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

[User]
[Star Wars] What if after Obi-Wan beat Anakin on Mustafar, he took the limbless Anakin with him on the ship?

Let's say he throws him in a bacta tank to cool off. Is Anakin going to try to kill him when he wakes up? What if Padme doesn't die during child birth? Would he chill out?

[Assistant]
He would die. Kenobi, Yoda, and Senator Organa did *not* have access to the resources necessary to keep Skywalker alive. The Jedi don't really have any ability to heal the wounds of others; that is, ironically, a Sith power. They would need access to advanced medical technology just to keep Anakin from flatlining. What they had instead was a single droid who gave up on a patient because she was *sadding to death*.

And then...well, they didn't even have the kind of cybernetics that Vader got in the films. They have nothing to do with the body, even if they can keep it alive. They would just be keeping him in some kind of stasis until his injuries killed him.

Or until Palpatine tracked them down, since he was obviously able to detect Vader through the Force.


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

[User] [Star Wars] Why cant sith force choke Jedi in battle?

[Assistant] They can, but there are tactical considerations. The biggest being that the person you are trying to use telekinetic powers on has telekinetic powers of their own. While you're trying to play a rousing round of "harder, daddy", they could be whacking you in the neck with flying debris, or force tossing a saber at you.


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

[User] ELI5: If bacteria produce ethanol through fermentation, and ethanol can kill bacteria, why are they not killing themselves with their own ethanol?

[Assistant]
Bacteria does not produce alcohol. Fungi called yeast produces alcohol.

However, your point remains true, alcohol still kills yeast. It's all about concentration. Beers and wine can be produced by yeast, up until about 15%. Past there, it kills the yeast. To make a harder alcohol, you have to distill (basically purify by boiling) the alcohol yeast produces.

Why does yeast produce a substance that kills it? Well, because it's a waste product. It's exactly equivalent to asking why a large concentration of CO2 or urine will kill you. Because it's waste you are try it dispell, and if unsuccessful, it will kill you.


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

[User] ELI5: Do sea mammals need to drink water? If so how to they avoid dehydration from the sodium?

[Assistant] They generally don't drink seawater.  They metabolize water from the food that they eat.  Seals and sea lions occasionally drink seawater and their urine is many times saltier than that of most mammals, their bodies are able to filter out the salt.  The actual salt content of their blood is not particularly different from humans or other land mammals.


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

[User] [Dr. Who] The Doctor once said: "Good men don't need rules. Today's not the day to find out why I have so many." What did he mean by that?

[Assistant]
A truly "good man" will always do what's right naturally, instinctively, and without much thought. Such a man doesn't need to be reminded what's right and wrong... Even if emotionally driven.

It's a quip to suggest that he's not such a good man and might just do what's not-so- "right" if provoked... It serves as a warning.


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

[User]
Do lights produce thrust?

I'm at my desk pretending my flashlight is a rocket. Does it actually produce any (super tiny) thrust if I left it going from the photons it emits?

Bonus question: if the answer is yes, how big of a flashlight would I need to leave earth?

[Assistant]
Yeah, the basic principle of rocketry is that momentum is conserved and since the emitted photons have momentum then the flashlight must be gaining equal and opposite momentum.

The force is actually very easy to calculate, since the momentum of a photon is simply p=E/c then the force is just F=P/c so, for a 100W LED flashlight (pretty hefty), the force would be ~3x10^-6 N. (this assumes all the light is shining in one direction and all the power is going twoards light not heat)

So for your bonus if we assume a person weighs 80kg then the force of gravity is ~800N which means we need approximately a light 10^9-10 times stronger than the 100W bulb  above, i.e. 1 tera-watt. A rough rule of thumb for terawatts is that 1TW is the total installed capacity of the USA (as in peak power production capacity). So you would need all that electricity to send you up (and that doesn't include the weight of the flashlight itself).


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

[User]
ELI5: What is acid, and how can it "burn" things into almost nothing?

My knowledge of acids are very limited: All i really know, is that it has to do with the value of the PH-scale.

[Assistant]
Acids are compounds that provide hydrogen ions when in solution.  Since a hydrogen molecule is just a proton plus an electron, a hydrogen ion is really just a proton.

These unattached protons are like groupies backstage at a rock concert, willing to make attachments with anything they encounter, whether they were previously attached or not.   If you have enough of them, especially in high concentration, they will break down existing substances as they destroy the molecular bonds in those substances.

They don't turn other substances into "nothing"; they just produce what are usually soluble salts, as opposed to the solids that were there before.  So, like the Wicked Witch of the West, those solids turn into liquid and melt away.


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

[User]
ELI5 What's the difference between stand-your-ground and self defense?

This came up recently in another thread and I was looking for a good explanation.

[Assistant]
Under traditional self-defense, you can use lethal force to defend youself from death or serious bodily harm *only if* you can't retreat from the situation.  This is known as the "duty to retreat."

There are some instances where there is no duty to retreat. Most commonly, there's no duty to retreat in your home, so you can use lethal force to defend yourself (again, against a threat of death or serious bodily harm) even if you could run out the back door. This is commonly called the "castle doctrine."

Stand your ground laws effectively eliminate the duty to retreat in public places.

That said, these are all somewhat nuanced concepts, which vary from state to state, and which don't exist in every state.


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

[User]
Why are economics degrees getting more and more focused on teaching mathematics at the expense of history and key ideologies?

I'm going to be graduation next year and the only essay I've needed to write so far has been about the financial markets in the first year of my degree (this is a top 20 UK university btw) The rest of the assessments and exams have basically been mathematics with economic applications.

The main focus seems to be on simply teaching economic tools with a large majority of universities no longer feeling the need to dive into the bigger picture of economic history and ideologies.

[Assistant]
That's because the way that professional economists now pit arguments against one another involves data. You want to argue that minimum wage is overall a net benefit? Well, here's a dataset, prove to me that what you say is true. Once you get to that stage, it's all based on is your model correct, is the sample biased, how do you correct for such-and-such.

In ye olde days we didn't have awesome, rich datasets that could answer a question. So arguments used to be mechanism-based, say, instituting a minimum wage does x and y, but we believe that because of z the effect of x outweighs the effect of y. And there was no way to really go and out measure whether that was true. So that's why we had ideologies and much more entrenched schools of thought, because it boiled down to gut feel at the end.

Most of modern microecon can be explained using a few very simple equations. Macro is... messy, in part because it's still very hard to use data due to unobservables (you can't run a randomized controlled experiment to balance those, for example).

It's a bit like the history of medicine - econ up to the 1950s was kind of like "there's four humors and you have to balance them", and now we've moved past that to germs and genetics. Not quite at epigenetics yet but we'll get there.


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

[User] Why is raising your heart rate through exercise good for you, but raising it with tobacco or other drugs bad?

[Assistant]
The question is: what is causing your heart rate to go up? In the case of tobacco, it's the fact that nicotine is a vasoconstrictor - it causes the blood vessels to shrink and thus raises your blood pressure. If you think about the circulatory vessels as an organ system, they also have their own health - healthy blood vessels are strong but flexible, and they can dilate in response to the demands of increased blood flow. When they cannot, the heart must work harder to provide the same amount of blood flow to your cells. Over time this effect worsens as atherosclerosis results in permanent hardening of the arterial walls (to which smoking is a contributor).

In exercise, meanwhile, there is increased DEMAND for blood flow from your cells, and your heart is working harder to meet this demand. Your blood vessels respond in kind, by deforming elastically under the additional blood pressure, and exercise in this case will also work them out, making them fitter and able to handle increased loads like this efficiently.

So, in short, while your heart is doing the same thing in both cases (working harder), your blood vessels are doing the opposite.


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

[User] [Home Alone] Why didnt the pizza guy call the police after he thought he was being shot at?

[Assistant]
Because once he got back in his car and started driving back to the Pizza place he worked at, he realized he'd just been pranked with a movie or the like after he gave it some thought.

He got paid for the pizza and didn't get tipped sure, but he also knocked over the house's lawn ornament with his crappy driving. This whole situation was not worth going to the cops for and hell, he could always tell his boss the place tips like crap and they don't have to prioritize the place in case they call again.


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

[User]
Having Python script run without having to install packages

I have an assignment where I must submit a Python program that my professor will then run on his computer. It is a web crawler that outputs data to a CSV. It requires a few packages such as Requests. Is there a way that I can submit a working assignment that does not require the professor to install the packages in order for the program to run? I have just started looking at Docker and think it could be a solution. I would be very grateful if anyone could point me in the right direction.

[Assistant]
I would see what your professor recommends.  This seems strange that they would expect this from you but not have their own plan.

Typically with something like this you should pip freeze into a requirements.txt file, double check that the file only contains packages required for your code and include this file with your code.

Your professor can then use this to recreate the environment needed to run your code.

Aside: If you are starting to look at Docker, start to look at virtual environments first. Virtual environment tools are built into python three and are amazing.


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

[User]
Does "postdoc" job title matter?

