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

[User]
Why are amalgomations of objects around a gravity source roughly disc shaped/flat? (ie Saturn's Rings, the Solar System, or the Milky Way)

I would not necessarily expect gravity to align randomly distributed objects into the disc shape that seems so prevalent. Will objects distributed in a random spherical shape around a large gravity source always eventually collapse to a disc shape in a way that is calculable based on the initial distribution of the objects? Or is there something else at work?

[Assistant]
You're really talking about three different things.

Consider a galaxy. It can be nearly any shape you can think of: spherical, elliptical, lens-shaped, or just blobby, like a cloud. Some galaxies in particular have a spiral appearance. These are the ones you were most likely thinking of when you asked the question.

As to why a spiral galaxy has a disc shape instead of any other shape, it has to do with angular momentum and self-interaction. A collapsing cloud of uniformly distributed dust will inevitably have some net angular momentum. As the cloud continues to collapse under its own gravitation, the dust interacts with itself such that particles with orbits outside the plane of the cloud's overall angular momentum tend to get perturbed into orbits that lie within the plane of that angular momentum.

The solar system is thought to have formed in basically the same way; not from a truly uniform cloud of dust, but the overall principle is the same. The planets in our solar system lie in a plane  mostly  because that's where the *stuff* was from which the planets congealed.

As for Saturn's rings, there are two conflicting theories about where they might've come from. One theory says the matter that makes up the rings used to be a moon  a moon with a name, believe it or not; it's called Veritas  that dipped too close to the planet and was pulled apart by tidal forces. In that case, the rings occupy a plane because the moon was orbiting in a plane when it came apart.

The other theory is that the matter that makes up the rings is stuff left over from when the planet and its moons first formed, but because of its proximity to Saturn it was unable to congeal together into a moon. In that case, it occupies a plane because the same principle that pulls spiral galaxies into a planar shape also pulled the protoplanetary cloud that became Saturn into a disc.

So basically it all boils down to conservation of angular momentum. Once you set something in rotation, that rotation doesn't go away, and due to self-interaction of clouds of stuff, it in fact tends to become more and more well defined as time goes on.


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

[User]
Why aren't polar deserts sandy?

I realise there's no requirement for a desert to be sandy, but I'm wondering if there's a particular reason that the polar deserts on Earth are nearly all rock or gravel rather than having sand. Is there a reason for it, or is it just one of those things? Is a sandy polar desert on an earthlike planet possible? What conditions would need to be met for a polar desert to become sandy?

[Assistant]
Eolian sand systems commonly associated to deserts (think of the golden dune fields of the Sahara), require a source of sediment. In the case of the Sahara for instance, there was a pre-existing layer of sediment emplaced during the Holocene Wet Phase. When aridification went hog-wild and the rains failed, this sediment layer was remobilised by eolian processes. These processes essentially did three things:

* They picked up fines as suspension load, such as clay minerals, and lifted them into the upper atmosphere;

* They moved sand-sized particules as traction/saltation load along the desert floor;

* They isolated areas of coarser material through deflation  (lag).

Of these fractions, the sand is interesting as it provides an erosive force susceptible to abrade coarser fragments and *in-situ* bedrock to generate additionnal particulate material. In other words, "Sand blasting" is a powerfull motive force to producing more sand.

Back to the poles now, or Antarctica really as the North pole is an ocean. Antarctica's dry valleys at the small end of the scale for deserts, And there has'nt really been a prolonged period of rainfall to get sedimentation and erosion going for a long long time. So there is very little sediment to work with from the start and get things going, on one hand. And when what little sediment is present gets remobilised, it gets relatively limited opportunity to interact with the substratum and generate additionnal sediment before getting carried away over the icecap.


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

[User]
ELI5: How do space probes fly such far distances without damage or fuel?

I read voyager 1 is almost out of the solar system!

How is this even planned?

[Assistant]
Distance: An object in motion stays in motion. There's negligible resistance in space, so once they've undergone the initial acceleration, they'll just keep going in that direction.

Damage: space is empty. Very empty. So empty that we don't even have to account for the asteroid belt when we fly right through it because it's unlikely they'd we'd get close enough to see any asteroids, much less hit one. There is wear-and-tear from dust and radiation, but probes are built to withstand that.


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

[User] [Marvel] If Ghost Rider's Penance Stare was used on Iron Man, would he feel the pain of all the people that got killed by guns he made, or would only the ones he directly sold count?

[Assistant]
Only the sins he committed.

It's not a sin to make a tool, it's a sin to use that tool. He would likely feel the pain of all the people he himself hurt who didn't deserve it, but not those indirectly.


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

[User]
Does math objectively exist?

I've always thought that math has an objective existence without humans. But someone on reddit has told me that it is a human creation? Does math objectively exist without humans? Can we "create" mathematics, or can we merely "discover" mathematics?

[Assistant] A supermajority of philosophers of math say that yes, it objectively exists. It probably helps to know that when these people talk about math they mean two different things. The facts objectively exist, but the human classification methods and human quantification of them is created. Imagine it like taking a picture of a mountain. You can call your picture the mountain if you want, but you created the picture. However, the mountain obviously existed before you took the picture. But people can be confused if you use the word mountain to refer to both your picture and the item itself. The word math refers to both the objective facts and the human interaction with them. So it makes sense people get confused.


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

[User]
How is the speed of a space probe measured?

We often hear that "probe A" is leaving the solar system at a speed of XXX km/h with a very specific speed. But if I remember my science courses correctly speed is always relative to something. And that something moves in space (e.g. the Earth moves around the Sun, the Sun moves in the Galaxy etc.). Shouldn't this influence the speed given for a probe (or even a space rocket)?

Thank you for your answers !

[Assistant]
Yes, velocity is always relative to something. In the case of probes leaving the solar system, we use the Sun-Centered Inertial (SCI) reference frame: The origin in the Sun's center of mass, the X axis points to the vernal equinox along the ecliptic plane, the Z axis points North along the Sun's rotation axis, and the Y axis is 90 ahead of the X axis along the ecliptic plane following the right hand rule. (The ecliptic plane is the plane of Earth's orbit).

There are other reference frames used for different missions; notably most satellites in orbit around Earth will use Earth-centered reference frames instead. Some of them are fixed with respect to distant stars, others rotate with the central attracting body (these are non-inertial frames), e.g. WGS84 is an Earth-centered rotating reference frame that you may know well because it defines latitude and longitude as shown by your phone's GPS receiver.

So if you've heard things like "Voyager is leaving the solar system at 17 km/s", that's relative to the Sun in the SCI frame.


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

[User] Why do other mammals not get food poisoning from eating raw meats yet humans do?

[Assistant] Humans are physiologically between carnivores and herbivores. Our digestive system is about 5-6x our body length. Carnivores generally have much shorter digestive systems, maybe 1-3 times body length, This means food is in their bodies for a shorter time, giving bacteria less time to produce toxins. Carnivores also tend to have much stronger stomach acid (dog stomach acid is about 10x stronger than human) which means fewer bacteria survive digestion.


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

[User]
[Half Life] Why didn't the combine eliminate all the humans after they won the 7 hour war?

I always wondered why the combine keep Dr. Breen and a small pocket of humanity alive. They clearly pose a threat and have formed a resistance.

Are they similar to the Borg in that they need other organisms?

[Assistant]
All human life will die... once the Combine is done with them. It boils down to 2 stages. In the first stage, humanity is used as a brute labor force to assist in the looting of Earth. In the second, humans are used as the base stock for a new slave caste, modified to suit the Combine's purposes. When everything worth taking is gone, what remains of unmodified humanity will be left behind in the husk that was Earth to await extinction. Nothing that we today would identify as human would last much longer.

When Half Life 2 starts, the transition between phases has already begun. If left to their own devices a while longer, the Combine would have driven humanity extinct in just a few more years.


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

[User] [Warhammer 40k] I'm a normal, non-heretical dude living with my family on a relatively uneventful human settlement in this universe. What does my average day look like?

[Assistant]
By weight, it's most likely that you're a lowly worker on a hive world who spends his day carrying out a task on an assembly line, just because hive worlds have so many people on them.

*But...* while everyone likes to jump right to that because it's common, it's misleading to think that's a good picture of the Imperium. You could be support crew for a military organization, doing paperwork or other non-combat tasks. You could be a farmer on an agricultural world. You could be a subterranean gang member who'll probably die before he's 25 never having seen the sun. You could be a white-collar worker, an accountant, or on staff at a religious institution; you could be a schoolteacher or trainer. You could be a hunting guide on a pleasure world who helps the rich and stressed-out unwind by bringing down mighty beasts. You could be living out a sleepy, rural nineteenth-century life on a planet that's hard to reach and disconnected. You could be local law enforcement or a prison guard or a doctor or a firefighter.

There truly is no one answer.


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

[User]
eli5: Why were laugh tracks so widely used on sitcoms in the past? Did people not know when they were supposed to laugh?

Im rewatching some older sitcoms and the laugh track is so odd to me.  I remember thinking nothing of it growing up, but now that Ive been watching sitcoms without it, it feels completely pointless.  Who thought it was a good idea and why?

