be possible to create convincing simulations of our universe within our universe using computers. Why, then, must we be at the "top" of the simulation stack? When you consider that any given "real" universe could contain any number of simulations, and that each simulation capable of supporting computation could also support any number of simulations, you suddenly realize that simulation universes become a ton more likely to be chosen at random from the universe pile.

It also explains some of the weirdness surrounding quantum physics. Why does observing particles seem to give them a history they didn't have before? Because our observation forces the simulation to update the particles and make them more than a probability field for us to observe!


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

[User]
What prevents the intestines from tangling themselves like my headphone cords?

Really, I've always wondered this.

[Assistant]
Dentist here. We concentrate on the teeth, but we do study the whole body in pretty gross detail.

The short answer to your question is that the intestines are attached to several different connective tissues, particularly mesentery and omentum. Mesentery is a very stretchy connective tissue that loosely holds the intestines in place. Omentum is a fatty connective tissue that is heavily vascularized. Together, these two tissues provide the intestines with most of the support they need to prevent tangles. Unfortunately, they are both very stretchy tissues, and some lengths of the intestine do not attach to them, leading to (luckily!) rare tangles and hernia.


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

[User]
ELI5: Why is standardized testing so expensive?

I live in a state where all high school juniors take the ACT.

Some of my students will be taking it tomorrow. Considering tests such as ACT / SAT / SAT II / AP are usually proctored by teachers and are offered at schools (though grad and professional schools seem to offered at testing centers) and that many tests are multiple choice, why are standardized tests so expensive? I know there's research and development and grading costs for essays / written portions, but at $50ish per test ($90ish for AP) these tests seem pricey for what they are.

[Assistant]
1. make the test.
2. advertise and promote the test.
3. proctor the test
4. grade test, mail test, respond to request for copies,scores, etc.
5. defend against lawsuits from crazy parents.

Given that it can cost 15-20 for 1 hour yoga class, you have to imagine that 4-8 hours in a proctored classroom is going to at least cost more than that.  Now add the others!


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

[User]
[Aliens] Why would a rescue crew take so long to help out the Sulaco?

As stated by Hicks, the Sulaco won't receive a rescue until 17 days *after* they're declared overdue. But how long is it until they're actually delcared overdue? Why such a lengthy amount of time?

Also, why would they leave literally no one on the Sulaco? If just one person had stayed on the Sulaco there wouldn't have been any issue getting the second drop ship down for a quick rescue.

[Assistant]
Simple answer is that humanity haven't developed the technology for faster than light travel. It takes weeks if not months to travel between worlds. This is why the colonial marines were put in stasis during the trip to LV-426.

The reason why they wait so long before sending a rescue team is because again due to the distance radio contact is sketchy at best. It costs money and resources and the company wants to be damn sure something happened before they send out a ship and a team. Remember that they get paid extra while deployed.

The reason why they didn't leave anyone on board is because they relied too heavily on automated systems to keep the ship running. So many levels of backups and checks were put in place so that a heavy ship like the sulaco could still function due to a skeleton crew and have said crew deployed to the surface. They didn't have to worry about aliens or pirates hijacking the ship because the ship would be useless to them without the proper codes.


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

[User]
[Star Wars] When a saber throw is utilized in combat, is the saber freely spinning through the air after leaving the hands or is it being controlled by the force?

If it is controlled by the force, isn't that a lot of effort on part of the thrower to be exterting? Might as well use that concentration to just make the opponent's heart stop or something.

[Assistant]
Most lightsabers have a dead man's switch that turns off the blade when the handle is dropped, so at the very least, the ignition button is being held down using the Force. Some models *do* have a switch to keep it going, but that's uncommon.

You're right' there are a lot of tactics that a Force user *could* employ in combat that they don't actually use. There are a few reasons for this:

First, Jedi see certain uses of the Force as anathama. Directly stopping another being's heart might go against their code, because they're directly using the "living Force" to create death. A Sith wouldn't have the same issues, howevr.

More importantly, Force users are able to actively prevent other Force users from attacking their bodies. Kylo Ren is able to use the Force to grab and hold people still, but that doesn't work against Rey, because she can use the Force to actively counter that attack.

Their ability to defend against direct attacks seems greater than their ability to defend against an attack using a weapon, like a thrown lightsaber, so that's what their combat looks like.


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

[User] ELI5: How come reddit posts only have about a thousand points, but ones on sites like 9gag have 50k?

[Assistant]
There is an algorithm that counts votes and displays numbers. The more upvotes a post has, the less an additional upvote is counted. The number of downvotes and upvotes shown are not direct counters on the clicks.

This was not the case very early on, so when you check out the top posts of all time some of the very early ones have larger numbers, even though there were far less users then.


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

[User]
CMV: Terms of service agreement should be simple, short, and easy to read

Pretty much very time you sign up for a new service or download a new app you have to agree to a new terms of service. No one reads them. They are usually extremely long, complicated and convoluted documents. Everyone just hits agree and moves on because they just want to use the app/service, and companies know this. They know no one will read a 5000 word terms of service agreement just to use the app, and because of this they can put sneaky things into the terms of service agreement which allows companies to violate our digital privacy use our data in ways that we wouldn't agree to if we knew exactly what they were doing.

To put terms of service agreements in context, the U.S. constitution is 4543 words. Terms of service agreements can range from 2550 on the low end to 15,000 words in length. And, these terms of service agreements are written in legalese. On top of that, many companies have separate privacy policies that are just as long if not longer than their terms of service agreements.

I think a law be passed that requires Terms of Service Agreements (TOS) to be short, simple and written in language that is easy to understand for regular people. It's not really an agreement if people are agreeing to things that they don't understand. How many terms are actually essential for a user to agree to before using the app? I'd argue, not much. There is no reason for a terms of service agreement or privacy policy to be over 1000 words and ideally it should be 500 or less, and it should always be written is language that is easy for everyone to understand.

CMV!

[Assistant]
You need the legalese because that's how you make sure you've covered everything. When you talk in broad strokes, you usually leave loopholes and technicalities open. When money is on the line, you need to make absolutely certain you're being as clear as possible, or else those loopholes appear and you have a nightmare in court.

Your own example of the US constitution actually works against you here: The US constitution has 4543 words, and for decades, you've been arguing about what it actually means, what the intentions of the forefathers were, and how it should be interpreted when it comes to making policy. The US constitution is a perfect example of a text that should have used more words to make itself clearer. If the 2nd Amendment was written in legalese and clear about what it meant for example, you would know exactly what the right to bear arms meant and would be having a much, much more effective conversation about how to reduce gun violence.

So, I'd offer an alternative: Terms of service should be as long as they need to be, but they should offer a layman-accessible summary at the beginning that gives them a reasonable overview of what they can and can't do. That way, people can read the general content of the terms of service, but still have access to the precise terms should they need them - for example, if they ever need to sue a company for breaching the terms of service.


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

[User]
[Star Wars] Why do some dark Jedi use masks that affect their vision so much?

I get that Jedi/Sith don't need their vision to perform optimally but it does help. Surely masks like those worn by Kylo Ren and Revan can only hinder their abilities?

[Assistant]
The trade-off is dehumanization. Revan and Ren may have lousy peripheral vision, but they benefit from the poor demoralized trooper with a blaster being unable to go "oh, that's just a man with a lightsaber." Darth Revan's mask basically just has one big eye-slit and a vertical red line where the mouth and nose should be, throwing off any ability to abstract a *face*. Same with Ren, only replace the red line with a perforated grill. Vader's mask is necessity because of his breathing apparatus, but his blank, bug-like eyes and triangle-frown mouth achieve a similar purpose: making a monstrous, unchanging face that denies an opponent the ability to empathize and understand what they're dealing with.