I accepted a position to start after my doctorate and now I'm a little antsy about whether anyone will care about the job title when it comes time to apply to more permanent positions. The original posted title was like "Statistician/Research Analyst" and it encouraged but did not require a doctorate. The PI and I talked about my goals and it being a postdoc for me, the PI set the position to pay the standard postdoc salary for the lab, and it is term-limited and grant-funded. I accepted this position because, compared to other offers I got, it's closer to my interests and there's a much bigger opportunity to publish a lot.

Will anyone care that the word "Postdoctoral" isn't in front of the job title? Is there anything for me to put on my CV to make this look better? I've seen some people who mention they have titles like "Research Scientist" or "Research Associate" as postdocs (without that specific title) in positions requiring or encouraging a PhD, but I'm kind of getting in my head about the eventual job applications if I stay in academia.

[Assistant]
It doesn't, as 'postdoctoral XXX' often isn't proper job title to begin with. Depending on the country, institution, department, and funding source, the title is often something like 'XXX assistant professor', 'XXX researcher' or even 'XXX staff', perhaps including 'special', 'temporary', 'visiting' etc. to indicate that it's not a full position.

The exact format of the CV is up to you, but if you list it as postdoctoral research without the exact title people will know what it means.


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

[User] How do we know that the concept of dark matter isn't just the observed gravitational effect of undetected black holes on their surrounding stars and galaxies?

[Assistant]
To get the correct rotation curves for galaxies, you would need to have large numbers of small black holes distributed in a roughly spherical-shaped halo around a galaxy. Small numbers of big black holes would stir things up and we'd notice that. It needs to be a fairly smooth distribution of matter.

Given there must be a lot of these black holes - roughly as many as there are stars in the galaxy - then quite often one of them will just happen to pass between us and a distant star. When this happens, the black hole bends the light of the star towards us, and the star gets a little brighter. This is caused *gravitational microlensing*. It also happens to a smaller extent just when any star passes in front of any other.

We have scanned large chunks of the sky for long periods of time to detect these microlensing events. Based on the pattern of how the background star gets brighter, we can learn about what sort of object is doing the lensing. And we have found a number of microlensing events. But what we have found doesn't give any evidence that there's an extra population of black holes (or dim brown dwarfs, which would work too) out there - it's totally consistent with the number of visible stars that we see.


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

[User] Did Newton ever try to describe electricity? Or, did he for example consider it a secondary or emergent force, unlike the fundamental gravitational force?

[Assistant]
There are a few mentions of electricity and magnetism in his Principia, but they reflect the very rudimentary understanding of the time...mostly regarding attraction and repulsion of charged objects.

For example
"Therefore the force of gravity towards any whole planet arises
from, and is compounded of, the forces of gravity towards all its parts.
Magnetic and electric attractions afford us examples of this ; for all at
traction towards the whole arises from the attractions towards the several
parts."


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

[User] ELI5: What's the connection between memory loss and depression? What causes people with depression to completely loose their memories?

[Assistant] The hippocampus plays a part in memory and in people with depression it is smaller. Conveniently some antidepressant helps the structure and function of the hippocampus though it takes two weeks, the average amount of time it takes for antidepressants to take effect.


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

[User]
[House MD] From a HR perspective what's the worst thing House did during the series?

Let's exclude driving into Cuddy's house; as I don't think he was on the clock for that.

[Assistant] Everything with Detective Tritter. He assaulted a patient, got busted for prescription drug abuse and prescription forgery, basically told a judge to go fuck herself ... that whole season was one long progression of actual crimes.


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

[User]
ELI5: How can the state of Florida sell 3,778 Black Bear hunting permits and try to control the limit of bears being taken to 325?

It seems like this is an impossible situation to regulate and way more than 325 bears will be killed.

[Assistant]
Not really. It's a no bait, no dog hunt. Spot and stalk, or ambush, basically. Bears are pretty shy critters so the bold ones, the actual nuisances, should be harvested pretty easily.

 The bears that aren't conditioned to eat from rubbish bins won't be in much danger, realistically.

The way the harvest size will be controlled is by giving hunters 12 hours to register kills, and nightly totals being called in. When the number gets hit, the hunt is over.


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

[User]
Why do moles grow such long hairs?

Some moles grow hairs much longer than the surrounding area, why?

[Assistant] They're called terminal hairs and we don't really know why they grow longer than normal hairs. They do appear to be influenced by hormones during puberty; so it could be that the mole hair follicle has a slightly different base level of receptors, or interacts differently with the bodies normal hormone levels.


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

[User]
[He-Man] Would Skeletor condone child abuse?

If one of his followers was hurting a child, would he call that out and punish the minion, or let it slide?

[Assistant] He would be disgusted with their pettiness. Not just because even Skeletor has moral standards, but because Skeletor beleives villains should have certain class. Hurting children, or doing any questionable stuff with the captured ladies is not classy. He probably would not even condone theft, unless its a theft of an important artefact he needs for his evil plots.


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

[User] Why didn't the H1N1 Pandemic affect the world as much as COVID-19 did and still is affecting it massively?

[Assistant]
It was just luck in 2009. H1N1pdm09 has a lower R0 than SARS-CoV-2 and a lower morbidity/mortality rate, but thats just the way it turned out. It was nothing people did.

Both viruses spread widely within regional human populations before being detected (pdm09 probably took longer to be identified). Both promptly jumped on planes and spread worldwide rapidly, in spite of attempts at lockdowns. Both viruses avoided attempts to limit spread - the response to SARS-CoV-2 was probably better and more effective than that against pdm09, at least in some countries (Taiwan, South Korea, New Zealand, Australia come to mind).

A vaccine against pdm09 was available faster than against SARS-CoV-2, because it was really the standard influenza vaccine, so that saved a few months. The pdm09 vaccine was available in fall of ~~2010~~2009, while SARS-CoV-2 looks like it will be early 2021 for availability and mid-2021 for widespread use. But where we are now, no pdm09 vaccine was available this time of year.

It was just luck that the 2009 virus wasnt worse. The pandemic playbooks that were made in response to that pandemic took that into account, and made recommendations based on the pdm09 response that did help significantly against COVID-19 in those areas that followed them. Unfortunately, not everywhere followed the guidance.

But you should be aware that H1N1pdm09 never went away. Its now one of the seasonal influenza viruses that travel around the world following the winter, infecting hundreds of millions of people every year and killing thousands. Over the decade weve been inflicted with pdm09, it may well have killed more people than Covid-19 has so far.


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

[User] Why do snowflakes form such unique and symmetric shapes?

[Assistant] Because they are crystals. Crystalline substances follow geometric patterns because it minimizes the energy of the molecular configuration, a beautiful example of spontaneous order. In the case of water, the water molecules align according to hydrogen bonding, forming "hexagonal" shapes (in 3D space, though). The way these shapes lock is rather fixed, but they are flexible in their growth, giving raise to many possible shapes. Chaos theory does the rest.


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

[User]
If Earth had a second moon hidden exactly behind the Moon, how would we know?

Assume that the second moon would be small or distant enough to be entirely eclipsed by our current moon. In addition, its orbit speed matches up with the moon's orbit in such a way so that it always stays exactly behind it from Earth's point of reference at all times.

What would we be able to detect in order to realize this body existed, short of sending probes far enough from earth to find it? Additionally, what effects might this second moon have on Earth, if any?

[Assistant]
The hidden moon would not be able to orbit with the same angular velocity as our regular moon. In a stable orbit, there's a simple relation between the radius of the orbit and its period: the ratio between the orbital radius cubed and the square of the period is constant, given a fixed central body (in this case: Earth). (for simple circular orbits, which is a good enough approximation here, but similar laws hold for elliptic orbits)

This means that if the second moon orbits at a larger distance form Earth, it will necessarily have a longer orbital period, that is, it'll take more than 28 days to complete a full orbit. And therefore it won't be able to stay hidden. The same mechanism is behind the reason why all geostationary satellites orbit at the same distance from Earth.

The only way to get around this limitation is if the hidden moon is actually a spaceship with engines that continuously correct its orbit.


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

[User]
What changes does the human body and brain go through between the ages of 18 and 25 ?

I'm 22 currently and feel like a totally different person in the same body compared to who I was at 18.

How exactly has my body and mind changed so far and what changes will I go through next as I heard you stop developing at 25 and then you just age.

[Assistant] I think the most dramatic development that occurs in the brain during this time is in the prefrontal cortex, which is responsible for decision making, planning, and inhibiting emotional impulses. In adolescence, the relationship between the prefrontal cortex and the ventral striatum (which drives exploratory and sensation seeking behavior) is imbalanced, leading to a lack of inhibitory control. As the prefrontal cortex finishes developing, it allows for "top-down" modulation, where the prefrontal cortex can properly regulate those emotional impulses.


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

[User]
[The Elder Scrolls] What is Moon Sugar?

I am asking because a friend of mines has started to acquire a taste for this substance. I only ever really see Khajit eat these things and I have heard stories of Khajit smugglers who help black market drug dealers with Skooma. My friend is an Imperial and I am worried this may be a gateway to Skooma. Am I just being silly or should I be worried?