[Assistant] Originally sitcoms were filmed with an audience, and you would hear their reactions. In the 60s, TV networks tried inserting laughter into sitcoms, and discovered that focus group audiences found the shows much funnier than with only "natural" laughter. So yeah, it does work. Laughter is contagious. Humans are weird.


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

[User] If I flip a coin. Tails I stop and heads I flip again. What will be the average coin flip before I stop?

[Assistant]
The number of Bernoulli trials performed until a success occurs follows the so-called *geometric distribution*. If the success probability is *p*, then the expected number of trials required for the first success is just 1/*p*. In other words, on average you will flip the coin twice.

**edit:** That's boring though. What if you flip until you get tails followed by heads (TH)? Not surprisingly, it takes, on average, 4 flips to get TH. Now what if you flip until you get two tails in a row (TT)? Turns out that it takes, on average, 6 flips to get TT. Kind of makes you question your intuition on the 4 flips for TH, right?


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

[User]
CMV: Stealing from a department store like Wal-Mart is not immoral.

When I filled out an application to Wal-Mart right out of high school, one of the survey questions asked if stealing from Wal-Mart is a victimless crime. I can't think of one person who is actually hurting from this type of theft.

I would consider it better than downloading copyrighted media. Downloading copyrighted music can prevent an artist to make the money they should have received, which is a lot less than the money going in department stores. Stealing from a Wal-Mart and stores like it doesn't even affect a single worker's pay. In the end, I'm guessing it can only hurt the Wal-Mart family, who are currently sitting on a ridiculous fortune. I cant even imagine them caring about theft in their store.

I'm not saying I steal from Wal-Mart,  and I'm not justifying theft. This is simply for the sake of the survey question. I currently work there to pay for college, but I can't think of one honest victim of theft. I understand that technically theft keeps the money from someone's hands, but who is that and do they really care?

[Assistant]
Stores factor in theft when it come to operating expenses. Every store has to earn x amount over operating expense. Higher expenses means the store has to earn more money. Higher theft means higher expenses. The store either has to pay more for security and this increase costs or just simply increase costs.

the more people steal the higher everyone has to pay for items.


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

[User]
CMV: Sanders and Warren will beat Biden if (and only if) one drops out and runs as the other's vp NOW

Assuming that Sanders and Warren are both ideology-driven candidates, running for the primary purpose of furthering their (mostly overlapping) agenda, they should form a running coalition in which one drops out to run as the other's running mate, thus giving them a fighting chance at one of them getting the nomination.

The number of progressive voters isn't large enough to beat Biden if Sanders and Warren split the vote, but almost certainly is if it is coalesced.

Currently, RCP has the following poll averages:

Nationally: Biden: 32.2 Sanders: 16.5 Warren: 14 Iowa:

Biden: 24 Warren: 15 Sanders: 14

I haven't looked at the overlap between Sander's and Warren's support (and maybe this would be an effective counterargument) but it seems that they occupy similar policy spaces and I would expect almost all of Warren's support to go to Bernie if she announced that she was running with him (or visa versa). It would almost tie them with Biden immediately, which we would expect given that roughly half of democratic voters identify as liberal and half moderate.

Furthermore, bringing one of the two candidates into the spotlight would allow progressive voters, volunteers, donors, media AND support organizations to focus their attention and resources on one of them. It would also activate and engage disenfranchised progressive constituents who are feeling discouraged about the current chances of either progressive candidate winning the race.

NOTE: I only intend to argue this from a strategic perspective. Really not trying to get into a debate about whether we should WANT any candidate to win, nor discuss the merits of different agendas.

[Assistant]
They share the same voter base, however from the last debate it is clear they don't want to attack each other. Which is weird cause the other "similar" candidates are trying to distinguish themselves from each other.

Likely they made a deal saying whoever of them "wins" (or at least is polling higher) will take the other as VP.  So as long as one of them drops before the primary vote they won't be splitting the same base, so there is no need for them to do it NOW.  Frankly the longer they wait the more the endorsement from the recently dropped candidate will matter.


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

[User]
[DCEU] If Lex hated Superman so much, does he hate Wonder Woman more/as much?

WW/Diana is ACTUALLY from Greek mythology. DCEU Lex hates God. Therefore, it should stand to reason that  if Lex had extensively researched the metas and supers  that he should hate WW even more than Superman.

[Assistant]
BvS suggests that Diana hadn't been active as Wonder Woman since WWI, and even then she's was sort of on the downlow as far as history remembers, and her divine origin might not even be know to Lex.

Superman on the otherhand is in Metropolis which is Lex's backyard and is the prime example of what a metahuman is to Lex and the world at large, which would put him higher on Lex's shitlist.


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

[User] ELI5: Do plants have unique DNA like humans? For example, if there were two gardenia bushes and a flower fell to the ground, could it be determined which one it came from like genetic testing etc on humans?

[Assistant]
Sort of?

Plants reproduce sexually like humans and animals, that is what seeds and pollen and stuff do and when they do that they they have different DNA.

plants also have a thing that animals don't, where you can slice a part off a plant and if you plant it carefully it will keep living and growing into a new plant pretty easy. People that make fruit and flowers and stuff love this, you can get a nice plant growing then slice parts off it forever and ever to make exact identical copies. So a lot of stuff like flowers and fruit are just 'cuttings' of other identical plants. Like we don't ever plant banana seeds, there is just one banana plant that everyone has copied over and over for decades.

So some sorts of flowers, yeah, you could find the bush, but some are grafts or cuttings and are basically endless natural clones.


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

[User] ELI5: Why does too much sleep cause headaches?

[Assistant] You sleep in cycles of REMs. If you complete a cycle you feel good even if you only slept like 5 or 6 hour. If you wake up in the middle of a REM cycle you feel tired. sleeping too much can make you wake up before completing cycles because you have had enough sleep already. Also lying too down the whole night inhibit blood circulation.


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

[User] [Harry Potter]We got a new teacher and he said he was here to teach is Evocation Magic. What can we expect to learn from him?

[Assistant]
Is he six and a half feet tall with a duster?

Immediately tell everyone to never mention Memory Charms.

Other than that you'll learn how to make fire lasers, eruptions, move large amounts of dirt around, and how to properly manipulate energy.


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

[User] What makes Jupiter's giant red spot red?

[Assistant]
The spot actually changes color. Ranging from dark red, to white, to blending in with the clouds around it.

The spot is a stable vortex caused by opposing currents of hydrogen and other gases that make up Jupiters atmosphere.

The reason for it's color is not known precisely but has something to do with the chemical composition which differs from that of the surrounding gases due to the nature of the disturbtion of gases caused by the vortex. The color difference could also have to do with the altitude difference between the gases in the vortex and the surrounding area which again would change it's chemical composition altering the wavelength of the subsequent light reflection.


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

[User] ELI5: Why are some letters basically the same capital and lowercase (O, W, P) and some vastly different (G, E, Q)?

[Assistant] Our alphabet is derived from the Latin alphabet.  The Upper case is essential the Latin.  The lower case alphabet is derived from the Latin through an intermediate font called Carolinian minuscule.  This is a smaller font derived from the Latin alphabet designed to be easy to read and quick to write.  Changes were made to some letters to make it easier to distinquish them.


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

[User] What is the most important piece of evidence for evolution?

[Assistant] Pardon me for saying so, but this is a strange way of looking at "evidence."  There is a massive body of evidence that demonstrates evolution - why would you bother trying to pick out one little piece?


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

[User]
[Batman:TAS] In the Gray Ghost we see that the year is 1992. What caused this Dark Deco stagnation?

The world is very different than ours.

[Assistant] Gotham City looks like that, but Metropolis in the same time looks like a gleaming sci-fi future. It's just the difference in architectural taste, the mood of the residents (pessimistic vs. optimistic), and Gotham probably has older construction since it is more economically depressed than Metropolis, which is fairly well-off.


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

[User]
Can undersea cables undergo creep rupture?

The pressure down there must be quite high. Is there any proof that undersea cables have undergone creep?

[Assistant]
Submarine cables used to fail for lots of reasons. Modern ones fail for three reasons: manufacturing defects at joints, dragging anchors close to shore, and deliberate interference.

In modern material terms the pressures involved are not that impressive. Transocean cables are laid at around 3-4km depths, which is only 400atm pressure. Yes, that's a squeeze, but it's a long, thin, solid structure. The external pressure is applied uniformly along the cable, so creep is not an issue.

Modern (laid in the last 15 years) cables are capable of operating for many decades unless cut accidentally or deliberately.


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

[User] Why is green always used in special effects like green screens? Why not yellow or purple or red?

[Assistant]
In theory, any color screen could be used. However, there are a number of reasons why green is preferable over other colors.

First is the nature of the subjects in front of the screen. In most scenes with a green screen (or the more technical term: chroma keying), humans are the main subjects in the scene. Humans tend to have very little green in their skin or their clothing, which makes it easier to replace the background without accidentally replacing part of the subject.

Another reason is more technical in nature. Digital sensors don't record R, G and B with the same level of detail. This is by design. A pixel in a digital sensor can only capture the total light intensity. In order to capture color detail, each pixel is fitted with a filter that only lets a certain color through. So you'll have red pixels, green pixels and blue pixels. A full color image, where every pixel can have a full range of colors, is reconstructed using this limited information. Since human vision is more sensitive to green than to other colors, the commonly used approach is to divide the sensor into blocks of 2x2 pixels and giving 2 of them a green filter, and the other 2 are used for red and blue. This is called a Bayer filter.