I think it's telling that of the two openly-Sith characters that don't wear a mask (not counting Sidious because he pretends to be a senator at first), one belongs to a species that looks like they're born metalheads. Maul's black-and-red skin and random bone-spikes from his head are intimidating enough without a mask to embellish them.


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

[User]
What would the light from a florescent globe be like if they didn't coat the inside of the glass with white paint?

Florescent globes come in colors such as 'warm white' with corresponding paint on the inside of the glass. What would the nature of the light be if there was no paint on the glass?

[Assistant]
Nothing visible.

Fluorescent lamps excite mercury vapor, that excitation releases ultraviolet light. The paint on the inside is phosporous which emits light in the visible spectrum when it's struck by the ultraviolet light.

If you took out the paint you wouldn't see anything and would be bombarded with radiation.

**edit
As others have pointed out below it seems there is a bit of visible light.
The name for a fluorescent lamp without phosphors is a gas discharge tube.


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

[User]
ELI5: Why do people say that supply-side, or trickle-down economics don't work?

It seems to be often stated as fact, but it kind of seems like something that can't actually be proven without hindsight?

EDIT: What do people specifically mean by "It doesn't work".

[Assistant]
Imagine you're a baker. You know that every day, 100 people will come in to buy your bread. You can meet that demand with your current equipment and staff. Then, one day, you receive a tax break. Would you use that money to hire another employee or increase your oven space?

If you're a responsible baker, you wouldn't. After all, you can meet the demand with your current staff and equipment. Supply-side economics doesn't work because in the real world, demand doesn't rise to meet supply. Supply follows demand.


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

[User] If liquid helium becomes too scarce and expensive, is there another substance that MRI machines can use for cooling?

[Assistant]
As long as we are drilling for natural gas, we will have a source of helium. As it is, with the USA selling off its stored reserves, the price is simply too low to bother with the expense of capturing it. When the economics change, then drilling operations will once again begin to capture it.

That being said, with current superconductor technology, the answer is essentially no. Most other common gases will freeze solid before cooling down enough to be useful.


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

[User]
CMV: It should not be normalized for people to state their pronouns when meeting each other for the first time

Firstly, I apologize if my views come off as bigoted or arrogant. I understand this may offend many people which is exactly the reason why I normally never talk about this kind of topic with anyone. I have been learning a lot about transgenderism lately, and while I definitely agree that we all deserve equality no matter gender or sexuality, I do not agree with all of the behaviours that the LGBT community is trying to push on straight and cisgender people.

I am all for respecting peoples pronouns, and if someone prefers pronouns other than he or she I will fully respect them. Of course, I do not completely understand the reasoning behind their preferences, but I will not use that to disregard their wishes. If you want to be referred to as they or Xe, I will do it. There is no point dehumanizing you over something as effortless to do as that.

I simply just dont understand why it should be normalized for all non LGBT people to introduce themselves with their pronouns. Approximately 5.3% of the Canadian population is considered LGBT (I am Canadian but when I looked up world percentage i couldnt find it), that leaves the other 95% percent of my countrys population as non LGBT. With that being the case, why is it necessary for me to introduce myself with my preferred pronouns to someone who has such a high chance to be cisgender and comfortable with their identity.

Again, if you want to introduce yourself with your preferred pronouns Im fine. I agree it should be known that some people do that, and it shouldnt have stigma surrounding it, but why is it so important to be normalized when 95% of the population is the same with their identity (cisgender and heterosexual)

Edit: Im sure a lot of you have noticed I havent replied to many of the comments. I would definitely be awarding deltas right now but there is a lot of info I have to read, plus this is my first post to this sub and I am not 100% sure how everything works yet, but consider my view partially changed.

Edit 2: A lot of people are making the assumption that I find it a burden to state my pronouns, which is a fair assumption based on the words I chose to use, but I want to emphasize that it was not entirely what I meant. What I really was trying to say was that I feel that stating your pronouns when introducing yourself doesnt have to be normalized because I find its ultimately irrelevant in my personal day to day life.

[Assistant] Is what you're saying here is that LGBT should feel free to state their pronoun on first meeting if they desire, but you also feel people should feel comfortable not stating their pronouns in which case whoever they're interacting with should have a right to use whatever pronoun they judge to be most accurate based on the appearance of the person they're talking to, with corrections if necessary?


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

[User]
ELI5 Why does water expand when frozen, when solid is supposed to be "denser" than it is in liquid form and gas form?

If we compress gas, we get liquid.
If we compress liquid, we get solid.

So, why does frozen water have a larger volume than when it was liquid?

[Assistant]
Water molecules are triangle shaped.

When they're liquid, they like to be close together and dense:

When they freeze, they like to line up in a triforce:

Certain points of the triangles like to be near each other.


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

[User]
Would it be possible one day to reach 100% renewable energy?

Would we be able to power our entire infrastructure with renewable sources such as solar and wind power, and perhaps also water if we could make it so it wouldn't damage the ecosystem? If so, what do we need that we don't have?

[Assistant]
Reliable, large scale electrical storage. The main problem with renewable energy resources is that, unlike traditional fossil fuels, we can't control them to match energy demand. At the current time, expected power surges to the grid can be controlled through increasing our levels of electricity production. With renewables, we would need large scale energy storage to take up that role in a 100% renewable electricity world. At the current time, we don't have anything suitable for this role, and until we do we'd need something controllable (whether it be fossil fuels or biomass) to stand in for it.

Further to this, Denmark is currently on the road to having a high level of dependence on renewables for its electricity. However to get round the problem, they have agreements and grid connections with both Germany and Sweden to export power to them in times of high renewable electricity production and import from them in times of low production. Obviously this tactic works in the current climate, but still shows they are dependent on traditional methods of electricity generation in times of low renewable resources.


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

[User] How do countries such as the US intend to pay off national debt if it keeps rising?

[Assistant] In practice debt is reduced not by paying it back but by growing faster than the debt grows. So if your GDP grows by 2% but the debt only by 1% the debt is smaller in comparison to your whole economy than before.


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

[User]
[Thor: Ragnarok] So what happens to Surtur after the ending?

He fulfills the prophecy of Ragnarok and destroys Asgard... does he just hang out in space for a while? Does he have other realms to destroy?

[Assistant] Ragnarok is often part of a cycle of destruction and rebirth for Asgard in different continuities.  If this ends up being the case for the MCU, Sutur will eventually return to his own realm and Asgard will be reborn in some way.  The seeds for this are certainly there.


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

[User]
What is the difference between "social science" and "hard science?"

Isn't all science the same or am I missing something?

[Assistant] Science is a method, but social science deals with dynamic units of observation. You can reliably repeat a chemistry or physics experiment, because the behaviours of the fundamental units do not change over time. Social scientists study people, and people change. We still use the scientific method, but it's more of a framework to deal with bias and the challenges of causal inference than in the hard sciences. Hence few "iron laws" of social science.


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

[User] [Star Wars] Both Anakin and Luke Skywalker were initially told that they were too old to begin Jedi Training. Why is Jedi training traditionally supposed to begin at such an early age?

[Assistant]
When they've grown up, they're more likely to have preconceived ideas of what is and isn't possible. Remember all of the times Luke said something couldn't be done before being proven wrong? Until Yoda pulled the X-Wing out of the swamp, that attitude would have crippled his Jedi training.

