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

[User] How are mathematical models of biological processes created? How can they be used to understand complex phenomena?

[Assistant]
I'll give a very simple example.

Mitotic cells divide with a certain period t. Each time the cells divide, there are twice as many. Thus, as a function of time t, the number of cells N can be described as N(0)2^t/T where N(0) is the number of cells at t=0.

This might be too simple, because not all cells divide at the same time, or with exactly the same periodicity. But if you have a large number of cells, then you know that the number of new cells being created is related to the total number (if you have twice as many they'll create twice as many new ones in a given time period). So you can write down a differential equation: dN/dt=kN where k is some constant. You can solve this differential equation to get N(t)=N(0)e^kt which is a similar form to our simple doubling equation (k is inversely related to T).

This might still be too simple. What if the cell's division is hampered when cells get too dense. This might occur because cells interact with each other, so there could be a negative term in the rate that depends on N^2 (how likely the cells are to interact with each other). Then you have dN/dt=kN-qN^2 which has a different solution (I think resembling logistic growth), and you can make it more complicated to reflect the circumstances.

This type of modelling is used for bacterial populations, predator-prey relationships, epidemiology, etc.


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

[User]
[Star Wars] If there can only be 2 sith at a time, how did they pose a threat against the Jedi in the past?

Did they have to hide in the shadows and rely on schemes and personal armies like how Sheev did? They couldn't really make a Sith order to oppose the Jedi order if they could only be 2 at a time.

[Assistant] There being only two Sith is a relatively recent thing, only happening in the last thousand years leading up to the Clone Wars. Before that, the Sith had a mighty empire with no limit on how many there could be.


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

[User]
Are we slowly undomesticating cats and dogs with spaying and neutering programs?

Domestication occurred through selective breeding, which leads to all these wonderful pets we have now.  But it seems to me with the neutering programs with pets, that the animals we have specifically chosen as being the best companions/the most tame, are being taken out of the breeding pool.  Instead, wild/abandoned animals provide most of the new generations without any input in behavior/development/etc.

Is this happening/Not happening?  How fast/slow?  Are the domestic pets as a species fairly stable now for some other reason?

[Assistant]
Short answer: no, mainly because the close relatives of pure-bred dogs and cats are constantly used to breed new dogs and cats. For instance, most Labrador Retrievers are neutered/spayed, but they are the offspring of labs owned by professional breeders. The breeding pairs owned by breeders produce a TON of puppies; a select few will not be sold, but instead will be kept by the breeder to ensure that they have a steady stream of lab puppies in the future. So as far as pure-breeds go:

* Advantages: taken care of by owners (very few puppies die, very few adults die of disease), there are always mates available if the breeder wants more puppies, and breeding pairs have lots of offspring (because they're healthy)
* Disadvantages: most offspring are spayed or neutered (but never all).

In contrast, wild/abandoned animals have a very different environment:

* Advantages: offspring are not spayed/neutered.
* Disadvantages: more adults die younger of disease/accidents/intentional killings (if impounded) and therefore can't reproduce as often, more puppies die before adulthood for similar reasons, poor health results in fewer offspring/litter, mates are not always available (they have to find them), etc.

As long as the domestic breeds are continuously bred by breeders, while the wild/abandoned dogs face substantial mortality and poor health, domestic dogs will not be 'undomesticated'.

To put it another way, the breeders are intent on keeping 'undomesticated' genes out of the pure-bred gene pool, and there never going to run out of 'domesticated' individuals as long as their still in business (people still want dogs). This means that domesticated dogs will never become 'undomesticated' unless we stop breeding them.


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

[User] ELI5: If the 'Giant Impact Hypothesis' for how the moon formed is true, why did the debris form the moon and not rings like Saturn has?

[Assistant] Two reasons. First, Earth likely did have rings for a while after the impact, but they all collapsed into the Moon due to gravity. Second, unlike with Saturn, the moon was far enough away that it hasn't been torn to shreds by our own gravity, like the cataclysm which likely caused Saturn to have rings in the first place.


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

[User] Why is so much computational power required for some simulations? Can't these simulations be run with less power, but at a slower rate?

[Assistant]
- If you want to predict the weather for Nov 1st, and the simulation gets you the result on Nov 23rd, it's pretty useless.

- While the simulation runs, people wait for the results. Salaries are expensive; computers, less so. So, you want the computers to give the results quickly so that highly-paid people can continue working.

- When you're trying to find a cure for some illness, you want it ASAP.

- When you're in competition against another company, you want to be the first to get the results.


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

[User]
During the carboniferous period, the oxygen level was ~35%. Now it is ~21%. There is less oxygen in atmosphere now. Where is that oxygen now?

During the carboniferous period, the oxygen level was ~35%. Now,the level is ~21%. There was a 41.5% oxygen decrease in atmosphere. Considering the fact that the level of CO2 were always negligible - at the beginning of the carboniferous period was only 7000ppm (~0,7%),now it is ~0,04% . Where is that oxygen now? I understand that breaking down lignin was difficult and it became coal but coal is mostly carbon. This explains the fact that carbon is trapped as coal  but where is that oxygen trapped now?

[Assistant] Oxygen gets locked up as CO2, which can be in the atmosphere (minor), or in plants, or dead plants and animals in the ground. This includes a lot in bacteria. Another major sink is capture by rocks, as in iron and silicate oxides.


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

[User] [Interstellar] why didn't NASA's best scientists realize that the messages coming from the tidal wave planet were also subject to huge time dilation?

[Assistant]
The theory of time dilation is one thing, but actually applying it is another. When they get away from the planet someone says something to that effect: "we should have known, we should have realised this happened".
The fact that they kept getting the all clear signal (although it turned out that it was just the same signal over and over again) for a very long time made it look like the astronaut had been there for a long time.


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

[User] ELI5: How do global rules of war work? How does one enforce the rules while at war with another country? What would stop an opposing power from breaking these rules?

[Assistant]
If you break the rules, you will be sanctioned. This makes it a lot harder to access the global market, making you poorer and less able to fight the war. If you lose the war then you may be tried in a court for war crimes and imprisoned.

Alternatively, the enemy may start to commit war crimes against you and your soldiers become scared and demoralized and become a less effective fighting force.


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

[User] Do the children of women who suffer from fertility problems have a higher chance of being disabled in any way?

[Assistant]
It depends.

Older women are more likely to have difficulty conceiving. Children of older mothers are also more likely to have congenital abnormalities. So if the fertility problems are associated with age, then they will also be associated with a higher risk of congenital abnormalities, some of which can lead to disability.

At the same time, there are plenty of causes of fertility problems that aren't associated with hereditary disorders.


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

[User] ELI5:What's honestly keeping us from putting a human on Mars? Is it a simple lack of funding or do we just not have the technology for a manned mission at this time?

[Assistant]
There is a few problems

* price
* getting there -> being shut in a capsule for many months is very bad for your mental and physical health
* landing -> our track record on that is not so super great with mars rovers
* staying there -> you need some concept to keep the people there alive (meaning: water, air, shelter, and nutrients), as shipping goods is absolutely prohibitively expensive.


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

[User] I remember reading somewhere that major cities that experienced catastrophic fires (ones that burned down the majority of the city) converted to gridded road systems, whereas those that had no major fires didn't. Is there any truth to this statement?

[Assistant]
Not really any truth to this statement. London is the perfect example to demonstrate this. London burned completely to the ground in 1666, but yet the road layout in the center of the city is over a thousand years old. In the days after the fire there were lots of plans to completely redo the road system, and the entire layout of the city. The plans still exist in a museum in the city. All these plans were dropped. Why? For two main reasons: Firstly, to redraw the entire map was going to cause a legal nightmare. Buildings may have been burned down, but people still owned all the land, and it was not possible to simply build a new road through someones land. Even in London centuries ago, the state didn't have the power to arbitrarily redraw maps  Secondly: the city needed to get back to business and life as normal, and the quickest way of doing so was to simply rebuild all the houses/businesses in the same places as before. Bakers etc. simply had their shop rebuilt and opened selling bread again a few weeks later.

In the case of London, all that the officials achieved was a slight change to the building codes stating how wide roads had to be. The roads were made a little wider.


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

[User] ELI5: Why are we supposed to open the window shutters during landing and take-off on an airplane?

[Assistant] In the event of a crash there might not be any electrical lights inside and it might become very dark. Also when the shutters are open passengers inside the airplane can look outside to orient themselves and decide the best way to evacuate. And emergency crew on the outside is also able to look inside the aircraft to see if there are any smoke or fire inside the cabin and more effectively direct their attention to where it is needed.


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

[User] What is the biggest philosophical realization that you have ever had that you wish more people would realize?

[Assistant] That whatever you believe, there's a very bright person who has devoted their lives to studying the issue and has come to a conclusion incompatible with yours. This person may also have presented very compelling arguments for their position, arguments strong enough to make you change your mind, except that there are equally strong arguments for your own position. It's hard to believe anything except tentatively, given this state of affairs.


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

[User]
[GENERAL SCI-FI] If you were to shrink a man, would he be able to breathe?

Our lungs are designed to absorb oxygen from air (or so I assume) but when you're shrunk to say 1cm tall - and have much smaller lungs - do they still have the ability to absorb oxygen molecules from air since said molecules became much larger in comparison? I'm assuming it would definitely be possible to breathe in / breathe out, but would it have any effect?