Because of this, the raw image data contains more green information than red or blue. That means that green features will have a higher resolution. Since the quality of chroma keying is very much affected by how accurate you can record the edge between the foreground subjects and the background screen, the increased resolution of the green channel allows for more accurate cutouts of the background.

Note that in the time of analog film, blue screens were more common, since the chemical properties of analog film resulted in a higher level of detail (reduced grain) for blue elements.


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

[User]
[Avatar: The Last Airbender] Why wasn't Azula offered the chance to become a better person?

By the time of Sozin's comet, Azula had completely shattered as a person. Everyone had left or "abandoned" her, which took a toll on her mental state.

Even Iroh, a man who is a believer of redemption and self-improvement, stated that Azula had to be 'put down', because she was crazy. Why didn't he -- or anyone, for that matter -- try to reach out to Azula like what happened with Zuko? Zuko became a MUCH better person, though not without enduring several trials.

[Assistant]
It's not like Iroh just took Zuko in and magically changed his entire character into a good person. Iroh saw that Zuko already was a good person at heart and wanted to nurture that side of him.

Azula on the other hand has never shown a shred of compassion towards anyone and has acted like a psychopath from early childhood. She is just too far gone for him to do anything. Ever her mother thought Azula was a monster.


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

[User]
[Harry Potter] If Molly Weasley had died in her duel with Bellatrix, would Ginny be protected from her with the same ancient magic that protected Harry from Voldemort?

Title pretty much sums it up. In the movies, Bellatrix attacks Ginny which causes Molly to step in and protect her. Molly ended up winning that duel but if she hadnt, would that have activated the same magic that protects Harry from Voldemort while at the Dursleys?

[Assistant]
I believe the suggestion is no. For the same reason that James death didnt protect Lily. Its not enough to die in the defense of someone else, you have to fully sacrifice yourself for it. Lilys sacrifice worked because she didnt fight back, had the opportunity to be spared, and chose neither of those options.

Molly was fighting. That removes the possibility for giving her protection. She also, once she and Bellatrix were engaged would not have been given quarter and would therefore not have the option of being spared.  Would she die so Ginny would live, almost certainly, but if thats all it took there would be a lot more people under that spells protection.


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

[User]
What's on the other side of a belly button?

If someone was to cut open my abdomen, what would they find on the inside of my navel?

What would they have found if they looked when I was just born?

[Assistant]
When you were a fetus, the placenta contained the umbilical vein for nutrients and all that goody stuff.

The umbilical vein runs from the navel to the fetal liver and through a vessel to the fetal heart. After you're born, it closes up and basically becomes a twisted fibrous cord.


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

[User] [James Cameron Avatar] Why are the navi able to link with the wildlife?

[Assistant]
To put it short, it could be evolution, it could be intelligent design.

To put it long, without a lot of up close and personal research into the development of the planet, we will never know and can only speculate.

What the Navi have is basically a form of perfect Symbiosis, that they can link with pretty much all forms of life on the planet. Evolutionarily speaking, this is an amazing trait to have for survival, not just of your species but literally of everything around you. They could be a species that branched off of what created humanity, to become Navi, that is centuries older than ours. They could also be in way more immature stage, and could have a while to go towards mechanical evolution.

Then to take the approach of Intelligent design, it would be an interesting experiment to see how intelligent omnivorous life responds and grows around semi sentient, and some semi sapient life that it can symbiotically link with. That begs the question of who brought it here, or designed it, but those kind of questions always take a while to get to the conclusion of.


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

[User] [MCU] Why is Klaue hunting for Vibranium in Black Panther when he was made a billionare by Ultron?

[Assistant]
Because he's not doing it for money. He's doing it because he can.

Sneaking into the most advanced nation on the planet, stealing their most guarded materials, rubbing it in their faces and then leaving with them impotently stamping their feat and roaring behind him?

It's the thrill of getting one over Wakanda not just once, but over and over again, knowing that he's the best that draws him in.

Sure he could just tell the world about Wakanda and watch as the new Oil Rush sets in and SHIELDRA sends in 100 B52 bombers with nukes to send them back to the stone age and get one over them that way... but he wants the personal satisfaction of victory.

It's even more personal after they branded him as well, every time he wakes up and looks in the mirror just resets his determination to show them just how much of a failure they are, how they can't catch him.


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

[User]
ELI5: How does LiDAR work, and how is it able to be so accurate?

I get that LiDAR works like Sonar and Radar, in that it sends out a pulse and measures the time which it takes to return to a sensor. I don't understand how we are able to measure precisely, when the time it takes light to travel the distance seems to be too small to measure. For example, if a person is five feet (1.524m) away from a LiDAR system, it would take about five nanoseconds for the light to travel one way, and about five on the way back. This is ten nanoseconds. Do we have the ability to measure this time with enough precision, and use the speed of light to determine distance? Or is there something else going on?

[Assistant]
Yes, there is something else going on. The LiDAR typically uses a technique called optical heterodyne detection, which allows for more precise time of flight measurements than a given clock speed would otherwise allow. Even with picosecond accuracy (one trillionth of a second!)

Imagine youre at a wave pool. The wave maker starts making a whole bunch of waves. When one of them hits the end of the pool it bounces off the edge and a smaller wave goes back towards the wave maker. When the top of that little guy gets to the wave maker, the wave maker can see it! Since the wave maker has been making all its waves exactly the same size and length, it can compare where it is at in the cycle to the top of that returning wave. Halfway through making another wave? A quarter?

Light moves so fast that in LiDAR applications, whatever distances were usually interested in, the light gets back before were done making another wave. And since we can figure out how much offset the returning wave is from the one were making, that gives us more precise time-of-flight than our clock can even measure.


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

[User]
[RPGS] Why do I keep finding fragments of journals spread all around instead of one place?

I can never find them in just one place or book? Why would someone tear out pages or type entries in different computers around the wasteland?

[Assistant]
Possibilities include:

1) There are many copies of the one journal, all of which were almost completely destroyed except for a page or two.   The same thing might be said of trying to recreate some old form of boat or machine, and there are very few of the parts still around.  Only the diligent will assemble a fully restored stock version.

2) The journal was written by someone with "Johnny Appleseed Kinetic Assembly Sickness" (JAKAS Disease) who wants to 'seed' his manifesto about the world.  Instead of copying it, he puts a page here and there.

3) Its a holy relic, and pieces of the 'One True Journal' were take by the faithful to places of worship scattered about the world.  Generations later, the worship has faded away, but the relics remain.

4) Ooooh, shiny!   Some animals found the pages of the journal useful for something, like nesting material.  Indestructible nesting material.  Now, hundreds of years later, the nesting material has been used countless times but it scattered everywhere.

5) It was a collectible.  Not holy, but cherished for some other reason, like "the mad writings of that famous screwball wizard" or 'forget the words, the illustrations on the other side of the page are amazing art" or something.  As such, collectors put them in their deepest safespots.  Now, generations after those collectors have died off, only the vaults (and vault keepers) are left.

and so on

Or for the boring reason, its a scavanger hunt to test for a worthy hero, blah blah blah.


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

[User] ELI5 how does torrent system work?

[Assistant]
In a traditional situation, you have a Server and a Client. The Server is basically a big computer that handles the request of the Client, if you for example want to download a legal copy of a movie, the server would send it to you.
That has the advantage of having a clear and simple structure and depending on the server, a reliable source for your movies.

A torrent system is a peer to peer system, which means there are no dedicated servers, just clients, but everyone fullfils a little bit of the role of the server.
If you want to download another legal copy of a movie, you would not download it directly, but download a file that basically tells you what you need to download, your client will than ask every other client if they can provide it to you (which is called seeding) and you download it from many different sources.
The whole system relies on the premise that you make yourself available for seeding after that, so far that you can only download if you seed at the same time.
It is basically a decentralized version of a server, stretched over many clients.


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

[User]
[Paddington Bear] Why does Millicent think killing and taxiderming Paddington will bring her wealth and fame? The British public don't seem to view Paddington as any different to a human child.

In the 2014 film, Paddington Bear, taxidermist Millicent Clyde repeatedly tries to capture Paddington, a sapient Peruvian Bear, so she can taxidermy his copse and become famous.

However throughout the film the general public seem to be well aware of Paddington's existence, to the extent that they don't seem to be fazed by a talking bear cub and even treat Paddington no different to a human child. I'm assuming that if Paddington's corpse suddenly appeared on display in the national history museum it would not be one of the greatest scientific discoveries, but rather one of the most horrific crimes in British history.

So is Millicent just a mentally deranged butcher trying to skin and taxidermy a kid, or does she legitimately believe that killing a sapient bear cub (who is acquainted with london's police btw) is her ticket to a life of fame and fortune.

[Assistant]
The Sapient Peruvian Bear, when active, exerts a mild memetic effect causing any other sapient organism to perceive it as equivalent to a member of their own species, despite knowing that it is in fact a bear, and not to notice anything abnormal about the situation.

Some individuals are, for unknown reasons, partially or entirely immune to this effect. Ms. Clyde either does not see Paddington as equivalent to a human child, or *does*, but notices that this is strange. The latter would be more likely, since most humans would be reluctant to harm any sapient organism, regardless of genetics; a creature with the power to manipulate one's own sense of reality, however, would be quite likely to inspire a homicidal, or rather ursicidal, response.