The Force won't work if you don't think it will, because you'll will it *not* to work subconsciously. When you start as a toddler, you won't have any ideas like "No one can move that fast" or "No one could lift that". Because the children don't know what is and isn't really possible, the Jedi can teach them their true limits, rather than what the outside world thinks their limits are.


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

[User] ELI5: Why is it when you freeze water theres a foggy hard bit in the centre compared to when you boil water first then freeze it and then the ice comes out clear all the way through?

[Assistant]
Regular tap water contains dissolved gasses so when it freezes some of it gets release as small bubbles. So it is the small bubbles that make the ice foggy.

When you heat up water there are bubbles releases before it boils and that is the same gasses. So if you heat water to boiling and then cool it down you have water with very little dissolved gasses and it freezes to a clear block of ice.


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

[User]
Foucault, 'the death of man'.

In the order of things, at the end of chapter 9, Foucault talks about man's disappearance. What exactly does he mean by this?

[Assistant] The idea of the 'the human' or 'Man' was, for Foucault, an invention of the enlightenment and modernity more broadly. The notion that man was an object or category that could be studied as a thing in itself. Foucault suggests that this is just a symptom of modernity and eventually wed get passed it and realize that it doesn't quite make sense to study Man because it isn't actually true that such a universal sort of category exists. He's sort of predicting the post-human turn in philosophy and social theory and popular culture as well, hence the figure of the cyborg as an example.


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

[User] Eli5: Is there a legitimate reason why printers cannot print in black and white when one of the other colors has run out or are they just trying to sell more ink?

[Assistant]
Not really.  The printer can certainly print a sharper black with the other colors, but it's not required.  As a couple others have mentioned changing the properties to grey scale should get it to print with only the black cartridge.

In almost all situations the best solution is to get a black and white laser printer.  They are durable, print faster, use far more economical cartridges, and don't dry out if they aren't used for awhile.  Really think about how often you honestly need color, for some it's important, but for most home office tasks a black and white laser is a much better investment.  If you really want color, there are color lasers, but you are back to the toner costing as much as the printer.


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

[User]
PhD Student Pitfalls and Blunders?

This type of question is my favorite question to ask because it teaches so much. In your personal experience and in your observations what mistakes/pitfalls or blunders do you see Phd students making? Could be rare mistakes or very common or somewhere in between!

I would prefer answers in STEM but other fields would have valuable input as well!

[Assistant]
- Treating your PhD like a class project
People will actually read your work and question everything you write.
- Lack of realistic goals and deadlines
No, you're not going to finish all your experiments in one week.
- Not talking to your advisor
This differs between labs, but they're supposed to be there to help and guide you. Try to get their input as often as possible.

And most importantly
- Seeking perfectionism
A finished thesis is never perfect and a perfect thesis is never finished. It might be ok to delve into interesting aspects of your project but know when to limit yourself. Going too far into the rabbit hole might not bring substantial benefits and delay your graduation significantly.


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

[User] ELI5: Where did "Righty Tighty, Lefty Loosey" come from, and how have we decided to orient almost everything to that rule?

[Assistant]
Basically everything tightens to the right because threads are cut clockwise.

It's easier to turn your wrist to the outside than to the inside - you're stronger turning your right hand clockwise, and your left hand counter-clockwise.  Most people are right handed, so the standard is the one that's easiest for right handed people.


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

[User] If you were in outside of the solar system with an apple. Would you have enough mass to have it revolve around you?

[Assistant]
If you were a point mass of say 80 kg, an apple could orbit you at a distance of 1 m in approximately 24 hours. Orbital velocity would be about 27 cm/hour. There are terrestrial slugs faster than this by orders of magnitude.

It would be impractical for two reasons:
The orbit would not be very stable because you are not a point mass. The apple will gravitate towards different parts of your body, uppsetting the orbit.

Establishing the orbit in the first palace will be difficult. At a radius of 1 m, the difference between a circular orbit and escape velocity is 30 micrometers per second.

Edit to say this: The gravitational gradient due to your body at the orbit of your apple is 67000 times stronger than the gradient in the suns gravitational field at the orbit of the Earth. What this means is that any disturbance from even your closest star would be neglible. You don't have to go through the trouble of leaving the solar system to try this experiment. You could just fail closer to home instead.


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

[User]
How do we differentiate redshifted light versus red light?

Hey, thanks for the explanations in advance!

So I believe I understand the mechanics of redshifting. The waves  stretch due to the acceleration/movement away from us. My question and lack of understanding is how we interpret and differentiate the redshifts.

Using completely arbitrary numbers for simplicities sake; assume we have a lightsource that emits light with a wavelength of 5 that we see with a wavelength of 10 due to redshifting. How do we differentiate that lightsource from another lightsource that emits light with a wavelength of 9 that redshifts less and we see it as a wavelength of 10.

Is there some other quality of the light that gives us hints as to its original wavelength, or are we just making educated assumptions based on other factors?

Thank you again.

[Assistant] Different elements have different emission spectrum. So for light from stars we can see, say the hydrogen lines, have been red (or blue) shifted because we know where they are on the spectrum when the source isn't moving relative to the observer.


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

[User]
Why are so many materials opaque? What's special about transparent materials like glass that sets them apart?

Also, why do other EM frequencies outside of visible light go through so many materials so much more easily?

[Assistant]
There are two requirements for transparency:

1. No absorption in the visible EM spectrum. Absorption in the visible spectrum is usually associated with electronic transitions in the material. Some of the most common materials we use like plants and metal happen to have absorption in this region but most organic compounds actually have none. They are opaque due to reason two.
2. None or very few interfaces. Most materials like paper or cloth are white because unlike glass they don't have one homogenous shape, but instead consist of countless little strands of material.  In this instance, the light gets scattered instead of passing through like through glass. Essentially it bounces around inside the material due to reflection and refraction. This gives it a white but intransparent appearance. Take a transparent crystal and crush it into powder and it stops being transparent. Naturally occurring materials have tons of little defects, rough surfaces, inclusions and so on that transparency would be extraordinarily rare.

Combining the two just doesn't happen a lot with natural materials, since being crushed into tiny bits or being a messy combination of several materials is kind of the default state of most matter in nature.

edit: Minor corrections: Saying that transparency is rare is actually kinda wrong. Water is transparent since its shape is defined by its container and always forms a homogeneous transparent body (unless heavily contaminated).

Regarding absorption: Metals (or conductors in general) are also a bit of a special case since they can also reflect light instead of absorbing it. No interactions with the visible EM spectrum would be more physically correct if a bit unspecific.


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

[User]
[3rd Rock From The Sun] How come the Big Giant Head doesn't have any way of knowing if we're actually there when Harry receives a transmission?

It's a pretty glaring oversight. Considering that our mission requires us to keep his existence secret, it seems like it would be a good idea to be able to make sure we're the only ones who hear his messages. We have the technology to travel faster than the speed of light and alter our own biology at will, I'm sure we could have come up with something.

[Assistant]
Because the Big Giant Head is the leader, not the technician. He leaves the technical stuff to the Big Giant Brain.

And, come to think of it, the Big Giant Brain isn't very good because it got it's position by kissing the Big Giant Ass.


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

[User] Do animals know if another animal is a herbivore or carnivore? If so, do carnivores see them as an easy target?

[Assistant]
As far as predator recognition goes it depends on the animal. A lot of aquatic animals use chemical cues to recognize predators, and some of that is learned and some innate. Mammals also seem to learn which other animals are predators. But most animals will also learn to generalize. So if (as a hypothetical) a squirrel has learned that a hawk is a predator, but a sparrow is not, he might also think that sea gull is a predator because of its size; and minnows will generalize trout, but then not extend that to pike. And robins that have never encountered a mammal will learn after one encounter that a stoat is a predator and will react accordingly the next time they encounter a stoat.