[Assistant]
Moon Sugar is a substance refined from cane plants native to Elsweyr and a common spice used by the Khajiit. The cats have a slight dependence on it, but generations of use have caused a massive tolerance to any adverse effects.

Men and Mer lack the tolerance though, and suffer from typical addiction symptoms. Amongst Men and Mer, Moon Sugar is almost always a lead in to Skooma use, which is a highly addictive narcotic even to the Khajiit.


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

[User]
ELI5: Wouldn't it be cleaner to build bathrooms with push-to-exit doors? Does any thought go into the decision to hinge the door this or that way?

All of the bathroom doors, even the newer ones, at LSU are pull-to-open from inside the room. Wouldn't this transmit poop stuff from people more than a push door?

[Assistant]
In many areas if a room has only one exit the door must open inward as a fire precaution.  If the door only opened outward and something fell in front of the door those inside would be trapped.

Fire safety is the bigger concern.


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

[User]
What is electrical energy?

In a circuit electrons are flowing through a wire from the negative pole to the positive pole. In this process they transfer a certain amount of energy to whatever consumes the energy in this circuit. My teacher pictures this energy as backpacks worn by the electrons, which are full before the energy is consumed and then emptied by the consumer after which the electrons move on to the positive pole of the battery. I would like to know what this energy actually is.

Thanks in advance!

[Assistant]
This energy is potential energy. At the negative end of the battery it's like the electrons are at the top of a hill, and they roll down the hill to the positive end.

The backpacks are full of potential energy, and the trade this for a backpack of kinetic energy. The trade happens many times through the circuit as the electrons accelerate and hit bumps (thermal vibrations, other electrons, defects in the wire) on their way down the hill which is what resistance is.


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

[User] If the solar system were the size of a little model in my room how fast would it spin?

[Assistant]
From Kepler's laws, the period of an orbit around the Sun is proportional to (radius of orbit)^(3/2) \* (mass of Sun)^(-1/2).

So if you scale down the solar system, you reduce the radius of the orbit things orbit faster, but you also reduce the mass of the Sun, and things orbit slower. So, which wins?

Partially this is a bit arbitrary, and comes down to how you choose to scale the system. But a sensible choice is to keep the *density* of all stars and planets the same as they are in real life. This means that if we reduce the length scale by a factor of X, then the mass of all objects is reduced by a factor of X^(3).

So the period decreases by a factor of X^(3/2) due to the radius decreasing, but the period increases by a factor of (X^3)^(1/2) =X^(3/2) due to the mass of the Sun decreasing. These exactly cancel out, and all the orbital periods are exactly the same, and it takes a year for the tiny Earth to orbit the tiny Sun.


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

[User]
CMV: "Stacy's Mom" is the best karaoke song ever written.

I think Stacy's Mom by Fountains of Wayne is the overall best karaoke song ever. By "best karaoke song," I mean that it will consistently provide the most entertainment for both the singer and the listeners. Here's why:

 - it is a song that many people know. It is instantly recognizable.
 - thus, people will be able to sing along, and the song also has a very catchy and easy-to-sing melody.
 - it can be sung by either a man or a woman to great effect.
 - it works for a group of people (some do the repetitions in the verses, and everyone belts out the chorus), but it also works with just one person, because the listeners are likely to provide backup vocals.
 - the lyrics are entertaining to listen to and fun to sing.
 - it doesn't matter whether or not you sing it well, because people will enjoy it anyway because of its nostalgic value and its catchiness. However, there is still a good payoff if you do sing it well, since the melody spans a large and potentially impressive range.
 - it is fast and lively enough that it is likely to pack the dance floor, or keep it going.
 - all of this rewards the singer; people are going to be happy that you chose the song.

Edit: I will give out a few deltas when I'm not on mobile anymore.

 I somehow forgot about Sweet Caroline.

Thanks for C'ing my V! This was a fun one.

[Assistant]
The correct answer is that Sweet Caroline is the best karaoke song ever written, to the point where I've seen a group of two dozen submariners leave a bar because someone sang it before them.

Every single point you made applies, only better, to Sweet Caroline.


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

[User] ELI5: why does the sweetness of most fruits like apples, oranges, and peaches vary by a lot, while the sweetness of most bananas are the same (given the same level of ripeness)?

[Assistant]
Commercially grown bananas are genetically identical and originated from a single source not that long ago. They are seedless clones, so are all the same. Apple's have thousands of varieties and have been cultivated for centuries for this variation.

 (Not 100% true but you wanted ELI5)


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

[User]
CMV: Depicting modern political figures as 20th Century dictators is disrespectful

Just saw a post depicting McConnell as Hitler and have seen some with Trump being depicted as good old Adolf too. You just cant compare a grossly incompetent President or Majority whip with a heinous, genocidal maniac. On one hand its disrespectful to the person but even more to the victims of those dictatorships by basically comparing your current position to the hardships they had to go through.
This of course works the other way around too with people depicting Sanders as Stalin.
STOP THAT.
Theres nothing wrong in disagreeing with a politicians opinion but there are just limits in drawing comparisons.
Also: not American, so neither democrat nor republican.

[Assistant]
>You just cant compare a grossly incompetent President or Majority whip with a heinous, genocidal maniac.

It depends, as Hitler or dictators in general aren't heinous genocidal maniacs from the start. Take Hitler as an example - he started his career as a populist who was chosen in elections and had a history of racist beliefs. This comparison may show a dangerous similarity when you compare beginnings of careers of a current political figure. If that comparison would be made in time when political figure would be comparable to "late-Hitler" tean time for warnings through comparison would already have passed.


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

[User]
How do you actually measure the mass of a mountain?

How do you know the volume? Density? What area is considered to be part of the mountain?

I've seen the mass of Mt. Everest mentioned as a comparison to other things in several videos, articles and such and I always wondered how this number comes about.

[Assistant]
first you make some assumptions on where the mountain starts and ends and get a rough volume, then you multiply by a average density of rock, dirt, soil, water and void spaces, roughly 2,500lbs/cubic yard.

While it won't be perfect it should be within 20% or so...


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

[User] ELI5: How different would programming for a quantum computer be as opposed to current programming?

[Assistant]
If Sastrabitrals explanation is too detailed, here's the gist.

It's going to change how the computer functions at its most basic level. They might add them on to current designs to boost up a standard computer's performance. Or they might build something new from the ground up.

But either way, the folks who put it together will create programming languages that shouldn't be much different (or much more complicated) than what is used currently.

Now, making new programming languages for them may be very different because a quantum computer doesn't use the on/off transistors that the entire digital age has been built on.


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

[User]
Is it common for someone to be published in a big research group paper and that person not be able to fully understand/describe all of the details in that paper?

There's a popular question right now about impact factor for publications, and I thought of this question because of it. I'm not up on my science, but I know a few people who are in large groups (10 or more people sometimes in a publication) and they can't even describe what all of their paper is about. There are some sections that go over their head because other members of the team performed those experiments. For example, an experimental side and a theoretical side. The experimentalist might not understand the work of the theorists. Is this common? Does this usually only occur in very large research groups, or in specific fields like Physics but not so much in Biology?

[Assistant] I have been told that it is customary that if you contribute SOMETHING to the publication that you get your name placed on the paper. That something can be funding, data analysis, running a sample, any number of things. One way to add emphasis on who actually did the majority of the work is to make them the first author. But in short no you don't  have to be able to fully understand/ be able to describe all of the paper to get your name on it =/


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

[User] ELI5: How are tracking numbers created and how long will it be until UPS, FedEx and USPS run out?

[Assistant]
Tracking numbers are randomized numbers and letters, typically in a HexDec system that allows for 16 character numbers, and are typically like in UPS's case, 18 characters long following the 2 character preamble.. This equates to a combination that is as follows:

18^18 = DAMN! or 39,346,408,075,296,537,575,424. That alone give you so many different numbers, that it is impossible to run out of tracking numbers.

For USPS, they use a 20 digit Number system with the first 4 numbers predesignated.

so 4 + 10^18 = 1000000000000000004. That is exactly 1 Sextillion combinations.

Tl;DR; we can track everything.

edit for the UPS snob at the bottom.


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

[User] ELI5: Why are razor blade cartridges so expensive?

[Assistant] Because there is not enough/strong competition for this market. Gillette is the strongest brand name in the market. They can price it whatever price they want to sell it. Look for coupons to save some money.


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

[User]
[The Matrix] At what point does the Matrix break down upon closer inspection?

Could you deduce you were living in a false reality by doing deep astronomical observations?  Or experiments on elementary particles?  Does every sample of soil have billions of organisms to examine?  Is the earth's magnetic field and seismic activity consistent?  What about at the molecular level and chemical reactions?

[Assistant]
I suspect that the Matrix is easier to identify based on simple intuitions (e.g., deja vu) than complex analysis.  Any complex analysis that we're allowed to learn is likely to be wholly handled by the Matrix programming (perhaps with histories about how certain particles can only exist in quantum states to lead us to believing that that is the case); whereas the more obvious, intuitive pieces are the one's that they can't really hide.