Presumably, upon Paddington's death, the memetic effect would cease, at which point Paddington would appear to be simply a dead bear. Ms. Clyde could still be condemned for the murder of a sapient being, but would perhaps not inspire as much instinctive horror as the murderer of a human child with Paddington dead and his memetic power broken.


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

[User] ELI5: Why are Americans frequently labeling socialism as un-American when FDR's socialist New Deal programs helped solve the depression in the 1930s?

[Assistant]
The American left would certainly make the argument that the New Deal demonstrates that we shouldn't be so scared of socialism. The right would reply that the New Deal didn't actually end the Depression.

FDR has a rather complicated legacy in American politics, which that just scratches the surface of.


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

[User] [Star Trek/Marvel] Wolverine gets transported into a Borg cube. What happens?

[Assistant]
So, first he probably stands around and looks confused. Then a drone bumps into him on its way to perform some function, and he pushed back.  It ignores him, so he punches it while saying something that ends with 'Bub.'

Wolverine is now classified to the Cube as a Threat. Several of the nearby drones scan him and determine a unique endoskeletal structure, and that Wolverine is already part machine, albiet very primitive. The Queen, millions of light-years away but connected by the collective link via their Transwarp communications net, takes notice, and directs Wolverine to be assimilated.

A drone comes up behind him and attempts to subdue him. He slices off its arm and then its face. More drones approach, and are dispatched with similar ease, until, approximately 20 seconds later, his claws bounce off a kinetic energy shield. Wolverine doesn't catch on right away and spends another few seconds furiously clawing at the drone.

Eventually, he realizes that this is not going to work. A drone reaches out and attempts to inject him with nanoprobes, but Wolverine dodges or blocks this easily. More drones approach, threatening to drown him in bodies, so he cuts away the gantry they're all walking on and swings down to a lower level while the drones simply fall.

This phase of the battle continues until the drones have had their implants modified to give them a certain level of gymnastic grace, or Wolverine hits the lowest deck of the Cube and the tactic is no longer viable.

Wolverine starts to flee in earnest. The collective, being a hive mind, easily sets up ambushes. Wolverine avoids them by narrower margins each time until he stumbles into the trap they've laid for him. A cloud of nanoprobes goes off in his face and he breathes some of them in.

This will be the Cube's final mistake.

By this time, the Borg have managed to injure him and have observed his healing factor. They want it for themselves. They *need* it, it will allow them to perfect themselves and then all other biological life forms. But they didn't count on how powerful it is. Wolverine has come back from being a bare skeleton before. The first nanoprobes into his system don't know what hit them. His immune system smacks into them like a black ops team taking out a three-legged puppy.

Wolverine realizes the cloud is some kind of poison or trap, and holds his breath, but the Borg fog the whole ship, and he can't run *and* fight *and* hold his breath, and soon he breathes in more, better adapted nanoprobes. They hold off his healing factor long enough to build a small comms transciever against his bones and use them as an antenna, and begin sending his genetic code back to the collective. They begin building other structures in him. Ocular implants. joint servos. Abdominal plating. Making him better. Stronger. More durable. One of the Collective.

They follow their programmed course and build a Collective uplink and shield modulators into him, at which point they have lost. Minutes may pass, or only seconds. Wolverine's healing factor drops the scattered defense on the rest of his body and begins healing his precious brain-meats. Their knowledge of how their shield adaptations work is passed to him along with the rest of their knowledge. He is hammered on all sides by information, some of which is *how to kill them*.

If the borg are very, very unlucky, the automatic nanoprobe course may have added a disassembler field to his claws, but it won't make that much difference. Wolverborgs healing factor allows him to retain his individuality, if not his sanity, and he begins shutting off Borg shields just long enough to tear out their spines. His healing factor means he doesn't have to regenerate. His healing factor purges the lactic acid in his muscles and keeps replacing the matter that the nanoprobes have cannibalized to build more machines.

Either he carves his way out of the cube to drift in space while his body finishes pushing out all the machinery, or the Borg blow up the cube in self-defense before he can infect the rest of the network with his individuality. Either way, he's adrift in space until another ship picks him up.

Wolverine vs the Kazons is not even worth documenting. He just wins.


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

[User]
ELI5: when watching traditional TV, why does a split second of the wrong commercial play sometimes?

I see this happen on all kinds of networks, how does the commercial load and why is there sometimes a mistake?

[Assistant]
Usually it's due to a mismatch between their national and local feeds.

Often with traditional TV the actual show you are watching is being broadcast nationally (or across a wide area) and just relayed automatically by your local TV station to their broadcast towers. But the adds you watch are sometimes tailored to your specific town/city so these are broadcast locally. Because they're on two different systems there's sometimes a lag between the two which is what causes this split second delay.

You'll notice this is more likely to occur on adds for local companies because they're the ones more likely to come from the local broadcaster.


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

[User] [MCU] Did Peter get his powers from a radioactive spider like the comics, or a genetically-engineered spider like the previous movies?

[Assistant] All we know for sure right now is that Peter in the MCU was bitten by a spider and got powers from it. We don't currently know what branch of science, magic, or extradimensional energy caused this bite to give him superpowers.


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

[User]
[Warhammer 40.000] If the Emperor did die, and rise as the fifth Chaos god, what would his overall theme be?

Khorne is about strength, bravery, justice and martial honour, Slaanesh is about sensation, Nurgle is sickness, endurance, life, death and renewal, and Tzeentch is change, hope, ambition and progress.

What would Chaos Emperor be about that isn't just a repeat of some of the above?

[Assistant]
I saw an intesting argument about this- he'd be Fear.

Not only is it the only major emotion missing, it fits his *modus operendi* and nature perfectly, right?

His whole personality the desire to protect you and yours so intense that you're willing to burn the galaxy to do it. Preemptive destruction of everything that could possibly pose a threat to you- you fear aliens, so you massacre every sentient being in the galaxy. You fear chaos, so you crush all freedom out of humanity. You fear war, so you create the greatest army possible and plunge everything into eternal conflict. In the same way the Elder go so consumed with lust they made a deity, the Imperium has dedicated every part of their society to stoking and enabling their fear, so that's what they'll make when they collapse.

The Chaos God of Terror, Paranoia, Self-Defense, Xenophobia and Sacrifice. What else would the God Emperor of Mankind become?


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

[User]
What was the temperature at Planck time and GUT transition?

During the early Universe the relation between time and temperature is given by
t = 2.4 * g^-1/2 * (T/1 MeV)^-2 s,
where g is relativistic degrees of freedom (which should be 106.75 at above the electroweak transition).

Is this the right formula to use to get the temperature at Planck time (5.39 * 10^-44 s) and similar to get time at GUT transition at e.g T=10^15 GeV?

The degrees of freedom, g,  should grow as we go back in time. Are there any estimates for this at the Grand Unified Epoch and Planck Epoch?

The reason I started thinking about this was that I kind of always though the temperature at the Planck time was just the Planck temperature...

PS: Short answers are welcome :)

[Assistant]
That formula applies exclusively for the radiation-dominated era. You can see that by reviewing the derivation. So it clearly only applies from the end of inflation up to matter-radiation equivalence.

Many people assume the GUT scale is around the end of inflation; in that case the formula should work for GUT and should not apply for Planck.


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

[User]
How do anacondas' stomachs shield themselves against the sharp claws of the prey they devour?

Very few organisms swallow their prey as a whole leaving them no choice but to swallow all the sharp accompaniments too. I was wondering how the claws of the prey don't scratch the insides of anacondas and the like.

[Assistant]
Snakes have a tendency to eat their prey head first, which makes it to where the claws won't catch on the way down. Since the limbs will be essentially bound in position as near everything gets digested, the claws don't have much chance to cause damage to the digestive tract.

I can't say if there's any protections against claws if the snake regurgitates the meal before it has a chance to break down.


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

[User] ELI5: What happens to heat in a vacuum? why is space cold and earth (with an atmosphere) warm?

[Assistant] Heat doesn't really exist in a vacuum.  Space is cold because there's almost nothing there, and almost nothing holds almost no energy.  If there is an object with temperature in a vacuum (such as a human being), the heat stays where it is until it very slowly radiates away.


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

[User]
Why do people appear to not be bleeding in images/videos of surgeries in progress?

Pictures/videos of surgeries always have no blood anywhere, and a gaping wound...they might wipe every now and then, but for the most part, there is no blood.
Is it all anti-anticoagulants?
Do they clamp off all the capillaries? Am I answering my own question?
Why do folks need multiple transfusions then? (during/after surgery)

[Assistant]
While it depends on the type, surgeries do tend to bleed a lot. Superficially there may not seem to be much bleeding, however a large amount of blood may have been suctioned away or hidden, collecting at the bottom of a cavity (e.g. abdominal surgery). However, unless there is truly significant blood loss, there is a tendency towards replacing fluid rather than using blood transfusions.

There are several methods used to reduce blood loss. Most of the surgeries I've seen used a diathermy (rather than a scalpel) - It's a device that uses an electrical current to cut and cauterise tissue, closing the smaller blood vessels/capillaries and preventing excessive bleeding. Laser surgery presumably achieves a similar thing.

