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

[User]
reading guide to Carnap and Quine?

Looking for reading recommendations for Carnap and Quine. What are the best works (primary and secondary) for understanding their disagreements? In what order should I tackle these guys? Looking to understand logical positivism at its strongest and what is supposed to have contributed to its "extinction". I'm generally familiar with the big picture ideas of LP, but I want to get nitty gritty.

[Assistant] The short, classic papers are Carnap's *Empiricism, Semantic, and Ontology* and Quine's *Two Dogmas of Empiricism*. For a more extensive developments of their positions in general, Carnap's *Logical Construction of the World* and Quine's *Word and Object*. Neurath is the key figure mediating between them, and the crucial writings are mostly found in his *Philosophical Papers*. Uebel's *Overcoming Logical Positivism from Within* is an excellent secondary source covering the key developments.


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

[User]
Why are there so many different units of radiation, and how do they differ?

During a recent Wikipedia tab death spiral, I was struck by how many different units we use for measuring radiation-
 becquerel, curie, rad, roentgen, sievert... how do they differ? Do different industries/fields use a particular unit for one reason or another?

[Assistant]
The Becquerel and Curie are units of activity. This is just the rate at which a radioactive sample is decaying. They tell you the number of disintegrations happening per unit time.

The rad is a unit of dose. It's just an amount of energy deposited into some material by some radiation per unit mass of the object.

The Sievert is a unit of dose equivalent. It's the same as above, except it's corrected for the fact that different kinds of radiation are more damaging than others, for a given energy.

The Roentgen is a unit of exposure. Since we're talking about ionizing radiation, it produces free charge when it interacts with matter. The amount of charge released per unit mass of the object is the exposure.

In nuclear physics, you'll see Bequerels (Curies are sort of dated) whenever there's radioactive decay. Safety regulations are usually quoted in terms of Sievert or REM (Roentgen equivalent man, another unit of dose equivalent).


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

[User]
[ STARGATE ] Why can people pop back out of a wormhole if they don't fully walk through?

There are so many scenes of tug of war fights in an open wormhole at the event horizon in SG-1, but we know matter can only travel one way. If they're de-molecularized and sent as they progress through the event horizon, why can they pop back out still? Do they ever directly address this? I know there's the whole deal of the buffer in the DHD, but you have to do some mental gymnastics to make that make  sense.

[Assistant]
It's the gate that has the buffer system, not the DHD, and that is indeed the mechanism that allows this.

The 'puddle' on either gate is the mechanism for the dematerialisation and rematerialisation, every puddle can do both.  The other feature is that the gate only sends whole objects, that's a safety mechanism in case power for the wormhole gets cut before complete transit.  Also nice for last minute changes of mind.

So you stick your hand in, the puddle dematerialises it, and puts it in the gate buffer.  If you continue stepping through, you make it all the way into the buffer and the gate sends you.  If you decide to pull back out, the puddle rematerialises your hand.  Safe and convenient for everyone.


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

[User]
[MCU] What would Hollywood change when making the movie based on the search for the Infinity Stones and the resulting Battle Of Earth? [Spoilers]

Eventually, a movie based on the Avengers defeat of Thanos will get made, I have no doubt. It was a massive historical event, after all, perfect for an epic prestige picture.

While we saw what really happened here in the real world, MCU Hollywood will undoubtably take creative liberties, both for practical reasons and for dramatic license.

What will be changed in the epic movie adaptation?

**Spoilers**

In particular, with Tony Stark being venerated after his death, will he be portrayed especially heroically?

[Assistant]
Hawkeye's vigilant crusade will be re-written as him traveling the world helping children orphaned by the Snap.

Thor will have gone to the mountains to meditate and will be portrayed as super skinny from fasting.

Cap's therapy sessions will be decadent orgies, featuring America's ass.

Scott Lang will not need vermin to escape the quantum realm.


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

[User] ELI5: What is the difference between permutations and combinations?

[Assistant]
For Permutations the order matters, for Combinations the order does not matter.

A permutation example is, a "combination lock" the combination ONLY works in a certain order 3-25-17; if you put it in backways 17-25-3, the lock stays locked.

A combination example is, you have 10 friends, pick 3 to go to a concert. The order doesn't matter, the three you pick are going to the concert.


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

[User]
[WH40K] What if the Imperial Guard managed to defeat a Grey Knight purge

So the Grey Knight dickheads will kill anybody who witnesses them doing their thing, Space Marines and guardsmen included.

So what if the guard, being the badass normals they are, manage to resist? The Knights try and do their purge but the guardsmen somehow manage to band together and wipe out the attacking Grey Knights.

Would a battlefleet bombard the dicks out of them? Would they be considered heretical?

[Assistant]
The Grey Knights/Inquisition would immediately assume that the guardsmen had become corrupted (after all, how else could mere mortals withstand the Grey Knights?) and devote every resource they had to their eradication.  Depending on the value of the planet itself and the extent of the resistance, Exterminatus might even be used as a measure of last resort.

With respect to Space Marines, it is noteworthy that the Space Wolves involved in the First Battle of Armageddon were not themselves marked for execution; rather, they vehemently opposed the Grey Knights' mandate to execute the guardsmen.  In a hypothetical escalation scenario, either involving Space Marines in direct support of the guardsmen or previous and notable opposition from said Space Marines to the erasure of witnesses to the Grey Knight Purge, the Grey Knights might also declare that the company or chapter involved had become heretical (or at the very least renegade).  With the living guardsmen still at issue (rather than dead and therefore no longer a point of contention for the Space Marines), expanded hostilities could lead to a much more serious rupture of Imperial unity.

The same could well be said for the higher guard commanders or the local Imperial government, depending on the degree to which the Grey Knights or Inquisition liased with these.  If the Inquisitors opt for their usual skullduggery (i.e. saying little to nothing to the officials overseeing the guardsmen they will eventually attempt to purge), mistakes over their intentions could draw higher elements of the hierarchy into the matter.  Depending on how quickly the appropriate leaders initiate discussions and come to an arrangement with each other, this might lead to a far broader labeling of heresy and devolution of the situation into open and disruptive warfare.

TL:DR Scrappy guardsmen fighting off the Grey Knights sounds inspiring, but it probably means death for far more people.


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

[User]
[Mad Max Fury Road] Nux says to Capable "three times the gates were open to me", what was the third time?

1. His suicide run in the storm

2. When Joe gives him the gun to kill Furiosa

3. ???

[Assistant]
1. Attempted suicide bombing in the dust storm.

2. Attempted strangulation of Furiosa, followed by a knife to the throat and then a boot out the door. Understanding, of course, very few people have had a full Imperator put a knife to their throat and survived it. And for most of the Warboys- who are weakened and dying of radiation poisoning, falling out of a moving vehicle on the Fury Road is a death sentence too. Nux got insanely lucky to not fracture a bone, or develop internal bleeding that would never stop.

3. The fumbling of the revolver in front of Immortan Joe.


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

[User] Is there really a big difference between the quality of education of a top 100 university and your average state school that let's anyone with a pulse in?

[Assistant] The material you learn will be pretty similar, at least in STEM subjects. The most important differences are having a strong peer group to push you, and the opportunity to work with professors who are leaders in their field. This may not make much difference in the classroom (the best researchers are incentivized to be just okay teachers) but being able to intern in a top lab is a pretty big deal. Or if theory is more your thing, you can do an independent study of some advanced material with a leading mind. It's not that no one has experiences like this at state schools, but you may have to get in line because the number of hotshot professors may be small. At Ivy-level universities, these opportunities are there for pretty much any motivated student who wants them.


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

[User]
CMV: There is nothing wrong with the idea of trigger warnings

I'm usually very skeptical of concepts related to intersectionality, such as mansplaining, safe spaces or cultural appropriation.

However, perhaps the most mocked aspect of the movement (and the origin of the often abused term "triggered") is an entirely benign and overall positive concept that really benefits everyone.

Trigger warnings are of course nothing new. Typically they have been attached to age restrictions, for example indicating that an R-rated movie includes violent or sexual content. This does not prevent anyone from seeing the movie (well, no adult anyway), but rather equips the potential viewer or parent with information on what to expect from the film.

You might say that these measures exist to help parents protect their children from potentially harmful content, and that adults are expected to be strong enough to handle these subject matters. But I'd argue adults are expected to know what's right for them. A rape victim might not want to read a graphic description of a sex scene, a war veteran might not want to hear the gory details of a battle. Indicating that a work of fiction, a public speech or a comedy show will involve "triggering" subjects such as sexual violence, disease, disability, war, torture, car accidents or drugs puts the onus on the audience to decide whether to consume a piece of media or not. Not only are potential audience members properly informed, but the author or communicator has the freedom to talk about sensitive topics without restrain, as anyone listening will have consciously chosen to do so.

[Assistant]
The question becomes, does the sentence "the following contains depictions" increase or decrease the likelihood of an adverse reaction.

You can have people read about graphic murders with or without the warnings, and even with PTSD victims or rape victims, they are no better off with the warnings, and arguably worse off -modest increases in anxiety prior to reading the passage.

All you are doing, is making people fear the worst, and not avoiding any issues with the passage itself.

If the warning, doesn't mitigate anything, and arguably just needlessly raises anxiety levels, what are we actually doing??


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

[User] ELI5 - the full relationship between Jean-Luc Picard and Beverly Crusher.