For example, physicists are more likely to believe in superpositioning than lay people are, but who is to say that superpositioning isn't an artifact of the Matrix?


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

[User] [DC] While Batman is high tech, the DCU is so much further ahead that he should be far more advanced. Why isn't he using reverse engineered alien tech or at least not using Wayne Enterprises to research as much of it as possible to adapt for humanity and himself?

[Assistant] Based on Batman's let's say...proclivity for planning and control, he likes to reduce unknown variables. Sure he might be able to reverse engineer an alien device and integrate it into his arsenal but there's always the chance he may miss something. You don't want to be in the middle of a fight against Man-Bat and randomly have your alien powered tech stop working due to some unforseen extraterrestrial stack flow error.  Batman needs to be one with his arsenal of tools to preform at his peak, and to him that includes end to end control of his gadgets from R&D to implementation.


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

[User]
[DC] So, Owlman is an evil Batman basically. But, why did he turn to crime where Batman turned to crimefighting? Same for all the other evil versions, like Ultraman vs Superman etc.

Is there any difference in their backstories? Is it ever explained why any of them became evil where their mainline counterparts are a force for good...

[Assistant]
Owlman is not Bruce Wayne from a different universe. He's Thomas Wayne Jr., Bruce's older brother from a different universe. Thomas Jr. was always power hungry, greedy, and evil from the start, and his greed only grew when he started to think his parents were managing the family's fortune poorly. He killed his own parents in order to take over running the family business. He also tried to get Bruce to help, but Bruce refused, so Thomas Jr. killed him too.

Ultraman was born on Krypton, but that's about where his similarities with Superman end. Like Owlman, he was born in violence and rage. He only stayed with the Kents on Earth for a few years (his Kents were not the kindly farmers of Superman's life, either) before he killed them and went on his maniacal spree to cause havoc. Also unlike Superman, Ultraman gains power from Kryptonite, so his goals largely involve hoarding it.

Super-Woman is not Diana from Themyscira, but another Amazonian who rebelled against her people's doctrine to stay out of man's world. She enjoys the literal power she has over 99% of Earth's population, and uses things like her lasso of submission to enslave people. For her, it's largely a big fun game where she can be as sadistic as she wants, and there are only a handful of people that can stop her. Fortunately, she is on their side.


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

[User] ELI5: Why does the captain needs to be the last one to leave the boat when it sinks?

[Assistant] A captain doesn't always *need*, but often should be last off. The captain is in command, and supposedly the most capable person on the ship. The crew and passengers trust the captain to make good decisions and keep them safe. In an emergency, it's the captain who should know best how to save the people who trust him. To literally ditch them in the water is a huge betrayal and deriliction of duty.


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

[User] ELI5: Why cant babies drink water but use water on formula milk?

[Assistant]
Babies are small. What would be a small amount of water to you, proportionally speaking, represents a much larger portion of their total body water. Basically, if babies have too much water without the protein, fat, carbohydrates, and electrolytes found in formula or breast milk, their blood electrolytes, and in particular their sodium, can get diluted and drop to dangerous levels. Kidneys are pretty smart and efficient even in younger babies beyond the immediate newborn period but sometimes too much water is just too much to handle.

Most frequently, we see a drop in the serum sodium level when babies are given plain water in excess or are given diluted formula (families will sometimes dilute formula to save money by stretching the formula supply). If your sodium gets too low, it causes seizures.

A good rule of thumb is that babies can have one ounce of water a day for every month of age they are over six months up til about 10-12 months of age (so a six month old can have an ounce of plain water a day, a seven month old can have two ounces, etc.).

Source: Im a pediatrician and Ive treated hyponatremic (low sodium) seizures many a time, unfortunately.


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

[User]
Can one code in binary?

Can you code using ONLY 0 and 1's. I'm not talking about dificulty or efficiency, but rather the possibility, like making a "Hello World" program in binary.

[Assistant]
Yes, it's absolutely possible.  But it'd be super difficult and would take an insanely long time with a lot of research.

There's nothing magical that a compiler does that you can't do.  It's just smarter and faster than you.


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

[User] ELI5: Why do people raise the pitch of their voices when talking to cute things?

[Assistant] Humans are hardwired to find deeper voices more authoritative and potentially threatening. High-pitched voices, especially when directed towards something young or small such as a puppy or baby, are used to convey no threat and put the listener at ease.


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

[User]
Why does the multiverse theory have an infinite number of universes?

Every time I see the multiverse theory mentioned on TV, movies, books, comics, etc. they have the same basic concept of infinite universes, some very like ours, some very different.

While the idea that there are different universes with different laws of physics sits fine with me, the concept of there being one universe exactly like mine but I'm made of corn, in another the only difference is I have a different colour shirt on, etc. seems ridiculous.

Why does the theory have 'infinite' rather than many universes?

[Assistant]
A cosmos which produced *all possible* universes would be a simpler thing than a cosmos which produced *only some* possible universes. The first one requires only a rule or pattern that produces universes, the second also requires additional rules to identify which ones actually get produced.

Let's look at a 'Level I' multiverse to illustrate this :

> Level I: A generic prediction of cosmological inflation is an infinite ergodic universe, which contains Hubble volumes realizing all initial conditions - including an identical copy of you about 10^10^29 meters away

Translated, that means: the universe is infinite, but the observable universe isn't. Let's abuse tterminology and call the observable universe the "universe", and the universe the "multiverse" - we can never ever get to the other "universes", there are infinitely many of them, and each one contains a collection of interesting galaxies and stars. Exactly what they contain is determined by their initial conditions (in practice, what they were like shortly after the big bang).

A universe that started off sufficiently like ours would still be very like ours, although a tiny difference in the starting state will *eventually* make the two diverge. In some (only a mindbogglingly tiny fraction), that divergence starts to become obvious today, with you picking a different shirt (although the divergence was always there, in fact, we just wouldn't have noticed until today).

Once you've picked a diffferent shirt, of course, human histories diverge radically. Different people spend different amounts of time talking to you, which slightly affects traffic flows in your city, which means different people die in car accidents or fall in love or argue with their boss or get pregnant. A week later there are different news headlines, different presidential tweets, different entrepreneurs starting businesses. The weather in a month is noticeably different, in a few decades the climate is. Our technology goes at a different pace, and a different direction. In one universe, our robots are off to colonise a nearby star, in another, we're off, and in a third, the robots are their own and we are no more.

To say this is not so, you have to explain why an infinitely large space-time would contain a universe that made you, but *not* others that made an almost-you. You need to specify extra (strange) laws of physics to prevent such a thing from happening.


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

[User] What's the reason of sudden advancing in human technology during 20-21th century?

[Assistant]
Ah, there's no alien technology found. All of these advances were made by good ol' fashioned human ingenuity. Our advances were fast because:

1. Great thinkers, mathematicians, scientists, and engineers have already discovered or developed a foundation that we can build off of. The unification of electricity and magnetism by Maxwell allows us to be able to generate power from hydro dams, for example. Newton already invented calculus, which we need to use to calculate things like how to build a bridge. We also need calculus to derive more mathematical proofs/equations, etc. This brings me to the second point:

2. The advancement of knowledge compounds. The rate of knowledge/advancement gets faster as more knowledge is discovered/created. For example, advances in computer technology allows us to build devices that can image smaller computer chips, allowing us to learn how to build even smaller computer chips, which would allow for greater computational power, which would let us build even better devices to image these smaller computer chips,....etc..

3. As a corollary to #2, rate of advancement grows because the advancement in one field of science/engineering can impact the advancement of a different field. For example, better computing power allows biologists to simulate protein structures, which allows biologists to learn faster about protein functions. This knowledge of proteins could lead to medical advances and cures for diseases. To make these cures, new engineering problems would have to be solved (i.e. better/faster ways of making these cures on a large scale), which would cause growth in another area of science/engineering. Now you are able to save more lives and support a larger population of people.

4. The increase in population is also a factor in scientific advancement. Ignore all the sensational BS that people like to say about how the world is over-populated and that we need to stop the poor people from reproducing. We have advanced so fast BECAUSE we have 7 billion people living at once on the planet. Knowledge is stored IN PEOPLE, NOT IN BOOKS. Sure, you can learn things from books, but nothing beats going directly to the person, and asking your very specific yet very important question. If you don't understand what something in a book says, you're screwed. If you don't understand what the person is saying, you can ask them for clarity. Then they can draw on past experiences to better instruct you. Remember that books don't advance science/engineering, PEOPLE DO.

5. We have so many people living at once learning and researching. They can also speak freely to each other and share ideas (for the most part). This sparks new ideas, and interdisciplinary collaborations that generate new inventions and devices faster. You need a new set lungs? That means you'll need a biologist to find a suitable donor, a chemist to synthesize the immunosupressants, a doctor to tell you how much immunosupressants to take, a surgeon to remove the lung from the donor, an engineer to build a suitable carry-case for the lung during transportation, another surgeon to implant the lung into you, and nurses to monitor your condition post-surgery. OH WAIT, you wanted an MECHANICAL LUNG? Well you need a biologist to figure out what materials are suitable for implantation, an mechanical engineer to figure out how to build the device, an electrical engineer to make the necessary electronic components, a surgeon to implant the lung, and maybe a computer engineer to monitor the status of the iron lung.