So prey species recognize the predators in their environment, but it's mostly learned.


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

[User] ELI5: When you get something small stuck in your eye, like an eyelash, and you can't get it out it feels like it "disappears." What happens to it?

[Assistant] Generally, it gets flushed out in either your sleep (That gunk in the corner of your eye in the morning.) or moves to an area where it won't irritate you and then flushed out when your eyes water next.


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

[User]
ELI5: Why are crocodiles much more widespread than alligators?

Is there anything specific that makes crocodiles more widespread?

[Assistant] Crocodiles have special adaptations that allow them to tolerate saltwater whereas alligators are strictly limited to freshwater areas. Since freshwater areas are generally isolated and separated by saltwater areas, this confines alligators but not crocodiles.


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

[User]
Quantum Electrodynamics is the most accurate scientific theory man has ever produced... what does this mean?

I was watching a documentary and it said QED is the most accurate theory man has produced.  If I recall correctly it said it is accurate down to 12 decimal places.

Gravity is also a theory, first modeled by Newton.  We now know Newton was wrong yet his predictions were extremely accurate.  Accurate enough to the point of getting us to the moon and back.

And what about Evolution?  That's a pretty air tight theory but how would scientist quantify its accuracy using maths?  I guess what I'm asking is how accurate is evolution in a mathematical sense?

Also... what has quantum electrodynamics ever done for us?  I hear talk about how accurate it is but I've never heard of its applications.  It seems, to me at least, only useful in the context of particle accelerators and what not.

What technologies owe their genesis to QED?  (stuff a layperson would of heard of)

(the point of this post: I'm looking for a reason to appreciate quantum electrodynamics, not necessarily understand it)

[Assistant] The computer sitting on your desk would not have been built without QED. Photovoltaic cells are another semiconductor example. Really ~~all~~*a lot of* modern chemistry is based on QED (especially D block chemistry).


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

[User] ELI5: Why do some orgasms feel amazing and others really weak?

[Assistant]
Length of time between orgasms, level of arousal, length of time to achieve orgasm, hydration and general focus are all factors in good or bad orgasms.

Abstaining from masturbation/sex for a few days can make for a great orgasm the next time you decide to do your thing.

For men specifically, hydration can really help with seminal fluid production, causing more contractions to ejaculate a larger amount of fluid and a more intense orgasm.


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

[User]
ELI5: Why is the AK-47 so goddamn popular worldwide?

Why does every bad guy have this weapon? I know nothing about guns, so I would like a layman's explanation.

Thanks.

[Assistant]
1. Ammo is super duper common, and cheap. It's been in constant use for nearly a century, and is used by many other guns.

2. It's prolific. It's been in production since 1947, by multiple manufacturers in multiple countries. There's more AK's out there than any other weapon. This also means they are cheap, and repair parts are easy to find.

3. It's easy. Anyone, even children, can easily operate and use with a few minutes of training. They are easily repaired as well.

4. They're basically indestructible. You can pull them out of sand, and they cycle with no issue. Drop it in mud? It'll shoot the mud out with the next shot. Bolt rust shut because you forgot it in the snow all winter? Kick it open, it'll work fine. No maintenance is a nice thing in the areas where they're used (jungles, deserts, untrained owners, etc). (FYI, guns like the M16 and M4 are basically ruined if you were to bury them in sand or mud and try to shoot.)

5. They're POWERFUL, almost twice the energy of 5.56mm rounds, the other common standard (used by M16/M4 guns, American standard issue). To give you an idea of the difference, it's 1,974 Joules vs. 3,275 joules.

TL;DR They're the most common, cheapest, most reliable, easiest to use, and most powerful weapon around.


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

[User]
[Star Trek] Why don't we see any R-bombs, relativistic weapons?

Seems like a biggish ship loaded with rocks could warp near a target and be sent off at full impulse to slam into a planet and create a new asteroid belt.

No life support or anything, just shields, thrust, and mass.

You also wouldn't have to hit an inhabited planet. Blow up Mars and Venus, say, and Earth'd pretty much have to roll over.

[Assistant]
I'd say its likely because M class planets are valuable.  Terraforming other planets is possible, but that takes time and effort, so capturing already inhabitable planets is far more desireable.  Otherwise, the the more aggressive 'Trek powers might be blowing up planets and stars left and right, since the tech is there for it (the Genesis torpedo, Soren's trilithium torpedo, Bashir-changeling's proto-matter bomb).

With weapons tech like that available, MAD probably plays a role as well, since the level of AI available allows for automated second strike capability. So if you start blowing up someone's planets, they are likely able to return in kind.


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

[User]
ELI5: Reoccurring sleep paralysis, what is it and why does it happen?

Ive read that most of the time hallucinations usually remain the same, but have been different each time, can this be explained? Also, can sleep paralysis be avoided or managed?

[Assistant]
Theres a lot of activity going on in your brain as you sleep so your brain releases this chemical that stops you from moving so you don't hurt yourself. It usually happens only in a certain stage of your sleep cycle that you wouldn't notice it, if it's happening too often then your brain chemistry could be a little off.

The first time it was scary for me too but then i started to play with it. Even on sleep paralysis you can control certain parts of your body like breathing. Try it next time to see which parts you can still control. Try breathing really fast then breath really slow.


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

[User]
ELI5: Red, Green and Blue make all the colors for TVs/monitors... Why not Red, Yellow and Blue?

We've all messed around with this function on a computer at some point, and I could never figure out why it was Green instead of Yellow. A simple color wheel would suggest this, right?

[Assistant]
Monitors emit light, so they use *additive* colour mixing. Paints absorb light, so they use *subtractive* colour mixing. The primary colours of each process are directly opposed.
You have red, green and blue in additive colour mixing because those are the peak wavelengths of the three kinds of cone cell in the typical human eye. You can mimic the mixture of cone cells activated by any visible wavelength by mixing different amounts of light at each of those peak wavelengths.
Then you have the subtractive primaries that each remove one of the additive primaries from white light. Cyan subtracts red, magenta subtracts green and yellow subtracts blue.


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

[User] [Game of Thrones] How much of a gamechanger was a dragon on the battlefield from the arrival of Aegon as well as when Daeneyrs finally arrived to Westeros with her 3 dragons?

[Assistant]
Really nothing in the modern or ancient arsenals could compete against a dragon. Hide all but impervious to harm. Able to crush several knights in plate armor with it's tail, claws, jaws, and it's own body weight. Can fly faster than any horse and most arrows. And flames so hot it can melt stone and steel like nothing and reach out quite far with it's breath.

Outside of an errant trebuchet or catapult shot only ballistas pose any real threat to dragons and they're not known for their vertical aim. A dragon can outrun any serious trouble. Outflank any defensive line. And simply overpower nearly all enemies on the battlefield. One dragon can win a battle with ease. Multiple dragons can win a war.

And given the unique capabilities of dragons anyone facing them will have to pivot all their efforts to wounding or forcing the dragon to retreat or risk being burnt to ashes long before any enemy soldiers can pose a serious risk. You either invest time and effort into countering dragons and get overrun by foot soldiers or focus on the foot soldiers and get taken out by the dragon. No one really could stop or win a fight against the dragons and the only reasonable options were to surrender or try to kill the dragonriders and hope it removed the beasts from the field which is still a longshot at best.


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

[User] ELI5: If our solar system is constantly moving throughout space, then how do these same asteroids/comets come back around and pass us?

