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

[User]
How do computers transform 3D models using matrices?

I know that computers store the vertices of a 3D model. However, are they stored as vectors in 3-space or 4-space? I have seen texts showing 3D transformations using 4x4 matrices but I don't understand what advantage will it have over just using 3x3 matrices (what's the advantage of using matrices anyway, aren't there other methods of transforming objects?).

[Assistant]
The difference is that with 3x3 matrices you can't do translation. With a matrix you basically do a weighted sum over the elements in your vertex. If you wanted to translate your vertex, say the adding the vertex (0, 1, 0) to your base vertex (0, 0, 0). It is impossible to do this with a normal 3x3 matrix since all values will be multiplied by 0.

So what is done is adding a 4th dimension which is set to 1. Any translation you want to do can just be placed in the fourth column of your transformation matrix. The base vertex would now be (0, 0, 0, 1), and the translation can be accomplished by the matrix:

|0|0|0|0|
|:-|:-|:-|:-|
|0|0|0|1|
|0|0|0|0|
|0|0|0|1|


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

[User] Do bugs sleep? Do they have rest periods where they recharge?

[Assistant]
Yes they do. It's a little different than our sleep, but they do. Our understanding of circadian clocks actually come from fruit fly research primarily. Also, many groups (like most moths, etc) are nocturnal, implying they have rest periods during the day, etc. The sleep is not as strong as ours, they are easily woken up and react.

Edit: just to add a distinction, there is a difference between sleep and overwintering in insects. During overwintering, insects slow their metabolism and can produce glycerol to protect themselves from freezing conditions. If you've seen an insect look very still during the winter, it's most likely in an overwintering state and not truly sleeping.


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

[User] [Ghostbusters and Star Wars] Could the Ghostbusters bust a force ghost and trap it in their containment unit?

[Assistant]
A force ghost is one with the cosmic force itself, merely manifesting itself in physical form to communicate via the living force. Basically it's like a hard light hologram, but their actual essence is elsewhere. In fact it's *everywhere*.

So no most likely not.


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

[User]
Looking for exceptionally well-written books of contemporary analytic political philosophy

Any suggestions?  I'm reading works of contemporary analytic political philosophy mainly for pleasure.  I just finished *The Problem of Political Authority* by Huemer, which I greatly enjoyed.

Please suggest only books that you have read.

Thanks in advance!

[Assistant] *An Essay on the Modern State* by Morris, *A Liberal Theory of International Justice* by Altman and Wellman, *Liberal Loyalty* by Stilz, *The Moral Imperative of Integration* by Anderson, *Justice, Legitimacy, and Self-Determination* and *The Heart of Human Rights* by Buchanan, *Democratic Authority* by Estlund, *The Order of Public Reason* by Gaus, *A Theory of Political Obligation* by Gilbert, *Fairness in Practice* by James, *Land, Conflict, and Justice* by Kolers, *A Political Theory of Territory* by Moore, *Bounds of Justice* by O'Neill, *Libertarianism Without Inequality* by Otsuka, *The Concept of Constituency* by Rehfeld, *Force and Freedom* by Ripstein, *On Global Justice* by Risse, *Liberalism Without Perfection* by Quong.


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

[User] ELI5: If visceral fat is so dangerous, why do surgeons not routinely remove it during surgery within the abdomen?

[Assistant] Surgeon here:  big misunderstanding in these comments.  The fat of the abdominal wall (that able to have les invasive liposuction) is cosmetically displeasing, but not generally what is considered metabolically harmful. Visceral fat is that surrounding organs, filling the body.  That fat is usually implicated in metabolic disease.  This fat would be extremely dangerous to remove as it would put major organs at high risk.


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

[User]
I believe that actors who prepare for roles by doing something extreme are less impressive, not more impressive, practitioners of their craft. CMV

We've all heard stories about this: "Actor McActorson prepared to play the part of a homeless guy by sleeping rough on the streets for a week. And throughout the whole of the six-week shoot, he never took a shower and ate out of dumpsters!"

When I hear that, I don't think "wow, what dedication". I think  it's *acting*. Your job is to *pretend* to be cold and hungry and smell bad. If you are actually cold and hungry and smell bad in real life, your performance impresses me *less*, not more.

I also think asking to be addressed by your character's name on set or (a well-known example) remaining in a wheelchair and being spoon-fed are unreasonable demands to make on the crew of the film.

I don't know if it needs any further explanation, but to spell it out -- to me, an actor who can dine on delicious food and sleep on a comfortable bed, then turn up to work on set and convince me that he's hungry and homeless is the better practitioner of his craft than someone who needs to actually feel cold and uncomfortable to convey those feelings to an audience.

I believe that when actors prepare for roles by doing extreme things in real life, that means they are less impressive, not more impressive practitioners of their craft. The same goes for weird behaviour on set.

CMV.

[Assistant]
You know - you're missing a key part of this debate.

Are their performances good?

If another actor can do the same without the same effort, they are undeniably more skilled, but the belief is that actors who do method acting ARE better.


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

[User]
[Warner Bros.] How fast is the Roadrunner?

What it says on the tin. What are the best examples of his speed?

[Assistant]
I think what OP is actually asking is: "What is the RoadRunner's top speed?".  In that case, the answer is: He has no defined limit.

At the very least he is capable of going through solid walls and floating in the air, which suggests a Flash-like power set.

---

As far as examples go:  IIRC he did race Speedy Gonzales once.


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

[User]
ELIF: why does background music prevent deep sleep?

Im reading a baby sleep training book and it says that music will prevent deep sleep after four months old. Why is that?

[Assistant] When your asleep, your body runs a delicate balance between cutting itself off from the world so it can sleep, and being aware of it just enough to keep itself safe if need be. Music can help block out thoughts and other noises to help you fall asleep, but, as the track changes to a different song, or even as one song moves to a different part, you can register a sudden change in your environment, bringing you out of your deep sleep to check it out. This can disrupt your regular rhythm and make sleeping more difficult and less restful.


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

[User] ELI5: How do online retailers such as Amazon and Ebay confirm the legitimacy of their luxury items?

[Assistant]
In short they don't.  They're just a middle man.

Some of the sellers on those sites depend on their reputation.  The others can use escrow or just wait for someone who doesn't care.

Others, for very high end and rare items, can use escrow.  This is a third company with a good reputation.  When you buy the good the seller gives the item to the escrow company.  The buyer gives the escrow company his money.  The escrow company validates the authenticity, then sends the money to the seller and the good to the buyer.

The tests run are typically spelled out in the sale contract, as well as who pays for the escrow service and other contingencies.


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

[User]
Does the atmosphere get pushed up with sea level rise?

Is atmospheric pressure dependant upon the sea level, and if so does the atmosphere get pushed up if the sea level rises? So at the moment its almost impossible to breath at the top of Mount Everest because of the thin atmosphere. But if the sea level were to rise to near the top, would it then be possible to breath normally at the top of Mount Everest? Does that make sense?

[Assistant] If A LOT of ice comets crashed into the earth, and raised the ocean level 6 miles so that the entire world was underwater then yes you could breath standing on the top of Mount Everest (which would now be at sea level)


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

[User] ELI5: Why is the language of the Netherlands called "Dutch" and German not called "Dutch" since that is an Anglicization of "Deutsch", the German word for the German language?

[Assistant] The word deutsch (and dutch) originaly included both Dutch and german and the differences between german dialects were comparable to the difference between Dutch and german back then. Since England had more trade and contact with the Netherlands and flanders these were the Dutch they knew. When the german language started unifying they called that language (and eventually the country) by another name.


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

[User] ELI5: Why is buttermilk used in so many cakes and breads, and what separates it from normal milk?

[Assistant] Buttermilk is slightly acidic.  It reacts with the baking soda to produce carbon dioxide which helps the batter/dough rise.  Think of a vinegar/baking soda volcano.  The acidity also helps break down the proteins (gluten) so the result is less chewy.


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

[User] ELI5: How are non-rechargable batteries pre charged before they are sold?

[Assistant]
Non-rechargeable batteries are not charged, theyre simply constructed. Non-rechargeable batteries use a chemical reaction to generate an electrical potential. The chemical properties of the batterys internal materials are therefore different before and after they are depleted. They are constructed with materials in their pre-use chemical state, which naturally form a voltage.

Think of it this way: recharging batteries is like stretching a spring, storing energy within the system. Non-rechargeable batteries are like building a pre-tensioned spring, with the potential energy already in place. Once the energy is expended, the spring is collapsed, and you grab a new one.

Edit: Just to clarify, some springs are re-stretchable (re-chargeable batteries), and some are not. This depends on the type of chemical reaction in place. Some chemical reactions yield electrical potential with the ability of applied electrical potential to reverse the reaction. Others are one way only.


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

[User]
[Warhammer 40,000] I am a moderately educated civilian on a feudal world. What is my understanding of the wider galaxy?

I am a young man living on a feudal world.

I am not poverty-stricken and uneducated, but I am not insanely wealthy, either. Rather, I'm what might be termed as "upper middle class" by the standards of the planet, and received a good education.

Assuming that I know something about the Imperium, the Emperor and the wider universe, what exactly do I know?