The argument that small lizards can breathe / bugs can breathe etc is not applicable here, since their lungs or organs that act as such are designed by mother nature to be able to absorb oxygen at that size.

[Assistant] In one episode of star trek deep space 9, a runabout was shrink down (so the air in the ship was shrink too, so they could breath) and when they had to use the teleporter to go in a micro circuit or something like that, they had to teleporte a buble of air before so they could breath, because the oxigen molecules would have been too big otherwise.


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

[User]
[Stephen King] What is the deal with the Stephen King multiverse?

I'm relatively new to Stephen King. I've read Carrie, Salem's Lot and Revival. I've also heard a lot about his other books and the small and major cross-overs therein.

My question is this: Which stories are set in the very same universe, and which ones are just in the same multiverse?

Some characters and places are referenced in different books, such as characters from IT in 11/22/63. Or characters from Carrie in other stories. Also places such as Salem's Lot in Revival.

 If these stories take place on the very same world, does that mean the characters that die in Salem's Lot go to the Hellish Afterlife in Revival?

 Do the people in IT know about the Carrie White incident? Wouldn't this sort of thing come up when they encounter seemingly impossible things? Like "well no one believed in TK either".

Are these places and characters just mundane versions that happen to also exist in these alternate universes?

[Assistant] If you want to complicate things further, keep in mind SK's universe is so "multi" that characters can appear in completely different settings and with virtually no connection to their other-universe counterparts. See for example The Regulators and Desperation.


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

[User] Why is the loudest sound possible 194 dB?

[Assistant]
What we perceive as sound is longitudinal pressure waves traveling through the air.  The "loudness" of sound is dictated by the amplitude of the waves - in this case, the deviation from ambient air pressure.  A sound of 194 dB has a pressure deviation of 101.325 kPa, which is ambient pressure at sea level and 0 degrees C.  Thus, the sound waves are creating vacuums between themselves, and no higher amplitude is possible.

For what it's worth, "sounds" can actually be greater than 194 dB, but the extra energy begins to severely distort the entire wave, and it's more of a shock wave than traditional sound waves.


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

[User]
ELI5: Why can people "sense" when they are being watched?

I'm a skeptical person by nature and disregard the paranormal, by and large. However, there seems to be good evidence that people can (sometimes) tell when they're being watched, without any discernible mechanism for being able to do so. What's up with that?

[Assistant]
What evidence?

People think they can do this for various reasons.  The primary one is that people rarely remember the times they thought someone was there but there wasn't.  They only remember the times they were correct.  This is known as "confirmation bias".

But there are also a variety of ways that one might notice someone nearby without ESP.  Soft, subtle sounds.  Vibrations. Air currents.

Having someone enter a room can even change the sound of the room in very subtle ways. The ambient noise that is present will take on a slightly different character.

These things might not be something that is consciously noted, but the brain is still picking up the information.


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

[User] ELI5: Why is spicy food so prevalent in Asian cuisine but not so in western cuisine?

[Assistant]
When chili peppers were brought from the New World they were introduced to India in the late ~~15th~~ 16th century by Portuguese traders. The peppers grew very well in the tropical climate of India and was quickly adopted into their foods. From there the peppers spread to southeast Asia where a similar thing happened.

However, chili peppers don't grow very well in Europe where western cuisine comes from.


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

[User]
[TNG] Why is the transporter room used?

If the transporter has the ability to directly transport someone/something directly from Point A to Point B (Point B being somewhere other than the transporter room), why is the room outfitted with a full transporter pad? This seems like a huge breach in security. If Picard was unsure of the safety of the item/being being transported, why not just transport it into a cell instead of sending a security team into the transporter room?

[Assistant]
Pretty sure this has been answered before, but whatever.

So, early transporters *couldn't* do a site-to-site transport, one side had to be on a pad.  Later on, however this changed to where site-to-site was possible.

However, even when doing site-to-site, the transportee is still routed through the transporter.  Essentially site-to-site uses two sequential transports, while keeping the subject dematerialized.  This uses an incredible amount of energy, thus why it's not preferred except under extreme circumstances.

Also, there's even less power required if the transport is pad-to-pad, as both sides "pay in" to it.


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

[User]
[Spider-Man : Raimi Trilogy] What if Harry never witnessed Peter drop off Norman's body?

The scene where Peter had dropped off Harry's body in a room at the mansion. Then Harry just saw Spider-Man and his dead father, and shouted, "WHAT HAVE YOU'VE DONE?!" then he pulls out a gun but before he could use it, Peter swings away out the window.

But what if Harry never saw Spider-Man there? Say Peter dropped off Harry, and got out as quickly as possible. Harry only sees his fathers corpse, with no way to connect it to Spider-Man.

How does this affect the trilogy?

[Assistant] Harry gets obsessed with finding his father's killer - though it's probably not a secret for long. Goblin is seen fighting spiderman publicly on at least 3 occasions, so he either assumes Spiderman did it (or finds fabric from his suit stuck in his father's gloves) or bribes Otto to bring him Spiderman simply for answers, discovers his identity, and then Peter admits what happened. Harry's superpower of selective hearing activates and he refuses to believe his friend acted in self defense.


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

[User]
CMV: Why Pro-life movement should support universal healthcare

Ok, ok, I knew I just posted an extreme controversial topic or just a shitpost among conservatives and liberals will bash me in comments, but hear me out:

Im a moderate conservative who believes that people should ban abortion after heartbeat can be detected except if the pregnancy is endanger mothers health or if the pregnancy is due to rape/incest etc.

However I might stand out from most conservatives on a few issues. For example I opposite death penalty unless its under extreme circumstances. I also believe any human, theoretically should enjoy healthcare. The reason being I support the right of life basically all the way. I think its justifiable to increase some taxes on rich people to give the poor the healthcare services as well as other basic services they needed as a life with dignity, as a human. I believe our country have the ability to provide a universal healthcare system and I believe it will help us Americans after all. Sure there will be some draw back, but I believe, if executed correctly, the benefits will far outweigh the draw back.

[Assistant] I think the pro-life movement seems to mainly concerned about the moral choice of abortion, as opposed to preserving the lives of embryos and fetuses. That the movement has never been concerned about healthcare, and especially universal access to pre-conception health, which could prevent many more lost pregnancies than abortion restrictions, is a clear indication of this.


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

[User]
[WH40K] What happens when a world does not meet its tithe?

Officials governing a world of the Imperium fail to pay Terra's Due. What happens to those governing? The planet's populace? Who takes action against this Hersey and what do they do?

[Assistant]
Murder happens. If the Inquisition gets word, they summarily execute their way down the government until someone complies. In the case of an uprising preventing the payment of the tithe, the IG gets called in to suppress it and set up a temporary military government to make sure the tithe is payed.

A planet can do whatever it wants as long as they worship the Emperor and pay their tithe. Fail in either of those and the shit comes down heavy.


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

[User] [Star Wars] Do average citizens of the galaxy believe in the Force as objective truth or is it one of many belief systems?

[Assistant]
You have to think of it as an average citizen would. Who was in power, what they allowed to let out, and how force users acted during the time.

In the Old Republic era, Let's say after the Sith wars, when everything has settled down, and a few generations have gone by without someone in a neat mask blowing up planets.

The average citizen is going to know about the Jedi, and if they have a decent schooling, will know *something* about the Sith wars. They'll know there's a group of secluded monks who work with the government who hail from that time, who are said to be spooky bastards.

Sometimes they'll come to someone's house and take their children, and it's normally some sort of honor for them to do so. Very few people will know of the powers and skills of force users, as the Jedi aren't flashy, and there's no BBEG for them to go after. The "Force" would probably just be one of many other types of religion floating around the galaxy, albeit a government funded one.

From there, it's an easy hop to...

The Empire era, the average citizen is going to be fed that this government sanctioned group of hermit monks has been in league with the Trade feds to murder the Chancellor. Crazy monks high on spice melted his face man! SPACE BATH SALTS!

Note how Han, in a new hope, treats the Force. He's aware of it, he knows people believe it, but its just "Hokey religion" to Han. Slight of hand or glitterstim or some other trick.

Remember Admiral "Chokesoncock" Motti? "Your sad devotion to that ancient religion" bit?

the only time people probably believed in the Force as an actual objective truth is during the Sith Wars, when you had a bunch of people tossing buildings at each other and lighting planets on fire with their minds.


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

[User] ELI5: Why is it so hard for veterans to find jobs?

[Assistant]
Veterans like to write about the things they did in the army in their applications. They write about the planes they flew and the time they spent with their fellow soldiers and all the medals they got.

However, when a potential boss looks at that application, unless he was in the army or likes reading about the army, he probably wont know what half of those things mean. He knows they're good, but not how good. But what the boss does know is the value of experience in a similar job gained by another applicant. So he goes with what he knows and takes the regular civilian.


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

[User] ELI5: The back of my debit card says, "Not valid unless signed". When would this ever matter?

[Assistant]
The use of these cards is partially governed by the agreements that the credit card transaction networks have with merchants. (Since your debit card probably has the option of using Visa, Mastercard or American Express for payment.)