[Assistant] The ones that return are part of the solar system too. That means they move with the sun, like the planets, but further out. Things are caught in the sun's gravity at distances far, far beyond Pluto. Even up to more than a light year away.


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

[User] ELI5: How can you calculate a day for a planet if it is tidally locked?

[Assistant]
If a planet is tidally locked, then it always faces the sun with the same face. So if you define a day as the amount of time it takes the planet to make one rotation about its axis, it would be equal to its year.

 If you define a day as the time between one sunup and the next, it doesn't have them.


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

[User] ELI5: What would happen if we used a global currency that was worth the same everywhere.

[Assistant]
We will get into big problems, as seen in the Euro crisis:

Countries with a low productivity can't create enough income to pay all their imports - they will get broke rather fast and also have their population impoverished (this happened in Greece). Those low productivity countries usually devaluated their currencies to fight this. Imports will become prohibitively expensive, while exports become much cheaper (as you pay nominally the same too workers, which is "worth" far less internationally). If one has a rather strict inflation control it also avoids the poverty problem - You can't buy the expensive imported goods, but the local produce is still affordable, which also strengthens the local economy.

The high productivity countries however will largely benefit, as everybody who buys from them has enough "hard cash" - at least in the beginning. Effectively concentrating capital there, however there is no mechanism to slow that effect down (i.e. a higher valuation of their currency, making products more expensive). So there is no real incentive to increase productivity or innovate any more...

In the worst case you will get something like the world of the "Hunger Games". Some rich decadent centers with a lot of impoverished countries around that.

However keep in mind that this just one theory (which is partly proven by the current state of the EU) and it will only apply with the mostly free globalized trade we have now. There may be a lot of measures to counteract this outcome (customs, subsidizing "low productivity" countries, immigration policies etc.) and nobody ever tried it. (The past experience with the global gold standard is IMHO not applicable, as economies where more separated, due to a lack of technologies back in the day)


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

[User]
ELI5: Why is Facebook buying Oculus such a bad thing?

So many people are upset but I'm not sure why. What will/can Facebook do to Oculus that will make their products turn bad?

[Assistant] Because typically, when a large, unrelated company buys a smaller company, the original vision of the smaller company gets twisted and abused into something not quite as good. Not always though - it's still entirely possible that Occulus will still be everything we hope it can be.


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

[User]
Would it be possible to survive inside a blue whale for a short period of time?

Slightly ridiculous question, I know, but it just got me thinking. Lets say you somehow find yourself inside the mouth of a blue whale. Could you survive for minutes? Hours? Is there somewhere where water doesn't breach, and is there any oxygen there?

[Assistant] The inside of their mouths are filled with water and whale spit. There is no air in there, so you would survive as long as you could hold your breath, then pass out and inhale whale mouth juice and drown. So minutes is the answer.


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

[User]
ELI5: Why is "implied multiplication" a thing ?

Why the equation "3a = 6" means "3 * a = 6"  and not, for example, "3 + a = 6".

[Assistant]
In short, 3a implies the multiplication of 3*a because if you say it out loud as it is written, it best complies with the concept of multiplication.

Instead of using the variable, let's change it to 3(2). If you say that expression out loud, what does it sound like?

"I have three twos."

If you have three twos, do you multiply or add them? You multiply them of course to get you six. If you say that you have three pairs of socks, that means you have six socks in total. If you say that you have 3 pairs of socks, it does not mean that you have five socks (3+2). It's the same principle with using a variable.

"I have three x's, and that total equals 6."

But saying the expression as so, it implies that 3 * a is equal to 6.

I suppose it would make more sense if the variables were written in the plural, such as 3a's = 6. Then it might be more obvious that you are multiplying 3 with a. However, the "'s" would clutter things up, so it is omitted.


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

[User]
[general time travel] The Earth travels through the Solar System which travels through the Milky Way so how is this dealt with? How do time travelers not end up floating in space?

I understand a device that can navigate spacetime can go anywhere any time but how does one establish exactly where to travel?

[Assistant]
This is why Hiro Nakamura had the abilities of time travel *and* teleportation; for time travel to not leave you stranded somewhere in the universe, you need to be able to do both.

You could handwave this, however. For example, gravity manipulates spacetime, so you could say that when you travel through time, you're automatically dragged by the largest nearby gravity shadow. This would mean, for example, the Delorean from *Back to the Future*, doesn't need to manipulate its location, because earth's gravity does so automatically.


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

[User]
ELI5 How quickly can germs move from your hands up your arms? Are they like little racecars or snails?

When you do something manky and don't wash your hand that exact minute,  how quickly can germs travel up your arms?  Do you need to wash up to your elbows after a certain amount of time?

[Assistant]
Theyre more like glitter than insects.

You can try all you want to keep them just on one part of your body, but they inevitably spread.  However, this doesnt take into consideration that your body already is covered in bacteria glitter, and its just a matter of which ones survive and regrow.


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

[User]
ELI5: How do photons have momentum without having any mass?

The only answer I keep finding is "Well the physics for objects with and without mass are different, thats why." Ok... then if their physics are different why do we use the term momentum between both sets of physics? I feel like I am missing something that is fairly simple.

[Assistant]
Master in physics here

That formula for momentum is an oversimplification for massive particles, as most of the time dealing with momentum you are not dealing with Massless particles.

We use the extended E=mc (as this doesn't cover photons either)

>Energy = Restmass * speed of light + momentum * speed of light
>
>E = mc+pc

(photon, mass = 0)

>E=pc

We need the energy of a photon

>Energy of a photon = plancks constant * Speed of light/ Wavelength
>
>E = hc/

Therefore

>pc = hc/
>
>p=h/
>
>Momentum = Planck's Constant / wavelength

if you insist on using the classical formula, we can give the photon an "effective mass" (speed of a photon v = c)

>p = m*v = h/
>
>m*c = h/
>
>m = h/c

Which is the effective mass of the photon, or the Photon's inertia.


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

[User]
[Harry Potter]  a couple of wizards are being chased by a few Death Eaters. The wizards are rescued by a SAS squad who know everything about the wizarding world. What ensues.

this happens in a forest. How can the SAS stop the death eaters from apparating out?

[Assistant]
Depends on environment, but in a sufficiently open area, like a forest, I'd say flashbangs and multiple cases of lead poisoning are what ensues.

In close quarters however, a 30cm-long wooden wand and non-verbal casting are far more compact and efficient than any firearm and considering there's no Death Eater that cannot Apparate... one case or another, the only reliable way to destroy a wizard with a Muggle weapon is if they are in some way unaware of the threat  remember that most Muggle combat is blind. Actively reacting to a supersonic bullet (as opposed to proactive shielding) is out of realm of possibility for any human, magic or not.


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

[User]
Are black holes literal "holes" or "rips" in space, or are they actual objects?

I've read about black holes that can "move" across space, orbit each other, and revolve.  I guess I always grew up thinking black holes were literally that: holes in space; that after enough mass has accumulated, that whole "collapsing in on itself" thing makes a hole, not an object.  Am I mistaken?  How could a "rip" or "hole" move around like an object without leaving a "tear?"

[Assistant]
We don't know what a black hole is made of, or if the question even makes sense; classical gravity theory tells us that it's a singular point, not a "rip" in space but a point where the curvature blows up, and there's no problem with that sort of thing moving around, because curvature can change. Compounded in this is that there's no such thing as absolute position, so there's no absolute notion of where a black hole *would* leave a "tear" even if it were possible.