For larger blood vessels, the surgeons can throw a few stitches (a ligature) to tie off the blood vessel, or close the vessel with a clip. Prior to tying/clipping the vessel, haemostats might be used to clamp close the vessel. For orthopaedic/limb surgery, a tourniquet can be used to completely occlude blood supply to that limb (which presents risks of ischaemia/damage).

Positioning the patient in a certain way can also reduce bleeding (e.g. a downwards slope with the head and chest lower than the abdomen and legs).

In terms of pharmaceuticals, the anaesthetist can use drugs to maintain a lower blood pressure to reduce bleeding. In scenarios with a high risk of blood loss, drugs can be used reduce bleeding (i.e. antifibrinolytics and coagulants). However, for the most part, patients are often given drugs to *decrease* coagulation. While excessive bleeding is undesirable, surgery also carries the risk of deep vein thrombosis and pulmonary embolisms - so anticoagulation/DVT prophylaxis is usually preferable.


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

[User] ELI5 Why does a home printer need all cartridges if Im just printing black type?

[Assistant]
Two possibilities:

First is the printer is overlapping all the colors to make black. (Not likely)

Second, its made by a scammy printer company that makes their money on ink cartridge sales. If you aren't buying ink, they aren't making money.

The best way to avoid that b.s. is to spend more up front on a laser printer. Especially if you are just printing black/white. Laser printers use toner. It doesn't evaporate like ink does. So it lasts a lot longer. Especially if you don't print often. Inkjets dry out even when you aren't printing, so you lose ink without printing. You spend more to start on laserjet, but will save money in the long run.


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

[User]
[Spider-Man][NWH] Why was Peter against killing in NWH but fine with it in Endgame?

In Endgame, Peter activated "instant kill mode" for his suit to kill a bunch of aliens.

But later in NWH, he doesn't want to send back his enemies to where they may or may not die, risking the fate of the whole multiverse in doing so.

[Assistant]
There is something of a difference between fighting a violent alien army that will not hesitate to rip you apart, on behalf of their leader who intendeds to kill everyone in the universe (and even if Peter didnt know Thanoss change of plan, *half* of everyone in the universe), forcing you to take out all the stops to not only stay alive in combat but help stop the genocide of billions of billions

and not wanting to send back whats essentially prisoners to what you know is certain death for them all, because you fucked up trying to fix a situation, when they are willing to go along with your efforts to cure them so they dont have to die and at least one offers to help you figure out how to do it. One is recognizing reality, one is having compassion. And its not like Peter didnt realize he made a mistake when everything went to shit and was still willing to kill Goblin even after recovering.


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

[User]
Is it true that human cells lose 100 base pairs from the ends of chromosome after each replication?

Is it true that human cells lose 100 base pairs from the ends of chromosome after each replication? Does that mean that as we age we loose more and more genetic information?

[Assistant]
So, lets talk about the end of replication problem and how it's solved in eukaryotes like us humans.

DNA replication requires the use of RNA primers that prime new synthesis of DNA since DNA synthesis can only occur in what we call a 5' to 3' direction (in reference to the 'directionality' of the molecule). These RNA primers are complimentary and, in the case of RNA primers in the middle of the chromosome, are simply cut out and filled in with bonafide DNA instead of RNA. This filling in can occur because new DNA synthesis has filled in to the RNA Primer 5' of it, so the new DNA can be used as the 'primer for the primer'.

In the case of the ends of chromosomes, there's no upstream 5' DNA to act as a primer, so when that RNA primer is removed, a little bit of DNA is lost! This doesn't happen in prokaryotes due to their circular genomes but with eukaryotes this is a big problem! The solution that we employ is to add tandem repeats of 6 nucleotides to the end of the chromosomes that can be replaced by an ribonucleoprotein (that is, a protein that contains RNA) called telomerase. When telomerase is active, it allows cells to replenish telomeric repeats, but when it's not around, DNA replication will slowly eat away the DNA about 20-40 bases per replication. In the case where telomerase isin't active, such as a dish of cultured cells or many of the somatic cells in your body, they can only replicate 30-60 times (Called the Hayflick limit) before entering a phase called crisis where they are no longer capable of dividing.

So what relevance do telomeres have to present science? Well, there's evidence that much of aging may be attributed to telomeres, and about 85% of malignant tumors have mutations that allow for the upregulation of telomerase making it an interesting target for anti-cancer medications.

So yes, we lose DNA every replication, but most of the time the DNA is non essential DNA in the form of telomeric repeats.


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

[User]
ELI5: Why is deep frying so much faster than baking?

Whenever I bake f.e. potatoes (even thinly sliced) it takes so much more time than if I would deep fry them. What is the reason? I've read that the temperature of deep frying is about 100C more than in an oven, but that can't be the only reason, can it?

[Assistant] Heat transfers faster through liquids then through gasses. You can be in a sauna without any harm to your body, but if you get covered with boiling water for a few minuites you at best will be covered in scar tissue and in pain for the rest of your life.


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

[User]
ELI5: Why are some elements solid, liquid or gas in normal Earthlike conditions?

As in:  Helium is a gas but Lithium is a metal, even though they're right next to each other on the Periodic table.

Or:  Carbon is a gas but Silicon is a mineral, even though their chemical behavior is exceedingly similar due to their similar position (on different rows) of the table?

[Assistant]
Well for starters, pure carbon isn't a gas, it's most common forms (allotropes) are graphite and diamond which are both crystalline like silicon.

As for why similar atomic numbered elements behave differently, i.e. Lithium and Helium the increasing number of electrons (in line with atomic number) is the biggest determinant of physical structure and state.

For example, the noble gases are grouped vertically because in that position of the periodic table they all share the same property, that their outer shell (valence) electrons are completely full. E.g. Helium has two electrons which fills the first shell, Neon has ten, two to fill the first shell and eight for the second.

As such the periodic table is mostly referred to by groups which form the columns because this (for the most part) is based on how many outer shell electrons they have which determines their bonding behaviour both with other elements and with atoms of their own element. These bonds have varying strengths with weaker strengths tending to produce gases and liquids and solids ever increasing in strength.

Tldr: Elements next to each other have different numbers of electrons in their outer shell whereas columns share this number and are therefore more similar in properties such as being solid, liquid or gas.


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

[User]
Can an object ever get hotter than the thing thats heating it?

I had the hot water running on my kitchen sponge fit a couple minutes and it got really hot and got me thinking - is it possible?

Object A is a heat source heating up Object B. Under constant heat can Object B ever end up hotter than object A?

Edit: thank you so much for all the answers. I had no idea there were so many solutions or that this question would be of interest to so many intelligent and educated individuals. I really didnt think this would get so much attention.

[Assistant]
So, temperature is defined by which way heat energy flows. AKA- if object 1 is a higher temperature than object 2, than heat energy will flow from object 1 to object 2. So, by the very definition of temperature, an object can never be heated up to a higher temperature than the object heating it.

However, temperature is not necessarily what makes something "feel" hot. If an object is really hot, but has a really low thermal conductivity (which is a measure of how fast something transfers heat), then you can touch it, and it won't "feel" hot, because very little heat will flow into you. You have likely noticed this, comparing air and water. For instance, being in 70 F air is comfortable, but being in 70 F water is really cold. Why? Because water has a much higher thermal conductivity than air, so a lot more heat leaves your 98 degree body into 70 degree water than 70 degree air. Heat flowing out of you is what feels "cold." Same the other way, being in 120 F air is uncomfortable warm, being in 120 F water is absolutely terrible and you can't survive it long. It feels "hot" because a lot of heat is flowing "into" you.


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

[User]
Since the Big Bang certainly influenced every event in the universe, does this mean that the origin of the Big Bang is in the past light cone of every point in the universe?

But isn't this also impossible, since the universe is more light-years across than years there have been *since* the Big Bang? Is there a concept that rectifies this?

[Assistant]
First off, dismiss the idea of the Big Bang as an explosion whose ejecta have been traveling outward. That is not the Big Bang.

The Big Bang is simply the event when all of space began stretching. The universe is very probably either infinite or finite-but-unbounded (a geometry analogous to the surface of a sphere, in which traveling far enough in one direction results in returning to your start point), and the Big Bang happened everywhere at once. So yes, the Big Bang is in the past light cone of every point everywhere in the universe, because it happened everywhere.


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

[User]
Can a 2D plane (as in space not airplane) be tied into a knot (that can fold and bend in a 3D space) without the plane touching (intersecting) itself in any place?

I know a 2D plane is always flat but in this instance it can fold and twist as many times as necessary as long as it doesn't touch itself.
I have a picture that further clarifies what I mean and illustrates what I have already discovered for myself, I'll try to find a way to post it in the comments.
Pardon my English, it's not my first language.

[Assistant]
Sure. You can define a simple closed knot with a parametric function

x=(cos(3 phi)+2)sin(2 phi)

y=(cos(3 phi)+2)cos(2 phi)

z=-sin(3 phi)

Then you can define another similar knot with a similar function except adding a constant to the x,y, and/or z functions, so you have two knots that are displaced slightly in space. The plane connecting the two curves satisfies your question. As long as the offset isn't so big that it causes the curves to overlap.