 Under those agreements, a merchant isn't required to accept an unsigned card, and it's recommended to check an ID of the person presenting it. By contrast, merchants should not require IDs of people presenting a signed card, and just compare the signature on the back to that on the receipt if desired. This is a courtesy to the cardholder.


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

[User] ELI5:When I eat a thick steak, or leg roast or other large cut where are all the blood vessels?

[Assistant]
A big cut of meat comes from a large muscle.  Big blood vessels (running to parts of the body other than that muscle) generally don't run through muscles (flexing the muscle would dramatically increase blood pressure), just the blood vessels that supply blood to that muscle (and the butcher cuts any exterior vessels off during the butchering process).  The ones that feed that muscle are in there (you'll occasionally see the main one on certain cuts) the smaller ones (like capilaries) aren't really very obvious.

Edit: Some rib steaks have a decently sized blood vessel.  You might notice it when eating prime rib.


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

[User]
Do gravitational fields travel through Portals?

If I were to place a portal on my kitchen floor and another on a neutron star, how would this affect the planet?

Can you use the portal gun on Black Holes?

[Assistant]
If you place a portal on a wall, another one on a ceiling and you stand near the one on the wall, you won't be "attracted" by the gravitation of the ceiling one so i tend to think that gravitational force doesn't travel through portals.

However, pressure difference can travel through portal (like the scene when Chell put one on the moon) so if you put a portal on a neutron star this may not be good for your kitchen..


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

[User]
ELI5: Why do some companies keep the "SALE" logo/tag/sticker on their products for years?

Seem to mainly come across this in cosmetic products. Even when the products are already on the market for years on end, and people know it, too. Is is all just marketing and sales psychology tidbits working at the mind of us simple souls?

[Assistant]
Basic psychology -- someone who's not abreast of line of products might casually walk by, and just the word "sale" triggers a response in most people that makes them think "I should buy this now, don't think about it, don't research it, buy it now because the sale might not last"

Same thing applied to those shady electronics stores in dense urban areas that have been having a "Going out of Business Sale" .... for the past 5 years straight.


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

[User]
Why do viscous liquids like honey coil when poured?

This is one science-y question for which I haven't been able to find a satisfactory answer. Most of my personal research has yielded the "nobody really knows" thing, but there have *got* to be *some* theories out there as to why this happens.

[Assistant]
If you pour honey so that it forms a thin column from the honeypot (heh) to, say, a plate, then it will form a little coil.  The coil is formed by the interplay of two forces - inertia/motion and viscosity. Consider the path of the honey in the absence of viscosity.  That's easy -- it's the path the honey follows for most of its descent, i.e. an approximately ballistic shape, with each piece of honey falling approximately independently of the others, so that the entire stream traces the path that a single drop of honey would follow.  Now, insert a plate or something.  When it impacts the plate, the stream has to deform -- it has to go from long and thin to short and flat (part of the spreading pool).  That is a severe deformation, and the viscosity opposes it.  How?

Well, viscosity is a quantity that relates *shear motion* to *shear reaction force*.  Shear motion is a style of motion in which the velocity (a vector quantity) varies in length, if you travel perpendicular to the velocity vector.  For example, on a freeway if traffic is slow in the right-hand lane and fast in the left-hand lane, there is a leftward shear in the forward velocity of traffic.  If freeways were viscous (they have effects that act a little like viscosity, but are more complex), then there would be a reaction force decelerating traffic in the left lane and accelerating traffic in the right lane.  The reaction force would be directly proportional to the *difference* in speed between those lanes, and inversely proportional to the width of the freeway.   The constant of proportionality is the viscosity.  Ahem.

So the viscosity prevents spread of the honey as it lands, which makes a little mountain of honey.  The weight of each little drop of honey then drives deformation by squeezing the drops under it (that fell a little earlier), so the whole mound is slowly falling down and squishing out sideways.  But it turns out that, for some rates of pour, a direct-pileup mound like that is rare.  Why?

Well, if the honey is viscous enough, it piles up a pretty high mound.  The mound is unstable to tipping over.  As it tips, the viscous forces keep the stream from disconnecting (easily), and force the next few droplets of honey off to the side.  Once they are off to the side, they pull the next few droplets and like that.  All via the viscous force.  Once the stream is going off to one side (call it a radial displacement from where it would land in the absence of viscosity) the geometry changes and it might come back to the center or move off in some chaotic path.  But for certain pouring regimes, you can get a stable orbit of the touch down spot.  In those orbits, the radial centering force imposed by the implacable fall of new droplets of honey (connected in the stream of course) is counteracted by centrifugal force as each droplet is whirled around slightly by the geometry of the existing mound of honey.  That makes the (in)famous coil.

Coiling is energetically preferred over direct mounding, since you don't have to deform the stream as much from a coil formation to get it to be flat.  In effect, a coil is already quite flat compared to direct pileup, so it doesn't take as much distortion to merge a coil with an existing puddle, as it does with a directly piled up mound.  So coil-mounds are shorter than direct mounds.  So once a coiling motion is started it's unlikely to change unless the flow from the pour changes drastically or the location of touchdown changes suddenly.


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

[User] ELI5: Why is it that in many states, an accident that occurs while turning left is automatically the fault of the driver turning left?

[Assistant]
The person turning left is the only one with enough information to determine whether a left turn is safe.  At a 4 way stop, there are potential collisions from the right, the front (oncoming) and the left.  The other drivers, if going straight or right, have no way to collide with the left turner unless the left turner enters the intersection.  The left turner is the only party who knows when the left turner will enter the intersection.  This information completely determines whether there will be a collision.  Since the left turner is the only one with this information, it is the left turner responsibility to choose to enter the intersection at a safe time.  If there is a collision, the only person who 100% had the ability to avoid the crash was the left turner.

Scenarios at other intersections are similar, so you end up with a general rule about left turns.


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

[User]
How does a virus, such as chickenpox or HSV, physically damage the skin to cause blisters?

What process occurs for a virus to cause wounds similar to small burns?

[Assistant] Usually a virus does not cause direct damage that you can see on a macroscopic level. The sores caused by some herpesviruses such as HSV1 are caused by self-directed immune responses which cause damage to your own body.


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

[User]
Why is radioactive decay exponential?

Why is radioactive decay exponential?  Is there an asymptotic amount left after a long time that makes it impossible for something to completely decay?  Is the decay uniformly (or randomly) distributed throughout a sample?

[Assistant]
Exponential decay comes from the following fact:

The rate of decay is directly proportional to how many undecayed nuclei there are at that moment.

This describes a differential equation whose solution is an exponential function.

Now, why is that fact true? Ultimately, it comes down to two facts about individual radioactive nuclei:

\- Their decay is not affected by surrounding nuclei (in other words, decays are independent events), and

\- The decay of any individual nucleus is a random event whose probability is not dependent on time.

These two facts combined mean that decay rate is proportional to number of nuclei.


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

[User]
[Blade Runner] If Deckard is a replicant why is he built so weak that he gets his ass handed to him by the androids hes made to hunt down and kill?

My answer is that he just isnt a replicant. But if we assume he is the only answer I can think of is that there are models designed for combat and if hes able to fight them, hed work out he was an android pretty quickly. I still think thered be a way around it if he was built like Arnie but Im curious what you think.

[Assistant] It's worth remembering that replicant-Deckard would have to blend in seamlessly with human society, both from their point of view and from his. Once he noticed he was far more physically capable than a baseline human, sooner or later he'd start to suspect something was different about him.


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

[User] [General Batman] Tell me about Bane. Why does he wear the mask?

[Assistant]
There is a prison, in a more ancient part of the world. A pit, where men are thrown, to suffer and die. But sometimes a man rises from the darkness, sometimes the Pit sends something back.

There was a child in that prison who Bane protected, one day when there was sickness, the child climbed out making an impossible jump, and Bane, her protector was beaten mercilessly by the other prisoners (presumably because her escape meant they couldn't rape her) and the surgeon in the prison was an addict and had shaking hands while attempting to "heal" Bane. After the prisoners and surgeon had done their work, Bane was left in complete agony from the mutilation.

The Mask has an anesthetic gas concentrated in it that allows him to function and deadens all pain. Thus granting him immense strength because he doesn't know his muscles are tearing. He was even capable of lifting a grown man in combat armor over his head with relative ease.


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

[User] If I take a two dimensional object and rotate it through the third dimension, it appears that the object has become a mirror image of itself to a two dimensional observer. Is there an equivalent to reflect a 3D object via rotation in the fourth dimension?

[Assistant]
Yes. In every 3d rotation, there is a fixed plane (the rotation plane) and a fixed line, the axis of rotation. This decomposition in rotation is required for galaxys, solar systems and atoms exist.

In 4d we don't have this asymmetric decomposition. Instead, every 4d rotation has two fixed planes. Solar systems and atoms can't exist in 4d because that fixed line in 3D becomes a fixed plane. We can try find a 4d rotation that produces a 3d reflection keeping this decomposition in mind.