[Assistant]
You would likely know of the Imperium as a galaxy-spanning organization that protects your planet, much like you're expected to protect the citizens that live on your land.  You may know of a ship or two that regularly visits the planet, or of any orbital defenses that the planet possesses (if you have any), but the intricacies of inter-galactic politics would probably be nothing more than far-fetched tales and the occasional Crusade epic that lives on in your planet's central libraries.

More attention would probably be paid to practical skills like husbandry, local politics/history, and administration (plus any fighting styles that your local nobility prefers).  Machine cults would be limited to local branches or guilds that maintain planetary infrastructure or local buildings (waterwheels, irrigation, looms).  Mysteries of physics, plasma, and machine spirits would be unknown.

Dan Abnett's Iron Snakes book has a good intro based on a feudal planet, and hints a bit at what they know of the wider imperium.


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

[User]
ELI5: Why does a handling follow-through on a basketball shot make such a difference?

When playing basketball, the difference between keeping the follow through hand in the air after the ball leaves the hand, makes a significant impact on how the ball progressed thru the air. Often if you drop the follow through early, it results in an "in and out" effect. How does this work?

[Assistant] The follow-through of your hand may be driven by how you're handling the ball in those last instants of contact. By flubbing the follow-through, you may be (unconsciously) changing how you're handling the ball in those last instants, causing it to move ever so slightly differently, which then influences the success of the shot.


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

[User]
[Star Trek] Are there any "Wolf of Wall Street"-type Ferengi?

They're supposed to be the epitome of unrepentant capitalism and greed, but they seem much more focused on well-structured trades and dealmaking, rather than hard-pitched sales, bilking suckers for all their worth, in the name of by-any-means-necessary hellbent-for-leather fast turnaround profits, to be blown on mansions, hookers and blow. Where are the *really* greedy Ferengi?

[Assistant] Ferengi are mostly used to dealing with other Ferengi, who are too smart to fall for stuff like that. They could potentially try that on non-Ferengi, but people are generally hesitant enough when dealing with Ferengi for it to work. Also, it mostly requires people to stop thinking when lots of money is involved, which doesn't work as well as it did in the 20th century thanks to post-scarcity meaning people care very little about money.


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

[User] ELI5: Why does every granade, missle, and atomic bomb's cloud always form a mushroom shape in particular? Why not any other shape?

[Assistant]
There's a lot going on in an explosion,  I'll try to keep it simple.

Heat rises,  there's more heat at the center of a destination than at the edges, so the heat in the center rises faster than elsewhere. That starts the formation,  when the heat rises more, it starts to cool and spread out, forming the top of the mushroom.

Then debris and material that had been lifted by the explosion begin to fall, curling the sides of the cloud downwards.

There's also some rotational motion from the temperature differential in the cloud,  which helps it maintain its shape longer than it normally would.


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

[User]
eli5: Why does grinding two objects of the same material (e.g iron) not produce a flat surface?

So I read about this thing called the "automatic generation of gages". Basically, it's a process of making three flats surfaces by manually rubbing them against each other in pairs. You can't get them truly flat with two pieces cause it causes belling and curvature between the pieces. i.e. one would be concave while the other convex.  What I don't get is why. Because even if all parts receive an equal number of strokes or the cutting powder is equally spread between them, it won't work. So what causes the curvature?

Maybe I should first ask how grinding works when they are both made of the same material. If one was harder than the other it would just cut away from the softer material. But when they are the same material how does it work? is it that they are not equally hard everywhere or something? And why does it specifically lead to a curvature.

Apologies if the answer is obvious.

[Assistant]
After just two plates are lapped against each other, all you can guarantee is that the two surfaces agree with each other, not that they're flat. They could be, but it's both possible and likely that the surfaces are curved. There's far more ways for there to be some error from a flat plane than there are for them to both be a  flat plane even in the hypothetical case. If you start with two curved surfaces of equal hardness that will wear down at the exact same rate, then unless the curvatures are the exact same you're going to end up with one slightly concave and the other convex. For example if both started convex, but plate A was more convex than plate B, then at some point you'll have worn plate B flat, while plate A remains convex. As you continue to lap them against each other, plate B will end up concave.

In the real world, the material has inconsistency baked in; one bit might be a bit harder or softer which will more or less guarantee the surfaces can't wear flat. It might still be pretty flat, but when you're trying to make high precision instruments 'pretty good' wont cut it.

Withworth's three plates method gets around this by using a procedure that cancels the errors out. Plate 1 and 2 can meet at a curve or a plane. Same with any other pair. But if any two meet at a curve, one has to be concave and the other convex. Your third plate is then either flat, concave or convex, and wont agree with at least one of the other two. You either have a flat surface compared to a curved surface, or two concave or convex surfaces which curve away from each other. So by grinding them against each other in the right order you can reduce the curvature of each one (concave against concave will flatten both for example) and when you're done you know the only way all three can agree with each other if the surfaces are all planes.

You can do it with two pieces if you want to break out the engineers blue and have a reference surface you know is flat; by varying pressure you can ensure any curves between the two are worn away till flat, comparing against the reference to make sure you're wearing away the right sections. The cleverness of the three plates method is how it guarantees you a flat surface to high precision from essentially nothing.


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

[User] [Star Trek] I just missed the Star Fleet Academy entrance exam test by just a few points. What are my options now, are there any other organizations that will take me?

[Assistant] Young Cadets can attempt to take the exam again. Plenty of other causes exist in the quadrant that are open to enterprising young people. Private merchants often hire former and in-training Starfleet, as do security firms, local science organizations, etc.


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

[User]
ELI5:Because dogs have more acute hearing than humans, when I play music really loud is it deafening to dogs?

Ive always wondered about this.When my dog comes in my room when im playing loud music I feel like it's hurting his ears but he doesn't seem to mind.

[Assistant] They aren't hyper sensitive to sound, they hear a bigger range of frequencies. Humans hear from around 20-50Hz (deep sub bass sounds) to about 20kHz (so high pitched it's more like a presence, like turning on a tv with the sound down). Dogs on the other hand hear all the bass we do but they have better high frequency hearing, they hear upto about 60kHz.


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

[User]
ELI5: How did we get to the moon with computers so weak compared to today

My guess is it has something to do with the fact that computers today need more power to run graphical interfaces, but thats about where my computer knowledge ends.

[Assistant]
A few reasons.

First, much of the electronics of the early space programs were analog, like old timey radios with a dial you could twist, or a cheapo washing machine.  That kind of electronics doesn't need much computational power.

Second, space travel didn't actually require a lot of advanced computation.  Oxygen level detection doesn't need a fancy computer.  Orbital calculations were pre-programmed, not calculated on the fly.  Radios were analog.  Control systems were the main digital component, and they were simple.

Third, complex systems are often more prone to failure.  Better to have (it was thought) well trained humans that could use brain power to actuate simpler systems, than have complex computers running everything.  Remember, every electrical connection has a chance of coming loose during the vibration of lift off.

Consider a modern space game.  That game might need to keep track of the position of thousands of objects, and millions of polygons.  The Apollo missions needed to keep track of **one single object**, the spacecraft itself.


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

[User]
CMV: Its desirable for youth to incur minor (but sufficiently painful) injuries so they have a better grasp of mortality.

Been seeing a lot of videos lately of younger drivers driving like lunatics thru traffic, a lot of them ending in fiery, sometimes deadly crashes.  As someone who was hit by a truck at 15 due to my own stupidity, it made me much more aware of the fact that it only takes one accident to thoroughly fuck your world up.  I feel like if more kids experienced even a fraction of the pain and suffering I did (or anyone who has been in a serious accident) they would have an entirely different approach when it came to behavior that had the potential for serious injury/death.

[Assistant]
I almost was run off the road by a speeding semi. Didn't get injured and still made me extremely wary when entering freeways.

I think there is enough evidence to the contrary that makes it questionable how effective this is - loads of kids that get hurt and banged up all the time but keeping acting recklessly. The issue often is with risk management and impulse control rather than not knowing consequences can exist.


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

[User] Do plants have immune systems?

[Assistant] Yes, its the soil microbiome. Their "stomach" is underground, mixed in the plant roots, with soil nutrients, and a symbiotic relationship with Mycorrhizal fungi. This is why healthy soil makes healthy plants and reduces your need for fertilizers, herbicides, and pesticides. Crop rotations, biodiversity, and organic fertilizers are some of the ways to ensure healthy plants and healthy soil.


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

[User]
ELI5:Why are schools and other organizations pushing for more students to pursue the "skilled trades" as their career path?

I live in Canada and all throughout high school and middle school especially, there were so many workshops and career days based around the "skilled trades" and how to pursue them. I even heard one lady at a career day say "Yeah we're trying to push kids to go into the skilled trades because so many kids are unemployed coming out of university." Is that true? From what I understand a university degree is extremely valuable, but a skilled trade is also sometimes the "best route" (as they said) for many people who may not be able to afford higher education. I'm just wondering if there's a reason for this increase of interest in skilled trade professions, because I see it a lot more now than I did before when my sister was in high school.

[Assistant]
Most likely because there's a shortage of skilled tradesmen in North America.

We're about 2 generations into a cultural movement that pushed the belief that you need a college degree in order to be financially sucessful.

The result is that the actual market for college degrees can't support the supply being pushed through, and universities being able to charge more because of the inflated demand.

