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

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

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

And finally play teaches young animals about their personal limitations. They’ll teach it to climb fearlessly because it knows what it can and can’t do. It’ll know how fast it can run, how far it can jump and so on. It’ll help them learn that their abilities increase as they grow because they run faster and jump farther than they could last week during the same game.

Play tends to be unique to animals whose abilities change and grow with them. You won’t see much play among insects, arachnids and most reptiles for instance. They’re born fully capable (even though practice and learning can improve their capabilities).

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ELI5: During a police interrogation, can you actually get away with not saying anything until you're provided with a lawyer?

Depends on where you live, but I assume you are talking about the United States.

In the US, the sixth amendment to the constitution says the following:

In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence.

Brewer v. Williams (1979) held that once adversarial proceedings have begun against a defendant, he has a right to legal representation when the government interrogates him.

So basically, yes, it works like it does on TV. At least, it does in the States.

Now, in practical matters, the police are allowed to lie to you. There’s nothing stopping them from trying to convince you that you don’t need a lawyer. You could say to them something like “I think I need a lawyer,” and they could say something like “Why do you need a lawyer? Lawyers are for bad guys. You aren’t a bad guy, are you? We just want to get a bit of information”

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ELI5: Why is so much importance held on the presidential election, but almost no attention is given to Congressional elections?

A)

The do get coverage, but there are a few reasons why they don’t get as much national coverage…

1) Very few races are actually competitive. Between gerrymandering of House districts and states’ entrenched political slants, maybe 50 of the 470 Congressional seats are actually races of any kind.

2) The races that are actual races, all that matters is the local voters. So here in Illinois, there is a lot of coverage of the Mark Kirk/Tammy Duckworth race for Senate because it’s a close race with the incumbent behind in the polls.

3) TRUMP. His constant antics are distracting the media away from everything else, even the more substantive issues of the presidential election. For example, this AM more coverage is going to Trump calling a former Miss Universe fat/Miss Piggy than analysis of the different plans to create jobs presented in the debate last night. 

B) 

It seems like this question was already fairly well answered above but I’d like to add to what he said a bit.

Most congressional races are lightly contested if contested at all. Meaning that very often incumbents have such a substantial lead, through name recognition and having an established track record, that their opponent doesn’t stand much of a chance. Beyond that, it’s not unusual for a strong incumbent to run entirely unopposed simply because any real challenger that would enter the race knows better than to take on a strong incumbent and instead will look for a weaker incumbent in another district or wait until a strong one is nearing retirement.

What’s amazing to me is that congress, as a whole, has an incredibly abysmal approval rating and has for a long time (I don’t know the exact numbers but it usually hovers in the high teens and low 20’s). Americans overwhelmingly feel congress does a poor job but they usually like THEIR congressmen. This is partially because of what the incumbent has done for their own district or state but that’s also part of the problem. Congressmen largely look out for their own electorate to the detriment of the nation as a whole because it gets them reelected. So what people dislike is OTHER congressmen acting selfishly for their districts and neglecting the good of the nation but when it comes to their own district or state people have no complaints.

That, IMO, is why congressional elections aren’t covered nearly as much. Short of a recent scandal, major policy misstep, or shift in local political philosophy, people love their districts and states incumbent politicians and those incumbents are almost guaranteed to win anyway so why bother covering it?

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ELI5: Where do internet providers get their internet from and why can't we make our own?

Answer #1

You can make your own. Go run some fiber from your house to mine.

It costs about $50,000/mile.

We can add others to our network as you get the money.

Answer #2

The Internet is the colloquial term for Interconnected Networks. Your ISP has an arrangement with one or more other companies, who in turn have agreements with yet more companies.

Some of these organizations spend lots of money to run physical cables across the planet in the expectation that their cables will be used to transport information between the two or more points that they connected together.

You can form an organization that connects to existing infrastructure and if you’d on-sell it, your organization is an ISP. You could also set up actual infrastructure, but that’s much more costly and risky.

Different countries have rules about this mainly to do with illegal use that you’ll need to abide by and since this is big business, many roadblocks exist to prevent your little organization from competing with the incumbent.

Some towns and cities, disenchanted with incumbent providers, have started their own networks and succeed in larger and smaller degree in providing their citizens with Internet connectivity. Various freenets also exist which allow information to travel within the group but not to the wider Internet. This often bypasses legal impediments to creating an ISP.

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ELI5: Is letting wounds 'breathe' a thing, if so, what purpose does it serve?

I’m a nurse and have taken a number of courses on wound dressing and healing. Here’s what I can quickly write out for you.