So let's try to reflect an object across the YZ plane and through the X axis. Let's have W be a fourth orthogonal axis. In a reflection, the plane of reflection is fixed, so that means that the YZ plane is one of our planes of rotation. But nothing happens to points on the reflection plane, so in 4d this has to be a zero degree rotation. But we still have the XW plane to work with. Since an object is moved to the other side of the origin, this suggests that we do a rotation through the angle pi (a 180 degree rotation) in the XW plane. It turns out that when you look at where a 3d object lands after a 180 degree rotation through the XW plane, while having a zero degree rotation about the YZ plane, you do get a reflection.

In fact, any N-dimensional reflection can be seen as a N+1 dimensional rotation.


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

[User] ELI5: Why is Greece so upset at Germany for its own debt problems - despite being bailed out numerous times? (I don't know enough about the financial system)

[Assistant] They're not mad because of their debt problems. They're mad because of the solutions Germany is proposing to their debt problems; specifically, that they should drastically cut social programs as a precondition of getting a loan. Cutting those social programs will hurt people, so many Greeks feel like the cuts shouldn't happen at any cost.


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

[User] What would happen if you peeled an orange and removed a segment from it while it is still growing on a branch?

[Assistant]
Nearly all living things have defense mechanisms for "exposed" or damaged tissue.

For humans that's anything from blood to calcified collagen.

For plants this is anything from low viscosity sap to bark.

The segment you removed would cause an upswing in activation of hardiness epigenetic activation.

This is why farmers introduce plants to cold/severe weather as slowly as possible or avoid it all together.

So youd see that section of the orange essentially create "plant scar tissue", stop growing, and only if the rest of the fruit remained viable would it continue to send nutrients.

This is also why you can still see rotten fruit on plants before they give up, they continue to try even if something went wrong until the fruit is no longer viable.

The fruit undergoes what is essentially a miscarriage and eventually detatches from the flower.


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

[User]
Are there any exam/certificates I can obtain to show evidence of my statistics knowledge?

Hi all,

I have a strange academic background - due to personal problems ... I had to repeat my A levels which I failed and did an access course before pursuing my bachelor degree.

I have a bachelor in Education (specialising in Early Childhood) and masters in Computer Science. I was introduced to data mining and statistics during my MSc. Due to my bad experience with a levels, regardless of my educational achievement so far - I still have a nagging feeling at the back of my mind stating that Im dumb and will absolutely fail any mathematics dilemma.

This has been holding me back professionally and academically, I have a plan to eventually do a PhD and I wanted to ask - are there any private exams/ certificates I can study to get certified in statistics?

Im based in the UK, thank you for your help!

Edit:
Thank you so much to everyone that replied! I appreciate it :)

[Assistant] Another thing to consider: certifications are offered from statistics coding companies, like SAS.  If you have a background in CompSci, you can get try out something like advanced SAS certification.  While this doesnt communicate specifically mathematics acumen, it does show youre serious about learning statistics-related subjects (which are more directly in your wheelhouse).


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

[User] ELI5: Why do we get so caught up in mob mentality?

[Assistant] It's similar to the reason we shitpost on the Internet. Being part of a mob gives people a partial sense of anonymity, allowing them to drop their inhibitions and behave with less fear of being held accountable.


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

[User]
ELI5: Why has Arabian nations been able to capitalize on their oil resources and become massively wealthy while Africa hasn't?

I understand that Africa isn't a hellhole with people wearing tribal clothing but we haven't seen Africa making the money Arabia has even though has huge amounts of resources. Why are we not seeing African oil sheikhs for instance? Why isn't Africa making huge money and isn't relying on a lot of foreign investment from places like China?

[Assistant]
Africa doesn't have the infrastructure to develop and market these resources. Drilling for and selling oil is both difficult and expensive. You need to have the drill rigs built, pipelines set up to move the oil from the fields to either a refinery or a large port, and then storage and transfer facilities at the port in question.

All of these are hard to accomplish with little foreign investment, a poorly educated workforce, and an unstable government. No one is willing to pour millions of dollars into an African oil field if there is a very real threat that the fields will be seized by an armed party in a civil war. Likewise, the pay for workers would have to be huge in order for them to risk their lives to move out there and work, since a local, trained workforce is small or nonexistent.


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

[User]
What do you make of this Nietzsche quote?

As long as you still experience the stars as something "above you", you lack the eye of knowledge.

Ive been fascinated with this quote for a long time but want to determine what it means. What does it mean to you?

[Assistant]
He's warning you against the idea that knowledge stems from a single, fixed perspective.

Note also that he uses the word 'experience' and not the word 'think.' It's easy to _intellectually_ understand that 'above' and 'below' are relative concepts. For Nietzsche that is not enough. You need to be able to sense and _experience_ things in their mutable inter-relatedness, not merely to intellectually reflect on them as such. To this end he talks about an _eye_ of knowledge (and not, say, a _brain_ of knowledge).


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

[User]
[Marvel] What would an Omaga level mutant with mastery over the Higgs Boson be able to do?

Like Magneto is an Omega class mutant because he has molecular/atomic control over the electro-magnetic spectrum would be able to shoot EMP, lightning, etc.

How powerful and what would a person with the complete mutant mastery over Higgs Boson field/particles be able to do?

[Assistant]
Make it possible for things to move at the speed of light, and collapse the universe, initiate the creation star systems. Move planets and star systems.

Jump really high and float down like a feather.
Making things light so he she could clear ruble as if it were leaves that fell in autumn would probably be the most practical super hero powers.

In fights negating an opponents mass would significantly reduce their hitting power.

If you are aware of a mutant as dangerous as this you are obligated to contact your local MRD office and inform them of this menace to humanity.


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

[User]
[Romeo and Juliet] What happens after the events of Romeo and Juliet's death?

The grudge between the Houses of Montague and Capulet has raged for a long time, now 6 people are dead, Verona is still in shock, the authorities have already stepped in and tried to defuse the situation by having Romeo exiled, but that only made things worse. What happens now, after the events of the play have run out? What happens to the families? How does Verona deal with this tragedy?

[Assistant]
From the prolgue we learn the tragedy ends the feud.

A pair of star-crossd lovers take their life;

Whose misadventurd piteous overthrows

Doth with their death bury their parents strife.

The fearful passage of their death-markd love,

And the continuance of their parents rage,

Which, but their childrens end, nought could remove,

So nothing but the death of those children could have ended the feud.


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

[User]
Would it be possible to dampen or completely cancel a Tsunami wave by sending the same wave pattern in the opposite direction?

Similar to noise cancellation that uses opposite sound waves to cancel ambiant noises, could the same technology be used to cancel a wave from a Tsunami? Would it be practical or even possible to install some kind of wave device along the shorelines of highly populated areas?

[Assistant] On a small scale it is. There are prototypes existing of structures that would redirect the wave around a town or village in such a way as to cause the wave to cancel itself out. On a large scale, you would have to create a wave of the same magnitude, at the same location, in the opposing phase at the exact time of the generating event to stop the tsunami entirely. With absolutely massive expenditures of energy, you could theoretically cancel the wave for a particular stretch of shoreline. By doing this though, other stretches of shoreline will be hit harder due to constructive interference. The noise cancellation you are referring to works to limit wave energy at a particular point (your ear), not large volumes.


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

[User]
What does it take to become faculty at a place like MIT?

Is it papers?
Is it education?
Adviser ?
Demonstrated success ?
Potential ?
All-around-good scientist?
Best-in-the field?
All of the above?

In short, what does it take to become selected as assistant professor (since associate and full professor probably changes the answer) at a place like MIT?

MIT is a placeholder here, it could be any top institution.

[Assistant] High impact papers, ability to get grants, interesting cutting edge work, how this work fits in with what's currently being done in the department (you probably shouldn't be in direct competition with other faculty, particularly senior faculty), and how much the faculty and chair like you for whatever the reason.


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

[User]
[General Sci-fi.] How does artificial gravity work exactly?

In any given situation, be it on a spaceship or space station, how exactly is gravity simulated off of a planet? And why does it seem that no matter what happens to the ship in question and no matter what systems fail, gravity rarely if ever turns off?

[Assistant]
[Star Trek]: Artificial gravity is created by graviton emitters. Gravitons, as we all learn in elementary school, are the quantum particle by which gravity is propagated through the spacetime medium. The ability to generate, control, and direct gravitons was one of the many products of Zephram Cochrane's original research into warp drive; warp drive itself is a form of spacetime wave manipulation, and the transition from gravity wave to graviton particle was an inevitable outgrowth of the original technology.

Gravity plating is the ultimate result of that technology. It is cheap, reliable, and runs on extremely durable microreactors contained within the deck plates themselves. Hence, even when nearly all ship's systems have been damaged or disabled, gravity plating remains operable. Klingon ships, of course run on the less-reliable central gravity generator system. This has proven fatally unreliable in cases where Klingon ships were disabled, and boarding parties equipped with magnetic boots were able to attack the Klingon crew who were unable to defend themselves.


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

[User] ELI5: How does a cell phone determine how much charge is left? My understanding is that batteries output a constant voltage until they are almost depleted, so what does the phone use to measure remaining power?

[Assistant]
Voltage isn't exactly constant.  A cell phone battery might be rated at 3.7 volts, but really it's 3.8V when it's fully charged, and 3.5V when it's empty.

