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If you’ve ever gone online trying to understand how something works…only to finish reading and somehow feel even more confused than before, trust us, you’re definitely not alone. Sometimes the internet explains the simplest everyday things in such a complicated, overly technical way that by the end of it, your brain just quietly gives up. And honestly, there’s nothing worse than looking up a basic question and ending up with 14 tabs open, three existential crises, and absolutely no answers.
That’s exactly why people love r/explainlikeimfive, a corner of the internet dedicated to breaking down confusing topics into simple, easy-to-understand explanations that normal humans can actually follow. From science and technology to random everyday mysteries, the subreddit proves that no question is too silly if you genuinely want to learn something. And let’s be real, sometimes the smartest people are the ones willing to ask basic questions in the first place. So sit back, pandas — we’re pretty sure this list won’t make you feel stupid…just slightly smarter by the end of it.
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#1
Eli5: How Come You Can Be Falling Asleep Watching TV, Then Wide Awake When You Go To Bed Five Minutes Later?
The brain is like a group of people talking to each other. When you're watching TV, the part of your brain that watches TV says "Shut up guys, I'm watching TV," so you can focus without thinking about cake or math. As a result, the others sit silent, grow bored, and fall asleep, until only the TV watcher part of the brain is left. Left by himself, he too gets bored and falls asleep.
When you're in bed, assuming you aren't counting sheep or something, the entire brain is kind of in free time mode, and any part of the brain can speak up if it wants to. They start talking to each other, and even if one of them starts to drift to sleep, the others wake it up either by deliberately talking to the sleepyheads or just being noisy. Eventually more and more of the parts of the brain fall asleep from sheer exhaustion no matter how loud the others are, and eventually the last one passes out and you are asleep.
RELATED:
#2
Why Can People Walk Many Miles Without Discomfort, But When They Stand For More Than 15 Minutes Or So, They Get Uncomfortable?
I work at a vein surgeon's office. I actually asked him this.
Basically, when you are standing, blood flow slows and "pools" in your legs due to gravity. But when you walk, your muscles contract and push the blood in your veins and vessels back up into your upper body.
On the side note, seasoned military personnels are able to stand at ease for long periods of time because they are actually swaying back and forth very slowly in micro-movements to contract their muscles and relieve the tingling and numb sensation you get when you keep standing for long periods of time.
Edit: As others have suggested, not locking your knees is also key
Edit 2: As others have mentioned, micro movements could be flexing your calves, distributing weight back and forth between your heels and toes, wiggling your toes, etc.
Edit 3: If you have persistent leg problems even without prolonged standing and even after conservative measures (compression stockings, exercise, etc.), I would recommend getting a referral to a vein specialist from your PCP (in the US) to get it properly treated. You may just have bad veins.
#3
There Are Infinite Numbers Between 0 And 1. There Are Also Infinite Numbers Between 0 And 2. There Would More Numbers Between 0 And 2. How Can A Set Of Infinite Numbers Be Bigger Than Another Infinite Set?
I think the problem is you are thinking of "infinite" to be "a very big number". It is not a very big number, it's a different kind of thing. A similar problem exists with zero, in that it's not just "a really small number", it's actually zero. For example if I take a really small number like 0.0000001 and double it, I get 0.0000002. If I take 0 and double it, I still get zero. 2x0 is not bigger than 1x0. If I have an infinite number of numbers between 0 and 1, then they are separated by 0. If I double all of those numbers, then they are separated by 2x0, so they are still separated by 0.
Edit: thanks for the kind words and shiny tokens of appreciation. This is now my second highest voted post after a well timed Hot Fuzz quote, I guess that's what reddit is like.
For a lot of us, science and math can feel a little intimidating. The second we hear words like “quantum physics” or see complicated equations, our brains immediately decide it’s time to mentally clock out. And honestly, school probably didn’t help either, because many concepts were explained in ways that sounded far more confusing than they needed to be.
But the truth is, science is actually full of mind-blowing ideas that become fascinating once someone explains them in a simple, relatable way. So while these posts answer everyday questions, we thought it would also be fun to dive into a few science concepts that sound completely unreal…yet are somehow absolutely true.