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

[User]
[Sword Art Online] Why don't they simply pluck the helmets of the gamers?

I know that there is a mechanism to prevent tempering with the NervGear helmet that any attempts at removing it will cause the microwave impulse to fry the gamers brain and I understand that. But in the episode "The Red-Nosed Reindeer " we learn that there is an item able to review a person during a 10 second period after there in-game death which means that there is a build up phase for the impulse otherwise reviving them in-game would be useless if there brain where already cooked in reality instantly at the moment of in-game death.

Knowing this it is hard to belief that it is impossible to quickly pluck the helmet of a gamer before the impulse is send seeing as the NerveGear helmets look like a one-size-fits-all bicker helmet with no stripes or anything to hold it more rigidly in place.

[Assistant] The delay in death is within the software of the *game*, as in, the death signal comes from the internal sensors. If the hardware recognizes itself being tampered with from an outside source, the zappidyzap comes immediately.


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

[User] [DC/ Justice League] people do seem to shit on aquaman a bit more than they should. Do the members of the JLA respect each other equally or do they seem to see each other as a weaker link?

[Assistant]
Probably the best answer is that *most* people are treated well, fairly, and respected for what they do. Some get a bit more flack because they can't do all that much or are very specialized, but there's a few that do get shit on constantly behind doors and publicly are pretty much kept out of the big jobs.

1. The Question. He's often mocked behind his back as being a paranoid delusional creep, and they're not wrong. Of course, he tends to be right about his Paranoias more often than not, so is it really Paranoia if they *are* out to get you? Then again it's hard to like the asshole digging through your literal trash and building complex theories as to why you're working for the bad guys (even more when he turns out to be right, all because of a fucking matchbook you had from some dive bar Sportsmaster was meeting you at).
2. Booster Gold. *Almost* no one in the League respects him. At best they tolerate him. At worst, they shit on him and give him the worst jobs to his face. This has to do with a few issues: he's a huge dick for one. For another he's made it clear he's in this for fame, glory, wealth, and chicks. And finally when all else is done, he stole his powers, came back in time, and uses some knowledge of the past to make himself look good (although his History Class Grades seem to have all been D's).
3. ~~Animal Man.~~ B'wana Beast. He's a serious machismo character, not *precisely* misogynistic or anti-woman, but on more enlightened times he comes off a bit as a Gym Bro or Frat Boy. A lot of the female JLers find him grating, but he is good at what he does and can be trusted to have your back, even if he does make inappropriate growling noises when no one's around.
4. Plastic Man. As a former Criminal turned good, he has issues. Once he's proven himself, he tends to be well liked and respected, but he has a *long* haul to get there. Batman famously doubts him and considers him barely a member (despite often being a *Founding* member or near enough.
5. Hawk Girl. In Justice League and JL: Unlimited her race invaded Earth and threatened to blow it up. She initially sided with her people, and was revealed to have been reporting and spying on Earth for *years.* It took a long time for her to get her trust back, and many JLers in the Unlimited Era distrusted her even to the end. However in most continuities she does not have this problem.
6. Batman. Respected and feared, but he makes a lot of mistakes in his loyalty. He's nearly killed the JLA off by keeping contingency plans for their betrayals and allowing those to be stolen by bad guys (R'as Al Ghul in the comics, Vandal Savage in one of the movies). He also trends to being the "guy who breaks the rules to save the day" in many other continuities often leading to the dissolution or break up of the JLA. Famously wrecking the JL in Young Justice season 3, joining the Resistance in DC: Injustice, and running off to form Batman Incorporated in New 52. There's also the whole "raises child soldiers for his personal war on crime and has cost many of them their lives, sanity, futures, and deep physical and emotional trauma" thingy he has going on.
7. Shazam/Capt. Marvel. He's usually super respected and beloved riiiiight up until people find out he's like 9. That's usually when everyone flips out and starts wondering why it's cool he's on the Team, saving lives, making major decisions, and risking his own life at such a young age. Some point to the Wisdom of Solomon guiding him, others point to Wisdom is not the same as maturity. Batman usually supports him, although his track record on raising Child Soldiers is spotty at best so take that iota of support with a Gotham sized grain of salt.
8. Guy Gardener. He's the biggest dick in the Justice League, and that's counting Booster Gold. He has a interstellar reputation for being a giant dick. People may not know what a human is, but they know Guy Gardener is one and he's a huge asshole. No one likes him. No one finds him funny. But damn, if he isn't powerful and effective. He's on the League because of his skills, power, and results. If it was by a  vote of character he'd been voted off decades ago. If he has two votes in his favor, even he'd be surprised.


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

[User] ELI5: Why do the refresh rates on computer monitors seem to always be 144hz or a multiple of 60?

[Assistant]
TV broadcasts in the US are 60Hz, so monitor refresh rates are usually something that divides nicely into this. The 144Hz thing is because people took displays that were 120Hz and overclocked them to get the highest possible refresh rate with that hardware. 20% over was more or less as high as the panels could go before crapping out. Seeing the market, some display manufacturers did factory overclocked displays with 144 Hz, and it became a standard. (Very few companies make the actual display panels - most simply buy a panel from one of the few manufacturers and configure them with a display controller).

The reason for 60Hz TV broadcasts is that AC current in the US is 60Hz. This means that traditional light bulbs actually vary their brightness at 60Hz, so if you try to film something at another refresh rates, you get an uneven brightness over time.


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

[User] [Star Wars] Why did Mace Windu decapitate Jango even after he was disarmed ?

[Assistant]
Disarmed in the middle of a battlefield where he can walk five steps and pick up another weapon? Or pull off another trick with some Mandolorian weaponry he's got tucked away?

He's not disarmed until he's either dead or in a cell, and there was an ongoing war to deal with.


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

[User] [Batman] Why have none of Batman's supervillains ever tried attacking Gotham during the day?

[Assistant] They have. If they attack during the day, Alfred wakes up Bruce and he goes to fight them on what little sleep he has, but Bruce is used to running on low amounts of sleep so it's not as big a deal. The real issue is that if Batman's rogues teamed up, so that they'd continue to attack in waves so that Batman didn't get any sleep. But that would require them to cooperate and work together, and that rarely happens.


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

[User] ELI5 How do rich people go bankrupt yet continue to be multimillionaires?

[Assistant] Bankruptcy occurs when some entity cannot generate the necessary cash to settle immediate obligations. An illustrative example might be someone owning a $10m home but has a bill for $500,000 that they cannot pay. On paper, their net worth is $9.5m but they can still be forced into bankruptcy if their creditors insist on immediate payment. Bankruptcy is a court mandated process that resolves the situation among the various parties - there are complicated rules around how this works.


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

[User]
[Doctor Who] What exactly makes an unhinged, evil Doctor more dangerous than say, the Master?

The Doctor abandoning his morals and rules is always treated as basically a threat to all of existence. The Master is like this all the time, is clearly shown to have a similar level of intelligence to the Doctor, and yet isn't regarded as nearly as big a threat to everybody.

I know there's the reason "The Doctor is there to stop the Master, if the Doctor goes bad, who stops him", but the Master doesn't spend all his time opposing and being stopped by the Doctor, right?

There's surely stuff the Master does in his personal time that results in lives lost, worlds broken and civilisations enslaved, and yet its never treated with the gravity that I feel it deserves.

[Assistant] Think of the Master and the Doctor like Batman and Joker. While the Joker is incredibly destructive, most of his destruction is done to and for Batman. But if Batman snaps the Joker isn't going to stop him and there are very few people who actually could. If the Doctor decided to take over/destroy the universe the Master would most likely cheer him on and see it as a victory, there'd be no one with the power to stop the Doctor.  Even if the Master tried we have seen multiple times he can't defeat the Doctor.


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

[User]
[Wonder Woman (film)] Why did the titular Wonder Woman refuse to [spoilers]?

Why did Wonder Woman refuse to kill Isabel Maru? Wonder Woman clearly lacks Batman's no-kill rule. We see her smash people in the head and through walls. Her victims don't get back up, and we never see any prisoners. One time she brings the top part of a church steeple down on one man. And don't forget the numerous Germans she assisted in the slaughter of by leading the Allied charge. And if that's not enough, she unambiguously kills General Lundendorff. So why does she pause when asked to kill someone responsible for countless deaths? Is it just to spite Ares? And it's not like this is a big turning point in her moral viewpoint on killing, as she then went on to kill Ares.

[Assistant]
The Amazons, Diana included, aren't simple killers. They're meant to be guardians of peace. Part of that-- perhaps the most important part-- is mercy. By that point in the battle, Dr. Poison is beaten and killing her won't bring peace or save lives.

Furthermore, it's a rejection of Ares's view of the truth, the idea that humanity is so depraved as to *deserve* death. Diana believed that Steve's life and death proved that humans were capable of doing good things, not just fighting and killing, and offered Dr. Maru a chance to live specifically to defy Ares.