But as it is we can't trust classical gravity theory at very close distances to the center of the black hole because at those short distances quantum effects become important, and we don't know how to make gravitational physics and quantum physics work nicely together. Until we have a theory which unifies the two, the nature of the black hole center - whether it's truly a singularity, or perhaps something more exotic - remains speculative.


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

[User] ELI5: Why won't gas prices go back to pre-9/11 prices if we are producing as much if not more oil?

[Assistant]
Market price has nothing to do with WHO makes it.

When the US comes up with an oilfield on federal land, the government makes out like gangbusters.  It's tax income.

The oil will ALWAYS be sold at market value, no matter where it comes from.  Even if you were so deluded as to say "we're gonna sell gas to Americans for $1/gal!" some American will buy up all the $1 gasoline and resell at $3/gal and laugh all the way to the Billionaire's Club.


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

[User] Why do we have to file our taxes if the state already knows how much we owe each other?

[Assistant]
Assuming you're in the US, they don't know, is the reason, because tax codes in the US aren't simple like they are in some other countries.

Consider the most important reason: deductions. These are various rules that say if you spent some amount on some prescribed good or service, or if you meet certain criteria, that you can reduce your tax bill by some amount.

In many cases, there is no way for the government to automatically know that you meet the requirements for a deduction (e.g., they don't track all your spending throughout the year, so how can they know what deductable expenses you incurred?). Instead, the system requires you to make a *claim* that you're entitled to certain deductions, and to be ready to provide proof of your claim if requested. This is why you have to do your own taxes: only you have the information required to determine your deductions.

The reason many other countries can get away with automatic tax-filing is that they don't have a deduction system like this. The tax code is much more streamlined, so that ultimately all that determines your tax bill is your income (which is reported to the government by your employer), and some basic family characteristics. Easy.


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

[User]
Why do so many philosophy texts seem to have an aversion to providing specific examples in addition to abstract definitions and statements and how does one deal with it?

As a learner, it drives me crazy and it makes it unnecessarily difficult to progress. Last week, I read a text on the philosophy of science that says falsification has become outdated as a demarcation criterion for what is or isn't science because it wrongfully excludes good science and includes bad science. Then the text simply moves on with explanations as if there was nothing more to say and doesn't name a single example of either. Why would you EVER make a statement like this and not add examples?

Not only would examples make it easier to understand what's going on, they'd also back up the claim being made and basically be arguments at the same time. I'm not even convinced that this is true, but if I'd been given two examples of each case, I'd buy it and probably remember it. As it is, I'm left with a claim I don't understand and doubt about its truth. What's the reasoning behind this and how does one deal with it?

[Assistant]
>What's the reasoning behind this

Dan Dennett briefly talks about using examples in '*Intuition Pumps*':

>"Some philosophers think that using examples in their work is, if not quite cheating, at least uncalled forrather the way novelists shun illustrations in their novels. The novelists take pride in doing it all with words, and the philosophers take pride in doing it all with carefully crafted abstract generalizations presented in rigorous order, as close to mathematical proofs as they can muster. Good for them, but they cant expect me to recommend their work to any but a few remarkable students. Its just more difficult than it has to be."


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

[User] To reach speed of light you need crazy amount of energy so Does light actually travels with the speed of light or slightly less?

[Assistant]
This is the speed light travels at.

For an object with non-zero mass, it would take infinite energy to get it to the speed of light, which is one way to understand why that can't happen.

But for photons (the particles of which light is made), things are different.  Photons have no mass, which turns out to mean they always have to travel at the speed of light. From the moment they are created to the moment they are observed, they travel at the speed of light.


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

[User]
[LotR] Why are Hobbits so great at resisting the One Ring?

Gandalf seemed to think that all it would take would be for him to take the Ring, and he would go crazy (Word of God is that he would have become a totalitarian dictator forcing everyone to be Good.) Elves and men, likewise, can't be trusted to bear the Ring. But what's so special about Hobbits?

I always thought it was that Hobbits aren't ambitious. But a friend pointed out to me that *neither is Gandalf* - he's a being of vast power, yet he essentially lives like a homeless person. His only "ambition" is to help save Middle Earth.

And ... Frodo, after all, seems to care about saving Middle Earth just as much; he endures incredible danger and hardship to trek the Ring across half the world in order to destroy it. Yet he was supposedly the perfect Ring-bearer. Why?

It *could* be power, I guess - Gandalf is vastly more powerful than an unassuming Hobbit, he just tends not to mention it - but there are a couple of flaws in that, too. Why would the Ring's corruption be tied to how "powerful" the holder is? And why couldn't a human be just as effective, when they have no more "special powers" than a Hobbit does? Heck, they have *less*, if you count the whole hobbits-are-great-at-hiding thing.

Why a Hobbit, then?

[Assistant]
Because in the end, men want to live forever, elves want everything to be as they used to be, dwarf want gold but the hobbits...

...they really just want a nice pint, a nice meal (or two) and to say "hello" to their neighbour.

The ring tempted Samwise to be the worlds most powerful Gardenr of all things. A Gardener! Of course Samwise just thought to himself, "Well, that's silly..." and went on.


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

[User]
[Lord of the Rings] What would have happened if Isengard was never trashed by the ents.

Say Saruman gives more simple instructions that Merry and Pippin are to be taken alive, or the orcs just disobey and chop their legs off and eat them. The orcs are slaughtered by the Rohirrim and Merry and Pippin are killed in the confusion, Treebeard is never alerted to the destruction of the forests by Saruman, and the ents never launch an assault on the fortress.

What might have changed in the war of the ring, especially in the Return of the King era?

[Assistant]
For one thing, there would have been a lot more orcs at the siege of Minas Tirith. Saruman may have been able to forsee events and guide Sauron's armies to seriously weaken the armies of men, if not destroy them outright. Rohan may not have come to aid Gondor and things get pretty bleak. The ents would eventually find the destruction of their forest and would ultimately act as they did, if not a great deal of time later. It would almost certainly be too late to change much, even if they destroy isengard.

What happens before that is a good question. Sam and Frodo would probably still have cast the one ring into mount Doom, ending Sauron's reign before it began. Perhaps Minas Tirith and Rohan had fallen by that point, in which case, orcs and the surviving men would live in Saruman's empire not unlike what he accomplished in the Shire, but spanning across all of middle earth. The elves still nope the fuck out to the undying lands and the fourth age is a much darker one than it would otherwise have been.

If the siege of Minas Tirith still goes well for the humans, you probably have the forces of Gondor slaughtered at the black gate either by the forces of Mordor alone, or in a battle on two fronts; Mordor to the east and the uruks from the West. If the ring is captured, there is no real contest between Sauron and Saruman over it, as Saruman was never in a position to take it, and neither would share power. Perhaps before returning to Eru, Saruman would realize his folly, but it would be too late unless the Valar or Eru intervene directly.

Either way, it's not great. At best the shattered nations of men are ruled by the iron fist of the uruk and their master Saruman. At worst, Sauron wins and everything is a fucked to death pile of shit into which the greatest of the Maiar sews his own discordant notes of creation as had Melkor before him. Eru isn't happy, and maybe decides to start over without demigods to fuck things up.


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

[User] ELI5: What is actually happening when you scratch your eyes too hard and you get a sort of lightshow behind your eyelids? What causes it?

[Assistant]
Pressure on your eyes puts pressure on your optic nerve.  Putting pressure on nerves makes them send signals that aren't really there. The occipital lobe of the brain (the part of the brain that controls vision) gets this signal and says the equivalent of (In an Italian accent) "Woah, woah, eh, c'mon!" to the rest of the supratentorium and this is perceived as light.

note: the brain doesn't actually talk in an italian accent.