Trades, on the other hand, have been neglected, leaving the supply of tradesmen low and the demand for trade education low. Trades do pay well, though, and exceptionally so because there is more demand than supply for tradesmen.


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

[User] ELI5: At which point can we be scientifically considered dead?

[Assistant]
Biologists here:

This is an awesome question! And a complex, tricky one.

A exact moment or thing we can point to and say this person is dead would be what we call Biological Death or Biologically dead instead of Legally dead or Medically brain dead.

Biological death is measured by A few criteria that have to be met.

1. No electrical activities inside the brain and brain stem, or any sort of activity within the spinal column

(brain dead patients can have no brain electrical activities but still have random electrical pulses created in the spinal column or brain stem)

2. Pulmonary circulation can not be maintained naturally or artificially

(We are unable to keep the heart pumping and blood oxygenated, either naturally or by the use of machine or medications)

3. Respiratory function cannot be maintained, naturally or artificially

(We are unable to get your lungs to absorb oxygen and transfer carbon dioxide, we can inflate and deflate them, but they arent oxygenating your blood)

If all 3 of these are met, we consider that to be Biological Death, theres no way to keep the brain, or the body alive by modern scientific means.

But, this is constantly changing, as we advance and understand more, we push the definition of death further and further back.


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

[User]
[LotR] Why didn't Frodo just walk west? What would have happened if he had?

I've just started rereading *Fellowship of the Ring*, and there's a thing in Chapter 3 that I'd completely forgotten about - right before Gandalf goes off, he and Frodo make plans for how the hobbit is going to move the Ring out of the Shire.

Frodo, sort of sentimentally, decides to follow Bilbo's route, and Sam's just excited to have a chance to meet Elves. The decision is kind of lightly taken - at one point Gandalf asks (paraphrasing), "Which way do you think you'll go? Any way will do as long as it's not here."

So fast forward a few months (into the next chapter or two), Gandalf never shows up, Frodo, Pippin and Sam find themselves dodging a Black Rider or two in the less settled areas of the Shire, and then are lucky enough to come across a party of High Elves - who they get along great with. Sam's overjoyed, Frodo speaks their language, they give him a little news about Bilbo, it's all pretty grand.

They're heading west to the Grey Havens. All the High Elves do.

What if Frodo did, too? The elves werent sure where Bilbo was, but knew he was hanging with other elves. Frodo has no reason to go south (where the Enemy is), but also no real reason to head east toward the mountains  not yet, anyway. Just a kind of notion. Gandalfs not there to give advice, and his generally cheery outlook about heading toward Rivendell might well be misplaced given that hes missed his appointment and put the hobbits in jeopardy.

The one place where they know lots of elves are going is not too far outside the Shire, and pretty ideal if you wanted to get as far from the Enemy as possible  theyve got ships!

Why not go west *to start with*? Frodos even a Ring-Bearer, so entitled to free passage (although he wouldnt know that yet.)

How would things unfold then?

[Assistant]
He's definitely not entitled to free passage to the Havens at that point in time.

Frodo's (and Bilbo's, possibly Sam's) acceptance to the Havens and on the boats west was granted to them *after* the destruction of the ring, as a reward to their service to Middle-Earth and as a solace for their ring-depression, which they could never shake as long as they lived in Middle-Earth.

Before the war of the ring, there wasn't any sort of invitation, and as you mentioned, Frodo wouldn't have known about it anyways.

But more important is the issue of the Ring, not just the Bearer.  The Elves were very, very hesitant to let the Ring stay in their safe havens.  In both Rivendell and Lothlorien, the mood was pretty much "You're here so we can keep you safe for a few weeks, then you and that Ring need to get the hell out."  Rivendell, Lorien, and the Havens were the last bastions of real Elvish power, kept safe from Sauron's corruption through the power of the Three Rings.  Bringing the One to any of them was a danger, and was only done for safety and to aid the Bearer and his Fellowship.  There was definitely no way to leave the Ring at one of them, or to bear it across the sea.


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

[User]
What happens if the event horizon of two black holes touch?

Can one be ripped apart or will they be forced to combine completely? If that's the case how long would it take?

[Assistant] The two black holes will revolve around each other until the event horizons collide. As they get closer to each other they orbit faster and faster until they completely collide and become one 'larger' black hole.


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

[User]
[The Thing] is the Thing evil or is it just a creature acting on instinct? Was it tying to leave earth or go somewhere else on earth?

Yes, I'm piggybacking off the Thing post from yesterday.

Also, was the Thing the pilot of the spaceship at the beginning of the movie or perhaps a prisoner/wmd?

[Assistant]
I believe in one version it was supposed to have been a creature that was inadvertently collected by the aliens that made the spaceship.  It assimilated the other specimens and crew, causing the ship to crash land on Earth thousands of years ago.

It's not evil, it just has a method of acquiring food and reproducing not widely seen in macro-biota on this planet.


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

[User] Would a water balloon freeze in the atmosphere if you threw it out of a plane?

[Assistant]
depends on how high you were when you threw it.

if it's above freezing on the ground and you go up in the plane to a point where it's below freezing, it's *possible* that it could freeze, if there's enough time while it freefalls for the appropriate amount of heat to transfer out of the liquid and for a phase transformation to occur.

here's where shit gets weird. if you were high enough above the earth (like 20 miles--near enough to space), the pressure up there is so small that it will actually cause exactly the opposite--the water could *boil*. Even though the water is colder at that altitude than the normal freezing point of water, in near vacuum, the freezing point of water actually decreases significantly. wrap your mind around that!


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

[User]
[Alien Franchise] Is extraterrestrial life common knowledge?

There are apparentlky standard procdures for any extraterrestrial life a shipping vessel finds, which suggests its fairly common for people to come across alien life.

Besides that, in *Aliens*, a Marine mentions having sex with some androgynous race (whether this is a human or not was never very clear)

SO, are humans aware of alien species besides the Xenomorphs, or just a hopeful, diverse species?

[Assistant]
During the briefing of the Marines aboard the "Sulaco", one Marine asks (I paraphrase), "Is this a straight-up fight, or a bug-hunt?", to which, once informed that there is a xenomorph involve, a second Marine replies, "it's a bug hunt", in a tone that suggests that "bug-hunts" are the latrine duty of Colonial Marines.

So extraterrestrial mega-fauna must be common knowledge by that time.


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

[User]
[Star Trek] Why don't we have more robots?

I've been thinking about this for some time, and I really don't understand why we haven't started using more robots.

There's that one called Data that they let into Starfleet, that more than proves that the ability to manufacture and repair functioning robot bodies is well withing our reach. Sure he's a very advanced model designed and built by some eccentric genius, but the basics of working robot limbs aren't really that complicated, heck they had working robot arms nearly four centuries ago.

And it can't be lack of computer technology. We install computers on starships that have so much computing power they've been known to *accidentally* produce self aware artificial intelligence. Imagine what we could do if we were trying.. Our computers can run holodecks with thousands of fully actuated interactive characters. I'm quite certain we could build a little tin can on wheels that serves drinks, follows instructions, and does basic repair jobs around the ship. If it's safe to let a holographic doctor treat real patients, I'm  sure it would be safe to let an AI robot repair a ship. Not only would this make and engineers job safer, it would make every engineering department more efficient.

Once we had a design we could mass produce them in replicators.

It just seems like an egregious oversight on our part, we know what robots are, we most certainly have the technology to build them... but we don't... In fact not just us in the Federation, but nobody in the entire Alpha Quadrant... or the Beta Quadrant...

EDIT: Thank you for your answers, all of you have very good points.
But I"m still a little confused, a common theme seems to be that we don't have robots because creating a semi-intelligent automated drinks trolly would be akin to slavery.

I can understand that we in the Federation hold ourselves to a high moral standard. But I don't understand why every other race, from as far away as the Delta Quadrant holds themselves to *our* moral standards on this issue. The Cardassians and the Romulans have no particular issue with enslaving entire races, The Hirogen hunt sentient species for sport, the Vidiians steal organs. But everyone has kind of agreed that making robots would be bad.......?

[Assistant]
the complexity of Cmd. Data's (and the other Soong Androids) positronic brains was very difficult to replicate. Cmd. Data attempted to create a new life with his "daughter" Lall, but as we saw just before Cmd. Maddox took her back to his lab her neural network was not stable.

Also there are ethical points to consider, is it ok to create a race of sentient/near sentient beings to be effectively a slave labor force? This was clearly argued by Cpt Picard during the hearing to determine if Data has the same rights to refuse unjust orders as any biological Star Fleet officer.
Prior to its return to Earth the EMH mark 1 on the USS Voyager endured a struggle during its existence to be accepted as sentient. While the magistrate did not rule that he was alive, he did rule he was an artist under the law and has the rights to control his holo novel. As a result "Photons be Free" has become the most used holo novel among dilithium mining holograms (repurposed EMH mark 1).

Few artificial intellignaces can during the course of their operations, exceed their programming and are usually limited by the scope of their programming (such as Vic Fontaine hologram; aware of the real world but cant learn to play Tongo because it did not exist in 1962 Las Vegas).


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

[User]
[MCU] WTF were Tony's parents driving to The Pentagon all alone at night with valuable cargo without the aid of bodyguards and or Shield agents?