The goal of wound care is moist wound healing. If wounds are draining plenty of blood/pus/serous drainage and it isn’t being removed from the wound by an absorbent dressing, the tissue can become macerated and will appear white. It’s too wet, the tissue is swollen with water. This is bad for wound healing. This is maybe where people got the idea of letting a wound “breathe” to dry up some of the excess moisture.

However, letting it dry out completely is not ideal either.

Natural healing involves developing a scab, a dry cover for the wound. However, if the wound were instead moist (not wet), you would have faster migration of immune cells, new cells, growth factors, etc. as they can move through a moist environment easier. This is what topicals like polysporin (besides the Abx) help to achieve. Petroleum products will moisturize without macerating.

And the other question everyone asks: should I use peroxide to clean it? no. maybe. Here’s the thing. You can clean a wound very well with water or saline (although who has saline at home). Many wounds wash themselves out by bleeding! Peroxide will kill bacteria, but it also hurts exposed skin cells/other tissue, and that can slow healing. The surface of your skin is mostly keratin and peroxide won’t affect intact skin, but when it’s cut, the deeper layers can be affected. Basically, don’t peroxide every wound, but something like a cat bite, go for it.

*edit: I’m aware now of how many people have saline. I pour like half a liter over new wounds, so I’m not sure people have that much contact solution. I have 25/20 vision privilege so am unaware. Yes, you should see a doctor quickly for cat bites. I’ve seen people need strong antibiotics 4x a day to avoid death from cat bites. Go to ER NOW if your wound starts streaking red up your limb. Helpful to outline areas of redness with a pen and the time you marked it to show how it’s progressing.

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ELI5: When sending a letter abroad, how does the receiving country's mail service get paid for their work?

There is a global unified postal service body called the Universal Postal Union . The Union creates a framework and standards so that ALL countries can exchange mail freely without forming individual contracts with every other country.

When one pays for the postage for international mail, a portion of the money goes to the home country’s postal service and a portion goes to the destination’s postal service. The portion of money exchanged depends on how much mail (in weight) each country is exchanging. This is set up so that the destination country receives money for delivering the postage. Countries that receive more mail annually get less money per kilogram of mail.

The fee paid to the destination county is called a terminal due.

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ELI5: why do you see weird patterns when you close your eyes and apply pressure onto them?

This phenomenon is called phosphene.

When light hits the cells in the eye, these cells send a signal to the brain to give an image of what is seen. These cells are called photoreceptor cells, and their main means of activation is when a photon of light hits them. Another way to activate them is via mechanical stimulation (aka applying pressure to they eyes). When you apply mechanical stimulation, the subsequent activation of the cells will be random (not patterned), and when this signal is transmitted to the brain areas that are responsible for generating an image, you will see weird patterns instead of the normal images that would be generated by photon-induced stimulation.

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ELI5: What exactly did John Oliver do in the latest episode of Last Week Tonight by forgiving $15 million in medical debt?

Whenever you take out a loan or get a service that you don’t pay for in advance, you owe someone money. If you don’t pay, they chase you down looking to get their money. For many of these people who are owed money, they want to spend their time performing services for people, not chasing down delinquent payers. So for a fraction of the total price of the debt, they sell the right to collect the money to some third party. That way they get some of their money back (more than they would without a bunch more effort chasing down the people who haven’t been paying).

So now the third party who specializes in chasing these people down will try to find the people who haven’t paid and get them to pay. What John Oliver did was buy the right to collect these debts, just like these third parties do, but then forgive the debts- tell the people who owe money that they don’t have to pay him back.

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ELI5: Why is menthol "cold"?

The people saying it’s because of evaporative cooling are wrong. Menthol’s boiling point is 212 Celsius, much warmer than your body.

Menthol isn’t really cold, it just tricks your body into thinking it is. There’s a type of nerve cell that responds to things like temperature, pressure, pH, etc. Some of these cells have what’s called a TRPM8 receptor on their surface. When menthol comes into contact with a TRPM8 receptor it binds to it, which makes the affected cell open an ion channel that admits sodium and calcium ions into the cell. This in turn causes the nerve cell to send a signal to the brain that the brain interprets as coldness. A similar receptor, TRPV1, is why the capsaicin in hot peppers feels ‘hot’.

Basically, menthol binds to a receptor on certain temperature-sensitive nerve cells, causing them to fire, and your brain interprets this nervous activity as coldness.