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

[User]
[Pirates of the Caribbean] Why is Mr. Gibbs trusted by pirates if he was working with Norrington when they first found Will Turner?

What happened such that he was a trusted member of Norrington's crew and also trusted by Jack Sparrow and other pirates?

[Assistant] Tons of pirates started out working with the Navy. In fact, to some extent, the explosion of piracy in the 17th century can be attributed to the fact that working for the Navy sucked so hard that sailors would rather turn pirate.


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

[User]
ELI5 Why do we frequently end words with 'y' when we're talking with children, i.e. mommy, daddy, doggy, kitty? Also, is this just an English language thing, or are there similar instances of this in other languages?

Edit: Thank you all for my most successful post ever.

[Assistant]
In linguistics, that's called a diminutive. In English, it's typically done with an "ee" sound (usually spelled with a y or ie).

In Spanish, for instance, the diminutive is represented with the suffix "ito" or "ita" (so seorita literally means "little miss").


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

[User] How are virus RNA sequenced and what makes sure its accurate?

[Assistant] There is an enzyme called reverse transcriptase that can convert an RNA sequence into DNA and then the DNA can be sequenced just like anything else. The way sequencing typically works now is you break the DNA into many fragments that are read in parallel and a computer pieces together overlapping portions of the reads to reconstruct the full sequence.


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

[User]
[Avatar the legend of Korra] How did Team avatar and Aang's family reacted to Korra?

I mean, she is literally your diceased friend/father/brother in law/husband standing right in front of you with an completely different personality.

What kind of psychological process did they have to go through?

[Assistant]
I assume for most of them, it wasnt that big of a deal. They knew he reincarnated. Toph even greets her as hey twinkle toes.

I mean Im sure theres a brief moment of reflection. But even though Aangs spirit is in there, shes still a different person. That was kind of the whole point of TLAs ending.


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

[User]
CMV: The current HGV driver crisis in the UK is what Brexit voters wanted

Logic:
1. (Some) Brexit voters felt that cheaper European immigration led to foreign workers coming to the UK to take on jobs that lowered their wages or put them out of that business.
2. With fewer European workers, businesses have now had to increase wages for HGV drivers and go on rapid recruitment drives.
3. This has lead to more native Brits getting (back) into the HGV job with higher wages.

Regardless of knock-on effects (e.g. prices passed onto customers, fuel crisis while HGV capacity doesn't meet demand etc.) this process leads to a perceived 'benefit' of Brexit.

I am not a Brexiteer, but I do see this crisis as being a short-term problem that will lead to a genuine result that Brexit voters hoped for, i.e. to higher paid HGV drivers with a greater proportion of British citizens in that job role.

Caveats: Brexit voters are of course not a homogeneous block, I'm talking about those who hold the above views. Also, whether or not this is a 'good thing' is not part of my view, just that it is consistent with a common Brexit perceived benefit.

[Assistant]
One way to think about whether this is 'what they wanted' is to imagine a situation where the Brexit voters really believed this situation would manifest, and whether they would willingly then vote for it.

Before the referendum any discussion of food or fuel or labour shortages, or in fact of any inconvenience whatsoever caused by Brexit, was met with the rebuttal "project fear" by most of those intent on voting in favour of Brexit.

The reality now is that - as you say - those shortages have factually occurred. And the resolution is either (1) more foreign labour or (2) increased cost to consumers to pay for the increased price of labour and logistics.

I suspect (1) will be what happens, when all the bluster dies down. But let's imagine (2) is what happens instead. Imagine the Brexit voters REALLY believed supermarket shelves would be empty, petrol stations would be shutting down and costs would increase, permanently! for the average person to pay for this situation to be addressed. Would they have so willingly voted for that?

I suspect not.


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

[User]
[Spider-Man 2002] Is pro-wrestling real in the Sam Raimi universe?

In the movie, when Pete decides to go toe-to-toe with Bonesaw, he initially gets the crap kicked out of him, but then he ends up coming out on top. This leads me to wonder: Is the whole Spidey franchise in kayfabe, or did Bonesaw just think he could beat up jabronis without a care in the world?

[Assistant] No. NYWL was one of the last holdouts of the practice of "hooking", a scam in which a wrestler offers to fight any member of the audience for money, then shoots on any challengers using a hold that is immediately disabling or painful enough to force someone who isn't trained in dealing with it to submit.


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

[User] ELI5: whats the science behind the difference in the nasal spiciness of horseradish/wasabi etc and the mouth spiciness of chillis?

[Assistant]
Different chemicals.

The spiciness in chili and other peppers is caused by capsaicin, which stimulates the heat sensing receptors in your mouth. Meanwhile Wasabi and its friends have allyl isothiocyanate which triggers a different set of pain receptors.


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

[User]
CMV: Zoo animals should generally not be killed if adults intrude on their habitats.

I really don't want to get into endless "what if"s about whether the adult is mentally incapacitated (i.e., the cognitive equivalent of a child). Let's just assume that the adult is a normal adult with normal cognitive function because this is all theoretical. Let's also assume that this adult PURPOSEFULLY intruded on the habitat, and that the zoo has access to this intent (e.g., if there's a huge fence, you have to climb it in order to access this habitat, so it's impossible for it to be an accident).

In this case, you basically have a win-win scenario: you get to experience this animal in a way that most zoo-goers don't, and you have a bunch of trained assassins (the police, whoever zoo security is, etc) unleashed to protect you. One might say that you are going to jail/pay a fine for this activity, but, since you basically have a 100% chance of getting caught, you literally get to decide that for yourself as a price of admission for this super-exclusive-zoo-experience, while the animal has no choice but to die for your reckless behavior. There are literally zoo dedicated to people who want to interact with animals--petting zoos! You are forcing zoos to become very expensive petting zoos and killing animals for your sick benefit.

One might say that human lives are more important than animal lives. Sure. But there are LIMITS. We are fine with delaying development in Latin American countries, which would definitely prolong some of their lives, to preserve the rain forests particularly because of the rich biodiversity. Moreover, the animals in zoos literally dedicate their lives to entertaining us--i.e., their entire lives are a public service to humanity. And, in the design of the zoo, there is no contest between animal life vs. human life. Animals are in often very cramped areas for human enjoyment where, if they stick to established boundaries, have only risk from other people--not the animals!

One may say that the animal is at fault for wanting to murder the person. Honestly, I don't know how to dismiss this argument other than my opinion that it's a dumb argument.

One may more reasonable say that the person wasn't reasonably well-educated. A lot of people think polar bears are really cute and cuddly, and not ferocious beasts. Similarly, tigers, lions, etc. look like big cats, and there are some Youtube videos of people petting those big cats, and them acting like big cats. This is the part that gives me a bit of pause, but I think it's incumbent on the ADULT person to do a bit of research before climbing a fence or going over a fairly-difficult-to-overcome barrier and interacting with an animal in the zoo.

[Assistant]
>Let's just assume that the adult is a normal adult with *normal cognitive function* because this is all theoretical

Is would argue that no adult who climbs willy-nilly into a literal lion's den has normal cognitive function.


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

[User]
ELI5: How I "don't hear" music when I'm falling asleep.

As someone that regularly goes to sleep with my iPod playing, I've found that I'll be lying there with my eyes closed, when I sorta "wake up" and realise I can't remember hearing any of the music that was playing in the past thirty seconds, no matter how much I try, despite the fact I am completely conscious of still being awake. How and why does this happen?

[Assistant]
One of the first parts of your brain to "turn off" when you go to sleep is the part that makes new memories. It's called the hippocampus. You've been listening to the music, and hearing it and probably enjoying it, but the whole time, you haven't been making new memories of hearing it. When you have a mini wake-up, the hippocampus kicks in again, but you have no memory of the last few seconds/minutes, because you never made those memories in the first place.

Same thing happens in the later stages of being drunk, by the way. You don't remember staggering around like an idiot and talking shit last night, because your brain had already stopped making new memories by that point.


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

[User]
[Marvel] Which hero has made the biggest impact on society?

I'm just a normal farmer and was wondering which of our many fine heroes has made the biggest splash on society?

[Assistant]
Doctor Stephen Strange.

Sure, Otto Octavius tries to destroy New York City every once in awhile, and Spider-Man stops him. Great, Wilson Fisk tries to stage a hostile takeover of New York City, and Daredevil beats some sense into him. Okay, Norman Osborn takes over America from time to time, and Captain America restores truth, justice, and the american ... well, you get the picture. And yes, occasionally Galactus stops by Earth to eat it.

Paltry attempts at villainy, all.

Doctor Strange fights enemies that eat entire realities. He goes toe-to-toe with literal gods. He wrestles with beings whose whims cause galaxies to vanish. Reality as everyone in the 616 universe knows it exists solely because of Stephen Strange.

And that was before he became the Black Priest.

Strange became what he once battled. He shattered worlds and destroyed planes of existence in order to protect his homeworld. He destroyed countless universes to prevent the ultimate collapse of the multiverse, and *created* reality as it now exists.

