ELI5: How does car insurance work and why it is mandatory to have it?

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The legal minimum is liability insurance. Since it’s very easy to cause hundreds of thousands of dollars of harm to someone else, states usually require you have some way of paying any damages in such a situation.

The preferred way is an insurance plan: you pay an insurer a monthly/annual amount and they agree to cover most of any claims you are responsible for paying in the event of an accident you cause.


A bunch of number nerds called “actuaries” run a lot of very complex excel spreadsheets and determine the amount of money auto related crashes, thefts and other losses will be in a given area. They take this educated guess and divide that by the average number of drivers in the given area. They add little things like “desired profit margin” and “agents commissions” and “advertising budget” to get an average premium. Then these number nerds figure out things that are likely to lead to having a crash or loss and adjust this average premium to an individual policy.


Insurance is what is called a shared risk pool. Everybody pays a monthly fee to mitigate the financial risk of having an accident. Everybody pools their money and repairs are paid out of that pool. Safer drivers in this situation are basically subsidizing the reoair costs of less skilled drivers. If you are a higher risk of causing an accident then you pay a higher premium every month because you are more likely to decrease the size of the pool by making a claim.

It is mandatory for 2 reasons.

1.) The bigger the pool the smaller the risk, which drives rates down.

2.) Unless you are particularly wealthy there is no reasonable way to expect you to be able to cover your liability in an accident, so the state requires you to carry enough liability insurance to compensate the other party for losses incurred by the damage you caused.

Most states will waive the insurance requirement if you can demonstrate an ability to cover your liability on your own without insurance.


Car lot of money. You crash you pay. Most people with Jobs can’t afford because a lot of money. You get insurance pay for car when car get accident.


Mandatory (liability) insurance exists to protect vehicle owners from possibly facing bankruptcy after an accident. Injuries and costs associated with repair of one’s vehicle can already be a significant burden by themselves – additionally being held liable for damages caused to others could absolutely devastate a person or household without liability insurance.


eli5 Why do militaries use depleted uranium in armor and ammunition

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It has properties that make it ideal for military usage, both defensively and offensively. It’s also cheap and readily available.

**Density**- DU is very dense, which means it can absorb a lot of energy, like from the impact of an incoming projectile when used in armor plating. Conversely, as a projectile it can *carry* a lot of energy- meaning it can be highly destructive for its size when placed into the core of a conventional bullet or projectile.

**Anti-Tank Weapons**- A big challenge on the battlefield is neutralizing enemy armor, such as tanks. Not only do you need a projectile that will penetrate its thick armor, but you also need to disable it- such as by killing the crew inside.
A DU projectile can do both of those things because it has two very appealing properties- it fractures on impact into razor sharp pieces and it readily ignites into ferocious flames when it does.
So with DU you have a high energy projectile that punches through armor plating, breaks into a swarm of deadly sharp spikes, and then incinerates the crew inside in a molten fireball. That makes it exceptionally appealing considering those rounds can be fired from a man-portable weapon.


It’s really heavy. That’s all there really is to it.

There’s a limit to how fast you can get bullets going, and the how-hard-it-hits factor is determined by speed times mass. So you want the heaviest (ie, densest, because there are also limitations on size) projectile possible. That’s uranium.

Pretty much everything else that people will tell you about uranium isn’t really about how *uranium is great at this* as much as how *uranium doesn’t suck at this as much as you might have though, considering we only picked it because it was super-heavy.*


It is as dense and heavy as metals can get. You want that in the core of bullet because more density/mass = more energy which, in turn = better armor-piercing capability.

DU also tends to break apart into deadly shrapnel rather than mushrooming like other metals do. That can be devastating to the people inside the target.


It is very dense and it is really cheap to get since it’s both found in nature and a byproduct of nuclear energy/production processes.

The isotope that is used, U-235, only emits alpha particles so it’s not *too* dangerous as long as you’re not licking it or eating it. Alpha particles can be “stopped” by putting a few feet of distance between you and the radioactive source, or using virtually any kind of material (from paper to lead or anything in between) to create a shield.