The phone then has (more or less) a look-up table.  The phone knows that when it's at 3.8V, it's 100% charged.  And when it's at 3.75V it's 80% charged, etc.  This is also why old phones sometimes go from 20% charged to 0% charged almost instantly - because the battery is old and isn't performing according to the lookup table.


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

[User] [Hobbit] How much is the Arkenstone worth?

[Assistant]
Making a ton of assumptions here, but let's break it down.  [Destruction of fourth wall required for further discussion] Assume the following:

* The Arkenstone is a diamond
* The Arkenstone is an internally flawless diamond
* Due to fine dwarven craftsmanship, it is cut and refined, and is externally flawless

The largest (uncut) diamond ever found in real life was the Cullinan diamond, weighing in at 3,106 carats.  It was approximately fist-sized, like the Arkenstone.  Assuming amazing dwarven craftsmanship, let's assume that they manage to make flawless cuts across its whole surface and only lose, say, that extra 106 carats, leaving it at a perfect 3,000 carats.

The most expensive diamond ever sold at auction was Elizabeth Taylor's 33.19 carat "potentially flawless" diamond, which sold for $8.8 million, or $265,697 per carat.  Applying that world record price to the fabulous Arkenstone of 3,000 carats, its total potential price would be **$797,091,000.**


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

[User] ELI5: Einstein said If you can't explain it to a six year old, you don't understand it yourself. How would he explain special relativity?

[Assistant]
Einstein used  trains extensively but for modern kids cars are more appropriate. Here we go.

Ok so you know haw when you are in the car driving down the highway and you arn't speeding up or slowing down or turning if you don't look outside its kind of like the car isn't moving at all. Sure when you turn or change speed you get pushed into the seat or the seat belt but when cruising you could be parked. So when you look out of the window its a little like the world is moving not you.

Now on the highway there are other cars on the road and they can be going in opposite directions so the cars going the same way as you can seem to move slowly while traffic in the other lane is very fast. And the thing that's cool is that feeling of standing still while the world goes by happens to everybody so if you compared what the different cars saw they would all disagree about how fast all the cars where going.

But here is the amazing thing if you can see how fast the lights from the headlights where going everyone in every car would agree on the same speed for everyone's headlights no matter how fast or what direction they were going. And the number they came up with would be the same number that anyone anywhere in the the world would come up with when they measured light speed.


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

[User] ELI5: How were/are video game cheats discovered?

[Assistant]
They were knowingly placed into the game by the makers, and released to various sources (Cheat magazines, websites).

Some only came out months or years after the game was released, some were rumored to exist and never did (the "Naked Lara" in Tomb Raider, for instance).

Especially when demoing, shooting a review, or just debugging, the ability to have infinite life/lives, skip levels, spawn weapons and vehicles, unlock characters, etc. is a nice feature.

"Glitches" are the things found by players. That's generally random luck to find and replicate, which is then spread through the online community.


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

[User]
[Marvel] Has Taskmaster ever considered doing something regular with his abilities?

He truly has an amazing gift. By regular I mean like, has he ever tried to take up a sport or some form of work or activity that requires skill? One that doesnt make him a threat to society and the Marvel heroes?

[Assistant]
He used his ability in HS to become a star quarterback.

After HS be basically immediately got into the "super" business but his amorality lead him toward the supervillain path as that was more profitable.

He works primarily combat instructor/martial arts trainer for both villains and superheroes. Though his clientele are rather irregular, the occupation itself is fairly mundane.


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

[User] Why do some people pass out when seeing blood?

[Assistant] I don't know about particular theories related to blood or violence in particular, but the "fainting" reaction related to all stressful situations is called a "vaso-vagal reaction." To some, a stressful situation is seeing blood or violence. The stress overstimulates the nucleus tractus solitarii in the brainstem. This in turn amplifies the parasympathetic system, in other words your rest and digest nervous system. This causes cardio inhibition and dilation of your blood vessels, which causes blood pressure to bottom out as a result. In turn, you faint. Ask if you have any more questions about the physiology of this process.


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

[User] [Star Wars] Does deflecting blaster fire with a saber feel like hitting an object with a baseball bat, or does it just bounce off?

[Assistant] Although a blaster bolt is just a blob of plasma contained within a magnetic sheath, there is still kinetic energy in the bolt. A person redirecting blaster fire with a lightsaber would feel a little bump as they hit it, but it would be much smaller than your idea of hitting a baseball, probably more like hitting a pingpong ball.


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

[User] ELI5: How Deodorant Works?

[Assistant]
People sometimes think sweat is stinky. Well, it isn't, really. The reason people sometimes smell bad when they sweat is that there are bacteria that like to hang out in wet and warm places like a sweaty armpit, and these bacteria do make bad smells.

Deodorant is made out of stuff that kills those bacteria. So when you put it on your skin, even if you sweat you won't smell because the bacteria can't live there.

They usually also add some nice-smelling stuff to deodorant just to make people smell nice when they wear it, but the nice smell isn't what makes deodorant work.


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

[User] ELI5: how do books sometimes have on the cover "the new bestseller". How can it of been a bestseller at the time the cover was designed and no copies had been sold?

[Assistant]
Because there's no formal definition of what a "bestseller" actually is or not so anybody can call anything they want a bestseller. You'd probably upset the bookstores you need to keep onside if you started calling shitty books by unknown authors bestsellers but you could.

There are lists of "bestsellers" out there but none that is official recognised as being the seminal authority (like the billboard charts used to be for music).

It's very similar to how movies will call something the "New Michael Bay Blockbuster" before it's even been released and they know what ticket sales are going to be.


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

[User]
Are there nerves in the umbilical cord?

I'm talking about the human umbilical cord, specifically, and I'm curious whether newborns feel anything when it's cut.

[Assistant] No. The only structures in the umbilical cord are two arteries and a vein, unsurprisingly called the umbilical arteries and the umbilical vein. The cord's not even made of muscle or skin. It's composed, apart from those blood vessels, of a substance called Wharton's jelly, which is the same kind of stuff that fills your eyeballs.


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

[User] [Revenge of the Sith] Did Anakin ever receive treatment for his extensive burns (bandages, skin grafts, etc)? Or was the Darth Vader suit simply placed right over his charred flesh?

[Assistant]
The initial suit was placed over his flesh as a stopgap to keep him alive, but through material later in the timeline we know that he can remove most if not all of it and get in bacta tanks.

How long he spent between the initial placement in the suit and when he first took a bacta dip is unknown.


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

[User]
How do you go about getting letters of recommendation for a job application when you don't want your current department to know you're considering leaving?

A lot of the job postings I'm seeing are asking for 3 letters of recommendation.  Do I go back to mentors and committee members from the department that gave me my degree, even though they don't have much experience with me as a full-time faculty member?

[Assistant] I'd reach out to the search chair directly and explain that although you're looking, you'd still like to keep the process discreet for the time being. It's possible that they will evaluate your materials in the absence of letters with the expectation that if you make it far enough in the process, you could produce them.


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

[User] Neurologically what is the difference between physical and psychological addiction?

[Assistant]
It's a little easier to explain as "chemical addiction" versus "behavioral addiction" rather than physical and psychological, which are very broad ways to look at it. They are also not entirely disconnected, as you can gain behavioral addiction to a chemically addictive substance (think of smokers who quit, but keep wanting to hold a cigarette despite not craving one), or start an addiction for behavioral reasons (a need to escape reality) and become chemically addicted. But they do work with different mechanisms at the most basic level, only to become incredibly complicated when you look at them from a little further away.

A chemical addiction upsets the balance of naturally occurring chemicals within the body, which then reach a new equilibrium, requiring escalating amounts of the outside chemical to achieve the same effects such as euphoria, adrenaline rush, etc, and in turn causing a deficit when there is an absence of those chemicals. This deficit takes awhile to work its way out of the body's natural system for equalizing, which is the source of many withdrawal symptoms. Heroine dependency slowly replaces your body's ability to produce natural 'pain killing' agents. At first, the surplus of the pain killers is euphoric, then as the equilibrium hits, you need more, and in the absence of the drug, you experience crippling pain and physical torment until your body recovers. This will drive you to seek out more of the drug. Then, if you are off of it for a really long time and go back, you could *die* from the dosage you were last adjusted to, as you OD on even... half of it, possibly, because your body has regained its natural equilibrium.

A behavioral addiction is based on using a behavior as an outlet which reinforces that behavior as a source of release. So for example, a behavioral addiction to MMORPGs (not as common as people claim, but not unheard-of) could begin as an attempt to find a social outlet while under the stress of chronic social anxiety, self-esteem problems, or agoraphobia. Then, as it fills a role as a social outlet and the person doesn't experience social anxiety doing it, they reinforce their attraction to that outlet as a coping mechanism. They then slowly become behaviorally dependent on it as an outlet, and it replaces all need for offline socialization in some extreme cases. Then, if removed from it, they panic like they've been cut off from their entire world. This brings out a sort of behavioral "withdrawal" that can drag out extreme anxiety, both buried from before the addiction and newly created by separation from the coping mechanism.

But you will rarely see one without some measure of the other, at least where a controlled substance is involved. On a neuroscience level, it would become more complicated as you get into dopamine reactions involved in learning, which are active in any process involving rewards. Both a chemical outlet (like euphoric escapism) and a behavioral outlet (like cutting as a pain inducer) will involved learn behavior, but the chemical addiction will have the more easily quantifiable methods for detection during withdrawal.