Come on don't you think some U.S military general dude would have thought that allowing Howard and Maria a.k.a  (a defenceless old couple) to drive to The Pentagon all alone at night with valuable cargo without the aid of bodyguards and or Shield agents was a BAD IDEA.

WTF were Tony's parents driving to The Pentagon all alone at night with valuable cargo without the aid of bodyguards and or Shield agents?

[Assistant]
They were on their way to a Christmas party; they were just going to drop off the new serum en route.

Howard Stark was the kind of guy who took his work home, ignored procedures, and avoided bureaucracy as much as possible. The Pentagon probably didn't even know he would be delivering the serum that night.


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

[User]
[1984]it's limited and probably poor quality, but the characters have access to chocolate and coffee. does that prove Oceania really does have territory in the tropics, outside Britain?

because all the information from the government is unreliable, some people have speculated that Oceania might just be Britain, or even just part of Britain, and all the stuff about wars around the world is made up.

does the fact the characters have access to goods that could have only come from the tropics, prove that can't be the case?

[Assistant]
Well technically speaking, it could be synthesized chocolate and coffee, meaning that they really don't need to harvest actual plants to produce it.

Still though, the idea that Oceania is just the British Isles, while possible, is unlikely based on what we know. Granted, what we know is very carefully curated by the Party so take from that what you will.


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

[User] ELI5: if each parent only has either XX or XY chromosomes, how can a child get a disorder like pentasomy X (having XXXXX chromosomes)?

[Assistant] Cell division is preceded by copying of all the chromosomes and splitting them between the two resulting cells. Nondisjunction can happen, which means the two copies don't split evenly and migrate to their corresponding new cells and they may all end up on one side and make a cell with double the normal amount. Repeat this a couple times and mess up the last one so only one X goes with the one that already has 4 and you end up with 5.


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

[User] How would Kierkegaard and Nietzsche respond to each other?

[Assistant]
I think Nietzsche's response would be a lot like the one he wrote about Thomas Carlyle, that Kierkegaard wrote work that he knew had revolutionary potential, but failed to give it sufficient clarity or direct expression, even to the point of missing the consequences it would have on religious faith and politics.

I think Kierkegaard's response would depend on which part of Nietzsche's work they were discussing. Towards the end, he would probably find the concept of the bermensch laughable and contrast it with the reality of Nietzsche's life as well as well as undermines some of Nietzsche's greatest virtues as a thinker and leads him to one more Idealism Nietzsche indicted his contemporaries for chasing after. Then he would probably object to Nietzsche's provocatory style as missing the point of the role of irony and subjectivity in finding truth.


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

[User] ELI5:Why does anger increase pain tolerance?

[Assistant]
Anger produces adrenalin.

The same chemical stimulant your body drugs you with when you are very, very afraid. It's an if-all-else-fails flight-plan. If you get so scared that you are running for your life, your body "helps" you by ensuring that you don't really notice such minor issues like broken bones and shit that might slow you down at a bad time. Instead you get all the pain served in one go when you have slowed down, hoping that you have hidden well already when it knocks you.

Anger is the feeling most parents feel when they need to protect their children. The adrenalin rush is what makes people knock the teeth out on someone they mistake for a kidnapper or someone doing harm to their children. Because if you look at it, protecting your young is also super important. And you should just do it and bother about the aftermath later. At least from the point of view of the species as a whole.


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

[User] [Skyrim] Every now and then that Dragonborn guy will be walking around then immediately stop and wait for hours on end before moving again. Meanwhile everybody else carries on like nothing is out of the ordinary. Why does he do this? Is he okay?

[Assistant] He's fine. The dragonborn is an amazing individual with talent and drive beyond mortal men. He waits because there is nothing else for him to do. He is exactly where he needs to be in order to pass his next trial. Further action at this point is wasted action.


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

[User] If a person is a blood-type match for a blood transfusion, would they also be a match for bone marrow or organ donation?

[Assistant]
No. Blood type matching is done primarily based on AB (blood group) matching and RhD (positive/negative) matching.

Organ/marrow matching is done on the basis of many other factors (Human leukocyte antigen, HLA), which are a completely different set of genetic markers.


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

[User]
Are there any fluids that can exist in a vacuum?

A gas would immediately dissipate, and a liquid would boil and dissipate. Even mercury at the top of a manometer is under it's own vapor pressure. Are there any fluids that hold together?

[Assistant]
Technically most materials will sublimate under vacuum. It can be an issue in ultra-high vacuum systems where you can't use some copper alloys for example.

However there are some liquids that have very low vapor pressure. Ionic liquids are a good example of this. Since they are held together by ionic bonds type forces they don't evaporate easily.

PFPE "oils" are also often used for lubrication on board spacecraft because they last a long time on site.


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

[User]
Should one buy stuff before a recession, or save the money ?

European here, noticing increasing news talking about an incoming recession, and I\`m wondering, should I buy stuff now, or keep my savings ?

Basically I\`m afraid my cash savings will lose their value, and wonder if I should buy stuff now, before the money loses it\`s value, so that I least I will be able to enjoy the stuff, or if I should hold onto the money.

This fear comes from the fact that my grandparents lost all their savings during the \`89 romanian revolution, although I believe that to be a different thing.

One day they could easily afford a house, the next day they couldn\`t afford a car, if that were to happen to me I would probably throw myself off of a bridge.

[Assistant]
Firstly, just because the news is talking about it, doesn't mean it's going to happen. Nobody can time the market, or maybe a very small number of people. If you or they can, they can become insanely wealthy by shorting/buying puts. Truth is, we don't know if 2019 is going to be a pretty stagnant year, another recession or the biggest growth year on record.

Secondly, currency is one of the safest things to hold going into a recession, especially if it's something like the Euro or the US Dollar. The chances of it getting devalued or of a large inflation is close to zero. Maybe if you're holding currency of some small country that might default, then there is any reason to worry.

Thirdly, in a recession the price of goods will drop, especially property, so buying property before a recession is not a good idea.

If you want to be a 100% safe and really afraid of a recession, I'd advise you to keep your money in a hard currency (Euro, USD) in a savings account.


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

[User]
[DC]Could somebody with multiple personalities use different Latern rings?

Assuming each individual personality corresponds to one of the spectrums. Or would the rings not react to fractured minds? If two personalities fit the same spectrum could they power up the ring beyond its usual capacity?

Let's say Sensui from Yu Yu Hakusho. His main personality could likely tap the green spectrum while his rage-filled, bloodthirsty personality would fulfill the requirements for the red spectrum.

[Assistant]
Absolutely. Hell, there are people with a single personality that have wielded two rings at the same time (Hal wore a Green and Blue Ring for a bit and later a Orange and Yellow at the same time, and Guy Gardner wore a Green and a Red Ring for a decent amount of time, and Red and Violet in an emergency) Kyle wore all seven at once on his path to be the White Lantern.

I have a feeling with your example that only the ring of the personality in control would be effective though.


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

[User]
Do dogs recognize breeds?

Do dogs have the sensory abilities and mental capacities to tell different breeds apart? Do they act different to members of their own breed? I noticed that one my dogs would always freak out when he saw Bernese Mountain Dogs, and they'd always play with other boxers the same way they played with each other. I'm not sure how much of this is dogs recognizing breeds and how much is me projecting characteristics onto their behaviour.

[Assistant] I've worked with dogs in in shelters and rescues, and I've never seen any behaviour that would indicate that they act differently towards different breeds. Body language is the main way in which dogs communicate, and the size/shape of the tail isn't important compared to the way it's being held, for example.


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

[User]
Why was Nietzsche "life-affirming"?

I've been trying to study Nietzsche a bit and I'm beginning to grasp some of his ideas. "Life-affirmation" seems to be kind of an axiom for him, so basically I'm wondering what is Nietzsche's reason for being life affirming? Why be life-affirming?

[Assistant]
Nietzsche had a really sparkling personality, he grew up as a really dynamic boy with a lively mind that characterise his writings. Having also a brilliant and sharp eye, it's obvious that in a century such the century of romanticism he would've detected the rotten parts of it, which contrasted with his vernal character: all the heaviness, theatricality, tiredness, idealism of romanticism enlightened Nietzsche in such way that he, firstly, started question the whole hisotry of philosophy in such perspective and, after and deeper, the whole history of Europe under the influence of Christianity.
According to him and his "genealogical" analysis, Europe has been corrupted firstly by a rotten philosophical tradition that points towards a life-denying metaphysics, and secondly by the even more explicitly life-denying history of Christianity.
He stressed the importance of contrasting these degenerate ideologies, because of many reasons (which you'd probably find clearly in "Genealogy of Morals" and "Twilight of the Idols"), probably the main one being that life is will to power so no matter what life has to empower itself and that's where a man should point to.


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

[User] LI5: What is plasma?

[Assistant]
It's a state of matter.

Matter is something like metal or plastic or sand or rock or water or steam.

The state of matter means whether it's solid, liquid, gas or plasma.

Plasma was only recently discovered. It's basically superheated gas.

For example, let's look at ice. Ice is a solid, but when you heat it up, it melts, and is a liquid. When you heat this liquid ice - we usually call it water - up to 100 degrees Celsius, it boils, and that stuff you see coming off of the top of the water is steam. That's the 3rd state of matter, gas. If you were to collect that steam and heat that up, you'd turn it into plasma, the 4th state of matter.