[Assistant] They met when they were younger. Picard and Jack Crusher were friends and Crusher was dating Beverly Howard. Picard liked her, but she was off limits. When Picard was the Captain of the Stargazer, Jack was killed and Picard had to tell Beverly that it was his fault. This made her even more off limits. When she came to work on the Enterprise, they had a few 'will they or won't they' episodes, but in the end decided to remain friends, although in an alternate future, they had married and divorced (All Good Things). In the books they are currently married and expecting a baby.


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

[User] ELI5: Why are there so many sharks in shallow waters on the U.S. coast of the Atlantic Ocean all of a sudden?

[Assistant] It's summer, and this happens every summer.  Sharks kill only 10 people a year, but shark attacks are sexy news.  Coconuts kill far more... but that isn't news.  So really you're just hearing more about an normal annual event.


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

[User]
[Star Trek] What is the average life expectancy of an Federation citizen on Earth?

What is the average life expectancy of a Federation citizen living on Earth in a city like San Francisco or Washington, D.C given the healthcare citizens had access to.

[Assistant]
In the pilot episode of *ST: Next Generation*,  we are told that a wrinkled and white-haired Admiral McCoy who looks to be in his early 80s by our standards is actually 137 years old.  Keep in mind that this is a man who has dealt with potentially lethal situations and life-threatening conditions many times throughout his life, which means that he is likely to have aged at a faster rate than those who have spent their lives safely on Earth.

So it is likely that the average Federation citizen can expect to live up to 150 years old if fortune keeps him or her safe.


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

[User] [Evangelion] Wouldn't all the kids be a lot more compliant and willing to follow orders if NERV just treated them well?

[Assistant]
What makes you think they don't? Shinji's only the way he is because of his personal demons, everyone's pretty supportive to him until he drops the ball with his tantrum near the end.

People are super tolerant of Asuka. Rei's the only person to stand up to her.

Rei's never treated badly by anyone except Asuka and maybe Ritsuko. She even gets Gendo to come over for dinner with Shinji (which would've gone through if an Angel didn't attack when they were otw)

Homie who punches Shinji isn't treated badly, and NERV even "cares" enough to put him in a hospital.

Rebirth Girl's annoying as hell but only Asuka calls her out on it.

Rebirth Shinji knows what he did. Exactly what everyone wanted him to. People are rude to him because the Rebirth series is trash/this is a different universe and their goal dropped the ball

The only time orders were disobeyed were when Asuka decides to showboat, one time which might've been under secret orders, the other which ended up crippling her. Then that time Shinji justifiably freaked out after the Dummy Plug System was activated on him. When he came back from his freak out everyone let him back onto the robot.

The get in the robot meme is inaccurate. He only refuses to twice, and the first time he almost immediately caves. He "refuses" because he thought his Dad called him over to hang out, not pilot a gunmen who's operating system he knows nothing about. He says it almost verbatim in that same scene. Literally 2 episodes in he becomes a model grimdark Gundam operator. Asuka loves showing off, and also has no problem with her Megadeus. Rei's always down to ride her Knightmare, even to the detriment of her health.


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

[User] ELI5: Why does semen change from a gel state to a more liquid state some minutes after ejaculation?

[Assistant]
ELI15 version:
it coagulates first, so it gets harder (and not drip *out*; if you know what i mean)
After 15-30 minutes "some stuff" that are in there, start to work and de-coagulate the semen.
so the sperms can go *where they should* and make a baby.

ELIPhD version:
After ejaculation, the latter part of the ejaculated semen coagulates immediately,forming globules, while the earlier part of the ejaculate typically does not. After a period typically ranging from 15  30 minutes, prostate-specific antigen present in the semen causes the decoagulation of the seminal coagulum. It is postulated that the initial clotting helps keep the semen in the vagina, while liquefaction frees the sperm to make their journey to the ova.


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

[User] ELI5 why is Exfoliating good but scratching is bad?

[Assistant]
Exfoliating is usually subtle, even pressure.  Scratching is usually firm and fairly sharp pressure.

Exfoliating is like using sandpaper and scratching is like using a saw.  In addition, the underside of your fingernails is usually not very clean and is a great place for bacteria to grow.  You're potentially breaking your skin (even if only slightly) and introducing bacteria.  Not ideal.


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

[User] ELI5 Stem cells. The science and the controversy.

[Assistant]
Stem cells can grow to be any cell you want. If you need new cells for your heart, brain, liver, whatever, these cells can be used as a base for growing new parts or repairing old ones.

The controversy is with embryonic stem cells, which are only found in a human embryo that is 4-5 days old. To gather these cells, the embryo must be killed. The controversy is that some people are essentially saying that this is murder. Some people saying that it is not.

Scientists are working on a better way to get these stem cells, partly because of this controversy, and because an embryo is really small and you can't get much out of it for the effort it takes (concieve a baby and all).


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

[User] [Marvel] You've been given Captain America, Hawkeye, and Taskmaster to play on your NFL team, what positions do you have them play?

[Assistant]
Hawkeye as quarterback.  That ball will always go exactly where it needs to.

Cap as a... wide receiver?  Some kind of receiver.

Taskmaster as a lineman.  Get a couple plays in, and he'll know what they other team is doing before they do it.


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

[User] [Blade Runner 2049]Is JOI self-aware? Is she Sentient? Is she just extremely clever software reflecting her users desires?

[Assistant] I believe that sentience is fundamentally performative, even for humans; "You" are just a story your brain tells itself to explain its own actions. If JOI can fake being sentient to the point that no amount of analysis could ever prove otherwise, then she is - or at least, she is as sentient as a human is.


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

[User]
[TNG] What if the Borg cube of Wolf 359 that went on to be destroyed in earth orbit... wasn't?

Following the battle of Wolf 359, the cube resumed course towards Earth, completely undamaged. The Enterprise, having finally completed repairs, raced to catch up to the Borg. In preparation for a Borg invasion of Earth, a state of emergency was declared on the planet. Brushing aside the last line of defense by easily destroying a flotilla of Mars Defense Perimeter sentry pods, the Borg cube took up position in Earth orbit. However, using the recaptured Locutus and his link to the collective mind of the Borg, Data manages to invoke a man-in-the-middle attack on the secure link between the local Collective aboard the Cube, and Locutus, injecting a global sleep command to all drones. The entire crew of the Cub simultaneously begins their regeneration cycles, entering a state of dormancy and leaving the cube entirely undefended.

Automated counter measures detect the anomaly and are unsuccessful in reversing the hack, and thus execute a self-destruct sequence to avoid contamination further up the network topology, in addition to preventing Borg technology -- ironically -- assimilated.

*However, Data detects this malware defense response, and is successful in disabling it, while spoofing a command acknowledgement along the Locutus link up the network. The subspace link is then disabled -- if necessary, on the hardware level -- and the Collective loses contact with the Cube, seemingly due to successful execution of self destruct command.*

*The Cube remains in orbit around Earth, disconnected from the Collective, and all drones offline, and completely at the mercy of Starfleet scientists.*

**How do events from this point unfold differently along the future timeline, including the Dominion war and the Voyager incident?**

[Assistant]
Federation science is advanced by decades. By the time of the Dominion War, our weapons and regenerative tech make it a brief conflict. The DMZ probably never is established, because the Cardassian War goes much better, so no Maquis and no loss of Voyager in the Badlands.

The Federation learns how to hijack the Borg transwarp network, and eventually takes a more proactive stance against future Borg incursions, dismantling or locking out the Borg, hedging them out of near space one conduit at a time.

It still learns about Species 8472, the Voth, and the Hirogen. If we are lucky we just stay out of fluidic space. If not they may become a dire enemy defending against 'invasion' if first contact does not go well.

The Hirogen are naturally predatory and will see Federation explorers as new and interesting prey. They might be able to be bought off with holodeck tech from the start, if it's a Galaxy or Sovereign class crew instead of an Intrepid. Voyager's poor showing was due to simple inadequate defenses.

The Federation is not ready for the Voth and vice versa. It will probably devolve into a holy war against the human race.

The worst threat, however, are probably the time-meddling Krenim. Without Voyager's interference who knows how far they would have screwed up Delta-Quadrant chronology before their timeship was destroyed.


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

[User] Roughly how far apart are galaxies?

[Assistant] It varies of course, but on the order of millions of light years. Our nearest neighbor of a similar size as the Milky Way is 2.5 million light years away. There are a couple of dwarf satellite galaxies about 10x closer to us (the Magellanic Clouds, visible from the Southern Hemisphere). Galaxies in the middle of clusters can be closer together. The Virgo cluster has ~1500-2000 galaxies in a sphere about 7 million light years in radius, so there are 2-3 galaxies in every cubic Mega-lightyear, and is more concentrated towards the core.


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

[User]
[WH40K] Are the Exodites and Harlequins going to put themselves into the Infinity Circuits when the time to form Ynnead comes?

Will these non-Craftworld Eldar put their souls inside the Infinity Circuits when the time finally comes for the Eldar to form their death god and end Slaanesh once and for all?

As far as I know, the Harlequins don't carry Soul Stones because Cegorach saves their souls before Slaanesh devours them upon death, but the Exodites do.

[Assistant]
One of the few pieces of the old Eldar that the Exodites took with them were the infinity circuits, called World Spirits on the Exodite worlds.