Depleted Uranium is very dense. It’s denser that tungsten so it does a better job of being heavy and still fitting into a cannon barrel.


ELI5: why does the moon look big to our eyes but when we take a picture it’s really small

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Others are right about your brain’s ability to focus, but also many cameras (including until very recently basically all mobile phone cameras) are very wide-angle. This is great for fitting in all of your friends from just arm’s length. It’s also absolutely awful at capturing things at a distance, since such a tremendously large area is in-frame.


It’s an illusion of perspective. When you look up at the moon, your eyes focus on it and your brain decides that everything around it is background. When you take a photo, the device decides that the entire image is important and doesn’t seperate the moon from the sky.


Focal length of eyes and cameras are different. As are the aperture and the ability of the brain to process the image compared to a cameras processing.

The human brain tends to stretch an image that is small and far away to make it more useful for us too!


A lot of good answers here, most of which are right.

I’ll just add the term ‘size constancy’, which is a thing our brain does with things we see. When something big like a truck is close to us we see it as a certain size. If that truck was instead far away *we can still tell* that it’s a big truck, even though it looks tiny because of the distance. Our brain takes into account the distance of the truck when figuring out the truck’s size. It does this mostly using binocular cues (how much our eyes need to move to join each eye’s image together) plus some other visual cues.

For the moon, we can tell it is very far away and we can also sense its size *in spite of its distance.* The moon is indeed real big, so our brains go all “damn that’s a huge bitch” which kinda warps what we feel about the thing we are seeing, which in reality is a rather small circle.

Photos don’t let our brains do this size constancy thing as much, so they show us the moon more as it really is. Luckily you can trick your brain into not doing size constancy. Try holding out your hand and ‘grabbing’ the moon between your finger and thumb. Then look at how much stuff is not in that little gap. You should suddenly be aware of the tinyness of the moon.


A few others have mentioned it, but not given any particular examples. u/kordiel mentioned the mental processing, which is accurate, but isn’t the primary reason.

The human eye sees at a focal length of give or take 50mm, which translates to a (estimated by me) roughly 90 degree viewing angle. The pictures you refer to taking are most likely from a phone, and phone focal lengths are something like 14-25mm. I’m not sure of the viewing angle on these, but I’d hazard a guess of around 110-125 degrees. This makes for a far larger amount of “stuff” you can see in the same image size (I know, I’m comparing an image to eyes, just pretend the picture is held close enough to your eyes to take exactly your field of view, no more no less, and it’ll work).

Because of the different viewing angles, and having more space in the same image size, the moon will take a much smaller percentage of the space, making it smaller.

If anybody wants actual numbers, I can do the math when I get home in the morning.

Edit: source – am photographer :p


ELI5: Would it be realistically possible to eliminate the common flu from the Earth, and would there be any kind of adverse consequences?

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If you’re talking about common flu, meaning influenza. It would be highly unlikely that it would be eliminated. The virus that causes influenza is an RNA virus. And because RNA is super unstable compared to DNA, it mutates way more. So even if we got rid of one type, another new completely different type wouldn’t be far away. Due to the mutations changing it.
Currently, there are a few different influenza types (Influenza A, B, and C) that have a whole heap of different species within those groups. And there’s a good chance that even more are hiding around the corner in other animals. All it takes is a mutated strain and bam! Another influenza is out and about among humans.

If you’re talking about the common cold. That’s even more unlikely. There are hundreds of viruses that can cause what we refer to as the common cold. And they’re all different types. Some may have the same tricky mutation skills that the influenza virus has, some may have other sneaky skills to avoid our attempts at eliminating them.

If, by a very very very (I cannot stress this enough) slim to assuredly no chance, they were eliminated. It would be hard to predict the consequences, adverse or otherwise. Mammals developed the placenta as a result of a virus influencing our DNA way back in the past. They’ve had a big hand in speeding up evolution of many different species all over the world. But they have also been implicated in some cancers and neurological disorders. So in answer to your second question – maybe, maybe not.