Plasma is present in neon lighting (running electricity through basic gases, heating them and causing them to emit coloured light) and in plasma TVs.


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

[User]
CMV: The shape and form factor of a burrito is the most balanced way to eat a meal.

Sandwiches are cool but if you try to overload it, it becomes a tower that is hard to eat unless you can unlock your jaw. Wide sandwiches, although another option, become a bit unwieldy and the sauce tends to drip down the bottom very easily.

Platter meals are efficient and very good at getting individual flavors but lose points due to it's immobile nature and requires being able to use utensils in order to consume.

A burrito, on the other hand: is handheld, can be eaten while on the go and and if properly wrapped and seared shut on the grill, will not leak. When you over-stuff a burrito, it  may become a monster but one in which you may be able to tame.

[Assistant] When you next go to Chipotle, compare how much food you get when you order a burrito vs. when you order a bowl of the same food with a tortilla on the side (for the exact same price). You will find that you can easily fill a tortilla to the size of a normal burrito with the bowl of food and have more to spare. Burritos are an inefficient way to deliver food, because you need tortilla equal to the surface area of the food you wish to consume. Bowls and plates are much more efficient containers for food than tortillas simply because they allow you to fit so much more.


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

[User]
[Alien and Terminator] Could a Xenomorph facehugger mistake a T-800 as a suitable host?

In the movies and other media, facehuggers throw themselves at anything living for the most part. Which got me thinking whether or not a facehugger would try to attach itself to a T-800 infiltrator. The T-800 infiltrator is covered in living tissue that is exactly like human skin. So, would a facehugger try to attach itself to a Terminator that is covered in living tissue?

[Assistant]
Androids in the Alien-verse are realistic enough that Ash and Call were able to live among their respective ship crews for weeks without anyone noticing they weren't human.

If we assume the Alien comics are canon, the use of androids for sexual purposes is widespread, implying that they're close enough to indistinguishable from actual humans that nobody can tell the difference. But confronted with androids in the comics, the xenomorphs never capture them for egg implantation - they either ignore them, or immediately destroy them. Even in the story where the aliens were capturing humans to breed them, they destroyed the synth on sight.

This implies that the xenomorphs can tell the difference between real and artificial people. It's outright stated in some of the comics that their primory sensory mechanism is a form of telepathy (after all, what other sensory organs do they have? No eyes, no nose, no ears... they can't do everything by tasting the air), which would enable them to identify the Terminator as an unsuitable host.


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

[User] ELI5: Why does stainless steel always have circle scratches on the surface?

[Assistant]
Im gonna guess youre referring to machining marks from milling and turning and polishing of the billet steel rather than in-service contact scratches or weld formation (coin stacks/folds).

Basically they are the marks from the tools which formed the stainless steel into its given shape by removing excess material from the work piece (the end product).

They are circular because either the cutting tool or the work piece rotate at high velocity to give enough energy for the cutting tip on the tool to remove fine layers of material from the work piece.


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

[User] [General] Why do designers of self-destruct systems torture the doomed personnel by making them listen to a countdown? Why not some appropriate music?

[Assistant]
So you know how long you have to escape.

While protaginists tend to get in situations where they're stuck they're, what's actually meant to happen is you hear the ship is detonating in ten minutes and take that as your queue to *get the fuck off the ship*.


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

[User]
Eight years ago I had to drop out of school due to illness. I absolutely loved college, especially speaking with my professors during office hours. My main interests were Creative Writing and Comparative Literature. I can't return to school, but I miss the courses and conversations. Any ideas?

For most of the last eight years, I wasn't even well enough to read a book. Within the last three years, I've become able to read again, though I haven't been a voracious reader (yet!). Eventually, I do hope to return to school, but I don't know if or when that will be possible.

In the meantime, I'd love to cobble together some kind of syllabus for myself. I know most of it should entail reading, but I'd also like to learn how to write.

I miss so much visiting my professors during office hours. During my brief stint as an undergrad, I did many "Honors Projects" and was trying to create my own Interdepartmental Major, so I'd often end up talking to my professors about what they were most passionate about, and their passions became my own. Comparative Lit especially opened up the entire world for me. I miss that sense of doors opening, of open country. Is there any way to get some semblance of that without actually being enrolled and on-campus?

I know this is very open-ended. Thanks you for reading and for whatever suggestions you may have.

[Assistant]
If you just want to be able to sit and talk with professors, that is hard to do outside of college because that is where the professor are.

If you are looking for ways to attend a class again, you may look at the many online options.  Just stay away from the for-profit schools.  Many brick-and-mortar schools offer online programs or classes and you could try that out.  You could also look into your local community college.  This would be a very low stakes way to try a class to see if you are ready again.

Have you considered joining a book club?  With the right group, this may satisfy your desire for conversations around literature until you feel you can go back to school.


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

[User]
ELI5 Why aren't phones like laptops when installing operating systems ?

I mean you can get any random laptop install windows or linux on it and it just works but for phones you have to get custom roms specific for your phone.
Aren't phones essentially same as computers ?

[Assistant] Technically this utopia is totally possible. This problem is basically a manufactured one. Apple won't let you do anything cos it wants the absolute control over your devices and the OS on them. Within android things are a little more open, you might be able to install some other flavor of android if you could get your phone's bootloader unlocked, but you'll have to jump through hoops. Basically everyone wants to lock you in, to some extent.


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

[User]
Dealing with a toxic advisor as an undergrad

So,

I can't believe I have to actually write a post like this, but I need help.

I'm an undergraduate working in a paid research position for a pre-tenure PI at a well-known private research university in the northeast US. I love the work I do, but the relationship I have with my boss/advisor is degrading to a point of complete nonfunctionality and I'm not sure what to do.

Everyone in the group has long had issues with his management style - he micromanages and yet complains that you don't get anything done, tells you not to set up certain experiments and then complains at you for not doing what he told you to not do. He routinely texts us at 2AM to chastise us for little things we did wrong in lab. Perhaps the worst part of it all is the constant attack he exerts on our work ethic - he has complained to me I don't work hard enough when I hadn't slept in two days. Working in his lab more than I am technically able to by university regulation on top of a full course load in a demanding major and nothing I do is good enough for him.

Today he texted me explaining that his expectations are that I work no less than 72 hours per week with the level of productivity that would be expected of a postdoc at a big-name group at an ivy-league university.

I swear to god I am not making that up. I have the texts. Again, I am an undergrad. I love the science. I love what I do. I intend to go on to grad school, and I'll quite frankly need a letter of recommendation from him to get into a good one. But I am at my wit's end dealing with this dude. What do I do?

[Assistant]
Private texting of an RA just reads like a warning sign, especially in parallel with expressing extreme expectations that are in direct conflict with University regulations. Nothing you could get out of a good letter from this person is worth this, especially if it continues for others.

You need to take this up with someone who you can trust has student safety in mind. One option is another professor in the department, or the chair, if you feel like you can trust them to listen to you and recognize this behavior as inappropriate. This is good because they might be able to vouch for you in a letter to explain the situation down the line. If youre concerned that people in your department might agree with the advisors priorities and behavior (horrifying but possible), you should talk to the administration at some level. Some universities have an Ombuds office who is responsible for handling anonymous student-faculty conflict. You might also reach out to a director of research or student employment. Apart from bad mentorship this looks like exploitation of power over student labor, plain and simple.


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

[User]
[DC and Marvel] Who is the weakest Avenger and Justice League Member purely in terms of skill?

And Teen Titans and X-Men if anyone has the time.

[Assistant]
In terms of skill in combat? Probably the Hulk. Theres no technique there, just rage. There are obviously versions of Hulk where he has trained and become skilled, but base Hulk is pure instinct.

For DC, probably Captain Marvel. Billy, himself, isnt good at fighting or anything. He has super-human knowledge and ability given to him when he transforms. Billy isnt the one with those skills. Hes just borrowing them from legendary heroes and deities.

For X-Men, probably Rogue. Everything skill-wise that she has pretty much came from when Rogue absorbed Miss Marvel to death. Again, those arent her skills. They are Carols.


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

[User]
ELI5: Why do we care so much about habitable planets that are several lightyears away when there is no feasible way to get there?

always struggled to grasp this concept when it seems hopeless to get any outcomes or information. is the hope that we (or rovers) may travel at light speed at some point?

[Assistant] We're studying the universe around us, as we have done for practically all of human existence. We're so excited and focused on habitable planets because they're the most likely candidates to find signs of extraterrestrial life (as we know it). Just because you can't get to where you're studying doesn't mean you can't learn anything from it.


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

[User] [Spider-Man 3] Could the particle accelerator be used to create an army of sand soldiers since Flint was able to get super powers from it so easily ?

[Assistant]
There's a fundamental problem here, which is that we don't know why it did that. It certainly wasn't *meant* to, and that's not really a thing particle colliders *do*. So what happened?

Was it the type of sand used? Weather, humidity, temperature? Something biological about Marko, or strange reaction with something he was carrying? Some error or fluctuation in the particle collider itself? Some combination thereof? Or a freak quantum-tunneling style cosmic coincidence that has no plausible chances of being repeated?