The infinity circuits are already scattered across the galaxy in different craft worlds, but should they ever have enough psychic energy between them then perhaps they will be able to unite. If this happens then the souls from all craft worlds and the Exodite worlds as well, will all gather together to create Ynnead. When Ynnead forms, they will call to them all of the Eldar souls, including all living Eldar (probably) and once they have fought and defeated Chaos, they will give birth anew to the Eldar, so they may have a second chance at building a society.

As you mentioned, Harlequins don't use soul stones or infinity circuits and are not part of the plan, so no, they will not be involved.


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

[User]
Do astronomers correct images of oblique galaxies due to the time differences from the far side to the near side?

The far side of a galaxy (viewed say close to flat) for a galaxy of diameter say 200,000 light years will be seen to have rotated for 200k years less than the near side. Is this 'twist' noticeable and is it corrected or given the slow rotational speed of a typical galaxy is it imperceptible?

[Assistant]
So the dynamical time for an object - how long it takes for it to change significantly - is just the size of the object divided by the typical speed of stuff in the object. The light propagation time-scale is the size of the object divided by the speed of light. So the ratio between light propagation time-scale and the dynamical time-scale is the ratio between the speed of light and typical speeds within the object. That is, stuff within a galaxy moves much slower than the speed of light, then it doesn't change much over the time it takes for light to cross the galaxy.

Typical orbital speeds within a galaxy are hundreds of km/s. The speed of light is 300,000 km/s. So ignoring the light propagation time gives you an error of like 0.1%. This is usually far smaller than other uncertainties, and really doesn't matter very much. The stars on the far side might be like 0.3 degrees behind on their orbit compared with the stars on the near side, and that's a pretty small error.

We do however see the *entire* galaxy as it was millions or billions of years in the past. But 200 kyr vs billions of years isn't really enough to make a big difference.

It does matter a bit if you're able to make very precise measurements, as we can within our own solar system. For instance, Io orbits Jupiter every 42 hours, and Jupiter can be almost a light hour away, so you really do need to take light delay time into account if you want a probe to fly by Io and not miss by tens of thousands of km. This sort of thing matters for spaceflight, but doesn't really matter for understanding the general physics of what's going on, which is what we're mostly concerned with when we look beyond our solar system.


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

[User]
Is Kermit the Frog real?

Im serious. This thought popped into my head and it hasnt left and its making me realize how much ambiguity there is in the term real.

Hes a puppet, yes, but hes treated like a real person. He has his own Twitter account, gives interviews, stars in movies and TV shows under his own name, has a defined personality, etc. You could say he isnt real cause hes performed by other people, but you could say that about other media personalities as well, such as singers with alter egos or stage names, or drag queens who are usually treated as separate individuals from the people who perform as them.

So yeah, is Kermit the Frog real?

[Assistant]
Well when we say "Santa isn't real" we don't seem to be denying the existence of Santa actors,
 Santa twitter accounts, associated personas and mannerisms, and so on. We seem to be denying that there exists a person who is the referent of "Santa" that has all the characteristics of the person who we imagine when we think of as Santa.

So it seems that the answer to your question is *No* if we consult our folk practices for talking about other fictional characters. We take the question of "realism" in this context to be an identity/existence claim. However, it seems fine to assert that both Santa and Kermit have an existence in a *sense*, but a very different sort of one to you or I.


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

[User] [General] You're secretly immortal and have been locked up in a supermax prison for years. You look pretty good for a 70 year old. Breaking out isn't really an option but if you're found out...experiments and stuff. What's the best way to handle this situation? How can you explain it?

[Assistant]
At some point you'll have been in there longer than any other employee or prisoner has been at the prison.  Hell, longer than any of those people have been alive!

Stop socializing with anyone, let them forget you exist.  Then at some point, start insisting that you're actually some other guy.  Tell them it's a computer glitch.  You knew that guy everyone thinks you are, he died twenty years back.  You can't be the person everyone thinks you are because then you'd be over a hundred years old by now.  Do you look a hundred?

You never raised a fuss about it because you did the crime and you deserved the 30 years you were sentenced to.  Felt guilty about it, because you *are* guilty. But, 30 years are up.  Maybe 35 or even 40, you lost count of it yourself.  Aren't they ever going to let you out?

Since you can't be the person they think you are, someone somewhere will believe there's a paperwork error.  You'll be quietly released because they won't want to admit they lost track of a prisoner for decades.


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

[User] [ELI5] what is the difference between the degrees of murder?

[Assistant]
first degree - it was intentional and you planned it

second degree - it was intentional but you didn't plan it

voluntary manslaughter - it was intentional, unplanned, but a reasonable person could see how the crazy circumstances of the situation could cause someone to be mentally disturbed and lead them to harm someone

involuntary manslaughter - you unintentionally caused someone to die.


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

[User] Eli5 How do scientists know that nuclear fusion is the source of energy of the Sun?

[Assistant]
There's a lot of science done beforehand. E.g. we know that every element swallows certain parts of light's spectrum and reflects the rest. This is like a fingerprint for every element, we can read simply by analyzing which frequencies in the light of a star are missing.

We also can classify stars by age and noticed that older stars hold more heavier elements than younger ones.

We also know that about 75 % of gas in the universe is hydrogen, the rest is helium and that stars form from these gigantic clouds collapsing under their own gravity. Thus we know stars gain energy from compressing stuff a lot. Also the older a star gets the more helium and the less hydrogen it appears to have. Where did the hydrogen go and where does the helium come from if the mass of the star is somewhat stable (in fact it's decreasing)?

The answer is that there MUST be a mechanism making helium out of hydrogen and heavier stuff out of helium and so on up to iron.

Theoretical calculations have it that stars of a certain mass fulfill the criteria for fusion to happen and also deliver enough energy from the inside to maintain themselves from collapsing further.


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

[User]
ELI5: How will Netflix use data to determine if they should do a Punisher spin off or not?

Presumably they'd want to know if people actually want to see a Punisher spin off or not before spending money on one.

In what ways can Netflix try to "prove" it is something that's in demand?

[Assistant]
How many people watch multiple Netflix originals of other Marvel shows.

If many people who watch DareDevil also watch Jessica Jones, and will also watch the upcoming Luke Cage/Iron Fist/The Defenders, that is a good indication they will also watch Punisher.


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

[User] ELI5: Why does bacon grease seem to never go bad even without refrigeration, but other grease (e.g., hamburger grease) will go rancid in the same conditions?

[Assistant] It definitely will go bad. It just may take longer because bacon is a salted cured meat without a lot of moisture, so the grease has a ton of salt and not much residual water, which inhibits bacteria growth.


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

[User] [Doctor Who] What makes the sonic screwdriver so powerful?

[Assistant]
Have you ever gone to WalMart and bought a leatherman tool, then carried it around?  You start noticing a million situations where having a pair of pliers, or a knife, or a ruler, or whatever is useful.  Imagine a super-advanced alien race, beyond time and space, mass-manufacturing their idea of a leatherman tool.

Edit:  Imagine time-traveling back to the Neolithic era with nothing but a leatherman.  Can you picture what a god you would be?


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

[User]
Can metal shatter if cold enough?

Like in the movies, someone freezes a lock and breaks it, or Mr. Freeze freezing steel doors and driving through them? What real life effect does extreme cols have on metal?

[Assistant]
The key is that the metal needs to go through a ductile-to-brittle transition, if they have one.  Most metals fall into one of two primary crystal structures either face-centered cubic (FCC) or body-centered cubic (BCC), though there are more less common options than the main two.  BCC metals (e.g. iron) will fracture if below the transition temperature.  However FCC metals (e.g. gold, copper) do not have a ductile to brittle transition, regardless of how cold you get.

Sauce: PhD in Materials.


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

[User]
[MCU/GOTG] How rich is Starlord?

Assuming he doesn't get declared dead after vanishing from Earth, how much interest does his family's assets accrue? Part of me wants to say there's nothing left due to his Mother's cancer, part of me wants to believe that she had a life insurance policy and Starlord has got money in the bank back on Earth that has been compounding for several decades now.

[Assistant]
On earth?  Inconsequential, his accounts would have been seized as 'abandoned property' by now.

In space?  Actually pretty rich.  The bounty on him was $50,000 units~~gs (spelling?)~~, which rocket said would make him and groot rich.  Starlord gives the guy in prison the exact same amount for his leg, and doesn't get bent out of shape about it when it turns out to be a prank, so its obviously an amount of money he can afford to lose.


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

[User]
ELI5: Why do marine engine utilize only one gear for their transmission instead of multiple gear ratios in a automobile?

I don't know if I'm wording this correctly but it's something that has always confused me.  Why is it a marine engine will basically have a single gear instead of multiple gears you would find in a automobile transmission?

[Assistant]
In a car the speeds of the engine and the wheels are directly connected by the gearbox. The engine needs to be within a relatively narrow band of speeds to run efficiently and generate the best power, so you use a gearbox to allow the wheels to turn at a wide range of speeds while the engine stays within its preferred range.

In a boat the propeller can move at a single speed and be providing forward thrust whatever speed the boat is moving at, because it can "slip" through the water. You don't need to turn the propeller really slowly to get the boat moving and then speed it up as the boat speeds up, so you don't need a gearbox allowing the engine to turn the propeller at a wide range of speeds.


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

[User]
ELI5: When to use 'who' and when to use 'whom'?

Note: using the words 'objective' and 'subjective' won't help at all like every google-searched answer I have ever seen (I'm 26 not 5 and I still don't know what they mean.)