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

[User]
ELI5: How is it rude to wear hats in buildings?

I never understood why or how this is rude.

[Assistant] It's merely a social condition. We've been taught to do that simply because our parents told us to, and their parents told them to, and so on. No one can really say when or why it became that way. Social conditions never have any practical reason for existing. If you think wearing a hat indoors is ok, then by all means, invite your friends over for an indoor hat party.


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

[User]
When I brush my teeth, what's more importantthe brushing or the toothpaste?

Which would leave my teeth better off: brushing my teeth with no toothpaste for a year or putting toothpaste on my teeth for a year without brushing?

[Assistant]
Brushing the important part, the mechanical action of the bristles break up the biofilm created by bacteria, loosening up the bacteria so they can be rinsed out and of course clears out food residue that may be stuck in crevices.

If you go without brushing, but just gargle with toothpaste and regular mouth wash you will get substantial buildups of bacteria which cause decoloration, plaque buildup, gingivitis and cavities. Your gums will be very vulnerable as you have no way to clean the crevace between your teeth and gums.

Brushing with just water is very effective, although flouridation has been shown to help as it can kill residual bacteria left after brushing and rinsing.

Many animals and humans in undeveloped societies use fibrous material to help clean teeth, such as fibrous wood, dried fruits or dried animal skins.


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

[User] ELI5: Why is water wet?

[Assistant] Well, it's a liquid, for one. It's also fairly non-viscous, which means it's thin enough to spread under its own weight, helping it to get everywhere. It's adhesive enough that it sticks to things slightly, and not cohesive enough to pull other water with it when it gets shaken off. It's readily absorbed into fabrics and stuff, too.


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

[User] ELI5: The Significant Factors that have led to the $1.7 Billion Price Tag for Healthcare.gov.

[Assistant]
This is a really big question that gets very complicated and political.

Basically, it had to take any number of complicated corporate systems with all fine print, discern what was needed and important, then translate that into a unified marketplace.  It also had to do it perfectly, because any misinformation meant the federal government helped a corporation kill grandma because she didn't know her heart pills weren't covered.

Insurance companies are betting you $/yr that you'll spend less than that on healthcare this year.  They profit by winning enough bets over a given populace. To help their odds, they will pre-negotiate lower medical costs with larger medical groups and put in exceptions like "We don't cover elective surgeries", then get shitty with the definition of "elective" in the fine print.  Shit like "That cancer surgery is "elective" because you haven't tried drug therapy yet".

Healthcare.gov needed to read ALL of that fine print, for every level of every policy, filter out the ones that don't 100% meet the 15,000 pages of ACA standards and then post the differences using less than a tweet's worth of characters.  All of this needs to be back checked with teams of lawyers to make sure it's presented in a way that a reasonable person can make an educated choice.

Then there's the technical side.  The website had to plug into at every participating insurance provider's unique and universally terrible corporate sales databases, transmitting application and payment information perfectly, and again making sure there's no fine-print switcheroos for every policy.  Think of the worst corporate management software you've ever seen.  Then consider a the slickest and most user friendly.  You get to write software that works with ALL OF THEM.  Each interface is it's own special shit-snowflake that you get to automate.  For every policy. For every company.

Oh, and every state has their own branch of the company, and set of state standards, so your fix for Aetna New Jersey isn't going to work for Aetna Missouri, because that has to flow through Mo.Gov's shit website too AND Aetna MO's database didn't get the update yet so they're still using the system from 2003 which is totally different anyway.  So now your shit-snowflake work just went up by a factor of 50.  Also, not everyone speaks english so everything for all policies, fine print, marketplace summaries, and user interfaces has to be accurately translated into a couple dozen languages.  Don't fuck that up or you're killing grandma again.

While the backend guys are designing a shit-snowflake shoveler, another team has to program a web interface that grandma can use.  See, for the first time EVERYONE was REQUIRED to have health insurance.  That includes your grandmother who browses family photos by dragging them into word documents because it's the only way she knows how.  It also includes the homeless guy who literally cannot read and was genuinely unaware that computers could be used for anything other than porn.  Your interface needs to be so simple that they can figure it out on their own.

Oh, and since it's collecting SSN's, addresses, and health histories, it all needs to be super secure and require a secure username/password when logging in.  If you're in the identity stealing business, it's goddamn christmas morning in there.  So the site needs to be easy enough to access that illiterate grandma can get in, but also hard enough that 1337HackerBoi69 can't.

Then it also needs to be ruggedized against political enemies that want the site to fail.  Obama's been telling everyone Sept. 29th is opening day, so how bad would it suck if the site was hit by a DDOS for the first week? Oh, and any fuckup from the aforementioned issues before will
definitely be blown way out of proportion, so build some lawsuit budgets into any work you do building the site.

And all of this needs to be done ideally within a year or two, because we've got a political schedule to keep.  Oh, also, Aetna MO finally got their system updated to the 2009 version so the plugins you hacked together for them stopped working and need to be rebuilt.


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

[User]
Why did Eurasian diseases not transfer to all of North America when the Vikings made contact, instead devastating the Americas post-Columbus?

Or maybe they did but the groups they killed were themselves isolate? But that seems so unlikely to me.

I realize the answer is probably something like "there wasn't *much* contact" or even "that contact is unproven" so my larger question is: how much contact do you have to have before disease ravages a vulnerable population? How much does chance play a role, and how precise is our knowledge of this kind of thing?

[Assistant]
So, the vikings got to North America in an expedition from Greenland, which was itself an expedition from Iceland, which was itself colonized from Scandanavia.   Epidemic diseases don't persist well in small populations, and Greenland was a small, isolated population colonized from a fairly small, fairly isolated population.  So probably no epidemic diseases managed to hop from island to island to island the few times the connection was made.

It's not a straightforward X percent of contact.  You could have one guy wash ashore freshly dead of smallpox and that could do the trick, or you could have a fair amount of contact provided no one carrying the disease happened to get by (long travel times and intermediate steps in the chain make transmission less likely).  But the nature of the Norse contact just didn't allow anything too nasty to take the jump.


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

[User] ELI5: For concert, sports and any other events, the tickets get sold out almost immediately, then gigantic swaths of these tickets show up on broker websites for scalpers. How are brokers able to buy so many tickets using the same websites that I find not even functional to buy one.

[Assistant]
The reason that websites like Ticketmaster are not functional is because scalpers use ticket-bots which hammer the website the second the tickets become available. This basically causes a distributed denial of service (DDOS) attack for everyone else while the bots purchase all the tickets to resell at usurious prices. CA recently banned these bots, but the industry (who primarily use tax-payer funded venues) hasn't really done a lot to fight this practice. Paperless tickets would resolve a lot of this.

However a little known fact is that promoters hoard most ,if not all, of the prime seats for artists, radio stations and credit-card companies and those tickets never even become available for direct sale to plebians, but they often show up for resale.


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

[User]
Undergrad asked to have lunch with some candidates for a non-tenure track position. How should I prepare?

Hi all, Im an undergrad (chemistry) whos been asked by my department along with a couple other students to have lunch with a few candidates for a non-tenure track position. Well be meeting with them one candidate at a time spread out over the next couple weeks, and attending sample lectures of theirs at some time to be determined later.

How can I prepare for these lunches to be as helpful to the department and the candidates as possible? Weve been sent the candidates CVs which Ive been going over. Should I take some time to read a publication or two? Do you know what else might be expected on our part for these meetings? What sorts of questions should I ask besides the obvious about their work?

Thanks in advance for any insight you might have.