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

[User]
If we cannot receive light from objects more than 14 billion lightyears away (Hubble length), then how do we know the radius of the universe?

The radius of the universe is said by WolframAlpha to be predicted at a value of 93 billion lightyears, about seven times this, but how do we know if no light reaches us from farther than 14 billion lightyears?

[Assistant]
Firstly, it is important to note that this is not the radius of the *entire* Universe. This is the radius of the *observable* Universe, that is the part of the Universe where light has had a chance to reach us.

So, if the Universe is only ~14 billion years old, how is it that we can see out to about 93 billion light-years? Well, that's because the Universe is expanding! After a distant galaxy released some light that began its 14 billion year journey, the space between us and that galaxy grew. Once the light finally reached us, that galaxy is now 93 billion light-years away. So we can actually "see" much farther than just 14 billion light-years!


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

[User] [marvel cinematic universe] How much of a military advantage is the Bifrst?

[Assistant]
It is likely the key to their sucess.

Roads and methods of quick transportation create and maintane empires - quick communications and movement of troops to conflict zones is key to sucess - without it's roads Rome would be little more than an Italian City State, without their ships and knowledge of the seas European nations could have never established global empires.

As time has gone on, new methods of getting troops to the battlefield, Mongolia moved their armies on horseback, in the second world war Paratroopers opened up the fronts for ground invasion and we all know the important role helicopters have played over the past fifty years.

The Bifrst is a goddamn game breaker, the ability to transport soldiers instantly to *planets* is something Alexander, Genghis et al. would have creamed their pants for.


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

[User]
Why did whales develop horizontal tails and fish develop vertical tails?

As the title states. Was it because of feeding habits, or because of predator/prey or just ancestry? Anyone able to shed some light on this for me?

[Assistant]
Exactly. Whales and dolphins are descended from herbivorous land mammals, probably hippo-like. Land mammals, like us, have differently shaped spines - not like fish spines at all. Because of the way our spines work, it is more efficient for them to move vertically than horizontally. Get in a pool and try it both ways.

Whale tails and fish tails are different because of convergent evolution. Like bird wings and bat wings. Not due to ancestry. That's why sharks (who share common ancestors with fish) have vertical tails, like they would.


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

[User] [Star Wars] What planets did humans evolve and learn space travel on? Why are humans so prevalent in the galaxy when other species seem under represented?

[Assistant]
Ultimately, it is unknown, but most believe that Coruscant is the original birthplace of Humanity. Our prevalence has been a point of contention between anthropologists since the beginning, but a popular theory relates to our being used as a slave race for an ancient empire. It is believed that we were shipped to every corner of the galaxy and, presumably, left to our own devices after the fall of this empire. Being a naturally inquisitive and adaptable race allowed us to make very early use of reclaimed hyperdrive technologies, further cementing our presence throughout the galaxy.

On top of that, we reproduce quickly and can adapt to most environments, which allows us to be found in such high numbers basically everywhere you look.


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

[User]
Does the intellectual content/technological advancement in CS progress faster in industry, or academia?

It seems like companies are coming up with new things all the time, esp. in data science, machine learning, AI, machine vision, etc. Do these innovations etc. move quicker in industry or academia? If it's in industry, what purpose does academic research serve CS these days?

[Assistant] Few companies (Google, Deepmind, Microsoft among the most notable ones) come up with new breakthroughs, and that's mostly in ML. Most of the "intellectual advancement" (aka research) in CS happens in academia, though it often takes decades to be adopted in practice (by companies). CS is a massive field and the topics you mention are only a part of it.


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

[User]
[The matrix] couldn't the humans of zion go on a genocidal shooting rampage while plugged in to destroy the machines' power supply?

They have access to a huge amount of weapons, enough to arm an army. Maybe even large bombs(?) By killing a bunch of the humans that are plugged in, they could stop or slow the machines, and humans still wouldn't be in danger of extinction because of the rest of the population of zion. Sure that's a lot of collateral damage, but it's not all that different than the conclusion of ww II right?

[Assistant]
First off, the machines didn't build the matrix to enslave humans and farm them for power, the energy is just a nice bonus.  After the war between the humans and the machines they realized that there was no way of peaceful coexistence, but still didn't want to eradicate their creators, so they trapped mankind in a simulation for their own benefit. Your plan wouldn't actually work.

But evidently the rebellion doesn't know that, so your question is still open. There are a few potential answers, maybe they're too stupid to come up with a plan like that, perhaps Zion has no way to kill enough humans for it to matter or most likely, moral concerns over commiting a genocide, even if it would help them win the war, prevent strategies like yours.


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

[User]
What will happen with bills if your country goes into lockdown because of the coronavirus?

Im worried that when/if the country (Australia) goes into lockdown we will be kicked out of our homes because we couldnt work to pay the bills after the pandemic is over. Surely there would be some type of pause on rent atleast? No way can even half of my country just pay outright for rent when its due. Can anyone offer any insight?

[Assistant] If the whole country goes into lockdown, things will be sufficiently disrupted that the government will have to take some kind of action to reduce frictions. Moreover, under lockdown enforcing evictions is going to be 1) difficult; and 2) not really the government's top priority (ideally).


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

[User] [My Hero Academia] Whats keeping a holder of One For All from passing the quirk down to multiple people?

[Assistant] Once you pass it on, you lose it. Any remaining power you have left is just a leftover that will eventually run dry. Think of  "One For All" as kind of like an apple tree (I know this isn't a perfect analogy but it should help illustrate the point). If you give the apple tree to someone else,  you still have all the apples you already harvested,  but can't collect any more.  You also can't give anyone else the apple tree because you don't have it anymore. So while you may still have some apples,  they will eventually run out and you won't be able to replenish your supply.


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

[User]
Why is it problematic that extremely wealthy people have so much money if the economy is not a zero sum game?

At least I THINK its not a zero sum game.

[Assistant]
"What causes wealth inequality?" is a positive economic question that can be answered objectively.

"How should wealth be redistributed?" is a normative economic question that be analyzed based on value judgements (i.e., given a social welfate function).

"Why is wealth inequality problematic?" is not an economic question. Some people value equality, some people do not. Value jugdements are not questioned in economics.


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

[User] ELI5 "Peeling after sunburn is our body's way of getting rid of damaged cells. This is necessary because cells damaged by the sun are at risk of becoming cancer". Why is it recommended to use an after sun moisturizer to help prevent drying and peeling of the skin?

[Assistant] The moisturizer is for two reasons... first it doesn't help prevent the peeling of the skin, it makes it happen faster. Second, is that one of the jobs of your skin is to keep in body moisture, when the outer layers start sloughing off you are less protected.


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

[User]
If one isn't so interested in making fusion an "energy positive" reaction, could one potentially use a fusion reaction to store energy instead?

I know fusion reactions are pretty high energy things, and then whenever we try to contain one, the energy required makes it an energy negative reaction.

However, if one forgoes an interest in making fusion energy positive, could one form an equilibrium with energy in/energy out to turn the fusion reaction into a battery? (A battery that leaks energy, but still "stores" it nonetheless)

My thinking is that if you feed X amount of power into the system, it will produce (X - (w)x) power, where w is the fraction of power that is wasted per unit of input per unit of time, which can be fed back into the input with the option of drawing more power (thereby "shrinking" the reaction) to charge a network of batteries that function as an energy buffer of sorts, which us humans then draw from.

Is there any sense in which fusion could work like this? Like, what can we do with fusion if we lose an interest in making it energy positive?

[Assistant]
It's conceivable. For instance, you could use endothermic fusion reactions to produce uranium-235. Then you've got a cache of ^(235)U to use for fission later.

Ultimately, you use up more energy than you get back. And this would be extremely inefficient monetarily speaking.


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

[User] Are the most popular searched terms on Google on Wikipedia a good measure of public interest, or public curiosity, in a subject?

[Assistant]
An indicator is exactly that: an indication of X. Often times we can't measure X directly because it's unobservable or unfeasible.

Campbell & Fiske (1959) were the first real champions of triangulation when isolating constructs (Fun fact: that '59 paper is the most cited paper in all of psychology).

Your best bet is to attack this construct in as many different ways as possible. If you're looking for how popular a topic is, how can we measure that?

We can measure # of google searches (or %), wikipedia edits/articles; headlines that include that topic in major news outlets (online vs offline); you can also measure it using dissertation or research papers on the topic.

Get creative!

The idea here is that all of these measures will converge on the same idea: "how popular is X at a particular moment in time". Each indicator will miss the mark slightly, but will hit the mark in its own unique way. We hope, as researchers, that if we spread out this risk (what Campbell & Fiske called heterogeneity of irrelevancies), the part where all indicators overlap will be the part you're interested in.


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

[User] ELI5: How is it that when women apply heat to their hair it becomes softer and shinier, but is actually damaging the hair?

[Assistant] When hair is heated the proteins that make up hair (keratin) are damaged (denatured). In doing so they don't hold together as well. This makes the hair softer.  In essence, damaging the hair through heat is what causes the hair to be softer. Not sure what causes the shininess though.


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

[User] [ASOIAF] Daemon Blackfyre smashes the royal army at the Battle of Redgrass Field and Aegor Bittersteel personally kills Brynden Bloodraven. Would he succeed in seizing the throne? How would King Daemon Blackfyre's reign be?