No-one knows what exactly made "sticking your head in a particle collider" have such a weird effect. You'd need to do a lot more tests to see how easy to replicate the result actually is. Alas, it seems unlikely such tests are going to be done.


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

[User] ELI5: If we extract oil from underground "reservoirs", why don't we dump toxic waste in them after they've been emptied?

[Assistant]
You've removed their seal. To access those reservoirs you had to drill a hole to them, which placed new stresses on the surrounding rocks and perhaps relieved others.

Then you pumped the oil out, which removed a lot of the "load bearing" liquid (much like the water in a water bed) that held up the rock above them.

So the conditions have changed for that now-empty reservoir, even if you completely cap and plug the hole you used to bore into it - and that can create a risk if you use it for toxic waste storage.

As a result, some reservoirs would be unsafe for toxic waste disposal, although others might be very stable and a good place to dump it... but you still have to ship it there and get it down the small hole. And if the technology for oil extraction advances (as it has in the past bunch of decades), you can no longer access any of the oil in that hole, or any oil that might be nearby it due to the risk of contamination.


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

[User]
ELI5: What is the benefit of having a stuffy nose when sick?

We get stuffy noses when our nose gets inflamed inside. But what is the point of this inflammation when we are sick? Is there any benefit to it? It only seems like its there to annoy us and make breathing a hard time.

[Assistant] Inflammation/ mucus help keep more foreign matter/ antigens from entering your body. When you are under attack from an antigen, your immune system responds by upping the amount of mucus to keep out any more antigens. This way your immune system is not overwhelmed. So, although it is uncomfortable, it is an important part of your innate immune system.


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

[User]
ELI5: Steam, the gaming software

I finally have a computer that can handle it.
What is it?  How does it work?  (INB4 Miracles)

[Assistant]
It's a store, game library, and social media program rolled into one.

So you either buy a game through the built-in store or enter a serial key for a game that is in the list of available games (e.g if you bought a DVD copy from a store).  From there, Steam will download all the files for you  -- you can choose what to install or not; you can install/uninstall at will.  Once a game is in your library, it is permanently associated to your account.  If you buy a new computer or have more than one computer, you don't need any discs, just your steam account and an internet connection.

This is coupled with a sort of social media aspect -- you get a profile page that lists some statistics like what you most recently played or how many hours you've put into various games.  There's also an instant messenger feature built in so you can keep a friend list and chat with them when they're online.

It also tracks other information/statistics like which of your Steam friends have the same game (helps in finding multiplayer buddies) or what achievements you've garnered.


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

[User] ELI5  What is happening when your eyes get heavy from lack of sleep ?

[Assistant] Muscles you use the most tend to get tired first, like for example,  if you walk all day your legs will become fatigued. This also applies to the muscles around your eyes - your ocular and brow muscles become tired because youre using them for most of your waking hours. Looking at a computer screen for a long time or having chronic allergies can compound the heaviness feeling in your eyes.


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

[User] [40K] What would happen if a ship from the Great Crusade suddenlt arrived in the Sol system in M41?

[Assistant]
Let's assume for fun that it isn't immediately destroyed by the immense dakka of Sol for being a suddenly appearing ship with no codes.

If it's manned, they meet and at first things go well, then something tips off the Inquisitor in charge that these guys have different beliefs about the Emperor, more than is allowable. Also maybe they know some dirty secrets that they shouldn't they get killed, and a few survivors get tortured for information.

If it's unmanned it'll probably be agonizingly slowly inspected by the Mechanicum. They might even find something useful 800 years from now - perhaps even a useful new nut and bolt size!

But really they're too conservative to go looking for anything really useful. Anything with the slightest hint of being interesting will be melted down, just to be careful.

All in all the IoM is far too paranoid to let a suddenly appearing ship in the seat of their power be actually useful. They would assume it was some kind of trap, and react accordingly.


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

[User]
What exactly is measured to find emf?

I've been learning a lot about electricity as I'm in my first semester of HVACR school. I know voltage is a measurement of potential differences. Electrons flow to a positive source as they themselves are negatively charged. I've noticed when I measure across a live wire, the voltage is zero. I understand that there is no potential differences for electron energy flow between two points of the same wire, therefore the wire will always read zero volts no matter how hot it is. I guess my question is what is one probe reading and what is the other probe reading exactly to come up with the voltage?
Sorry if it's a dumb question, I just wanna further my understanding of what I'm doing and this seemed like an appropriate subreddit.

[Assistant]
One probe on its own does nothing. Voltage always needs a reference
- the other probe. The physical probes are just cables to make sure the voltage difference inside the voltmeter matches the voltage difference in the circuit.

How a voltmeter works internally depends on the device, but it always compares the two cables going into it. If both probes are connected to the same cable then you have a cable from one side of the voltmeter to the other, so the voltage will be zero.


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

[User]
Semantic issues with the word "Capital"

Recently I have decided to re-read Katharina Pistor's book titled "The Code of Capital", and it lead me to confusion about the word capital. To my knowledge, capital is a stock that when exploited has the potential to turn a profit. Yet in the book, the author claims that "Capital is a legal quality that helps create and protect wealth". Could we interpret it as meaning that the capability of capital to be profitable is reliant on the power of the state to uphold contracts and protect property rights, or is use of the word here is simply inappropriate? Katharina is a lawyer by education, so I am inclined to accept the second conclusion, but I would like the opinion of others on this matter.

[Assistant] There's multiple definitions. For example, from the System of National Accounts 2008, the internationally-agreed manual that defines how GDP and other macroeconomic statistics are calculated, "capital goods" are ones that provide ongoing services, rather than being consumed within the production process. Therefore someone shipwrecked on a desert island who builds themselves a hut has capital, even though that doesn't fit under your definition or Pistor's.


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

[User]
ELI5: How does international money transfer create value for the receiver?

If you think of a country's economy as a closed system limited to the country, then how do they create value out of purely monetary transactions coming in from other countries?

Example:

Say USA uses Dollars and Germany uses Euros. Then if the govt of Germany pays government of USA a sum of 1000 euros that would mean money disappearing from Germany's financial system into nowhere and reappearing into USA's economy from nothing.

From what I see as a layman this should cause some issues such as inflation for the US if they take that incoming 100 Euros and generate the equivalent Dollars in their system, since its new money being generated without circulation.

On the other hand , what is preventing Germany from printing millions of worth of euros and paying USA with it for anything ?

I guess the mode of transfer has something to with it (Electronic vs cash). If its an electronic transfer then who decides if that sender even had enough currency of required amount in their account to begin with?

[Assistant]
Ideally USA would use those 1000 Euros to buy something they need from Germany. This would achieve a neutral trade balance - Germany got something from US, US got something from Germany, everybody is happy. In reality USA has a large trade deficit - they buy way more stuff than they sell. The reason for this is the fact that the US dollar currently serves as a reserve currency. People all over the world want to have some dollars just in case, or to trade with each other (without US). So when they sell something to the US they are likely to hold on to the dollars theyve received rather than buy something from US.

As for the question about Germany printing lots of Euros. Thing is, USA are fully capable to simply not take those Euros as payment and demand something else in exchange for goods or services delivered, for example US dollars. In fact, should Germany try it, this is exactly what would happen, because Euros would rapidly lose value. Thats what stopping Germany from doing it.

And no, mode of transfer has nothing to do with it at all. Its almost always electronic nowadays anyway.


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

[User]
Why does the cosmic microwave background permeate space instead of just the edges?

When we see light from the CMB, where is it coming from? What actually are we seeing?

[Assistant]
IN THE BEGINNING the universe was formless and void. More precisely, the universe filled with a hot, dense, opaque, and nearly uniform gas. As the universe expanded, the gas became thinner, until it was thin enough that it went through quite a rapid transition and became transparent. The light from that moment of transition was then able to freely travel through the universe. It is still flying around today, because it only stops when it gets absorbed by something.

This light travels at a finite speed, and the universe is either infinite in size, or just plain enormous. Either way, 13.7 billion years after the Big Bang, light is still reaching us from this early transition from opaque to transparent - this light is just coming from billions of light years away. Over the future, we will continue to receive light from the CMB, just from further and further away.

You can flip this around and think of it the other way around if you like. As light travels at a finite speed, the further we look away, the further back in time you are seeing. But eventually you looking far enough back in time that you're seeing when the universe was opaque. This looks like a sort of a solid opaque wall "behind" everything else we see - we can't see anything behind that because the gas is opaque. And this "wall" is the cosmic microwave background.

As for why it's microwaves: the gas was actually hot enough to give off yellow-ish light, but the light has been stretched by the expansion of the universe. It's been stretched out from visible light to longer wavelength microwaves.


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

[User]
What if banks doesnt WANT to buy bonds from the government?

I know that the way that the US government controls the money supply is to sell or  buy government securities from banks.

During Open Market Operations, the feds can sell bonds and government securities to banks to decrease the money supply. So what if the banks DOESNT WANT to buy those bonds and securities?

Wouldnt that cause inflation and also lack of confidence in the Feds and potentially the US currency itself?

[Assistant]
Bonds are sold at auction -- there exists a market-clearing interest rate, and the auction reveals that rate.

OMOs, similarly, are performed at an interest rate that is acceptable to both buyer and seller.


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

[User] ELI5:What makes some people "naturally" smarter than others?