EDIT: Okay, evaporative cooling probably does have something to do with it, and it isn’t necessary for a substance to reach it’s boiling point to evaporate. However, I’m willing to bet that the cooling sensation is caused overwhelmingly by TRPV8 activation.

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ELI5: How do people solve rubik`s cubes in <10 seconds?

Rubik’s cubes are actually solved with a formula, or simple set of rules. Once you know those rules by heart, it just becomes a matter of applying them in the most efficient way (to minimize the number of moves required) and then moving your hands very, very quickly. Those with good memories for images can actually look at the cube once then put on a blindfold and solve it from memory.

Fun fact - every possible (valid) permutation of a Rubik’s Cube has a solution which is no larger than 20 moves. This is called “God’s Number” and it took about 30 years to determine this number. Over 99% of all possible permutations require 16-19 moves to solve.

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ELI5: When you go on a roller coaster or drive fast down a hill, why do you get that stomach drop feeling? What is actually happening inside your body that causes the feeling?

“The honest answer is that no one knows with absolute certainty,” said Dr. Brad Sagura, a surgeon at University of Minnesota’s Amplatz Children’s Hospital.

“There’s a cast network of nerve connections within the body, handling messages between the spinal cord, the brain and other structures,” Sagura said.

When you hit the peak of a roller coaster and start dropping so quickly, things inside start to shift around.

“The liver and spleen are relatively secured by suspensory ligaments,” Sagura said. “But the intestines themselves are relatively mobile. While your body is secured by your seat belt, the organs are free to move about by some extent. That contributes to the free-fall floating sensation that either calls us back for more, or has us running to get sick from nausea.”

The movement isn’t only the movement of the organs, it is also the movement of what’s inside the organs.

“The intestines, the stomach, they hold liquid,” Sagura said. “The bladder; the same thing. “It’s relatively fixed, but the fluid within those structures probably plays a role in that sudden drop.”

Sagura said there’s no long-term danger from your organs slightly shifting around. They go back to where they started. But the movement is enough for your nerves to notice that something’s happening, he said.

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ELI5: Why do pens dry out when the cap is left off, but the caps themselves have holes?

The pens dry out because the ink contains solvents. The solvents are volatile and will evaporate if exposed to the air too much.

The caps slow this down but they don’t completely prevent it. The solvents will still evaporate but will largely just sit inside the lid if there’s no air moving past the pen.

The holes in the lid are there so children are less likely to choke and suffocate if they swallow one.

The pen cap holes are also useful to pass a balloon catheter through the cap to aid the removal of the cap from the child.

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ELI5: Why do we recognize that mirrors are "silver" when they appear to be the exact same color as what they are reflecting?

Not all mirrors are perfectly reflective, and things can be done to a mirror to make it less reflective (like fogging, smudging, etc).

If you look at something like the side of a butter knife, you can see that it has a color, despite also reflecting the world around it. If you polish the side of that knife enough, eventually you’d get a usable mirror.

Common household mirrors are a thin layout of silver on the back of a pane of glass, so their color when less than perfectly reflective is the same as the color of unpolished silver.

As had been pointed out, modern mirrors use aluminum, since it is almost as good but a lot cheaper. Still, the language evolved in a time when aluminum was less common.

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ELI5:How does rabies make it's victims 'afraid' of water?

The virus affects the entire body, and especially hits us neurologically. What happens when you’re thirsty and you see water? You salivate in anticipation of relieving that thirst. Salivation leads to swallowing, lest we drool. Well for someone in the later stages of rabies, swallowing becomes a very painful act…and as with anything painful, the mind tends to not want to repeat the act that leads to the pain. The Rabies virus causes severe muscle spasms in the throat, and even the sight of water can set them off. If that were happening to you, wouldn’t you be ‘afraid’ of water, too?

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ELI5: What is the purpose of the tiny parachute that is usually on top of the large parachute.

It’s called a pilot chute. It’s a miniature parachute that is several feet in diameter and is attached to the peak of a parachute and whose function is to draw the parachute out of its pack and extend it in position for opening.

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ELI5: The Panama Papers.

In business, you can avoid taxes by investing in something. If a company makes one million dollars, but spends 500,000 on investing in new technology for their product or something like that, they’re only taxed from the remaining 500,000 because that’s all of their “profit.” (I’m not a businessman so I’m not sure on the complete legality of all the kinds of spending but I think this is a basic summary). This is all normal and fine; all companies require investing in order to grow their company.