It is difficult to eliminate diseases that have a wild reservoir.

Influenza A has a natural host in aquatic birds and occasionally jumps over to domesticate poultry, pigs or humans (like h1n1, h2n2, h3n2 and etc.)

Influenza B is mostly in humans the only other animals known to have it are seals and ferrets. It mutates slowly compared to A so most people have immunity to it from childhood. Because it is so slow to mutate, and because there are few species that carry it, it ensures that pandemics from it don’t occur.

Influenza C is in dogs and pigs too. It can cause local epidemics, but it is less common and generally only causes a mild disease in children.

Influenza D has not been seen in humans. It’s only in cattle and pigs.

We might be able to eliminate D and possibly C since the animals are domesticated, but it might be difficult to vaccinate village dogs.


It would not be realistically possible.

Even if we managed to eliminate the major flu subtypes that most may consider “the common flu” from the human population, it would not be gone. It would still be found in animals. The flu would then jump back into the human population from the animal reservoirs.


An interesting idea that sparked due to the current pandemic, is researching a way to target all coronaviruses by means of altering our own cell functions so that the virus can’t replicate rapidly.

So, instead of targeting the virus’ DNA (which is a wild goose chase needing different drugs due to all the different types and constant mutations), we could instead use one drug that temporarily inhibits the DNA replication mechanisms in our cells. So we could deprive the virus of its reproductive mechanism for a little, while our immune system ramps up defenses.

I found this an interesting approach that if successful and properly advanced, could protect us widely from viruses (or at least, pandemics) in the future.


With the current technology, no.

There’s always the possibility we will develop a different approach to immunity/eradication in the future which could eliminate it.

That said, there would be no negative impact from cold/flu going extinct. Unlike pest animals, there is nothing that feeds on viruses, so there would be no ecological impact.

There would be an uptick in human population, which some might consider a negative, but it isn’t inherently negative.


ELI5 how does active noise cancellation works and is it more harmful to your ears than normal headphones or earphones

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Sounds are moving air. Active cancelation uses a microphone to listen to the sound, and then make an “opposite” sound by pushing air in the other direction. These opposite sounds are added to the music coming through the headphones.

By the time it gets to your ear, the combined air from the original (ambient) sound and the opposite sound created by the device cancel out (mostly), so you hear more of your music with less outside noise.

The music quality is a bit less because the music has extra sound added on top, but there’s no more danger to your ears than listening to regular music.


No, it’s not harmful. Noise cancelling headphones just play a tone that cancels out the noise around you. How does it work?

Picture a sound wave, with peaks and valleys, coming out of a speaker. Now add a second speaker playing the exact same sound. If the peaks of the first sound wave line up with the peaks of the second sound wave, the overall sound gets louder. If the peaks of the first wave line up with the valleys of the second sound wave, they cancel each other out.

Noise cancelling headphones have a microphone to “hear” the sound around you. They take what they “hear” and produce a sound that’s the same, but shifted, so the peaks line up with the valleys. This cancels out the sound around you.

Many people with normal headphones will crank them really loud to drown out the noise around them. This can damage your hearing. With noise-cancelling headphones, people don’t feel the need to crank them because there’s hardly any outside noise. No cranking means less damage to your ears, so noise-cancelling headphones can actually be beneficial. 🙂


Sound travels in waves like the ocean. Now imagine that you have 2 oceans, with one wave pattern, and another ocean with the exact opposite wave pattern. The two waves will cancel each other out, and leave a calm area of ocean. The same with ANC (Active Noise Cancellation.) A mic is listening to outside noises, and then generating the opposite sound wave to cancel out that noise. If you listen to this it just sounds like white noise(static), but as soon as you listen to it with the outside sounds, they’re much quieter which is why alot of ear buds have the technology to isolate outside noise.

There is no harm in ANC as its the exact same as noise you hear everyday, but opposite. I hope that makes sense.