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

[User]
ELI5: what happens when we jump?

So energy from our feet makes us rise and stay up for a few seconds?
Why does gravity pull us down if it allowed us to float in the first place?

[Assistant]
Gravity is a constant force. On Earth, it always exerts the same amount of "effort." When you jump, your muscles are exerting a much greater effort. When you add together the force of gravity and the force of your jump, the net result is an upwards force that accelerates you up.

Once your feet are off the floor, you stop pushing up, so the only thing left is gravity. Gravity is still pulling you down at the exact same rate it always was. As you move up, gravity accelerates you downward, eating away at your upwards velocity until you stop, but only for an instant. Then, it continues pulling you down (as it always has been) and you fall.

Gravity did not "allow" anything. You have been fighting it every moment of your existence.

Also, something funny that happens when you jump: technically, because of how gravity and forces work, the Earth momentarily fell "up" from *you*, before falling back as it was attracted to your gravity. Sure, it's too small to see, but it did actually happen.


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

[User] When a photon redshifts, it's wavelength becomes larger, which corresponds to a lower photon-energy. What happens with this energy difference?

[Assistant]
If you mean redshift due to a doppler effect, then energy is still conserved *in an inertial reference frame*. A doppler shift changes reference frame by moving at a different velocity when the shift is observed.

If you mean in general relativity, then there is no conservation of energy in this case. (Energy is not in general conserved in general relativity.)


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

[User]
When a solid is broken, why don't the atoms re-bond when pressed back together?

Say you have a gold brick. I get that this is basically a mesh of many atoms, all of which have the same amount of protons, neutrons, etc, and that these atoms all bond with each other. Now say you split it cleanly in half. If you press it back together, what is stopping the atoms from re-bonding back to the original state?

[Assistant]
Oxide layers rapidly form when the surfaces are exposed to air, and macro/microscopic contaminants (including air itself) get trapped between the surfaces when you press them back together, preventing the bonds from reforming. Not to mention that whatever method you use for cutting the material probably didn't leave a microscopically smooth surface, meaning that the only pieces in contact unless you apply a lot of clamping force will be the small hills sticking out from the surface.

But your instinct is right -- this is possible with clean cuts in a vacuum.


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

[User] Why is aluminium 100% recyclable but other metals aren't?

[Assistant]
All metals are recyclable, and contrary to popular belief, most metals *do* actually get recycled. Even low-alloy steels and cast iron can be remelted and either used directly or blended as necessary with virgin stock to dilute impurities. High-alloy steels like tool steels, high-speed steels, and stainless steels are more valuable, so they get recycled separately. Other base metals like copper, zinc, and lead are even more widely recycled. Their main applications leave them relatively unsullied at the end of life, making it easier to separate them for recycling. Needless to say, more exotic metals like platinum group metals and refractory metals are completely recycled.

In general, the more expensive a metal is, the greater the lengths people will go to in order to recover it. Iron is pretty much the only metal so cheap that recycling is often not economical. Aluminium cans just happen to be the most visible example of metal recycling for the average consumer; other metal recycling happens behind the scenes at scrapyards and electronic waste processing facilities.


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

[User] What determines the axis of a black hole's accretion disk? Is its orientation always stable?

[Assistant]
The accretion disc of any collapsing dust cloud emerges from the shape of the cloud and the initial velocities of the particles. As opposing momentums cancel and similar momentums combine, the cloud gradually develops a spin which reinforces itself by first accelerating the surrounding orbiting particles into having a complementary momentum, and then pulling them into an impact which adds to the angular momentum of the disc.

After a stellar object (and an accretion disc) have built up this angular momentum, its orientation is very resistant to being changed, exactly like a gyroscope's (and why we put rifling in our guns to make bullets spin when they are shot out). The orientation can change, though, similarly to how there's a precession in the Earth's rotation. It just takes enormous forces to do so.


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

[User]
[Star Wars] Enjoying his favourite opera, Mace Windu overhears Palpatine's Dark Side speech, and decides to investigate the Chancellor further. How does this change events?

In this situation, Mace has decided to take a day off to go see his favourite opera. He senses Anakin nearby, and realises Anakin has accompanied Chancellor Palpatine to the opera. "Not favourable, but not a big issue." Mace thinks, recognising how much time Anakin is spending with the rather manipulative Chancellor. Deciding against confronting them, Mace enjoys the show from beneath them. He overhears Palpatine recounting a Sith Legend, and suspects he might have more than a passing interest in the Dark Side of the Force. After discussing matters with several other Jedi Masters and meditating for hours, Mace is pretty certain Palpatine is the Sith Lord they've been searching for. Mace manages to convince the Council of his theory, barring Yoda and Obi-Wan who are still skeptical.

Mace decides to still proceed with his arrest of Palpatine, arguing that the Clone Wars are reaching a pivotal moment where Palpatine's arrest could bring things to a peaceful end if his theory  is correct. Any suggestions he might be wrong are rejected by Mace, as he suggests he knows he's right on this matter.

What transpires now? Would Mace take his usual team of Jedi for an arrest? Would Yoda and Obi-Wan postpone their missions to accompany him? How would Anakin react, given he'd only learn of these events after they transpired?

Ninja Edit: I'm aware Palpatine would almost certainly try to deny allegations before he was ready to enact Order 66. However in this situation, Mace cannot be dissuaded. Either Palpatine decides to drop the act, or Mace continues his investigation in secret to find damning evidence.

[Assistant] Well if Obi-Wan and Yoda havent left yet then they would probably accompany him. However, since Anakin doesnt know that Palpatine is a Sith yet because hes kinda thick headed, if the Jedi try to arrest or attack Palpatine he might fight against them. So we would probably have a Anakin and Palpatine vs Yoda, Mace, and Obi Wan fight.


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

[User] [John Wick] Why give John only seven cartridges for his pistol, minimizing his chances of success and increasing the likelihood of an expensive and bloody turf war? Just because you don't like the guy?

[Assistant]
1. He is obviously much more competent than most assassins and much more dangerous. His chances of success are less minimized and more slightly reduced.

2. He hates the guy and wants to punish him.

3. If he gives too much overt aid there's more chance of retaliation if John Wick is killed. A single gun could have been stolen or robbed. A full set is harder to explain.


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

[User] ELI5: why can I eat the center of baby corn but not regular corn?

[Assistant] You could eat the cob of a normal sized ear of corn. It's all fiber and there's really no nutritional value. We eat baby corn whole since it's way too much work to get it off the cob and since it's smaller it's bite sized anyways.


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

[User]
(Star Trek) Why havn't Starfleet developed anti-phaser protection yet?

It seems that no combat personel ever wears armor in Starfleet. You could say that phasers outclassed even the most durable armor, but other civilizations like the Borg and the Kelvans have developed something to protect themselves from phaser shots. The Borg armor allows them to adapt with each shot, thus neutralizing most weaponry eventually, and the Kelvans have a sort of energy field projection that works similarly to a deflector shield. Why haven't Federation developed something similar considering that combat situations on the ground are a regular occurance.

[Assistant]
Hand to hand combat simply isn't all that common.  Its impossible to beam over without first lowering shields, and an opponent that has destroyed the shields in combat between starships has already "won" the engagement.

There are numerous exceptions recorded by exploratory vessals, such as the enterprise, and voyager which are popularly shown, but they are popular specifically because of how rare and exciting the event is.


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

[User]
ELI5: How well do fluids besides water actually hydrate you?

Let's take for example sugar free Gatorade, or pedialyte. That in itself, is it effective at hydrating you?

[Assistant]
A lot of people who don't know science in this thread.

Your small intestine absorbs pure water very poorly. Water is mostly absorbed via a sodium/glucose/water symporter. That means that a drink with a proper balance of sugar, salt, and water offers the quickest form of hydration. One can find this mix in "oral rehydration salts" that are given to cholera patients. Another oral rehydration solution is Pedialyte, and it is very good at rehydration. Gatorade, as it turns out, has way too much sugar and too little salt to provide optimal hydration. If you mix it with water in about a 50/50 ratio, however, it comes close. It's even closer if you mix up a quart and then sprinkle a tiny tiny pinch of table salt into the mix. This will rehydrate you faster than water or Gatorade alone.

All that being said, if you've eaten a big meal, you have enough sodium and sugar in your digestive system, so your digestion will best be aided by pure water. In this case, it's needed, not just for absorption, but for hydrolysis of proteins and carbohydrates into amino acids and sugars so they can be properly absorbed.


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

[User] [Game of Thrones] Why Lord Varys conspired against the king that was neither cruel or mad and was able to rule the Seven Kingdoms for 15 years without a war?

[Assistant]
Robert's reign was only peaceful and prosperous due to his hand Jon Arryn who actually ran the realm while Robert drank and whored around.  He had no interest in the details of ruling.  Also Robert spent way too much money (which had to be borrowed from the iron bank).

Then you have the issue of Roberts heirs, Aside from them not being his children, Joffery was not suited to be king, and Tommen was too soft and Cersei had her own problems,  Stannis too rigid.


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

[User]
[V for Vendetta] V says that the Norsefire Party created the bioweapon project in Larkhill, but would a political party not in power would have the right to do so?