The All New, All Different Marvel, the first reboot of the main continuity in the history of Marvel, was brought to you by Dr. Stephen Strange, MD, Master of the Mystic Arts, Sorcerer Supreme, and hierophant of the Black Priests.


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

[User] Why does the Osprey use propellors instead of jets?

[Assistant]
They do use jets. It's a turboprop powered aircraft - jet engines are driving the propellers.

They use (very large) props because it's much easier and more stable to hang a heavy transport aircraft's mass from below a rotor/prop disc than it is to balance it on top of jet blast.

It's also much more energy efficient, which is the same reason why commercial aircraft now use extremely high bypass turbofan engines instead of plain old jet engines like they did at the start of commercial jet service. The vast majority of the thrust for a turbofan comes from the fan blades being powered by the turbine, not the turbine itself. It's also quieter, since you can use a smaller jet engine with a larger fan disc and most of the exhaust thrust gas is slower.

For something like the Osprey to use only jet engines the engines would have to be massive and would reduce range/payload. It would also burn more fuel per minute so you'd have to carry more fuel, which would also reduce both range and payload.

The you have landing field requirements. With a jet you likely couldn't land on dirt or unimproved landing sites like you can with a helicopter or Osprey.

Harriers and other true VTOL aircraft can't just land anywhere. They generally only take off and land on concrete strips or aircraft carriers. If you tried to land a Harrier on a dirt/grass/sand field it would tear it up so bad and throw debris and dirt so far into the air that it would likely destroy the engines due to debris ingestion or otherwise make it unsafe or impossible to take off again.


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

[User]
ELI5: If a magnifying glass will magnify the suns rays, then wouldnt wearing prescription glasses actually be dangerous for our eyes?

If so, does prescription glasses that come with photochromatic or polarised lenses help to combat this?

[Assistant] All lenses focus light, including the lens in your eye. Prescription glasses just move that focal point to where it should be, they dont collect any more light than your eyes do. That being said - Do you look directly in the sun when you wear glasses (or when you arent)? That is dangerous, with or without glasses because sunlight is strong enough to damage your retina permanently.


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

[User]
(As an example) How is it decided, the price of cocaine?

I am not an economist, but come from more of a philosophy background. I am sorry if I am having trouble articulating this. My question takes, first, the illicit substance cocaine as its example. Whether you pay 50 or 150 dollars per gram of cocaine, what, ultimately, determines that price? Is it that we have commonly judged the experience of taking the drug is worth that amount of money? Or are we simply paying for what it costs to produce, etc. as well as profit from it? I see at least these two factors, sort of "wish" and "necessity," entering into the price -- since it has been determined that raising the price of cocaine reduces usage, demonstrating that people have a sense of value for money when they purchase it, and also tend not to overspend. I also think there is an interesting corollary in the sense of it being a quasi-Veblen good at a conventional price point, if I have understood this concept, but then I am sure if it could be made cheaper, it probably would be.

The question is less salient if we take instead, for instance an Xbox. I think most people would say $500 is high for a game console, and $300 affordable. There is more complexity in the supply chain here, meaning that there are more factors determining what would be a "necessary" price, but have we as consumers essentially pulled prices out of thin air (or, what we can reasonably afford with our purchasing power) when it comes to the question of what is good pricing? Probably, there is some relation between our "ideal price" and the de facto price of a product, based on what is usual; I am used to paying $8 or more for lunch, and view that as basically fair, which when deconstructed is quite strange, and when I was younger I thought it was expensive.

I guess that I am looking for a sort of ontology of "market value" which goes beyond "supply and demand" and deals more specifically with individual relations. I think that possibly, the sense of "fairness" in a transaction (not always at hand) extends from a sensed commonality between these real and imaginary factors I have outlined, pointing actually to the currency in question moving "efficiently and correctly" from an altruistic perspective, rather than just marking the so-called correct price.

Is there any work in economics which deals with this kind of question, as much as I have failed to distill from my thoughts this higher distinction which agitates them?

[Assistant]
It's really just supply and demand.

Cost is not *that* relevant, if supply and demand is as such that the price is below cost, you don't produce that good, but that's about it (well, at least in a basic sense).

Now you have to make a distinction between aggregate supply and demand and individual supply and demand. Aggregate supply/demand is what determines what the market rate is, let's say just for the sake of having an example, 50$ per gram of coke.

Your personal demand on the other hand determines if *you* buy that good. That's where for example your personal sense of what's a "fair price" comes in. If you think 50$/gram is adequate, you buy that good, and if you don't, you don't.

What makes up the aggregate demand really is just lots and lots of personal demand curves, same with supply, to the point where aggregate supply/demand is at a point where the highest amount of total "value" (goods/price) changes hands.

>pointing actually to the currency in question moving "efficiently and correctly" from an altruistic perspective, rather than just marking the so-called correct price.

In a sense, the "correct" price *is* "altruistic". Supply/demand at equilibrium is as such that neither consumers nor producers can extract a surplus.


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

[User] ELI5: How did people get horses to charge into lines of spears when horses are spooked so easily?

[Assistant]
Extensive training and blinders. These horses were **war horses**. They were bred and trained for the sole purpose of charging into lines of spears and fighting in the thick of battle.Ever since they were young, they were around training camps, getting used to the noise of battle. It was their whole life.

Most animals can be trained for very specific purposes if you breed them well and keep them training.


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

[User]
What's the point of MAC addresses when devices have a private IP address

You can also change both your IP and MAC address, right? It seems like 2 things that have the same purpose.

[Assistant]
You can't change your MAC address, although you can spoof another MAC address. The MAC address is unique to the piece of network hardware.

The real reason for the difference comes down to the function of the layers in the TCP/IP network stack. The MAC address sits at the data link layer, one of the lowest layers of the stack and is the unique address ID of the hardware. That's its role - to ID your computer to other computers. But it doesn't give you any more information than that, such as the location on the network.

The IP address is used at the network layer. It is useful because the formatting of the address and the range of values tells you information about the location on the network of the computer you're looking for. To give a simple case, if the first number of the IP address is 127, you know it is a local address, which limits the space you have to search to find the corresponding machine. Thus, generally speaking, an IP address is relative to the network that it's on. It's true that you can have a static IP address, which is useful for stuff like web servers, but even then the address values mean something.

So IP addresses are useful for network management, but are not normally unique, because the number of possible addresses is not large enough. MAC addresses uniquely identify a computer, but are not flexible to make it easier to find a device. It is similar to the reason computers have both IP addresses and URLs. The URLs make it easier to handle things at a more abstract, human-friendly level, and can be mapped to an IP address for network purposes.

To use a non-computer example, it's like the difference between your house having an address formatted with house number, street name, and city. With that info you can find the house even if you've never been there before. A MAC address would be like assigning your house a random unique number. It's ideal for uniquely identifying the house, but no help at all in finding it.


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

[User]
[The Thing] If the SCP Foundation managed to capture The Thing then how would they contain and study it?

AU where The Foundation discovers The Thing and its UFO before the norwegians, What would be its article page on the wiki be and containment procedures be like? How would The Foundation scientists even be able to study The Thing and learn the full extent of its abilities without being assimilated?

[Assistant]
Containing a dangerous shaoeshifter and alien beast? Bro that's Tuesday for the Foundation.

Containment would likely contain a sealed vault with no routes leading to the outside and constantly guarded by specialized site personel. Likely using codes, implants, and other equipment to make sure none of them end up being impersonated. Wouldn't be shocked in xray is used to make sure the guards are anatomically correct. Kind of like how in Parasyte they handed the parasitic organisms there.


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

[User]
ELI5: What happens to the blood after you internally bleed?

Does it just stay there forever? Where does it go in the first place? Does it dry up? If so, how?

[Assistant]
It does not stay there forever. Generally your body reabsorbs blood.

Bruises are a good example. For larger quantities of blood you may need surgery to relieve or drain the blood from your body cavity or interstitial space. Draining this blood doesn't remove all of it, some of it will still be absorbed.

It doesn't dry up, it clots.

A very basical description of how it clots is because of a series of enzymes called prothrombin and thrombin. Prothrombin stimulates more thrombin and thrombin can stimulate clotting factors. Fibrin is basically a sticky protein that can form a mesh to collect platelets and then other blood cells into a single mass.
Platelets and fibrin bind together to become as solid mass(or clot!).

If you are more interested in the minutiae of the clotting process, look up the coagulation cascade.

Macrophages are a type of white blood cell, they can digest other cells. This includes digesting blood that has spilled and clotted within your body. This is what happens to internal bleeding including why bruises fade over time.


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

[User]
ELI5: What actually changes in your body when you build cardio endurance?

How does endurance actually work? Why do you have to actually run to gain endurance for a marathon instead of just doing strength training? What changes in your physiology when doing endurance training besides getting muscular?

[Assistant]
Endurance comes from a process that converts glucose and oxygen into energy.

There are many steps in that conversion process, and each of them gets optimized in a certain way.

A top endurance athlete will have more red blood cells to carry oxygen, a bigger heart muscle to pump the blood faster, and more mitochondria (the little furnaces that combine glucose and oxygen) inside each cell.