Sound waves are made up of crest and troughs (loudness and silence). The loudness comes from the air getting pushed and pulled by the speaker. Now imagine what would happen if you could somehow set up another speaker that detects the sound and quickly emits the opposite. So if it detects and loud pushing sound, it’ll emit an equally loud pulling sound. They would cancel each other.

That’s what a noise cancelling system does. It has a sound detector that converts sound into an electrical representation. That electrical signal is fed into an inverter which converts it into the opposite electrical signal. This signal is then fed into a speaker to turn it back into sound. Since it’s the opposite sound to what was detected, they cancel each other out.

This system only works because electricity is far far faster than sound, so the inversion process and the sound emission process are almost instantaneous, so they’re able to cancel the original sound before it travels away.

And no, unless the sounds involved are very loud, noise cancellation shouldn’t damage your ears any more than the original sound might have.


Noise cancelling headphones do two things. They isolate the noise with the padding around your ears and muffle it a bit. Like what your regular headphones do. The second thing is that they have a microphone built into each side that records the abient noise and inverts the signal in real time. Constant sounds with constant bandwidth disappear ( like jet engine sounds in a plane). Irregular sounds with varrying bandwidth like talking are muffled and almost silenced because irregular sounds are hard to invert quickly.


ELI5: what is the difference between shampoo and just soap or shower gel.

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Shampoo has a mix of ingredients that are better at removing oils. In short, it’s a bit more aggressive than soap intended for skin.
I work on my car, and if I have grease or oil spot on my arm or leg, soap won’t remove it, but shampoo usually will.


Chiming in just to say there is no difference between men & women’s besides possibly fragrances. It’s all marketing.


Soapmaker here: shower gel and shampoo actually gave more in common with each other than soap. Real soap is made of fats saponified by lye. This is generally better for your skin (depending on the fats used) because of the leftover fats and the glycerin byproduct of the process (glycerine draws moisture to the skin).
Handmade soaps are better than mass produced, because mass produced soaps strip out most of the glycerin fur other uses.

Shower gel and shampoo and the like are made with surfactants. These are basically detergents, and bubble a lot (we are lead to believe bubbles=clean). The shampoo bars a lot of companies sell are actually really bad for your scalp. They are basically cakes of surfactant, and can be very drying to the scalp.

There are soap based shampoo bars, but they have to be made of certain fats, and can take some adjusting.

Legally, they can’t call it soap if it’s not made like soap, hence why a lot of commercial “soaps” are called “body bars.”

Two ways to tell if it’s real soap: 1. It will say soap right on the front, or 2. Look for the names of the saponified oils. Soap is a kind of salt/sodium, so saponified coconut oil would be sodium cocoate; saponified palm oil would be sodium palmitate; saponified tallow would be sodium tallowate, and so on.

Hope that helps. I’m new to this reddit, so hopefully, I explained things simply enough.


Middle aged bald guy here…Dove moisturizing body soap head to toe. Shampoo, conditioner and combs need not apply.


I started dying my hair during covid. First time ever for me. I noticed immediately why women’s hair products are so different. The bleaching process really destroys the hair and it feels and acts different after bleaching. It becomes very dry and clumps together and feels wet hay or something. The dyes I’ve been using wash out VERY easily. So I started using real women’s shampoo which is designed to moisturize the hair and specially formulated to try to make the dye last longer in your hair. I also started using conditioner because it makes a very big difference in the look and feel of the hair that has been bleached. Without conditioner, my hair looks whispy and it just doesn’t feel good.

Protip – and I have no idea if this is good/bad. I use a facial lotion after showering. I always have extra lotion all over my hands after trying to get it all over my face, so I run my hands through my wet hair to try and get as much off as I can. It seems to really make my hair softer and feel thicker. It is a close to it’s natural look and feel from before bleaching it.

Y’all should probably take what I wrote as nonsense from a newbie because I have nothing to base my info off of. This is all new to me.