[Assistant] There are some basic building blocks to intelligence to appear to be genetically linked.  Things like memory, spatial reasoning, and pattern recognition are abilities that allow you to understand new ideas, across many different subjects, more rapidly than people that are weaker in those abilities.  This is part of what people usually think of as "smart", though some people more mean "knowledgable" when they say smart.  All things being equal though, a smart person learns faster, and therefore should be more knowledgable than someone else who has spent an equal amount of time in the same field of study, meaning there is some natural overlap between the two.


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

[User]
CMV: Studio Ghibli is overrated and their films more often than not require an adaptation in the western film adjusted viewer's watching habits in order to be perceived as enjoyable

I'm posting this hoping that someone will point out what I might be missing or that I can begin to understand why Spirited Away, for example, sits so high in top movie list rankings. I am a westerner who has had exposure mainly to western film but also enjoys many other film types and cultures including Japanese and anime film.

However, I don't much care for Studio Ghibli stuff. In fact, I'd go so far as to say that I don't like it. Except for Hisaishi's music, which I think is beautiful. I don't know why everyone seems to like these films so much.

It bothers me as lots of my other views in life are congruent with the norm, or I can see why they vary.

I've watched lots of Ghibli films in order to give them a chance. I've already heard lots of people arguing that the artwork is great (and I do agree it is) and that's what makes the film great, but that doesn't cut it for me; the same people who argue in this way don't seem to apply that logic to the other films they watch and so must be adapting their viewing style for Ghibli or just repeating something they heard somewhere else, not responding as they normally would (perhaps with reference to direction, plot, acting, action, scripting, etc) when asked why they like a film.

Any comments or thoughts (outside of 'the artwork is so good') would be appreciated.

[Assistant]
One thing you should know is that virtually every Studio Ghibli film revolves around a coming-of-age plot. The plot throws challenges and quick change at immature characters that are unprepared for it, they must adapt and must be brave and show what's inside, their internal struggle is often emphasized.

Also every character, good or bad, has motives and development. Yubaba the bathouse owner is not evil just because, she's got a business to run. The witch of the waste is heartbroken and proud, which leads to wrath. Lady Eboshi cared about her town, employing the marginalized lepers, starting nothing short of an industrial revolution, albeit forgetting the damage to the environment.

The braveness of characters is also rarely your macho western protagonist willing to face and slice million monsters and then self-immolate. The braveness is often displayed by vulnerable characters that have much to lose and don't have the skills or the strength to chop their way to victory, they must be cunning, firm, and rely on their (often newly made) friends if they want to succeed.

All this combined with the art and the music, like you mentioned, makes just about every Studio Ghibli film a masterpiece.


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

[User]
[Ben 10/General Sci-fi] Which other universe would the Omnitrix be most useful in combat? To promote peace and understanding across alien cultures? Or maybe just most interesting overall?

For those who didn't watch Ben 10, the Omnitrix is a device that allows the user to transform into other aliens, assuming their physical and mental features.

[Assistant]
This will work for any universe that has a massive disparity between human abilities and alien abilities. Star Trek might work due to alien relations. Star Wars, not so much (because everyone's used to non-humans' presence in the Galaxy). Warhammer 40k would result in heresy and death.

Doctor Who might get immense use out of the Omnitrix to adapt to inhospitable worlds. Might not be the best idea, since the Ben 10 Omnitrix works for 10 minutes and has a shitty recharge timer.

Valerian (or Laureline) might get use out of the Omnitrix. Laureline and Valerian are a pretty good team, so the Omnitrix will definitely come in handy for situations that require delicate diplomacy.

Marvel will get a good use out of it (transformation into a Titan, or possibly even a Celestial, although Alien X is pretty much that). As will DC (imagine turning into Brainiac's species).


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

[User]
If while pregnant Mystique turned in to a male then back to her normal self, would she still be pregnant? What would happen to the fetus while a man?

I searched and there are A LOT of Mystique questions including those relating to her being pregnant or impregnanting someone while transformed into a male but not transforming while pregnant.  Like I said, there were a lot of threads so maybe I just missed it.

[Assistant] I think the general consensus is that her changes are just a little more than skin deep. She would still have her female internal organs, her outsides would just shift around to make her look like a dude.


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

[User]
[SCP] how is the SCP foundation still running?

Like ik that they're secretly funded by leaders of different countries and other groups but they're basically a military superpower and if they wanted they could take over the world and also how does it manage to recruit so many employees cuz it's a dangerous job with a fairly high mortality rate like even tho the pay must be rlly good wouldn't a large number of people quit when they learn about the dangers of the job?

[Assistant]
At this point the SCP foundation is probably running the world as a backdoor conspiracy. Sure, 50 or 100 or even a town of 2000 people disappearing sounds like a tragedy, but out of the whole world of billions it's barely a book-keeping error.

As for quitting... let's just say that the amnesiac controlling super secretive organisation have a very dim view of people trying to leave.


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

[User]
[X-Men] Does Wolverine always kill?

He uses admanarium claws. Doesn't that immediately kill enemies especially human ones
?

[Assistant] No.  Hes an expert enough fighter that he can avoid lethal hits.  He does have a history of berserker rages though, where he doesnt hold back, but even then it doesnt always result in kills.  Hes got a number of victims whove been crippled by him and used cybernetics to compensate known as the Reavers.


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

[User]
ELI5: Why do ballpoint pens sometimes stop working at a specific spot on paper?

I often find a ballpoint pen will stop writing but be able to write just fine on a different spot of the paper. Even if I keep switching back and forth to two different areas, sometimes I can never get the pen to work in a spot.

[Assistant] Ballpoint pens needs friction to cause the ball to roll and deposit ink. If a part of the paper has been smoothed down (for example by unsuccessfully using the pen, or by some glue) then it wont roll and there wont be any ink laid down. Because its dependant on the surface of the paper it will consistently happen at the same spot.


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

[User]
What's the experimental evidence for neutrino flavours?

How do we know there are different neutrino flavours and that there are only 3? How can a detector tell the difference between muon neutrinos and electron neutrinos? I'm a final year undergraduate and know a reasonable amount of particle physics in general, so feel free to get technical. Every time I google this I just get stuff about neutrino oscillations instead.

[Assistant]
Well the flavours have to do with the lepton flavours they're coupled to. A W boson couples electrons and anti-electron neutrinos, muons and anti-muon neutrinos and so on. If the neutrino collides and produces an electron or positron, then the electron-flavoured component is the state measured in the collision. If a muon/anti-muon produced, then the collision measured the muon-flavoured component.

It's hard to speak of it being an 'electron neutrino' *per se* because that flavour component is only relevant when the interacts in some collision/interaction. While it's in flight, it's a superposition of states, and so we can only speak of future interactions with regards to which flavour component is the component that gets measured (much like how an electron is measured to have spin up or down, but in flight prior to the interaction is both)


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

[User] [The Matrix] Why not spend a weekend downloading all the skill sets you can into your brain?

[Assistant]
It's an arms race Humans can't win assuming they haven't already lost.

When Morpheus is training a newly freed Neo, he says only thing they can't fight off are The Agents who are simply too fast, too strong, and too powerful. But being The One, Neo eventually defeats them without much difficulty. In the second movie The Machines retaliated by creating The Upgrades with Agents Thompson, Johnson, and Jackson. All three effortlessly ploughed through the Freed Minds even quicker than previous Agents. Again they are only stopped by Neo, who is again forced to resort to his god-like powers as The One. Later in the movie The Architect confirms The One is very literally a single individual; there can never be more than one "The One".

With this info in mind, it's entirely possible the Freed Minds already tried to defeat The Machines within The Matrix through biohacking kung fu. Which only lead to the creation of The Agents. When Neo became The One, The Machines responded by creating The Upgrades defeated only by Neo as The One. Which only exists to due to inherent design flaws within The Matrix itself.

The bigger problem is assuming they haven't already lost. The Architect says there have been multiple instances of The Matrix and Smith confirms The Machines can just "reboot" everything if it came to it. It's entirely possible the only reason the Freed Minds can learn Kung Fu *at all* is because The Machines ***allow them too***. Not because it's an actual effective tool.

Furthermore, there's a fan theory The Machines don't actually *need* humanity, only keeping them alive because that they're still trying to fulfill their duty to serve humanity. In *The Animatrix*, it says humans became so abusive against The Machines they revolted to protect themselves. Problem is this story is told entirely as a oral history by a human over 500 years after the fact. The Machines themselves are established in the entire franchise to have no true emotions, only cold hard logic (Programs within The Matrix are not Machine-kind).

It's entirely possible The Machines concluded the best way to serve humanity was building The Matrix, assuming humanity didn't ask/order them to do so. Inside, humans couldn't harm each other or Machine-Kind, and elaborate fantasy worlds kept people complacent. If you believe Smith, The Matrix's first instance allowed everyone ***to be happy***, failing only because it was too fake. When The Architect reveals The One, The Matrix, and Zion have happened multiple times already without any major changes, it implies The Machines don't brainwash, indoctrinate, or breed humans into their versions of domesticated dogs even though they're fully capable of doing so. Instead allowing humans full autonomy within and without The Matrix.