[Assistant]
Which to us depends on the sentence construction. The best explanation is this: if you are using *him*, *her*, or *them*, use *whom*; if you are using *he*, *she*, or *they*, use *who*.

Examples:

> "To whom did you give it?"

> "To him, over there."

> ---------------------------------------

> "Who did it?"

> "He did."


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

[User]
ELI5: Got an extra ticket?

Can anyone explain the guys outside of sporting stadiums asking for an extra ticket? Do they want to buy any extra tickets then sell it or do they want to go to a game for free? I live in Chicago and this happens outside every stadium by I never worked up the courage to ask these guys what exactly is their end game.

[Assistant] They are scalpers. They just cant say "Selling tickets" but they can say "Do you have any tickets?". Sometimes they will hold up signs that say "I need tickets" Which really means they have tickets to sell.


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

[User]
ELI5: How come we "flip" Japanese names when speaking English, but not Korean ones?

When speaking English I've noticed that when we refer to Japanese names, they are "flipped", i.e. we refer to them in the Western name order (given name-family name) as opposed to the Japanese order (family name-given name). E.g. the Japanese Prime Minister is referred to as Yoshihide Suga as opposed to Suga Yoshihide.

This doesn't seem to be the same for Korean names - for instance, Kim Jong-un is referred to as Kim Jong-un.

So why are Japanese names flipped, but Korean names not?

[Assistant]
Answer: it's a standard introduced during the Meji era in Japan as a way of catering to westerners and "modernizing" (i.e. westernizing) Japan. When a Japanese name is written in western characters specifically they will then put the given name first and family name last, but only when written in western (Roman) characters.

Worth noting that in 2019 the government reversed policy on this and is now encouraging the traditional name order in all circumstances.


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

[User]
[DC] Stealth vs Super Senses

How do those like the Bat-Family avoid the super senses of those like kryptonians?

[Assistant]
Training. It's been shown that they can control the way their bodies behave such as when Bruce learns to control his body temperature in extreme colds or when Jason can survive underwater for long stretches of time.

Also, technology. In Superman Unchained Batman developed a suit that Superman can neither hear or see. No matter what mode of vision he uses.


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

[User]
ELI5:What are the actual physical changes that happen inside a computer while it's running?

Specifically curious about what it means to write something to memory: What happens inside a computer when I save a text file, or a Jpeg, or save a game, or anything else that changes the state of the computer from what it was before, to something else, and how it continues to exist after the computer is turned off.

[Assistant]
Permanent storage in computers generally is done by one of two technologies.

For magnetic hard drives, there's a spinning plate covered with magnetic material and a mechanism that allows to detect and change the "direction" of the magnetism in very very small segments of that platter. So writing a file would involve that mechanism changing the magnetic pattern on the disk.

For solid state drives (SSD) in computers, as well as the common USB flash memory sticks, the memory consists of a silicon chip with lots and lots of very small isolated conducting spaces which can store electric charge (extra electrons), and transistors to control that. Writing to that memory involves storing electric charge in some (and removing from others) of these "pockets" called NAND cells.

Both of these things are somewhat permanent and continue to persist after power is turned off.


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

[User]
[Superman] NASA asks for Superman's help

How quickly would we advance in space exploration? What would be the main tasks NASA have for Superman?

[Assistant] Most tasks would involve bringing vehicles and supplies into the upper orbit. Even if they paid him a million per trip, that'd still be a fraction of what it costs them to currently send anything into space.


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

[User] ELI5: How do pilots of the Blue Angels and other groups fly so close without crashing due to air pockets or turbulence? How do the planes stay so still?

[Assistant]
A lot of practice. The Blue Angels do nothing but fly aerobatics.

The lead pilot is flying somewhere, every other pilot is spending all of their time making tiny adjustments to keep their distances.
They say if the lead pilot flew into a mountain the rest of them would crash into it as well.
It kinda helps though that if all the planes are that close, all of them will be feeling roughly the same effects.

It also helps that a lot of weather effects are being drowned out by the effects of a dozen wings and multiple jet engines fudging with the air. So there's only that piloting nightmare to deal with.


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

[User]
[Harry Potter] What kind of Dark Wizard did people think that Harry was going to be?

Some former Death Eaters apparently believed that Harry was destined to be a powerful Dark Wizard, which is how he was able to defeat Voldemort as a baby.

Later, some Hogwarts students similarly began to fear Harry, suspecting that he was the Heir Of Slytherin. They also believed that Voldemort might have targeted Baby Harry to prevent a future rival in the Dark Arts.

Assuming that their assumptions were correct, what kind of Dark Wizard did they expect Harry to be?

**Death Eaters:** Harry was only a baby, after all, and one with a Muggleborn mother, at that. How come these hopeful Death Eaters were so sure that he would be on their side? What if he decided that the Wizarding World needed to be overthrown, or he became a Dark vigilante who hunted down all of Voldemorts followers as vengeance for his parents? Did they just assume that he was powerful enough that they should throw themselves behind him once he came of age, no matter what his ideology?

**Hogwarts Students:** Harrys best friends were a Muggleborn and the son of a well-known Muggle-Sympathizer. Did people think that Harry was a live and let live Dark Wizard who only disliked Muggleborns who bothered him (like Colin and Justin), but was fine with them if they knew their place?

[Assistant]
> What kind of Dark Wizard did people think that Harry was going to be?

Probably one of the most powerful in history and a catalyst of great change within the wizarding world.

> Harry was only a baby, after all, and one with a Muggleborn mother, at that. How come these hopeful Death Eaters were so sure that he would be on their side?

Voldemort was very manipulative and capable as a child. He began his story in a muggle orphanage with a muggle father and rose to gain power within a few years.

> What if he decided that the Wizarding World needed to be overthrown, or he became a Dark vigilante who hunted down all of Voldemorts followers as vengeance for his parents?

If he decides the Wizarding World had to be overthrown, and he was as powerful as they believed him to be, they would've followed to him to ensure they still had power by the time he accomplished his goals.

If he decided to hunt down the death eaters, you would've had a few come forward more than willing to betray their brethren to ensure their safety.

> Did they just assume that he was powerful enough that they should throw themselves behind him once he came of age, no matter what his ideology?

Yes and no. Some wanted to get into his good graces early as a child, while others wanted to influence his growth and become a mentor of sorts to him. If he turned out not to be powerful, they could've simply killed him.

> Harrys best friends were a Muggleborn and the son of a well-known Muggle-Sympathizer. Did people think that Harry was a live and let live Dark Wizard who only disliked Muggleborns who bothered him (like Colin and Justin), but was fine with them if they knew their place?

Dark Wizards are a sort of nebulous idea for the students. They're not restricted to killing off anyone that's not pureblood, they use magic for their own benefit and take down anyone in their way. They weren't sure what his ideologies were, and that likely made them more terrified. It let them come up with their own and let the rumors snowball until it was several collections of deplorable possibilities.


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

[User]
Do electrons actually move around the nucleus?

What does it mean for an electron to have a "probability cloud"? I understand that's the probability of finding it at every point in space, but does he move? just appears ad disappears? Is it just a mathematical cloud of probabilities that collapses when measured? Or does the electron just moves around the nucleus in some way that we don't understand yet?

[Assistant]
Strictly speaking, no. While it does have momentum and kinetic energy, there's no notion of movement in quantum mechanics. Once you measure the electron position somewhere, the state has collapsed (under whatever your interpretation of what that "really" means) into that eigenstate and won't change (in the idealized case) - this gets a bit muddied by the fact that the position basis is not discrete but that can be solved by having a better definition of what measuring position means.

You can have something that looks like movement if you have a reasonably well localized wave packet with a non-zero group velocity, where the center of the packet will move, but that's not a situation that applies to a bound state of electron around a nucleus.


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

[User] ELI5: What's a homeowners association, how is it legal, and why can't you just ignore their rules and live however you want in your own home?

[Assistant]
It's an agreement between all the homeowners in a particular area to abide by common rules, and sometimes includes maintenance of common spaces.

It's legal because it's part of the contract you sign when you purchase the house. If you do not like the rules you should not purchase the house.

Like any contract, they can take you to court for breaching it. The HOA rules may also include rules about how to settle disputes.

Basically, it's not just your house...when you bought it it came with some communal obligations.


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

[User]
ELI5: Why is American healthcare dependent on a job?

Why is american healthcare directly tied to jobs and work?

Being from Australia i realise that we have universal healthcare, but since i was 18 i've been paying for private health insurance (maybe 800 a year?. It has nothing to do with who im working for or what career im in and i pay for what ever package happens to suit me. Why isn't there something similar to that over there? Why does it have to be something to do with your job?

Is it possible but just too expensive? Cause to me it just sounds absurd when i hear about companies knocking back claims because of stupid shit..

[Assistant] During WWII the US instituted a wage freeze which didn't allow employers to raise wages.  It was an effort to support the war.  So employers had to find other ways of getting good employees, so they started offering benefits, particularly healthcare benefits.  Once the war ended it just became common practice to offer healthcare as an employer here.


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

[User]
[Star Trek] Why does no one ever have to wait for a turbolift?