ELI5: How does frying ice cream not melt it?

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It does, but the oil solidifies and incases it so quickly that it only half melts and you end up with a great treat with a cruchy outside, melted inside, and heart disease on the side.


You don’t just fry the ice cream. The ice cream is covered in a layer of crunchy bits like oats and crushed corn flakes and such. You start by making ice cream balls, covering them in the crunchies and freezing them to very firm. Then you dip them QUICKLY in the hot oil, which browns the crunchy layer but doesn’t have time to melt the ice cream. Then you add toppings (whipped cream, fruit, chocolate syrup, maraschino cherries, etc) and there you have it.


I know the secret. The ice cream is kept in a special freezer in a deep freeze. The outside is funnel cake dough that cooks quickly. It’s only in the frier for a minute tops and the ice cream doesn’t melt but becomes the regular temp for ice cream.


The ice cream doesn’t stay in the oil long enough to completely melt. Only the outer layer (usually covered with a batter or some other coating) has time to reach high temperature.


Other people have mentioned the answers (hard frozen ice cream and quick fry) but this brings up a goal I had a long time ago which was to make hot ice cream. Via some interesting hydrocolloids I was able to make an ice cream base that solidified when heated and “melted” as it cooled but it tasted lousy, like ice cream but chewier because it was basically a gel. It may have lended itself better to other flavors than the standard vanilla base I used. Googling it I saw other people that made similar preparations with the same principles but I don’t know if any of those tasted any good


ELI5: How is race a social construct?

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Focusing on the DNA tests, they don’t measure the amount of “Korean-ness”. They measure the presence or absence of hundreds of different harmless mutations. Some of these mutations are most commonly found in people from a particular region, so the more of them you have, the more of your ancestors probably came from that region.

But those mutations didn’t necessarily *originate* in that country. For example, the DNA test might associate “Korean-ness” with one gene that originally mutated in China and was brought to Korea through migration 2000 years ago, another that was brought by Mongol invaders 800 years ago, a third that originated in Korea but is also now found in Japan and Manchuria, and a fourth that originated in Japan and was brought over during their invasions in the 16th century.

None of these genetic tags are uniquely Korean, they’re all found in other parts of northeast Asia. All the genetic test can tell you is that that particular combination of genetic tags is most often found in the modern people who’ve chosen to call themselves “Korean”. But those people have ancestors from all over the map.

Nobody’s a pureblood, everyone’s a mongrel, and it’s been like this for thousands and thousands of years. “Race” is nothing more than a set of sharp-lined boundaries we humans have chosen to draw across the blurry mixture that is human variation.


The idea that a person is “White” or “Asian” or “Black” is a social construct, because those categories are made up by people, and what counts as “white” varies from culture to culture, and from person to person. The idea of dividing humanity into sub-groups based on ethnic origin is a social construct, something that humans invented. The idea that certain humans whose ancestors came from specific regions are going to have minor genetic differences is science, but how we divide people up into groups is based on social norms and ideas.


there are genes more common in certain areas of the planet, but all that shows is where some of your genes originated.

think about this, why is it italian? Italy wasn’t unified until the 1800s. So, why is that report showing italian and not something like sicilian or roman? Or even Etruscan (iron age) or Remedellian (copper age). If it wanted to show where the genes originated, it would be something like 42N 12W (the approximate location of Italy), the alps, or the Tiber river (major geographic landmarks).

“Italian” is a label that the people currently living in the areas mentioned call themselves. It’s just made up. If you reset italy from back before the copper age, you’d end up with a completely different group of people with a different history that all called themselves something different. Your genetic makeup would be the same (probably), but your report wouldn’t say italian.


There is no scientific definition of race. Human is a species. There are no sub-species or “breeds” of human. And the socially constructed definition of race has changed significantly over time. For example, you’ll never hear anyone say a person is of the Irish race anymore, but 100 years ago you would have. Just as nationality is a social construct defined by made up borders, so race is a social construct with rather poorly defined borders. For example, is someone from Egypt a member of the African race? After all, they live on the African continent. Or are they of the Arab race, because of their culture? If it’s because of their culture, then if an child whose parents were born in Sweden were raised in the Arab culture of Egypt, would they be of the Arab race even though their ancestry is nordic?