[Assistant] Your main role in these meetings is as a representative of the undergraduate population. Most of the interaction that undergrads have with their professors is through course-based teaching, so ask them about their teaching experiences, teaching philosophy and how they feel they'd fit into your department as a teacher. Ask them about their supervisory experience and whether they're interested in taking on undergrads for research positions. And ask them about their research, but evaluate the answers from the lens of the undergrad population -- their communication skills are a reflection of their teaching ability.


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

[User]
[Star Wars]What's wrong with my face?!

I'm playing knights of the old republic 2 and after getting fairly into the dark side I look awful! My skin has started to grey, my eyes have turned a sickly yellow color, and now my entire head has turned all veiny; everyone even feels the need to make hurtful comments about my appearance including on bartender who said his race makes great ointment for 'people like me'. Why do I now look like a moldy raisin?

[Assistant]
The Dark Side corrupts everything it touches.  That includes your face.
The Force has an essential connection with all living things, so when you bend and pervert it to your own dark purposes, that perversion seeps into your cells and scars your flesh.


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

[User] ELI5: Why does a little moisture on your feet make them STICKY while a lot of moisture makes them slippery?

[Assistant] When you only have a very thin layer of water, your finger ridges break through the layer of the water and directly touch the thing on the other side of it. When you have a thick layer of water, You are just moving it around.


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

[User]
Why do rechargeable batteries lose the ability to hold a charge over time?

When I bought my laptop, it had about 3 hours of battery life. Now it has about an hour. People say not to leave things charging, and to let them go completely dead before doing so. What is happening, chemically, when a rechargeable battery loses its potential for charge?

[Assistant]
The primary reason batteries lose their charge, is gradual cell oxidation.  In lithium ion batteries (like those in most laptops), the charge is stored in the anode, and as you use the battery, lithium ions move through an electrolyte to the cathode.  When you charge your battery, this process is reversed.  Over time, the process is rather harsh on the anode and cathode, which become coarse, covered in patches of oxidation.

More in depth investigation in the last few years has also revealed that the anodes and cathodes which (in some Li-ion batteries) are covered in nano-filaments to increase efficiency, can see those nano-filaments get coarse and knobby, decreasing surface area exposed to the electrolyte, and increasing their resistance to lithium ions trying to transfer a charge.


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

[User]
Was Aristotle aware of Confucius?

Hi guys, new user here.  I did a google search and could not find anything on the subject.  I have read almost everything Aristotle has written and am a huge fan of virtue ethics.

I am planning to study abroad in China this fall and decided to get better acquainted with Eastern thought.

In reading Confucius' "Central Harmony" it seems that many of his ideas on man in society parallel Aristotle's own thoughts on the matter.  Do smart men who spend their lives thinking actually reach the same conclusions? Or was Aristotle aware of Confucius' writings and didn't credit his sources?

Thanks in advance.

[Assistant]
There is no way that Aristotle could have known about Confucius, because there was no transmission of Chinese texts to the Mediterranean or vice versa at that time. This is for any text. Additionally, we know of no texts of the *Analects* that are older than about 140BCE--like most traditions of this time, Confucianism took some centuries to be consolidated into a canon of texts, meaning that by the time the *Analects* are compiled and are being passed around, Aristotle is long dead and buried.

There are important and interesting simularities between the ethics of Aristotle and Confucius, but every indication we have is that this is independently arrived at. This wouldn't be surprising, given the subject-matter: the native dispositions of human beings to flourish best in well-ordered social settings. If it really is a native disposition, then you'd find it everywhere there are stable human populations.


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

[User] ELI5: How did we decipher ancient texts in extinct languages, like the complaint tabel to Ea-nasir?

[Assistant] For example, we have learned how to read Ancient Egyptian thanks to the discovery of the Rosetta Stone - an ancient monument inscribed with the same text in three scripts: Egyptian in two different scripts and Ancient Greek. Since we already knew Ancient Greek (weve never stopped knowing it since ancient times) we were able to decipher the Egyptian version and use that knowledge to decipher all the other Ancient Egyptian inscriptions. For other extinct languages we usually need something like that too - al least some kind of clue linking the text to something already known. If there arent any clues, then we cant decipher the language, and there are numerous such indecipherable ancient languages in the world.


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

[User] ELI5: Why do powdered drink mixes like Kool-aid go from pale to brightly colored when the water is added?

[Assistant] Most of the powder is sugar, and maybe a pinch of salt. The sugar is white making the powder quite pale. However when you add water the sugar is dissolved turning invisible. But the pigmentation that creates the color does not become invisible. So you only see the deep color of the pigments rather then the light color of the sugar.


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

[User]
ELI5: Why are there pigeons everywhere?

Everywhere I go in the world that I've been to has had the same looking pigeons, why?

[Assistant]
Pigeons are descended from rock doves.  They spread due to purposeful introduction and accidental. They are not native outside of Europe and Asia.   Pigeons are well adapted to cities as their natural habitat is rock faces on the oceans which building replicate.  Along with a lack of predators and abundant resources they have expanded populations along with humans.

Pigeons increase the size of their clutch based on how well fed they are.

Since there's a ton of resources in cities for them they breed near the maximize, then reach an equilibrium as food runs scare.  Killing them doesn't eliminate the problem as the remaining pigeons will simply have more resources and breed faster.

Removing the food sources is necessary to starve and shrink the population.


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

[User]
ELI5: Why are most animals seemingly unaffected by / unafraid of the presence of most other animals but immediately flee at the sight of a human

An example of what I mean would be why birds and squirrels or a deer and a hawk or a dolphin and a sea turtle coexist within close range unphased by each others company, but flee when they see a human.

[Assistant]
Eyeballs. Predetors usually have their eyeballs on the front of their heads (think human, wolf, lion) where prey have their eyeballs on the side of their heads (think deer, rabbit, mouse).

It's like a big red flag for animals.


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

[User] ELI5: Why aren't there "Coffee Bags" in the same way that there are Tea Bags? Why is making coffee more complicated?

[Assistant]
There are, but there's a few reasons why they haven't caught on as well as teabags.

* Most avid coffee fans prefer coffee that's made with some form of pressurized heated water. An espresso tastes quite different from  a standard drip coffee machine's output because the water aids in forcing the volatile oils out of the bean, something that doesn't happen if you just steep it.

* Regular coffee drinkers typically want their fix in a convenient fashion. Coffee that has to steep in a bag slows down the process. Tea's typically a drink for a more relaxed mood so waiting for it to steep is more acceptable.

* Coffee requires more input ingredient than tea to make the same relative amount of strength. Compare how much coffee you use versus how much tea you use to make a beverage in something like a French Press. So stuffing all of that coffee into a "soaker" bag is a little bulkier.

* Coffee has an "instant" form for people that are in a real hurry. Just a spoonful from a large package can make a cup without any steeping or waiting at all, just a source of hot water.

**TL;DR**: They do sell them and they're great for some applications, but other forms of making and serving coffee are more convenient.


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

[User]
Philosophers who wrote about the concept of space

Hello, my next year's philosophical field of study will be "Space". It involves space in every meaning of the word. I'd like to learn a few things in advance.

I've thought about the relations between human and space, how space is used to dominate men, the space of the body, the space of a stadium, a prison, spatial causality...

Can you recommend me a resource that revolves around space? Whether it is a specific article, a book, or a philosopher that has significant work about space.

[Assistant] The Leibniz-Clarke correspondence is a classic debate about absolute vs relational conceptions of space.  Kant's transcendental aesthetic argues that space (along with time) is the "form of intuition."  There is also an early essay by Kant called something like "On the Nature of Directions in Space" which has the famous incongruous counterparts thought-experiment.