At the time when Larkhill was established, Sutler was not the government and he still had people abducted from their homes. Are we given an explanation as to how the government at the time and the other opposition parties allowed this to happen?

[Assistant]
because norsefire was a brutal paramilitary authoritarian group who scared the shit out of the opposition.  As for how they were able to...incubate safely, the more fucked up shit they did secretly or with the help of ideologically corrupted police, or against opposition leaders and members themselves.

the question was not if they had some "right" to do so, they killed those who opposed them and a lot of other people on top of that.


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

[User] ELI5: What is the Dodd Frank bill?

[Assistant]
The Dodd-Frank bill is a US federal law, proposed by then-president Barack Obama in response to the economic crisis of 2008.  This crisis is generally regarded as being caused by poor lending practices by banks, among other issues.  Then-president George W. Bush "bailed out" several banks, lending them hundreds of billions of dollars of government money.  The Dodd-Frank bill greatly reduced the amount of money the Bush government had set aside for lending to the failed banks, and specified how this money could be used - insisting that it be used for stabilizing the businesses rather than expanding them.  This was done to keep taxpayers' money from being "gambled" away by the banks which had proven themselves prone to poor business decisions.

The Dodd-Frank Act also includes many other provisions, aimed at ensuring that a similar economic crisis would not occur again:

* New agencies are created whose job it is to keep an eye on the economy and try to detect impending crisis before it occurs.  This includes monitoring of both the banking industry and the insurance industry, among others.  Other agencies are abolished or combined.
* A fund is set up to repay a bank or insurance company's debts if it fails, including customers' bank accounts.  This fund is paid for by extracting fees from any financial business worth over $50 billion.
* Banking executives have been required to register with the government and provide reports on their activities since 1940.  Dodd-Frank increases the number of executives required to register and report, and increases the information they must report.  This is meant to help the government predict impending economic crisis.
* Investment businesses are prohibited from certain types of investment, in particular *proprietary trading*.  Proprietary trading is a practice where the investment business invests its own money, instead of investing its customers money.  Proprietary trading is frowned upon because it does not benefit the customers, it is seen as risky, and it may create conflicts of interest (the business could profit at the expense of its customers).
* The practice of "selling debt," which is seen as a cause of the 2008 economic crisis, is regulated and subject to government approval.
* The powers of the Securities and Exchange Commission (SEC) are expanded.  The SEC is a government agency in charge of oversight of some of the finance industry.  At the same time, stricter requirements are placed on the SEC, ensuring that it is performing its oversight correctly.
* Grants are created to help poor people establish bank accounts or take out small loans.
* Mortgages (money loaned so people can buy a house) are regulated.  Banks are prohibited from loaning money to people who are unlikely to pay it back.  Banks are prohibited from charging exorbitant rates, unfair penalties, etc.  Values of houses must be appraised by a professional to make sure that the money loaned matches the price of a house.


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

[User] Really dumb question, why doesn't C++ have a default error for integer overflow instead of spitting random numbers?

[Assistant]
Because CPUs do integer overflowing for free with the mathematic instruction. Checking and throwing an error is an additional instruction, which means best case performance is halved (for integer math).

You can in fact check the appropriate variable yourself if you want to know if an overflow has occurred.


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

[User] ELI5: If a hole that went from one side of the planet all the way to the other side, and you fell down that hole, what would happen? Would gravity just keep you in the center of the planet, crushing you?

[Assistant]
Assuming no air resistance, and assuming the hole through the planet has infinite strength and will not collapse, and assuming the planet is not rotating:

You would fall through the Earth.  As you got closer to the center, you would keep accelerating, but the rate of acceleration would decrease as you approached the center.  At the exact center of the Earth, you would have no acceleration on you, but your momentum would keep you flying through the hole.  After passing the center of the Earth, gravity would work against you, slowing you down.  The rate of deceleration would increase as you got farther and farther from the center.  Eventually you would come to a stop at the exact height you jumped from, but on the other side of the planet.  Then you would fall back the other way, back through the planet again, back to your original spot.  Then you'd fall back through again, and again, forever.  You'd oscillate back and forth through the planet until the sun exploded.

Of course, that's with the three assumptions up top.  With air resistance, you would lose energy every trip through the planet, so each oscillation would be weaker and weaker, and you'd eventually end up motionless at the center of the planet.  Without an infinitely-strong tunnel, gravity would simply collapse the tunnel and you'd be crushed.  With a rotating planet, the difference in rotation rates between you and the tunnel will slam you into the walls and kill you.


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

[User]
ELI5 Why does caffeine help relieve headaches?

Whenever I have a headache, I usually go for a soda or energy drink over Tylenol or Advil because it just seems to relieve it better. Why is this?

[Assistant]
Most headache and migraine medicine has caffeine as an ingredient, because it stimulates and promotes vasoconstriction. If your headache is from caffeine withdrawal, obviously this will resolve the symptoms. If it is not, the caffeine shrinks blood vessels and promotes higher blood pressure, which moves a lot of blood around your head and scalp, thus lessening the  painful symptoms of a headache.

Headaches are very well researched, but not very well understood. The main thought has to do with blood throughput to the scalp area, but we don't know why.


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

[User]
Why do we need to compile separate 32 and 64 bit versions?

Can't the CPU run 32 bit instructions and vice versa? Or at least simulate it?

[Assistant] Sure, and one cpu does just that. But 64-bit code has several advantages. For one the address space is bigger, so you aren't limited to using only 4 gigs (in practice closer to 2 gigs) of ram and can use up to terabytes of ram for a single process if you want. For another the 64 bit instruction set is a bit better and more "powerful" in general. There are more registers, for example, and this enables 64-bit programs to achieve higher performance on the same cpu.


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

[User] [European History] Why did France and Germany always fight for control of Alsace Lorraine?

[Assistant] I think it has something to do with that part of the world being on top of the Emperor's secret labratories. His massive psychic powers make people in that area uneasy, so minor conflicts tend to get out of hand very quickly. It's why Alsaice-Lorraine has a reputation as one of the most blood soaked parts of the world, and was the location of both the Rwandan and the Australian-Aborigine genocides.


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

[User] How will Ukraine war impact grain production? Will this lead to higher prices for food and what effect will this have on poorer countries?

[Assistant]
Ukraine and Russia both are large fertilizer exporters, as well as large exporters of grains. Nitrogen fertilizer, which is largely used for corn and wheat, is produced in an energy intensive process, usually with natural gas. Hence, the spike in European natural gas prices has shut down some nitrogen fertilizer production in Europe. Therefore, there is a *significant* global shortage of fertilizer, particularly nitrogen based fertilizers given Russia sanctions, Ukraine production offline, and high natural gas prices in Europe.

This means fertilizer is very expense and suggests that the global wheat and corn crop will be smaller as farmers either (1) cannot afford to pay up front for fertilizer or (2) as they try and substitute with less effective fertilizers. This means higher grain prices in 2023.

Given the existing sanctions on Russia and the events in Ukraine, there is also a massive disruption of the current crop outlook. Therefore, prices for corn and wheat have increased significantly. This means food prices increase globally and there is a significant chance of famine and social unrest.


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

[User]
[Mass Effect] CMV: Using the genophage on the Krogan was the best possible solution and a cure should not be found.

The Krogan are unable to monitor their own reproductive rate. If left unchecked the Krogan will use up all the resources available to them before moving on to the next planet or population center.

The genophage doesnt even render them sterile it just returns their reproductive rate to that of their pre-industrial society. If the Krogans wanted to they could repopulate and have a net positive population growth but they would rather kill each other and fight amongst themselves.

[Assistant]
The mistake was the uplifting. They essentially tried to integrate a primitive species into a hyper-advanced space community.

The Krogan's never had the chance to properly develop into an equal partner so they just did what they had always done. Wage war.

With several centuries gone past and an bonding experience with the rest of the galaxy (fighting the Reapers) it stands to reason that the integration process will be much smoother this time around. And remember, with Eve there is a factor in Krogan politics that has never been there before.

And there is enough space in the galaxy, there aren't that many relevant species but literally billions of stars.


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

[User]
ELI3: Trying to explain gravity to my three year old niece. I'm failing to explain it to her. Can you help?

At the dinner table my bread fell off the table seemingly on it's own. My niece screeches and exclaims "WHO DID THAT?!".

I explained that no one did it, that gravity caused it to happen.

Which has now been three days of me trying to explain to her what gravity is. Apparently I suck at explaining things to children, because I can't quite figure out how to teach something so profound to a three year old (nearly four).

Help ELI5!!! Please!

[Assistant] You are likely making it to profound. When you drop things they fall down.  The earth wants to pull everything towards it, so everything always wants to fall down. (she might ask why)  Because things that are VERY VERY BIG like to pull on everything that is around them.  (She might ask why again) It's a law of nature, Gravity pulls things towards the earth centre of the earth because the earth is so big.  Don't make it to complicated, just try to keep it at her level and then move the conversation to a topic that is more at her level of understanding.  Like discussing how big the earth is and what a planet is and so on.  Gravity is abstract enough that all she needs to know right now is that things fall ween dropped.


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

[User] ELI5: why do houseflies get stuck in a closed window when an open window is right beside them? Do they have bad vision?