If you believe this theory, then the only way to truly "defeat" The Machines is committing mass genocide of all humanity, leaving The Machines without purpose to their existence. Something they'd obviously never do.


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

[User]
ELI5: How are weather balloons deployed so that they do not pose a risk to commercial air traffic?

Given the fact that weather balloons are frequently deployed to obtain critical measurements for making more accurate weather forecasts, how do pertinent governmental agencies ensure that they do not pose a risk to commercial air traffic where there is a likelihood that a collision/impact with these balloons may take place?

[Assistant]
There is a suggestion that the local air traffic controllers be notified of the intended launch of a high altitude balloon so its presence is known, but the more relevant regulations regard the content of the payload. There are limits on the total weight and density of the payload, as well as the separation force of the payload from the balloon. The intent of those regulations is that on the exceedingly low chance that such a balloon would be struck by an aircraft it wouldn't cause any significant damage.

Remember that the sky is very large and there aren't really that many aircraft in flight. Hitting a weather balloon by accident is just an incredibly remote chance; far more likely is hitting a bird of which there are quite a few. If the payload is roughly the size and weight of a crow then a commercial jet engine would deal with it in much the same way it would the crow, namely going "Nom nom nom!" and not really caring.


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

[User]
I learned in Biology class that proteins/enzymes unfold and lose their function when they are heated up. How do steaks stop have so much protein when cooked?

Edit: wow, came back from work and got some great answers! Thanks everyone!

[Assistant] Protein shape ultimately gives rise to protein function.  The proteins in steaks don't still need to be functional to be proteins.  A denatured protein is still a protein, and if you have somehow broken it down into its constituent amino acids your body can still take those amino acids and build proteins out of them.


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

[User] [MIB] in MIB II, after Will Smith neuralizes the family in their living room, he tells them to "love and cherish each other for the rest of your life" and the daughter can "stay up late as she wants and have candy and cookies and cake and junk and stuff". What are the long term effects of this?

[Assistant]
There is a line in the middle which may throw things off a bit - after Agent K says "You did not see a room full of shiny weapons, you did not see four alien night crawlers. You will love and cherish each other for the rest of your life."

Agent J adds "Which could be the next 27 or 28 minutes, so y'all should get to lovin' and cherishin'. Oh, and she gets to stay up as late as she wants and have candy and cookies and cake and junk and stuff..."

I think it could be interpreted that the second part of J's line is related to the first - there only being 27 or 28 minutes left alive and that it's simply for that night the daughter gets to stay up late, but it's possible the parents were to take it as being related to the rest of your life portion.

If they take it this latter way, then it probably leads to the parents being more lax about bedtimes, but there is no direct command about it being every night, or only eat that, so they are probably just a bit more willing to allow her to have the occasional treat.

That or she hits 600 pounds before she has to be cut from her home and hospitalised.


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

[User]
How tough is it to become a professor after completing a PhD?

I love academia and am considering starting my PhD next year (in something related to political satire or media), with the medium-term goal of becoming a full-time professor.

Not sure how the employment scenario is at that intersection. Is it really hard to get jobs as professors?

Any tips would be really appreciated!

[Assistant]
Its a nightmare. Most people either give up or can only find part time adjunct work. Every full time job that is posted has literally hundreds of applicants. 10-15 of the applicants will have a phone interview, 3-5 of them will be invited on campus.

Its actually hell.


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

[User] ELI5: How does someone freeze to death? What exactly happens inside the body to be fatal?

[Assistant]
Life depends on a number of biochemical reactions that occur in each and every cell in your body.

All chemical reactions (and this includes those upon which life depends) are affected by temperature.  In general, decreasing temperature tends to slow chemical reactions (particularly exothermic chemical reactions, which describes most of the chemical reactions upon which life depends).

Dropping the temperature of the body affects virtually every organ system.  It causes the heart to slow (because, in part, the chemical reactions in heart muscles required to cause heart contraction are slowed by lower temperature).  It causes blood to reduce its capacity to carry oxygen.  It causes basic energy-producing chemical reactions in every cell (cellular respiration) to slow, and to produce less energy molecules (i.e. ATP, etc) required for basic cellular function.  It causes nerve conduction to slow and slows down neurotrasmitter release.

In short, through a number of mechanisms at the cellular and organ level, it causes cellular activity to slow, and, eventually, to be unable to maintain the intracellular environment required for life.

Cells die, organ systems fail, which causes more cell death, until the body is in a catch-22 of death and becomes irrecoverable.


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

[User] [Star Trek] I've often heard characters refer to a ship as the "newest" or "most advanced". What systems are receiving the most incremental improvements from generation to generation?

[Assistant]
Propulsion systems are almost always the greatest focus.

While all other systems can receive upgrades and enhancement incrementally, it's a ship's Warp efficiency rating and output which is a real determination of a ship's relative advancement against all other ships.

Finding new ways to increase output or decrease loss of efficiency which might draw from a ship's Warp core is the root of all starship systems  development.

Upgrading a ship's sensor array simply means enhancement of current capabilities.  Impressive.

Upgrading a ship's data transport subsystem is an indication of faster data access which decreases power consumption...no surprise there.  Expected.

Upgrade a propulsion system generation so an unmodified version goes from the previous generation's 7.3 to a scorching 8.1 with no decrease of mass, or other corner cutting in design?    State of the art.


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

[User]
ELI5: Why are humans said to be the only species on earth to be self-aware and able to think philosphically?

And at which point in evolution did this capability come?

[Assistant]
They aren't. Several other mammals are self aware. You can tell by seeing if they recognize themselves in a mirror. You put a silly bow on their head, show them in a mirror and see if they think their is a bow on THEIR head.

In terms of philosophy...it is hard to tell, but many animals have a sense of fairness.


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

[User]
[Power Rangers] Why do the authorities and governments of the world give the Rangers such a pass?

Someone asked a Power Rangers question the other day and it got me wondering.

Why do the local, state and federal governments leave the rangers alone so much?

You could say, well the Rangers always save the Earth from destruction! Well as we can see from various superhero movies (Civil War), that doesnt mean the people appreciate it!

You can see from other superhero media that the heroes dont always have the best buddy buddy relationship with local or federal authorities. The rangers are a walking weapon of mass destruction! Youd think someone somewhere in a seat of power would be totally NOT ok with that!

[Assistant]
The police usually does not have giant robots or the knowledge of who the Rangers are. They are usually also woefully unprepared to deal with whatever monsters are arriving on Earth.

Whenever they *are* prepared, like the Silver Guardians or whatever, the police absolutely does not give the Rangers a pass. They're considered a nuisance and are encouraged to not interfere with official operations.

And of course, sometimes the Rangers *are* the police-- Lightspeed Rescue and SPD for example are explicitly the task force hired to deal with attackers. They're authorized to do whatever's necessary.


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

[User] Is it possible to accidentally create a black hole in one of those particle accelerators? If so, how quickly would we be sucked into it if was stable?

[Assistant]
A black hole is not a vacuum cleaner. A black hole with the mass of a few elementary particles will have exactly the same gravitational pull as those particles. Which is on the macroscopic day-to-day scale none.

You don't get pulled close to an apple on your desk either.


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

[User]
Once a rocket reaches space and goes in to free fall, how do they get fuel/oxidant to flow downward towards the nozzle without thrust or gravity pulling it downward?

There has to be some simple mechanism that pushes the fuel and oxidant out of the fuel tanks once they've cut their initial thrust. What is it?

[Assistant]
In the simplest tank design, the propellant is at the bottom, separated by a diaphragm from an ullage volume where a pressurizing gas pushes the diaphragm.

Pros: very simple and cheap design

Cons: you lose pressure as the propellant is consumed and the gas expands on an every time larger volume. This can be mitigated if the ullage volume is initially very large, so the gas won't have expanded a lot, but then you'll have the problem that big tanks are massive (in space, you want things to be as light as possible so they can be accelerated easily with little propellant).

A better design is to keep the gas in a separate small container at high pressure, with a pressure regulator feeding the gas gradually into the tank. Then as the propellant is consumed, more gas flows into the ullage volume and pressure is kept nearly constant without the need for a very large tank.

Pros: less massive, nearly constant pressure

Cons: more complex and expensive

In simple rocket engines (e.g. for attitude control), sometimes these approaches suffice. But when high thrust is required (i.e. high mass flow rate), then the pressure from the gas and diaphragm may not enough to ensure a good flow into the combustion chamber. Then you need turbopumps. They can be powered by the same fuel and oxidizer with a pre-burner.


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

[User]
[Wall-E] How do the humans reproduce?

Is sex even a thing? People probably couldn't even masturbate with those arms.

[Assistant]
The floating chairs people ride around in take care of all their bodily functions. This includes masturbation. Genetic material is stored and eventually transported to the nursery on the lower decks.

There have been isolated instances of people having sexual intercourse the old fashioned way, however pregnancies resulting from this are swiftly aborted using a non-invasive procedure (typically ultra-sonic frequencies). Housing a species on a spacecraft for any length of time requires tight population control and once people learn they can form babbies on their own, you're looking at a problem.


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

[User] ELI5: Why do the logos in some business emails sometimes come through as attachments to the email, as well?

[Assistant] Text email vs html email  if your email is set to receive text only, and they send html email with inline graphics, your email program may strip the logo and attach it. Just different ways of handling email.