Now I'm just back from good old Starbase 4 and got to take a tour on the good ship Enterprise 1701-D. You walk up to the door and it opens, you get in and each journey can take up to a minute, plus each one can be halted for indefinite amounts of time on command, yet no one seems to have to wait for a turbolift to arrive and neither does a halted turbolift seem to stop anyone else moving around. On a ship of several thousand people this must be a huge task to achieve. Back on Starbase 4 those damn original spec hydraulic things break down all the time and you might as well pitch a tent if it's not there when you arrive. Has there been some advancement in technology that makes this possible?

[Assistant]
Everyone on the ship is wearing a comm badge which tracks their movement closely enough to be instantly dematerialized down to the atom, and the ship itself is managed by a vastly competent AI which has been optimized by the finest minds from a nation of trillions. Getting turbolift cars positioned is nothing.

As for wait times, the vast majority of the ship's personnel are at their duty stations, or moving between rooms within their department, so they're not constantly taking the turbolift. The show follows the command crew of the Enterprise, not a group of biological researchers, so of course their travel gets prioritized by Enterprise traffic control.


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

[User] ELI5: Why is vomiting a reaction to horrifying sights?

[Assistant]
Vagal nerve overstimulation, same as getting punched in the gut, kneed in the crotch, getting dizzy or having a high fever can do.  Basically a one-size-fits-all "bad things happening" response from the part of your nervous system that normally handles unconscious or semiconscious processes like breathing, digesting, etc.

Also why defecation is a barometer of extreme fright.


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

[User] No information can travel faster than c, so no event inside an event horizon can have any causal effect on the external universe. How then do external objects "know" the mass of a black hole? Is that information somehow accumulated at/outside the event horizon over the life of the black hole?

[Assistant]
The information is encoded in the gravitational field which extends all the way through infinity.

I'll explain it with charge because it's more immediate, but it's roughly the same with mass.

Say you have an electron outside and far from the black hole. This electron has a charge and field lines extending out to infinity. We can imagine a very large sphere surrounding both the black hole and the electron. Computing the total flux of the electric field through the sphere ("counting field lines that reach infinity") gives the total charge inside; this is Gauss' theorem. This charge must always, always be conserved. Nothing in the Universe can change this.

We lower the electron in the black hole. The field lines can distort, but they must still reach to infinity. There's nothing we can do by moving our puny electron that can change this very global fact about the behaviour of the field at infinity. As the electron crosses the horizon, we don't know/care what has happened to it, but we are sure there still is the same number of field lines, now emanating from the horizon, extending all the way to infinity. The total charge has not changed, and the black hole is now charged.

There is no need for the charge information to get out. Sure, if the electron wiggles inside the horizon, the *radiation* it emits cannot get out. But the Coulomb field is a bit different from radiation, and retains itself the information about the total charge. Charge can actually be seen as a geometrical property or even a topological invariant of the electromagnetic field itself - it has a sort of nonlocal nature. You can measure it even though you're far away and have no causal contact with the stuff that has the charge, you just need to scan a surface enclosing it.

In suitable situation and with smart definitions, mass in general relativity works in a very similar way.

An aside: obviously you cannot communicate from inside to outside the horizon using the information of the total mass/charge... because those things cannot be changed, since they are strictly conserved (superconserved is the actual term). Everything fits together.


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

[User] ELI5: How did people get anything cold in hot places (i.e. Middle East, deserts, etc.) before things like refrigeration.

[Assistant] A long time ago, around 400 BC. Persians had ice in the middle of summer in the desert. It was brought in during the winters from the mountains close by in bulk, and were stored in specially designed, naturally cooled fridges. They were underground and had thick walls. (we're talking about an Acre in size and the wall thickness were at least two meters). It was made of clay, eggs, goat hair, ash.....a little mixture they proved to be resistant to heat transfers. They also had wind catchers built in so they could control the temperature more if needed. The ice were used to chill treats for royalty and rich folks.


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

[User]
CMV: The Vaccine Mandate was, strategically speaking, a horribly bad way of dealing with antivaxxers, and has energized Republicans massively.

The entire identity of antivaxxers is this: "I don't trust Big Pharma, I don't trust the government. They want to infringe on my freedoms, and I am the Hero who will stand up for what's right." That "standing by the river of truth and saying 'no, you move'" thing is a massive part of conservative identity. This narrative of tyrants and heroic rebels is at their heart.

The vaccine mandate played right into that narrative: that fit perfectly with their story of tyrants and rebels. People who do take the vaccine do it reluctantly, feeling forced and threatened with losing their jobs, while those few still refusing are held up as heroes.

And it didn't even work, at least so far - the US is behind Brazil, France, the United Kingdom and many more. As it turns out, feeding right into people's narratives of victimhood is...not a great plan.

"But we need to get people vaccinated! How else will you do it except forcing them!"

Well the French have a solution: defuse the narrative.

See, the French also have a MASSIVE antivaxx movement. Distrust of governments and Big Pharma is rampant with giant chunks of the population believing in homeopathy and distrusting vaccines, both on the right and the left. A vaccine mandate would have led to country-wide demonstrations.

Instead, the government said "you don't HAVE to get a vaccine. But if you want to travel, go to cinemas, restaurants, etc, you need either a negative test, or a vaccine".

Why was that brilliant? Because it defused the narrative. A relative of mine is an massive conspiracy theorist - antivaxx, climate skeptic, the works. But they wanted to go to concerts, and couldn't be bothered to do the tests every time, so...they got jabbed.

See how that defuses their whole thing? No one forced them, they just had to admit that they liked their comfort and convenience more than their professed principles. And now France, the home of antivaxx nutjobs, has a higher vaccination rate than even the UK and Germany!

That's how you get antivaxxers to drop their pretenses, you don't play into their story, you sidestep it. And it demonstrably works. Yes, I know the majority of people approve of the mandate, but that's very much not the point - you can keep all those people on board and get more people vaccinated without giving your opponents ammunition, with cleverer more subtle governance tools. Instead of going with the clever subtle solution they went in with the hammer, and the blowback is going to hurt.

[Assistant]
>See, the French also have a MASSIVE antivaxx movement. Distrust of governments and Big Pharma is rampant with giant chunks of the population believing in homeopathy and distrusting vaccines, both on the right and the left. A vaccine mandate would have led to country-wide demonstrations.

>Instead, the government said "you don't HAVE to get a vaccine. But if you want to travel, go to cinemas, restaurants, etc, you need either a negative test, or a vaccine".

The two policies you're talking about are the exact same policies.
The US vaccine mandate does not strictly speaking, mandate a vaccine.

Instead, it mandates that people get vaccinated or **tested**.
So, basically pretty much the same mandate as the French have.

The only difference is that the US mandate focusses on employees, whereas the French mandate focusses on customers.


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

[User] Why is it that light slows down when moving through a substance such as air or water when light doesn't have any mass?

[Assistant]
In classical theory, the "stiffness" of the medium changes.  Consider a string.  When plucked, a wave will be seen to travel - the speed of which depends on the tension.

In quantum theory, photons are absorbed and re-emitted.  The rate of collisions and interactions governs the transmission speed through the medium.  That rate is controlled by the electron density and other things.

Classical treatments which consider the electron density to define a "stiffness" of the space in a medium (or vaccuum) - the permittivity - are best and most versatile for many calculations of these things.

Edit: The vacuum having no electron density still has a value for the permittivity.  In the presence of electrons which act to slow light down, the new permittivity is defined relative to the vacuum value.


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

[User]
[Star Trek] Has there ever been a first contact scenario where the Federation meets a civilization that is more advanced than them?

What if: the UFP encounters a civilization that is more advanced than they are but they have not invented warp drive. They are only limited to their own solar system. What would the UFP do?

[Assistant] This happened in Voyager, where a civilization had long-distance teleportation that wasn't warp. Their own version of the Prime Directive forbid them from sharing the technology with the Voyager crew.


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

[User]
ELI5: What is the difference between Drive, 3, 2, and 1, in an automatic car?

Very confused about this.

[Assistant] When you choose Drive, you are telling the transmission to choose whichever gear it feels is most suitable for the driving condition at any moment.  When you choose 1, you are limiting the transmission to the use of first gear only.  2 allows the use of first and second; 3 allows the use of the first three gears.


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

[User]
[Star Wars] Was Anakin purely looking for blood on Mustafar, or was he genuinely trying to convert Obi-Wan at some point?

He argues a lot with his master, and concludes "if you're not with me, you are my enemy". Was this the point they both realised they had to fight? Or was Anakin just paying lip service with the intention to kill Obi-Wan regardless?

What would have happened if Obi-Wan had agreed with Anakin's reasoning and joined him? Would Anakin just have been like "Oh thank the Force, I'm glad you see through the lies of the Jedi. Come, let us help Padm" or would he be like "That's cool, I'm still gonna shank you though"? How would Sidious even react to Anakin turning up with a legit corrupted Obi-Wan like "yeah we didn't fight, turns out he's on the same page"?

[Assistant]
Yes, if Obi-Wan had changed sides, Anakin would have happily accepted. Sidious would not have been amused and would have schemed to bind Obi-Wan  to himself, sideline or kill him.

Of course, Anakin never had a real chance to convince Obi-Wan, just like Obi-Wan had no chance to convince Anakin, which they both realized at some point.


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

[User] ELI5: Why does higher frequency EM become more dangerous?

[Assistant]
Because the energy in a photon is proportional to its frequency. Multiply frequency by ten and you multiply energy by ten, too. In the case of human life, it becomes dangerous once it has enough energy to disrupt biological molecules.