There are real differences between people, but which ones are considered important and worth classifying, and how they are classified are up to humans entirely. One person may be considered different races depending on who’s judging, for example. Who counts as which race has varied quite a lot over time.

>because if we have dna testing that can show someone’s ancestry is this much % Italian and this much % Korean, how is that a social construct if it’s in our dna?

Italy and Korea, and any nation, is a construct of humanity. Nothing is fundamentally different in the planet itself on one side of a country’s border or the other. If the land were divided in a completely different way, you could still pick out alleles (gene variants) more common in one area than another and classify people that way. Also, some people have tried sending their DNA to multiple DNA testing companies and got results that were different! A lot is up to subjective, human interpretation.


ELI5: How does Spotify codes work if the design is so simple?

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There are over 20 lines of varying sizes in one of those. You can arrange 20 things in over 2 quintillion ways (2 followed by 18 zeroes).

Spotify has a long way to go before they run out of codes. If they do, they can just add another line in the code, and now they have 3 more quintillion codes.

Edit: yes I was too lazy to count the actual number of lines.


There are 23 bars, that can have 8 different sizes. The first and last bar are always the smallest size, and the middle bar is always the largest size (this is done for calibration). That leaves 20 ‘information’ bars with 8 possibilities each, which can have 8^20 unique combinations.


ELI5: How does tape stick?

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Ok since the existing posts are a little over 5yo level here’s my attempt.

Most surfaces (even extremely smooth ones) are actually very complex / textured at a microscopic level.

Tape uses pressure adhesives that are normally solid, but temporarily become a very thick liquid when pressure is applied.

So when you press tape against a surface the adhesive becomes this thick liquid goo, which is able to make its way into the nooks and crannies of the surface. When the pressure is removed, it becomes solid again and it’s physically locked into place.

The fascinating thing here is that you would think it’s a chemical / molecular bond but in reality it’s physical.

That’s also why you can use tape over and over again. There’s no chemical reaction that is ‘spent’ when it’s adhered. The only thing limiting its stickiness over time is when the surface gets dirty.


Tape was only invented about one hundred years ago. The “sticky” on the tape makes it adhere to another surface with pressure. The sticky is made out of long chain polymers plus resin. Essentially, the polymers act like they are wet. They’re almost liquid, with weak bonds that interact with what you stick it to via wetting. Some adhesives get stuck harder over time; they dry out. Adhesive also doesn’t stick well on already wet surfaces and stick very poorly with oils.

The molecules in the polymers also have and make a weak electrical bond with what it sticks to, though Van der Waal’s forces. Electrons help largely with cohesiveness of the tape – stuff sticking to itself.

Different adhesives have different properties, some stick hard and some stick less, some stay sticky and some can bond permanently. This comes down to what polymers and resins are used.


It depends on the kind of tape, but AFAIK the adhesives used in tape – like most other adhesives such as glue or even just sticky things like paint – have to do two main things. The first thing they have to do is “wet” (or spread out all over) the substrate to which you’re trying to adhere, sort of like water, but more like a thin layer of play-doh or silly putty. It needs to get into all the nooks and crannies, and almost every material (even smooth glass!) has these at both macroscopic and microscopic levels.

The second thing adhesive has to do is resist getting pulled back out (water is only just OK at that), and the third thing it to do is resist getting broken apart from itself or separating from the tape strip. These two jobs are what make tape “stick,” and are sort of at odds with each other. There are different ways to make adhesive not want to separate from the substrate, including some crazy molecular-level interactions that are kind of like static electricity or magnets. That is a question for your next ELI5 though.


Tape has microscopic claws that latch onto the surface, think of them as the claws on the end of a spiders legg. 🙂