[Assistant] Yes if he won the battle the throne would've been his, honestly from how he's described and through his actions he would've been a good King especially it terms of military matters. Biggest problem is Dorne would probably reject the crown and declare independence making the Iron Throne one kingdom short . There's also the matter of the remaining targaryen heirs if they escaped the slaughter similar scenarios like the blackfyre rebellions would be rampant considering Maekor and Baelor were pretty competent and stubborn there would've not been peace in westeros for a long time to come.


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

[User]
CMV: If you supported Bernie Sanders, you NEED to vote for Biden

Hi! Genuinely asking this question, and also doing so with from the perspective of a Democrat, specially, a progressive. I understand that a Republican would disagree with a lot of this so I am not necessarily asking you if you are Republican.

Anyway: I am a very passionate Bernie Sanders supporter. I donated, phonebanked, and even drove out of state to canvass. I was sorely disappointed that he ended his campaign but now Biden is THE nominee against Trump. I see a lot of people on Twitter not endorsing Biden or saying they wont vote for him, but whats the endgame there? Isnt not voting exactly what Trump would want? Isnt discord in the Democratic Party exactly what Russia would want? To me, a Sanders supporter, voting for Biden is paramount to get Trump out of office, as well as appoint judges that wouldnt immediately attack any progressive or Democratic legislation plus Bernie himself said its the thing to do. What is the argument AGAINST voting for Biden?

[Assistant]
1) voting for the democrat you dont like because they are the lesser of two evils has never worked. The greater evil has always won and the suckers who voted for the democrat rather than empowering a third party simply screwed themselves over for the next election.

2) Democrats in general dont tend to undo the evils of their republican predecessors, but codify it. Obama ran on undoing the lawless degradation and corruption of the bush regime, but instead he codified it and doubled down on the worst excesses.  And Biden is far more right wing than obama. Every evil of trump youre hoping he will fix, he will not.

3) liberal judges - Bidens while career has been about placating the right wingers. Hell elect a conservative judge weather or not he needs to politically.

4) climate change, wall street regulation, fewer military conflicts and drone assassinations, the war on drugs? - Biden either doesnt give a shit about fixing them, or in some cases was a driving force behind then.

As horrific as trump is, the Democratic party has shit the bed once again and selected a man who is as close to trump as possible. Youre only hope long term is to vote third party. If a third party gets 5% then they get a mass of funding and ballot access for future elections, which attracts more high quality people to run, more votes and more donations.

The democratic party is broken and cannot be fixed, only replaced. Every time you dont vote third party you delay that necessary change by another four years.


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

[User]
[Star Wars] Why does Princess Leia have a coke nail?

It seems that the princess has one long, suspiciously cut nail on her pinky finger. What is the purpose of this nail? Why would a person such as her require it?

[Assistant]
It's Alderaanean fashion for high class citizens to affix small jewels and such to it. She doesn't usually bother to do so with the Rebellion because she's too busy and, later, the others are too dead.

(Of course, we know the real reason is that Carrie Fisher was a gigantic cokehead. She nearly overdosed on the set of Hoth and later possibly contributed to John Belushi's death by supplying him with cocaine while he was making an effort to break his addiction.)


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

[User]
Do different gases convect heat at different rates?

Metal and wood conduct heat at two different rates, but do gases behave the same?  If there is a difference, would the effect be noticeable by touch?

[Assistant]
Heat transfer due to natural convection is not trivial, and there are many different, generally empirical, approximations that apply in different circumstances (see Nusselt number).

In general there are a few material properties that affect the rate of convection and resulting heat transfer:

\- Thermal expansion coefficient. The more a fluid expands as it warms the greater the buoyancy force, which is the driver of natural convection.

\- Thermal diffusivity. If heat diffuses (conducts) easily through the fluid then there won't be strong thermal gradients to drive convection.

\- Viscosity. Clearly convection involves mixing of fluid and so viscosity is relevant. Viscosity of gasses is lower than liquids so perhaps less important for the former.

It would certainly be possible to set up scenarios where certain gasses would generate strong convection currents and others would generate noticeably weaker ones.


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

[User]
ELI5: Why is it that my whole finger tip starts to hurt when I cut my nail too short?

I know that there are a lot of nerve endings there, but what actually causes them to be agitated?

[Assistant] When you cut your nail too far down, you expose the hyponichium, which is the skin that connects your nail plate and your finger. The hyponichium is very sensitive and does have a lot of nerve endings. And since the hyponichium is usually not exposed, it has no need to be "tough" like your regular skin.


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

[User] [DC] How high above his weight class can Batman punch (and win) if he has no prep time or prior experience fighting his opponent?

[Assistant]
If they dont have blatant superpowers or unreal technology then he can probably beat them. In one storyline Hugo Strange tosses him into a room with three or four people that he genetically experimented on into monsters and all Batman can do is escape because he knows that he cant take them out single-handedly without prep time.

At best he couldve taken out one of the monsters, who were probably similar in power level to Killer Croc or Solomon Grundy, so thats probably the upper limit he could handle without any prep or experience fighting them.


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

[User]
I've read that the observable Universe has a 45 billion ly radius - how can that be if the Universe is only 13.7 billion years old?

I mean, light surely does not go faster than the speed of light.
But that means, something that is ~40 billion light years away, is "only" ~13 billion years old...

I don't understand! :)

[Assistant]
>I mean, light surely does not go faster than the speed of light

Correct.

>But that means, something that is ~40 billion light years away, is "only" ~13 billion years old...

Correct.

The issue here is cosmological expansion. Objects emitted light when they were closer to us, and then moved away. Moreover, that light wasn't really approaching us at the speed of light because it was 'swimming upstream' so to speakit was always moving toward us at the speed of light, but the distance between it and us was also increasing. The net effect of this is that light emitted from sufficiently far away that it's taken 13.5 billion years to reach us was emitted from points that are currently about 45 billion light-years away.


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

[User]
Can an 'anti-star' exist?

Can a star made of the anti-matter counterparts to normal stars exist?

[Assistant] Can it exist? Yes, nothing about antimatter expressly forbids it from forming into a star.  However, there is no evidence that one does exist in our universe and the prevalence of matter makes it highly unlikely that it would be concentrated enough to form into a star let alone survive as one for any length of time.


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

[User] ELI5: Why does the coastline have beaches in some places and Rocky cliffs in other places, even right next to each other?

[Assistant] Different water currents. Normally cliffs would just keep eroding, and waves would wash the sand away. But in some places the currents *re-deposit* the sand up onto the shore, refreshing the beach so it doesn't disappear.


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

[User] Google wasnt clear on this, but how is the brain able to throw a object or catch a object and predict when, where, etc etc. All on its own? Its like advanced trig near instantly?

[Assistant]
It doesn't do calculations in the way that we do in, say, physics. It's just learning. Your brain knows that if the ball flies like this, and you put your hands like that, you'll catch it. It knows it from experience.

Same goes for everything else. For example, we can use geometry to precisely measure distance to an object by observing it from two points and doing the math. Your eyes observe things from two points, **but they don't do the math**. They just know from experience that an object of that size and with this eye focus is about that far, because it has seen it before.


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

[User]
[Endgame] If the Quantum Nano suits could create Iron Man then why did the War Machine one have to be different?

All of the Avengers wore their quantum suits that looks functionally identical and form fitting to their body shape.  This includes Tony Stark's which became a suit of Iron Man armor when he needed it to.  So why was War Machine's suit so much bigger than the others?

[Assistant]
Tony always saves the best toys for himself. This is partially due to paranoia - he wants to be able to take down any threat, even if that threat was once an ally - and part of it is simple pride.

The quantum suits the Avengers wore were not capable of performing the same functions as Tony's nanotech armor. There was some overlap, like the way the helmets form into place, but there's nothing to indicate that they could form weapons, fly, and so on.

So it isn't that Tony's quantum suit became the nanotech armor, it's that Tony's nanotech armor became a quantum suit. The War Machine armor is based on older tech, and can't become smaller when not in use, so the quantum suit that wrapped around it needed to deal with its actual physical size.


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

[User] [the Purge] if a criminal breaks out of jail on purge night, would anyone ever care?

[Assistant] I mean....they can still go get him back. His crime of breaking out of jail wouldn't be illegal, but he would still be a criminal with time to serve. It wouldn't negate his sentence, it would only not add on charges for escaping.


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

[User]
CMV: If you don't pick up after your dog in public spaces you're a disgusting garbage human

\*\*Should have made it clear I'm talking about those who DELIBERATELY leave dog waste behind with no consideration for others, not someone who ran out of bags and couldn't. Sorry\*\*

Anyone else sick and tired of not being able to enjoy a walk and scenery because you have to be laser focused on the ground to avoid stepping on a "land mine"? Even more so no in the fall since leaves are dropping and hiding the piles...

Doggie bags are cheap, often provided for FREE in public parks and it literally takes seconds to pick up the mess so that humans and other dogs don't step in it or roll in it. How about the fact that dog waste is classified as a pollutant in water runoff or that it attracts vermin.

Have some consideration for everyone else and be a good person. Pick up what your dog is putting down.