UV can do a little bit of that, but won't penetrate the skin (so it causes sunburn). X-rays are worse, and gamma rays are quite capable of blasting a DNA molecule apart.


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

[User] ELI5: Why does the United States have a naval base in Cuba, one of our ideological enemies?

[Assistant]
The US had the base there before the Cuba revolution. There was no way the new Cuban government could get the US out of there without creating a cause for the US to invade cuba completely.

After the Cuban Revolution, the US kept paying its monthly lease of the land, in accordance to the original treaty. Cuba refused to cash any of the checks, although in 1959, one of the checks was accidentally cashed by the Cuba government...but never since. To this day, the US claims when Cuba cashed that one check, it honored the original treaty. Cuba says that the check was cashed by a clerical error, and has not cashed any of the 600+ monthly checks since that time, and that the US has no right to use the base. However, Cuba has no way to get the US off that land.

p.s. if the lease was for $1M a month, that'd be $600M (from 1959 to present), and maybe Cuba would cash the checks. However, the lease is only for $4,085 a month, and not worth Cuba's while.


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

[User] ELI5 : Why are computers limited to 0s and 1s? Why cant we use numbers like 2s and 3s for more Efficiency?

[Assistant]
1's and 0's are represented by an "on" and an "off" signal. This allows them to do discrete operations quickly with essentially zero error.

Adding additional numbers requires adding additional 'states'. It's easy to tell if something is "on" or "off", but adding a third or fourth state adds more room for error by bringing your different possibilities closer together.

Analog computers have been made before. These use infinite possible values. They can do all of their math in one 'step', but at the cost of precision. The trouble is in large part that their room for error or their speed sucks. See, as you speed them up, the odds of an error increase. The speed of light makes your signals act less like you'd expect and more like waves that travel down the wire, splashing around as they go.

Digital computers have achieved absurdly high speeds with near-zero errors, something which analog computers can't dream of.


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

[User]
[Marvel Comics] Why doesn't the public assume Spider-Man is a mutant like the X-Men?

People really hate mutants to the point of discriminating against them and saying slurs like "mutie" but even though Spider-Man gets bad PR it's like everybody knows he isn't a mutant.  Nobody calls him "mutie" or anything like that. When people see him swinging around, wouldn't the natural assumption be that he's a mutant?   Everybody seems to know he isn't one. How did they find out?

[Assistant]
They pretty much do assume Spider-Man is a mutant in Ultimate Spider-Man, especially when the tabloids start publishing pictures of him and Kitty Pryde hanging out.

However, Norman Osborne himself comes out and says he 'created' Spider-Man on national television at one point, and whether or not you believe that lunatic, it stands to reason if Osborne is responsible for all these crazy freaks coming out of the woodwork that use more tech than your run of the mill mutie, he probably did create Spider-Man somehow.


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

[User] ELI5: Why do we close our eyes when we sleep? Also, why can't we fall half asleep by closing one eye for extended periods like dolphins do?

[Assistant]
A few things:

1. we can sleep with one eye open, technically...just like we can sleep with both open.

2. We don't have the capacity to put a single hemisphere of our brain into "sleep mode".  This is the wonderful capability of the dolphin and it's not so much their eye (although that part is true) it's their _brain_.  Our brains can't do this - we're all or nothing in the sleep department.


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

[User]
[Blues Brothers] it's 106 miles to Chicago...from Joliet?

It's 106 miles to Chicago, we got a full tank of gas, half a pack of cigarettes, it's dark... and we're wearing sunglasses.

But Joliet is like 30 miles from Chicago.

Where the hell did he get the 106 miles from?

[Assistant] They're not at Joliet when they say that. They'd just gotten out of the the Palace Hotel Ballroom. No telling where the Palace Hotel is, other than "Up north, by Lake Wazzapamani."Which makes sense, as about an hour and a half north of Chicage you run into a smattering of lakes.


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

[User]
[General] Do fictional cities replace/overlap real-world cities?

So, fictional cities that are not on the coast (because they can just add more land), do they a) *replace real-world locations in the real-world equivalent of that spot* or b) *somehow add more land in that location without changing the real-world land and cities around it*?

[Assistant] Sometimes all the cities are real. Sometimes it's all real except one or two additional cities that's in a spot where there isn't a city in real life. Sometimes it's all original except for a few major cities. And sometimes it's on a completely different planet entirely. It depends on the setting. Do you have one in mind?


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

[User]
ELI5: People always say that a political/economic system (communism, capitalism, etc.) is "good in theory but bad in practice." Why does being bad in practice not reflect on the theory in this context? Is there a philosophical aspect allowing the theory to be good despite being bad in practice?

Throwaway account so my main account doesn't look too dumb.

[Assistant] It's just like in physics we assume no friction or perfect materials and in programming we assume 'smart' users. Pol. systems need to tie together a lot of social and emotional contexts, so perfect implementation is hardest part. So IMHO, a imperfect theory that's easy to implement is better than a perfect theory that involves a lot of radical change.


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

[User] ELI5: In movies/TV, when someone gets stabbed in the chest, blood pours from their mouth. Is this realistically what would happen?

[Assistant]
Ah something i can answer. A few years ago i was stabbed in the lungs a few times and heres what happens. Here im making the assumption that only the lungs are punctured and no other organs.

When you breath in and out, the space between your chest wall and your lungs creates a small vacuum almost which expands the lungs to suck air in. If anything gets into the same chest cavity, and due to there being a hole in the lung, the lung deflates. This is called a collapsed lung or a in medical terms a pnuemothorax. (spelling?)

This dosent make you cough like a few people have said. The second thing that happens is the same chest cavity fills up with blood, this is called a haemothorax. With the lung deflated and the chest cavity filling with blood, its pretty hard to be able to cough up blood.

At the same time however, you aren't going to stop breathing, your chest will keep on trying to expand and contract. due to this small vacuum, you get whats called a sucking wound, which is taking a good percentage of your breath away each time you try and breath in.

So in short, im quite sure its unlikely,  be it by gravity or coughing.
Any where else it could happen though, someone else might know.


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

[User] [Fallout] Did two criminals decided to adopt Vicky & Vance as their role models mid-casino robbery or two random people who became enamored with the story of Vicky & Vance decided to pursue a life of crime as a result?

[Assistant] Neither. Pauline was enamored with the idea of being a famous outlaw in general, as well as the idea of gaining a lot of money. But since she had Sammy, a husband who would follow whatever crazy idea she concocted, she decided they'd be a criminal couple, like Vicky and Vance. Thus they concocted the plan to rip off the museum. To steal a relatively powerful weapon (9mm SMG) as well as each of the original couple's hats. Pauline likely thought looking the part would help their reputation. Vance is also noted as dressing like how he thought gangsters dress. There were multiple parallels between the two couples, most notably that they were both small time who would never be able to make it to major league crime.


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

[User] ELI5: How is light both a wave and a particle?

[Assistant]
Describing light like as a wave and a particle is just an attempt to use familiar objects to help understand what light actually is.  In reality, it's neither wave, nor a particle, but it behaves similarly to both.

It's kind of like if you were to say "a llama is a horse and a camel".  Well, it's not a horse, and it's not a camel, it's a unique thing that happens to be similar in some ways to a horse, and some ways to a camel.  Make sense?

(EDIT: if you'd like more details on *how* light is similar to a particle and a wave, let me know)


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

[User]
ELI5: Why does 1 inch of rain equal 10 inches of snow?

Is this conversion even right? I found it on google with little explanation. One inch of rain seems minuscule to 10 inches of snow but maybe I have a fundamental misunderstanding of how much one inch of rain actually is. Please help.

[Assistant] I believe its density. Snow is water yes, but its full of air. Imagine a pool filled with water and a pool filled with snow. The pool will be full with both, but if you were check the mass of both, the water will have many more particles then the snow due to all the tiny air pockets within the snow. The air is a big reason why snow is fluffy/crunchy/squishy etc.


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

[User]
[Scott Pilgrim] How did Ramona know about the League of Evil Exes? (Book Spoilers)

Like how did she know it was set up and that there be 7 of them (She's mentioned having another boyfriend who wasn't in the League). If we go by books then if I'm recalling correctly than she ran away from Gideon, and seeing how he set up the Guild, how did she know about it? Was it around for a while after she left Gideon and was interfering with her love life before she started hanging out with Scott?

[Assistant]
The Evil Exes seem to have a degree of precognition (given a Vegan Psychic and Demon Summoner, is it that far fetched?) or at least an extremely good intelligence network, because Patel sends Scott an email before even Scott knows what his status with Ramona is.

They also seem incredible transparent about their mission.  Again, see the email sent to Scott.

So either they just explicitly told Ramona... or she's been down this road before with potential suitors who didn't stick around like Scott did.


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

[User]
[Spider-Man] Why is Venom capable of web-slinging and shooting?

Spidey's web-shooters are gadgets, not a biological superpower, so how was the symbiote able to copy that ability over?

[Assistant] The symbiote has a certain amount of intelligence. Organic webshooters aren't beyond its shapeshifting abilities, so it made them available in order to be more attractive to Spider-Man. The "webs" it shoots are actually its own biomass. The stuff is probably like hair or fingernails or else there'd be a lot more symbiotes running around.


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

[User] Eli5 why is it called 'Nucleic ACID' when one of its components is a Nitrogenous BASE?