So a company in Panama basically made a business in creating fake businesses. Companies could “invest” million of dollars and then it wouldn’t be taxed, because according to legal documents it isn’t profit, it’s an “investment,” which is untaxable, and then they would get their money back from the fake business. So imagine if that $500,000 of investments from my above example was fake, and after awhile 90% of the money was given back to the business (I’m assuming the Panamian company took a cut of the money as payment). 2.6 TB of data in total, over 11 million documents and over 200,000 fake companies. According to the website that published the news of the leak, they were contacted by an anonymous source with encrypted files with the data sometime in 2015. Here’s am exerpt from the article:

Over a year ago, an anonymous source contacted the Süddeutsche Zeitung (SZ) and submitted encrypted internal documents from Mossack Fonseca, a Panamanian law firm that sells anonymous offshore companies around the world. These shell firms enable their owners to cover up their business dealings, no matter how shady.

Apparently there’s several trillion dollars of money that should’ve been taxed and wasnt. Not sure if that means trillions that should’ve been taxed off of, or trillions of dollars of straight tax money, but either way it’s a LOT.

Many political leaders (many seem to be in the Middle East), and celebrities are involved as well. To prevent any one person from being blamed for the leak, hundreds of news organizations are going to release further full details tonight (that’s what Ive heard, not sure how true it is) but the list apparently has thousands of people/companies on it. There’s 11 million documents though, and even though hundreds of journalists have been going through the data for months, there’s still information that has yet to come to light.

This goes much farther than tax evasion, and includes Syrian war crimes, human trafficking, and more. Here’s a video explaining it.

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ELI5: What is a 'Straw Man' argument?

It means that you’re not arguing against what your opponent actually said, but against an exaggeration or misrepresentation of his argument. You appear to be fighting your opponent, but are actually fighting a “straw man” that you built yourself. Taking the example from Wikipedia:

A: We should relax the laws on beer.
B: ‘No, any society with unrestricted access to intoxicants loses its work ethic and goes only for immediate gratification.

B appears to be arguing against A, but he’s actually arguing against the proposal that there should be no laws restricting access to beer. A never suggested that, he only suggested relaxing the laws.

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ELI5: Why do flavors like garlic and onion stick around in the taste buds so much longer than others?

There is a compound in garlic called allyl methyl sulfide (AMS). It is a gas which gets absorbed into the blood when you are digesting the garlic (and onions and shallots). From the blood it is transferred to the lungs where it is then exhaled. A big part of flavor reception is through the nose so you get that lingering taste that way. Some of the AMS compound is also released through the skin.

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ELI5:How come people can't be cryogenically frozen safely as the ice crystals destroy the cell membranes, but sex cells such as sperm are kept frozen for long periods of time yet remain functional?

I work in a lab where we freeze down cells all of the time. We freeze our cells in a medium that contains 5% DMSO, which among other things can be used as a cryoprotectant. However, DMSO is also toxic to cells at the concentrations necessary for cryoprotection. Consequently, when you freeze cells in DMSO, you add the DMSO medium at ice-cold temperatures and don’t allow the cells to warm up. When you later thaw the cells, you have to dilute out the DMSO as quickly as possible without causing osmotic shock, which can pop the cells. Such restrictions on freezing and thawing would basically be impossible to control at the level of a complete organism.

However, to contradict a lot of previous posts, individual cells can be recovered from freezing with high viability. When performed properly (and this varies quite a bit by cell type), you can expect >90% of cells to be alive following thaw.

The chemicals that allow cells to survive freezing are toxic to the body. Keeping the cells cold minimized the damage that this chemical does to the cells. With single cell solutions, adding the chemical at ice-cold temperatures and immediately diluting it out when you thaw the cells can keep 90% of the cells alive. There’s no way to do this with an intact body.

It’s also worth noting that this is probably not the only reason that this technique doesn’t scale to organisms.

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ELI5: Does a sonic boom only occur at the moment you break the sound barrier or is it constant and if it is does it get louder the faster you go?

It is constant.

A sonic boom is a shock wave that travels outward from the plane. It follows the plane wherever it goes. When the plane flies by a person on the ground, the shock wave will hit that person (and be heard as a “boom”) shortly after. Since the boom moves at the speed of sound, and the plane is moving faster than that, a cone shape develops, with the plane at the point of the cone. Here’s an example image.

As for speed vs. loudness, it’s actually the opposite of what you’d expect. The faster the plane, the skinnier and pointier the cone. As a result, the energy of the shock wave gets spread out over a longer distance. Additionally, super-fast aircraft tend to fly at much higher altitudes, meaning the boom travels through a lot more air before it reaches the ground, dissipating it. So sonic booms actually get quieter the faster the plane flies.

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