[Assistant] I agree that its terrible to not pick up after a dog. That being said, Ive definitely run out of bags and dont realize. Luckily we were near a store and ran in to get a bag. But if we were in a cul-de-sac, what do we do? Pick it up with our hands? It is biodegradable at least. Not saying its okay to leave it, but sometimes you dont have a choice.


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

[User] [Lovecraft] Generally when people look at the old ones they go insane. But what if they look into the far future of humanity? Would we be so advanced in the far future that someone now looking at us would also go insane?

[Assistant] Sort of (generally, Lovecraftian protagonists go insane as a result of cumulative trauma; seeing the creepy-crawly (or more accurately, gaining enough information to grasp the true implication of the creepy-crawly) is one last horrible shock after a period of sustained, brutal horror), but it would be less that we would be "more advanced" and more that humanity would be either A) as warped and twisted as the old ones themselves or B) dead and replaced with odd roach creatures. The tales related to Cthulhu and the Great Race of Yith in particular suggest that humanity will degenerate into nothing but a bunch of cultists, particularly once Cthulhu wakes up, which in turn will lead to the decline and death of humanity. This in turn will open the field for the intelligent species that rise and fall between humanity's extinction and the rise of the species the Great Race plans to take over en masse to escape their own apocalypse.


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

[User]
[Jaws] Why didnt the mayor just close off the area of the beach 10-20 feet beyond the water line?

The only people who go there are boaters and some surfers who make up a relatively small percentage of beachgoers.

If he didnt want to cause a panic about the shark, couldnt he have just made something up? Like Sorry folks, theres scheduled maintenance on the power lines or something.

[Assistant]
Might not have helped. That dog was eaten in shallow water, and Alex Kintner didn't go out particularly far.

And it's sort of like asking why climate change deniers don't compromise by banning the worst emissions sources. Their position is that there is no problem whatsoever, so even a small amount of give on the situation is like an acknowledgment that they are wrong.


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

[User] ELI5, why can't we divide by zero?

[Assistant]
10/5 = 2

    2 * 5 = 10

So you see you are basically asking what number will multiply by the number on the bottom to get the number on the top. Since every number times 0 is zero it's impossible

i.e.

10/0= ? because no number times 0 is 10.


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

[User]
[DC] Why does Batman scare the police?

It makes sense for Batman to strike fear into the hearts of criminals, but why would this need to cause fear extend to law enforcement when he is trying to help them catch criminals?

[Assistant]
The police in Gotham, at least when Batman first started, were insanely corrupt. Think Capone era Chicago corrupt. They were basically an extension of the mob. So when Batman began his crusade, there was really no distinction between police and criminal, with the exception of Jim Gordon and a few cops loyal to him.

Once Gordon became Commissioner he was able to root out the corruption and restore integrity to the GCPD. At that point, Batman became more of an ally to the police though some still dont like him for a variety of reasons ranging from dislike of vigilantism to him being the guy who got their buddies fired and thrown in jail (thin blue line type of stuff).


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

[User] ELI5: Pineapples have a 1 year growth time before it can be harvested. Why are they relatively cheap despite them having a long growth time?

[Assistant] There are a lot of plantations that grow them rotating fields so that they have an almost constant supply. Because of this supply is high despite the long growth time and thus costs are relatively low.


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

[User] ELI5: Why do elicopters have 3, 5 or more blades, why isn't one number of blades "the best" ? When would 5 blades be better than 3 or 4 or... 10 blades?

[Assistant]
There is not a single definition of "the best".

Fewer rotors means they have to spin faster, producing a different noise profile.

More rotors cost more money.

What's "the best", cheaper and louder or more expensive and quieter?  Like all engineering problems there are many solutions when there are different priorities.


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

[User] ELI5: How did we create non biodegradable things like plastic from what I'd assume is biodegradable materials?

[Assistant]
Plastics have properties which make them resistant to biodegradation.

Firstly, plastics are water resistant. Without moisture, bacteria/fungi cannot grow on it. Also, any digestive enzymes released by these organisms will be repelled from the surface.

Secondly, producing plastics is very energy-inefficient compared to biological cellulose or other biomaterials. So nature has never bothered to evolve plastics and the enzymes to digest plastics.

Also, plastics are very similar to wood (cellulose). When wood was first evolved, there were very few organisms capable of digesting it. This led to dead trees piling up everywhere and filling the earth with wood, which all eventually became coal. This period of earths history is the Carboniferous period, where almost all coal on earth came from this pile of dead trees.

If plastics become as widespread as wood was, something will evolve to digest the abundant source of energy.


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

[User]
[Matrix] How does Cypher get into and out of the Matrix without anyone knowing to have the meeting with Agent Smith when you need to have assistance in and out?

Throughout the movie you always see someone, Tank or whoever,  there to help the person in and out of the Matrix.. so how does Cypher have the meeting with Agent Smith without anyone helping him, getting permission or anyone knowing this meeting occurred?

[Assistant]
People think he's in the practice program, banging the woman in the red dress.  If you decide you want to have some "alone time" with her, one of the other people will connect you, and they leave the monitors off.  Nobody really wants to see Cypher get freaky with that chick.

For his part, Cypher is smart enough to secretly connect to the real Matrix, while simultaneously having a dummy program running that makes him look like he's in the Construct.  If anybody walks by and glances at the computer screen, they see all the normal code like he's banging Ms Red Dress.  "What's he doing now?" asks Morpheus.  "It looks like she's got him tied to the bed, and he's asking her to... you know what Morpheus, you don't want to know," says Mouse.  They all turn away in disgust and don't look at the program anymore.  At the pre-arranged time, they disconnect him.  He just has to be sure he's near a phone in the Matrix when they do that.

Since he's one of the main computer guys, he knows enough to be able to do this without the rest of them stumbling across it.  It isn't that he's that much smarter than them, it's that they aren't looking for it.  They don't suspect it at all.


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

[User]
[The Flash series] The flash running through the truck in the flash series.

In the flash series, when Barry ran through the truck he had to vibrate at the same frequency as air, but the bomb was attached to him so shouldn't it have also been vibrating at the same frequency as air and passed through the truck?

[Assistant] The point was to make the bomb fall off where he'd be shielded from the explosion. That's why the timing was so critical - not just for passing through the truck, but for not letting the bomb fall away too soon.


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

[User]
Why does pregnancy ruin your teeth?

I was just at the dentist who mentioned that he gets a lot of new mothers who need serious fillings or root canals, even if they had really healthy teeth pre-pregnancy and took good care of their dental health. I didn't get to ask deeply about it but physiologically, how does getting pregnant affect dental health so badly?

[Assistant]
It has to do with nutrition and vitamins! Basically when people make jokes about babies being parasites, there is a reason for that. The body has to provide to make the baby, and it just so happens that calcium is one of the things they need a massive amount of- for all those bones and calcium rich body parts (like teeth!)

Its also why some folks bones become more fragile during pregnancy.


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

[User] [Independence day] Was Russel casse actually abducted by Aliens? Or was he just a nut?

[Assistant]
The novelisation might be informative. When Russell first sees one of the city destroyers, he is convinced that the same aliens that abducted him are in there, and the novelisation describes Russell's experience in substantial detail.

However, there is also a scene that isn't in the movie: when Steven Hiller comes across the convoy of trailers and recreational vehicles, he shows several people the alien he was dragging in his parachute, and Russell was horrified because the alien was totally different to what he remembered. He suddenly finds himself questioning whether his abduction actually happened at all.


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

[User]
[Marvel] Why was Steve Rogers known as Colonel America in Marvel Zombies?

Was it ever established what the reason was for the various pre-existing divergences in Earth-2149 before the arrival of the zombified Sentry, such as Colonel America's high ranking and presidency? Various other differences to the mainstream Marvel universe are made apparent in a way which makes it clear that the Zombiverse was following a different course of events which were not parallel to its counterpart. Was there a specific point from which this universe differed from Earth-616 before the introduction of the plague?

[Assistant]
Every universe is different, no reason to think that in one universe Cap couldn't have been offered and accepted some promotions for his actions. Just like in a lot of Universes Tony never directed Shield.

It's called the multiverse for a reason - each snowflake is unique.

To answer more specifically though - everything Marvel Zombies I've ever read doesn't give a reason for him being Colonel America.


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

[User] ELI5: By what process did the first electrons, neutrons and protons to form into atoms?

[Assistant]
Different atoms formed through different processes.

The lightest atoms (hydrogen, helium, and lithium) were formed immediately after the big bang in a short window where pressures were still high enough to smash these particles together but high energy light had dispersed enough to not blow them apart.

All elements heavier than lithium but lighter than iron and nickel are formed in the cores of stars.  Pressures and temperatures there are high enough to force light atoms together into heavier ones in a process that releases energy and fuels the star.

Everything heavier than iron and nickel *consume* energy when fused, these atoms only form when massive stars implode under their own weight and briefly crush heavy elements together before destabilizing entirely.


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

[User] ELI5:Why is the use of gas in war so important to prove when we have facts that innocent people are being killed with ferocious violence with guns or torture.

[Assistant]
Gas warfare is against international law. it has been outlawed since the end of WWI. No nation approves of the use of poison gas by any other nation. It is a weapon of mass destruction which cannot be aimed at a specific target such as at fighters.

Torture is done individually on a captured individual basis.

Guns are aimed at specific targets.They are weapons of destruction but they are targeted towards armed combatants supposedly.