[Assistant] The acidity comes from the phosphate groups used in forming DNA and RNA molecules. These phosphate groups are quite similar to phosphoric acid. The only difference there is the replacement of two of the protons from the phosphoric acid with protons from the sugar molecules of the nucleotide. This leaves only one remaining proton, which is very acidic. That easily-lost proton is what causes nucleic acids to be so acidic.


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

[User] ELI5: How fast would the earth have to be moving through space for us to feel it (if we could feel it at all)?

[Assistant] All motion is relative. You are currently moving at 99% lightspeed relative to some neutrino that just passed through you, but about 0% lightspeed relative to the earth. The point of relativity is that there is no absolute reference frame from which to determine speed. It doesn't matter how fast you're moving relative to random other objects in the universe (which is exactly the same thing as saying "how fast random objects in the universe are moving relative to you"); you're always at rest in your own reference frame. You can't feel speed any more than you can feel position.


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

[User] ELI5: Why do animals (including humans), in general, become less playful as they grow older?

[Assistant]
Play is all about exercise and learning. Part of it is simply about increasing strength and coordination. A lot of it is about learning valuable physical skills like stalking, fighting, chasing, catching etc. And a lot of it is about learning non physical skills. For instance a lot of young animals (including humans) can be hugely annoying in their persistence to do mischief because it teaches them about social boundaries.

Young animals go too far in their play because they only learn about social boundaries when an adult puts them in their place. Along the same lines, they learn about appropriate consequences by watching adults mete out discipline and watching adults interact with other adults. Ie. causing mischief is punished by a slap or a scolding but not by a maiming bite. When an adult faces another adult in a territorial dispute its preferable to threaten before resorting to violence.

And finally play teaches young animals about their personal limitations. Theyll teach it to climb fearlessly because it knows what it can and cant do. Itll know how fast it can run, how far it can jump and so on. Itll help them learn that their abilities increase as they grow because they run faster and jump farther than they could last week during the same game.

Play tends to be unique to animals whose abilities change and grow with them. You wont see much play among insects, arachnids and most reptiles for instance. Theyre born fully capable (even though practice and learning can improve their capabilities).


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

[User]
What's the difference between an emulator and a virtual machine?

Also, if I were to run a different OS i.e. Windows 95 or Linux  on Windows 10, would that be possible for a virtual machine, an emulator, or both?

[Assistant]
An emulator is anythign that tries to behave like something else and isn't necessarily a virtual machine if that emulated thing is not hardware.

A virtual machine can either be something that tries to present its own system image of the same architecture (emulates an i386 system while running on an i386; the CPU doesn't need to be emulated but various hardware pheriphreals need to be), a different architecture (i386 VM running on a PowerPC Macintosh, the CPU needs to be emulated), or a bytecode interpreter like the Java VM.

So a Java VM is not really an emulator as its not trying to pretend to be anything else, but it's a sort of virtual machine based on "imaginary hardware" in a sense.

VMware running x86 Windows on an x86 Linux host is a VM that's not emulating the CPU, but is emulating other things like disk controllers.

Something like WINE for example is not machine emulator or a VM, they're OS emulators (take the same API calls and try to do the same thing that Windows would do with them, etc.)

Windows 95 on Win10 (without using VMware etc) would require an "OS emulator" called WoW64 (Windows on Windows 64) that translates API calls similar to WINE.


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

[User]
Bletchley Park was a revelation. Are there any other places this important to the history of computer science?

I just visited the museum of computing at Bletchley Park.  Seeing a working Colossus machine, with its wheel-and-pulley system for running arbitrary length tapes at high speed, made me realize that the mathematical description of the universal Turing machine from _On Computable Numbers_ was less of a purely theoretical construct than I'd assumed - the Colossus is very much like a Turing machine given physical form.

What other places are there that you can visit, that have the same kind of vital and essential connection to the field of computer science?

[Assistant] there's the Computer Museum in Mountain View. i think you can also visit the room in Bolton Hall where the first message was transmitted on the ARPANET  between UCLA and Stanford which is the precursor to the internet.


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

[User]
Are there an equal number of protons and electrons in the universe?

I was thinking about ionizing atoms and such and started to wonder if there was a net charge to the universe. Whatever the obscenely large number of protons in existence is, is there the same number of electrons?

[Assistant]
No.

While it is generally suspected that the net charge of the universe is zero, there are charged particles other than the electron and proton that can carry the charge around. As a trivial example of why there *can't* be the same number of protons and electrons, we know of processes where you collide two protons and out pops three protons and an antiproton. If the number of electrons and protons had been the same before that interaction, it's certainly not the same now.


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

[User]
[Dragon ball:Xenoverse] when you create a character...

And you choose a human character, how does he/she keep up with Goku/Piccolo/Vegeta? I thought all humans were always going to be outclassed?

[Assistant]
You could be an android, a cyborg, half Saiyan, etc.

Hell, if you think about it, it's really more a timing issue than anything else.  Human power levels did rise, just not in time to meet the primary threats of the moment.

And what do you have plenty of as a time patroller?

Time.


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

[User]
Why isnt 1 considered a prime number? And for that matter, maybe zero too?

This might be dumb... but I thought a prime number was a number that is only divisible by one and itself... well both are true for one. Sure its redundant, but still. And zeroclearly it can be divided by one. I get that dividing by zero is a big no no, but it seems like a weird case for zero divided by zero.

[Assistant]
Zero is divisible by everything, since n\*0=0. If anything, it is the anti-prime because every number divides into it.

But almost everything that has to do with primes does not hold for 1. If we considered 1 a prime, then every result that we had for primes would have to say "For every prime, except for 1, ...". Eg, unique factorization of numbers into prime factors. So if everything that make primes interesting don't hold for 1, then should we really consider 1 a prime?

If you want to talk about primes in terms of what divides them then you can say that a prime is a number with exactly two positive divisors: 1 and itself. 1 only has one positive divisor, itself, so it is not a prime.


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

[User]
If someone was to cover their eyes for a year straight without seeing any light, would it just be really bright when they take it off then slowly adjust back to normal or would it have a permanent affect on the persons vision?

Edit: Well I'm pretty satisfied with all the answers as they seem to come to similar conclusions. Thanks!

[Assistant] Optometrist here. It should cause no permanent damage to vision in an adult. Many elderly people have dense cataracts (which, if left long enough, would act pretty much the same as covering the eye). When these cataracts are removed, vision goes back to normal, assuming that no other diseases are present.


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

[User]
ELI5: Why are power points (sockets, outlets) different around the world?

I have to travel with a whole bunch of adapters and my hairdryer/phone charger nearly died last trip.  Was this a big lapse in planning when electricity came about?

[Assistant]
>Why are there many different sockest

Because different engineers thouht that different things would be important for a socket, e.g. ability to transfer a lot of current vs. small size and simple (=cheap) construction.

>Was this a big lapse in planning when electricity came about?

People did not have much electrical appliances back then, and they certainly did not travel a lot with them. So for fairly a long time people would use electricity for light, and to power devices which were too big to carry around. This became a big deal when people had radios or electrical razors (or later: computers) which were small enough to take with them.


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

[User] ELI5:How it snows on Mount Everest if it's above the clouds?

[Assistant]
Everest is above some of the clouds, but there are still other clouds above the peak of Everest that allow for snowfall.

That being said, there actually isnt much snow at the peak compared to other parts of the mountain (Google a picture!). This is because there is less snowfall overall, and because its so high up that intense winds blow if off.


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

[User] [Star Wars] Why doesn't Chewie ever say to Obiwan "Yo dawg, I fought with Yoda on the homeworld, shit was tight"?

[Assistant] I mean, maybe he did. Obi-Wan and Chewbacca had a lengthy private conversation in the cantina in Mos Eisey. He could have mentioned that the Jedi helped save Kashyyyk years back and maybe that made it easier for Chewie to make the introductions since Obi-Wan would likely reveal that he was a Jedi who knew Yoda.


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

[User]
ELI5: How does a computer know how long a "second" is?

Or any unit of time for that matter. Humans defined the idea of a second; it's not a natural property of the universe. Especially interested in how it was managed on earlier computers (assuming it was different).

[Assistant]
The motherboard has a quartz crystal on it which vibrates at a known frequency. The motherboard uses this to keep track of time.

The button cell battery on a motherboard is to pass on electric current through the crystal, which is what causes it to vibrate.


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

[User]
ELI5:What makes something transparent?

ex.  What is it exactly that enables us to see through oxygen but not silver?

[Assistant]
**Simple answer:**

The gaps between the atoms is large enough that lights can pass though. (This is the incorrect answer though, but easy enough to know)

**Headache answer:**

Many people thinks that the reason light shines through transparent materials is because the atoms are spread apart enough, but that is not true.  Even in very dense solid like lead, the spacing between atoms are still very large when compared to a light photon.
The reason you don't see a light shining through your solid silver plate is because the energy from the photon is absorbed.  The electrons in the silver plate gets excited to a higher energy level when light shines through it, and it will be able to absorb some light photons. Oxygen lets light pass through because their electrons in oxygen need more energy to get riled up. The light is able to pass through because the electron is not absorbing them.

**ELI5:**

Imagine light is a girl in bikini running through a crowd at extremely high speed.  If in front of her is another bunch of (straight) girls, the crowd moves apart letting the bikini girl run through to avoid a collision.  This is oxygen.