[Assistant]
Flies have very simple brains. Through their evolution it has been enough to fly towards light; then along came us tricky humans and put transparent glass in their way.

In a similar situation we can observe, learn and devise a strategy to escape. Flies can't, so this is less an issue of vision and more one of brainpower.


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

[User] How many days do B-cells need to create new antibodies?

[Assistant]
New B cells are always being made. Technically the antibodies are made immediately. However the antibodies are made randomly. By chance some might bind a new antigen with low affinity, those are then selected and refined through intentional mutation. The process is constantly repeated and so your immune system will continue to refine the antibodies to bind with higher affinity.

In general it takes a week or two after exposure to a new antigen to produce very high affinity antibodies against it. This is of course the basis of vaccination and boosters. Exposure to an antigen lets your immune system build up higher affinity antibodies and subsequent exposure allows for the affinity maturation process to further refine them.


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

[User] ELI5: Why do hotels have open WiFi with a landing page to type the password, instead of a regular passworded WiFi network?

[Assistant] Many hotels have you log in with your room number and last name, so that only current guests can get access. For the ones with a single password, it's probably so they can make you agree to the terms of use.


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

[User]
I believe contracting to paramilitary groups like Blackwater is wrong and should be illegal. CMV.

Now, I will admit at the outset that this is not a topic I know very much about, but I cannot for the life of me figure out what the justification is for having groups like Blackwater working alongside troops in war zones.  I cannot figure out what benefit there is in hiring mercenaries when we already have the most powerful military in the world.  The only possible reason is to have them do things that we don't want our soldiers to do, but in that case, they probably aren't things anyone should be doing anyway.

Furthermore, when you're paying a group of people to kill, you lose all the oversight that the military has.  You're giving private citizens the authority over life and death, with no guarantee of the training, discipline, or accountability that soldiers in the military have.

[Assistant]
Private Security firms like Blackwater are not authorized to engage in offensive operations in combat. However, they are authorized to defend themselves against threats. In the kind of irregular warfare we saw in Iraq they often were target of attacks as frequently as coalition troops leading to them be involved in altercations.

Private Security Firms primarily escort supply convoys and VIP's to their destinations. Outsourcing these jobs allows the military to focus primarily in engaging enemies or protecting extremely at risk convoys.


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

[User]
[Marvel's Avengers Movie] Loki had freakin two infinity stones. Did he lose because he didn't properly use them or the Avengers overpowered them?

Like I get, he used the tesseract to open the portal and the sceptre got knocked off, but could be have used them better and won? Or were the Avengers powerful enough back then to beat two infinity stones?

[Assistant] Coulson said it best; Loki lacks conviction.  Whenever he spoke with Thor it's clear he wasn't really invested in winning. Doing overly complex plans to show how clever he is sure. If he wanted to win he could have just used the space stone to teleport the avengers into a star. He doesn't want to rule. He just wants acknowledgement.


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

[User]
If light has no mass, then how is it affected by the gravity of a black hole?

If light has no mass (which is how they go the speed of light, which is the fastest velocity possible) then how can it be 'sucked in' by a black hole? Wouldn't gravity have no effect on massless objects like light?

[Assistant]
Two ways to think about this:

(1) anything with energy is affected by gravity (rest mass is just one form of energy)

(2) gravity is a curvature/distortion of space-time, so light follows paths that reflect the presence of the black hole.


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

[User] [Asia middle ages] What were the effects of the black death on China and on expatriate Chinese? Was any association made between the Chinese and the plague?

[Assistant] The very first historic outbreak happened in China. The plague spread along the Mongolian Empire, its armies' supply lines, and through the Silk Road itself. There are numerous Chinese records on disease and social disruption survive from this period, but no one has studied these sources in depth.


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

[User]
ELI5: If Space is made out of vacuum, how come satellites, like Voyager, are able to capture sound?

Serious question, not in any way shape or form trying to prove some kind of "government conspiracy", just curios.

[Assistant] They don't capture sound. The instruments that still function measure radiation. You can convert that data into sound waves; its analogus to displaying the data on a graph, it's just another way of looking at it, but doing so isn't much more than a novelty for a press release.


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

[User]
Since Pluto's eccentric orbit crosses that of Neptune's, will there be a point where both collide?

Reading Neil Degrasse Tyson's 'Death By Black Hole' where he mentions Pluto has an orbit much like an asteroid with an eccentric orbit, to the point that it crosses the orbit of Neptune. Is it possible that Neptune and Pluto could collide in the future?

[Assistant]
No.

Pluto's orbit doesn't intersect Neptune's in three dimensions, and they don't even come close. Pluto's orbit is at a considerable angle to the ecliptic (the plane that the solar system mostly lies in).

Additionally, Pluto's orbit is in 3:2 resonance with Neptune's, providing further protection from a collision.


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

[User]
ELI5: What determines whether a prisoner goes to a minimum, medium or maximum security prison?

Is it just likelihood for them to try to escape? Does the severity of the crime factor into it? Length of sentence? Risk to the prisoner from others?

[Assistant] One aspect that hasn't been posted yet is revenge. The guy that spied for the Russians and was named the biggest spy in US history is also serving his time in a supermax prison in solitary confinement despite not being a violent criminal. It is the government taking revenge.


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

[User]
There is nothing wrong with Well Done steak. CMV

I'm somebody who normally orders Steaks done Medium, and even then I'll often have people telling me how wrong I am. Probably best that I don't tell them that I also like well done steak (if it's cooked right). And have you ever seen somebody on Reddit mention that they like Well-done Steak? Every time they will get torn to pieces by the "Rare Master-Race", without fail.

It just seems that people get way too wound up about steak more than almost any other foodstuff. Whatever happened to letting people eat their food the way they like it done? You don't have to approve of it, but it's not doing you any harm!

**Quick Edit:** I've also heard the argument that it's a waste of a good steak, and it's only okay to do it to poorer quality steaks. Well, to that I say people are entitled to eat the steak that *they pay for* any way they want, regardless of the quality. Also, beef is a renewable resource last time I checked.

**Not-so quick edit:** Some very good answers so far. Also some people I think might be members of the Rare Master-Race, but whatever. Just to clarify one thing; I do actually want my view changed. I'd like to be shown why Well Done steak is inherently worse than any other kind. That said, I'm still gonna eat Well-done steak because I like it.

**Progress edit:** Okay, now we're getting places. So far, the two most compelling reasons I've been given as to why Well done steak is inherently worse than other types of Steak is because it is (a) Nutritionally inferior, and (b) has potential negative health effects. As you can see, these kind of answers completely avoid personal preference.

**Additional progress edit:** The points about the economical downsides of having your high quality steak well done are also quite good. Not as strong as the two aforementioned ones, but they've still given me something to think about.

[Assistant]
A practical reason for not ordering well done steak in a restaurant (according to Anthony Bourdain in his expos of the restaurant business *Kitchen Confidential*) is that the quality differences in steaks are far less apparent to the customer and as a consequence the chef will save the least appealing cuts for those who order steaks well done. The restaurant owner gets the same price for a steak of lower quality, one that is unlikely to be sent back.

It's a bit of stereotyping, sure, but steakhouses are businesses--if you can give a customer a product of lower quality, get them to pay the same for it, and have them just as happy as a customer ordering a top-flight, aged steak cooked medium rare, then why not?


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

[User] ELI5: How effective is barbed wire / razor wire as a defensive measure in combat? I feel like in movies all they do just make two snips and continue on.

[Assistant]
It's good at slowing people down since actually making that clearing takes time, and during that time you are shooting at them with pre-ranged weapons since you know where the slow-down will happen.

It also forces them to go through only a few locations, since not every soldier is going to make a separate opening.


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

[User] ELI5: If the Mt. Tambora eruption occurred in Spring 1815, why did it take over a year for the effects to be felt globally ("Year Without a Summer": 1816)?

[Assistant] Because the gases and particulates ejected into the atmosphere have a cumulative effect over time. Reflecting a few percent of the sun's radiation for a day our two won't have a huge effect.  Doing the same thing foyer months or years becomes a serious problem.


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

[User]
Which IR theories are the most popular today? Which contemporary IR theorists are the most cited?

I live and study in Poland and I can't help but think that the curriculums in our universities are a bit outdated when it comes to international relations theory. Even the university libraries don't really have anything newer than 2000 or if they do, it is just a reiteration of the works from the 20th century. It is difficult to learn which are the most dominants theories/paradigms/schools in the second decade of the 21st century and which currently living scholars contribute the most to the discipline.

Can anybody fill this gap for me? Where should one look when trying to analyse the current status of IR?

[Assistant]
Your main three are probably Realism, Institutionalism (Liberalism), and Critical theory. None of these are particularly new, but critical theory is the most recent. All of these were mainly developed by 2000 so you should be able to find some information on them.

Foreign policy ideas of course are always changing in the contemporary. You could check out the most recent pop-theory Why Nations Fail. It was a great read.


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

[User] Could one possibly gain more weight from eating a certain product than the weight of the product itself?

[Assistant] Directly, no. That would violate mass conservation. But it you could conceivably eat food that makes you retain water or other substances, in the opposite of the way that alcohol and caffeine cause you to lose water.