There are other adjustments as well, but those three are the most important. Note that none of these adjustments involve any physical change in the size of the muscles, other than the heart.

As for strength training, that primarily involves an energy pathway that does NOT use oxygen. Bigger muscles will not help much with endurance, as long as the athlete has enough basic strength to keep the body stable. Otherwise, big muscles just end up as added weight and bulk that can slow down an endurance athlete.


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

[User] ELI5: The Lymph System kills dangerous cells, so why doesnt it kill cancer cells?

[Assistant]
Immune cells can kill cancer cells. But cancer cells are able to induce local immunosuppression, basically sending signals that tell the immune cells not to attack it. Additionally, cancer cells look very similar to human cells. They can look completely normal to our immune system because theyre still fundamentally human cells. This means that our immune cells see them as normal and wont kill them or detect them as dangerous for targeting.

Lastly, cancer cells are heterogenous. A single cancer cell, as it divides, undergoes more mutations. Cells that cant cope to such a strange environment die. cells that get targeted by immune cells die. Through evolution, the most hardy and, stealthy cells survive.


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

[User]
[Marvel] What does the Silver Surfer think of Galactus?

Does he hate him, love him, fear him etc.

[Assistant]
As Facebook would say, it's complicated.

The relationship has changed throughout time and as the Surfer has learned more about Galactus.

In the beginning, Galactus chose him as a herald in exchange for saving his homeworld. Being a scientist he had a certain level of detachment, but let's be honest, Galactus came to eat his world. Hard to like a guy like that. So there's that, but then he was good enough not to eat his home, so there's a certain level of gratitude that's due, isn't there?

Then Galactus forces him to go out and find other planets to consume. The good news is that Galactus isn't exactly a micromanager, he makes simple commands and is easily satisfied. The Surfer, of course, tries to work around the margins, leading him to life-giving but uninhabited planets.

Of course to Galactus this is the equivalent of dumpster diving, so he puts a stop to that. Suddenly Norrin Radd is killing whole fleets of planetary defenders and listening to the death cries of entire populations. He was never a fan of war and violence in the first place and now he's a direct contributor in straight up genocide. Yes, he ends up bearing quite a bit of animosity about that, but it's not like he can ever express it or do anything about it, Galactus really hasn't allowed him any wiggle room to resist his will.

Eventually it becomes the status quo that Galactus gotta eat, and people die when he does. The Silver Surfer forgets about home, forgets about what he's doing, and really just gets into doing what Galactus wants and leaving all the deep thinking to the time he gets alone between meals.

Then comes Earth. it's a long story, but in the end, Norrin remembers what love is, and in the process gets the equivalent of being forced to sleep out in the barn with the fieldmice. Thing is, he learns to like the fieldmice. At this point he pretty much hates Galactus, and since he survived the last tangle he had with him, thinks he can at least successfully resists him if he needs to.

The real secret of this situation is that Galactus is learning what loyalty is too, and actually has a soft spot for the Surfer. This is why he didn't just straight up remove his mind entirely or execute some nasty punishment to seek his compliance. He did, however do a lot of pretty low things to manipulate the Surfer's psyche, and even took his capacity for emotion for a while, trying to get his lap dog to sit properly.

Eventually, though he and the Surfer and come to terms, deciding that the Surfer keeps his free will and power cosmic and they separate amiably with the idea that when called upon the Surfer will have Galactus's back, and that he doesn't mess with Galactus's feeding schedule. For a while, it's a situation of mutual respect.

Since that day there's been a lot of shifts in their relationship, but the Surfer has learned that Galactus is as deep and complicated as a creature who had been alive since the birth of the universe should be.

The truth about how he feels is...all of the above. He hates him, loves him, fears him, respects him, understands his place in the universe and despises it regardless. He has seen Galactus be petty, noble, idle, decisive, let others die callously or risk his entire existence for his own reasons.

Galactus is the entire reason for his existence as the Silver Surfer, he is the cause of the very evil things that have happened to him and his people, and every good thing that has happened to the universe due to the Silver Surfer was ultimately because of Galactus, as well. Can you describe all of your feelings about the beings that created you in one word? In one sentence?

Norrin Radd probably can't, and neither can I.


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

[User]
CMV: The Good, The Bad, And The Ugly is the greatest western film ever made.

I'll start right off the bat with stating that the main purpose of this thread isn't intended to be "let's shit on The Good the Bad and The Ugly", it's to present other westerns that are possibly superior to it.  The Good, The Bad, And The Ugly has it all.  It's got three great leading actors.  Clint Eastwood is an absolute badass, and at his very best in the film as Blondie.  Eli Wallach similarly gives the performance of his career as Tuco, a character that is humorous, that you can't help but like even though he is a disgraceful human being.  Lee Van Cleef is always excellent, and as Angel Eyes he presents a character who just wants to make money, and will do whatever it takes to accomplish that goal.  The story is riveting throughout the nearly 3 hour runtime, a true epic of cinema.  The civil war backdrop works so well with the race to the treasure in the foreground.  The final standoff might be the greatest standoff of all time, this one is tricky for me because I really love the standoff from For A Few Dollars More (so much emotion in that one!).  I saved what might be the strongest element for last:  THE SOUNDTRACK.  Oh my goodness!  So good!  Even if you haven't seen the film, you have heard the soundtrack, and associate it with the western genre.  My man Ennio Morricone knows how to score a film, I'll tell you what.

[Assistant]
The Good, The Bad, And The Ugly is a great Western of its subgenre, but it fills only one niche in a wide field.

Blazing Saddles, for example, has great leading actors, many of whom are legends in their craft. Mel Brooks, Cleavon Little, Gene Wilder, Madeleine Kahn, Harvey Korman and Dom DeLuise, all had stellar stage and cinema careers.

It touched on many issues; civil rights, government corruption, disability, urban renewal and more, all with a light enough hand to keep the audience engaged.

The score by John Morris was also excellent, helping set many scenes and adding to the hilarity.

Cinematically, Blazing Saddles amplified the third wall breaking innovation of auteurs like Jean Luc Godard by bringing the techniques to a wider audience.

There's no doubt The Good the Bad and The Ugly was a great film as you say, but it's great within its traditional Kurosawa-derived Western limits. Blazing Saddles transcends those limits, and is therefore clearly a greater Western.


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

[User]
Hiring question

I am a faculty member at a rural two-year college. I have just been assigned to be part of hiring committees for a new department chair and a new vice president for the satellite campus that I teach on. What kind of questions should I be asking, or what kind of information should I be seeking out, in the interviews? Thank you for your input.

[Assistant]
Chair:

* How do you see your role as between faculty and administration? Try to tease out if they are a coalition builder or a divider. Does your school have a contentious relationship between faculty and admin? Or is it more collaborative? Do you need a chair who is going to fight for your faculty or one who will build relationships? Do you need someone who just transmits info from admin, or one who creates policy?
* How will you support faculty as they prepare for tenure or promotion? How do you support faculty who have already gained tenure or promotion?
* How have you dealt with / will you deal with faculty who are not meeting expectations?
* Various behavioral questions, various targeted questions applicable to your department/campus. What's something specific to your school that has caused problems in the past? Ask them something about that.

VP: What are they going to be VP of? This is going to affect the questions...are they staff side or faculty side? The VP of Student Affairs is different from VP of Academic Affairs (or whatever). The VP of a satellite campus could wear a lot of hats or have a strict focus. No matter what, ask about disaster planning and support for faculty in "these trying times..."


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

[User] If I injure multiple ants in a given area, would they go back to the colony and warn the rest of the ants not to go there?

[Assistant] Actually, when ants are injured, their body sends a chemical signal that other ants pick up on and come to rescue the first ant. That is why if you kill one ant, one will come along soon, and if you kill that one, another will come looking for it.


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

[User] ELI5: Why humans fat mostly stores, or at least shows, at the stomach and doesn't so the same effect on the back.

[Assistant]
There is an evolutionary advantage to having the majority of your mass close to (Edit: close to, or slightly below) your center of gravity. Having fat evenly distributed around the body would mean that movement of arms and legs would require more energy. Keep in the limbs relatively lighter than the torso makes it more energy-efficient to move (think of how alloy wheels are used in performance cars - that's because lighter wheels need less energy to rotate them fast).

Humans evolved to be able to walk long distances. We can outlast almost every single land animal in terms of endurance because walking on two legs takes less energy. Keeping those two legs light is a huge advantage too. Having all the fat stored around the middle (tummy and butt) makes it easier to maintain balance. If we had big arms and thin legs, we would be top-heavy and easy to topple over.

Basically it is all about saving as much energy as possible, and being as agile and stable as we can be.

As to why it doesn't collect or show on the back ; presumably because we evolved from creatures walking on all fours (see dogs, cats, cows, etc - all have their spines as a support structure, while the fat hangs below).

So before we walked on two legs, several species previously, we too used to have the same structure where our spine acted as a support beam and all our organs and fat would be suspended below it. That also kept the center of gravity as low as possible, making those animals much more stable. When we finally stood up on two legs, there was no evolutionary disadvantage to continuing storing the fat in front and so it persisted.