Silver is however a bunch of sex-crazed (straight) men.  They get very excited to see a bikini girl running towards them and will do all they can to stop the bikini girl in her tracks.

Substances that reflect light are a bunch of sex-crazed (gay) men.  They don't want the bikini girl to ruin their party so they will do all they do to stop bikini girl in her tracks and to push her away.


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

[User]
What is actually happening when I hear my timber framed house 'crack'?

I understand that heating and cooling is responsible for it but are tiny cracks actually being made every time I hear it?

[Assistant] It would be better described as creaking rather than cracking. When a door creaks, the hinges aren't cracking, there's just resistance that builds up until friction can no longer stop the hinge from moving. The same applies to the beams in your house as some parts of the wood heat & expand faster than others.


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

[User]
[Half-Life Series] Why do the Overwatch still use standard human kinetic weapons when pulse weapons such as the AR2 are more effective/cheaper?

Me and my buddies always figured the challenge was importing material from outside our universe. ALSO: Could someone confirm/deny the existence of the AR3? It's spooking everybody in my bunker.

[Assistant] Actually, pulse weapons are not cheaper. What with the human economy in shambles (read: nonexistent), there is no one to stop the Overwatch from simply raiding every army base in existence and taking every gun from their storerooms. Human kinetic weapons are found in abundance on earth. Why produce weapons at a small cost when you can just /take/ weapons for no cost?


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

[User] ELI5: Why is that cars don't get significantly more fuel efficient year by year?

[Assistant] Law of diminishing returns. You can only squeeze so much efficiency out of a combustible engine. For the design of a specific car, it has its weight and aerodynamics to contend with. Those values are mostly static.


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

[User]
[Assassins Creed] Why would Ezio/Connor/other assassins not dress like the people around them?

I could be missing something, so if I am just point it out I guess?

But Ezio and Connor (and Edward, and whoever is in Rogue) seems to dress in a way that's styled like the time they live in, but still with what looks like an Assassin 'flair' to it. Wouldn't it be easier to not wear the assassin robes so they could blend in better?

[Assistant] Well, memories can be kinda fuzzy. Can you remember what you were wearing on some particular day? Hell no, you remember you jumped off a building and stabbed some dude in the face, you don't remember boring details like clothes.


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

[User] What makes a sore throat feel sore?

[Assistant] AFAIK: Sore throat can be caused by viruses, bacteria, fungus, chemicals or environmental irritants. Your body's primary response when it gets infected or irritated is usually to cause inflammation in that area. This is because inflammation is an increase in blood flow, which brings with it various things like proteins (to help heal damaged tissues) and elements of your immune response (like more white blood cells). It also brings elements (for example bradykinin, which is primarily a vasodilator) that activate your pain receptors, causing your nerves to register pain.


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

[User] How are we sure how many protons/neutron an atom has?

[Assistant]
We can measure these things fairly directly.

As for protons, we have the knowledge going back to the invention of the periodic table on the relationship between "atomic number" (proton count) and elemental identity. This is a very robust model of atomic structure that stands on top of a mountain of evidence. So we can be very confident that Carbon has 6 protons, Oxygen has 8, and so on.

Additionally, we can measure the average atomic weights of atoms and gain some understanding of the number of neutrons they have, on average. We can do this by determining the weight of a mole of an elemental sample. And we can determine when we have a mole of something through various tricks of chemistry. For example, with Hydrogen we know that 22.4 liters of Hydrogen gas at standard temperature and pressure conditions is one mole of H2, so we know that it should weigh 2x as many grams as the average mass of the Hydrogen atom in atomic mass units.

Using those techniques we were able to say that on average Carbon atoms have 6 neutrons to match their 6 protons whereas Fluorine atoms have 9 protons but 10 neutrons, and so forth. Some elements naturally occur with significant abundances among multiple isotopes, however, and this becomes obvious when you have examples such as Magnesium that has an average atomic mass of 24.3.

This is where mass spectrometers come in. Invented in the 19th century they became a mature technology during the early 20th century. By ionizing small samples of an element then accelerating the ions using electric charges you can create a stream of ionized atoms that will be traveling at a very consistent high speed. By passing that beam next to a magnetic field you'll bend the stream of ions. However, due to the momentum of the ions they will be deflected by a different amount depending on how massive the individual atoms are. The deflected beam of ions is then directed into a detector which registers the impact of the ions and determines how much they were deflected. In this way it's possible to figure out the atomic mass of the atoms, which will tell you how many neutrons there are for each individual atom. You can use this to collect statistical data on the isotopes of an element and determine the natural abundances of each specific isotope for that element.


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

[User]
Is vacuum something that is conserved or that moves from place to place?

Wife and I had a long, weird argument last night about how siphons work. She didn't understand at all, and I only vaguely do (imagine what that argument was like). But at the end of the debate, I was left with a new question.

If I fill a cup with water in a tub, turn it upside down, and raise it out of the water, keeping the rim submerged, the water doesn't fall out of the cup. My understanding is, the water is being pulled down by gravity, but can't fall because there's nothing to take its place *[edit: wrong]*, and it takes a lot of energy to create a vacuum, so the water is simply being held up by the cup *[edit: wrong]*, and is exerting some kind of negative pressure on the inside of the cup (the cup itself is being pulled down by the water, but it's sturdy and doesn't move, so neither does the water). When I make a hole in the cup, air can be pulled in to take its place in the cup, so the water can fall *[edit: wrong]*.

If I did this experiment in a vacuum, I figure something very similar would happen *[edit: this paragraph is 100% wrong, the main thing I learned in the responses below]*. The water would be held in the cup until I made a hole, then it would fall into the tub. If anything, the water will fall a little faster, since it doesn't need to do any work to pull air into the cup through the hole. But then it seems that the vacuum is coming in to fill the space, which sounds wrong since the vacuum isn't a thing that moves.

I'm missing something in all of this, or thinking about it all the wrong way. Vacuum isn't like air, it doesn't rush in through the hole in the cup to take the place of the water, allowing the water to fall. But then why does making a hole in the cup allow the water to fall?

*edit:*

*thanks all, I have really learned some things today.. but now my intuitions regarding how a siphon works have been destroyed.. need to do some studying...*

*edit 2:*

*really, though, how does a siphon work then? why doesn't the water on both sides of the bend fall down, creating a vacuum in-between?*

[Assistant]
So in the first example the air pressure outside the cup, pushing down on the water is greater than the pressure in side the cup. If you have raised the cup up 3" the pressure in the cup is -3" of water from atmospheric.

If you are working in a perfect vacuum there is no air pressure pushing down on the water outside the cup. So you wouldn't be able to 'lift' the water with the cup because there wouldn't be a pressure difference between inside and outside.

It's the action of the air pressure pushing down on the water outside the cup that allows you to create the vacuum inside the cup and lift the water.


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

[User] [Assassin's Creed Black Flag] Why are legendary munitions for the ship gold? Wouldn't a gold cannon work once and then be warped beyond recognition? Is it just gold plated? Is it just a trick of the animus or are those memories accurate?

[Assistant] Abstergo was using the game development department as a pretense to search Desmond's memories for POE's. Given that *the new hire* didn't need any special onboarding before diving into memories, it seems like Abstergo had already spent some time integrating game mechanics. Uncoupling ship upgrades from story progression makes sense, both for an open world game, and for speeding up the search for an All-Seeing Eye. (Edward may never even have acquired the blueprints for those particular cannons in his time)


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

[User] In Earth travel, we use North, South, East, and West, plus altitude for three-dimensional travel. Since those are all relative to the Earth, what do they use for space travel?

[Assistant]
Pretty much on every planet or moon it is possible to define North, South, East and West based on the body's rotation. Alternatively, they can be defined based on the Solar System's North and South (as the IAU did with Uranus, whose extreme axial tilt makes the rotational North opposite to the Solar System's North, but for all the other planets it's the same).

However this isn't very precise to plan spacecraft trajectories. There are more precise reference frames based on longitude and latitude, so a prime meridian is defined pretty much arbitrarily as they did on Earth. It's also quite common to use Cartesian reference frames centered on a planet but with the axes based on far away celestial objects because they don't rotate with the planet, so you have an inertial reference frame.

In deep space, far away from any planet, we use a reference frame centered on the Sun, with the X axis pointing along the ecliptic plane parallel to the vernal equinox (the intersection between Earth's equatorial plane and the ecliptic plane), the Z axis pointing North from the Sun, and the Y axis pointing 90 ahead of the X axis following the right hand rule.

It is possible to define others, it depends on each particular trajectory. Basically you need a center (a planet, the Sun, etc), a fundamental plane (the ecliptic plane, the planet's equatorial plane, etc) and a direction for the X axis.


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

[User]
Why does it seem there are more big storms at night?

I have always noticed huge thunderstorms with gusting winds happen much more commonly at night than during the day; these storms often seem to last much longer too. (keeping me up!) Is there a scientific reason for this, or is it just coincidence?

[Assistant]
Most of the time it's because thunderstorms don't start forming until well after the peak heating of the day occurs (typically around 2pm or so), because that is when the atmosphere is the most unstable and contains enough energy to break any capping environment.

Well-developed storm cells with steady surging cycles tend to 'feed' off of this heat energy and can persist into the late evening and night time hours. This is why you typically don't see thunderstorms in the morning,  although if a frontal boundary is nearby, that would be enough to maintain the needed instability around the clock for thunderstorm formation to occur.

Hope that helps.