#4
Why Is 12 Hour Time Even Taught? Wouldn’t It Just Be Easier To Remember 13:00 Instead Of 1:00pm?
12 hour time is a very ancient system that traces back to the Mesopotamian empires.
They had a cultural fixation on the number 12, used a base-12 numerical system, and divided up most things into 12ths whenever possible - including day and night.
The 12 hours of day and 12 hours of night system spread throughout Europe and the Middle East and has defied multiple attempts to change it over the centuries.
#5
Eli5 Why Do Humans Need To Eat Many Different Kind Of Foods To Get Their Vitamins Etc But Large Animals Like Cows Only Need Grass To Survive?
In addition to the 'efficiently breaking down grass' thing, and the 'they eat a variety of plants' thing, there's also the fact that species typically evolve the ability to make vitamins that they can't get easily in their diet. For example, humans make vitamin D because there aren't many food sources of it, but we can't make vitamin C, but can find it in food. But other species can make their own vitamin C.
It's a trade off between needing to find a variety of food and not needing the cellular machines to make more stuff.
#6
Eli5 If Diamonds And Other Gemstones Can Be Lab Created, And Indistinguishable From Their Naturally Mined Counterparts, Why Are We Still Paying So Much For These Jewelry Stones?
Marketing and monopoly. Diamonds are not unique or rare on this planet. The DeBeers corporation has a long standing monopoly, and an incredible marketing campaign stressing that you should spend 2 months salary on a ring if you really love your future wife.
Truth be told, lab grown diamonds are so perfect at this point, that DeBeers is spending millions trying to figure out how to tell the difference.
Let’s start with something called quantum tunneling, which honestly sounds like science fiction but is very real. In normal life, if you throw a ball at a wall, it bounces back because it doesn’t have enough energy to pass through. But tiny particles like electrons don’t behave the same way. In the quantum world, particles act more like waves of possibilities instead of existing in one exact place.
So when an electron hits a barrier, part of its wave can actually stretch through to the other side. That means there’s a small but real chance the particle suddenly appears beyond the wall without breaking through it. Basically, it’s like a ghost casually walking through a locked door. And weirdly enough, this bizarre bit of physics is also what helps power flash memory inside smartphones and computers.
#7
Eli5: If Ants Love Sugar, And Bees Make Honey, Why Aren’t Bee Hives Constantly Attacked By Ants?
Ants are constantly trying to attack beehives. Other bees and insects will also try to attack the beehives. This is why a large number of bees is dedicated to protecting their hives from these intruders.
#8
Eli5: Why Do You Need A Master's Degree To Become A Librarian, Especially When The Median Salary Is Barely Above $50,000?
I'm halfway through my master's right now. Classes center around three topics. (1) The philosophy of librarianship (2) The business side and management aspects of running a library (3) The nitty gritty of turning raw information into a searchable form and organizing it into something relatively intuitive for the layman.
Compared to most degree programs, it's not difficult. But there is a lot more to it than people realize.
I'm willing to get the degree and spend the rest of my life making a five-figure salary because I'm passionate about reading, history, knowledge, democracy, sticking it to the man, helping people realize their full intellectual potential, and - yes - getting a pension and medical for life. I used to work for the most hated bank in America and I didn't like myself or what I was doing to the poor people in my community. Now I like waking up on Mondays. Do you know how good it feels to talk Harry Potter with a seven-year-old? Or help a woman covered in bruises find legal aid to escape her abusive husband? It feels amazing. It's worth it to me.
#9
Eli5: Military Officers Swear To Protect And Defend The Constitution Of The United States, Not The President. Can The Military Overthrow The President If There Is A Direct Order That May Harm Civilians?
A lot of the Constitution is set up to protect the peaceful transfer of power. Basically, the only way the government should ever change hands is through different candidates winning elections.
So while the armed forces swear to the Constitution, not the president, the Constitution itself includes a couple of methods (impeachment and the 25th amendment) by which a bad, crazy, sick etc. president can be removed and replaced. Ideally this would remove the need for the army to overthrow the president, because the other parts of our government (legislature and judiciary) could handle it. The problem with the armed forces doing it is that a.) it's not a peaceful transfer of power, and b.) the armed forces are now in charge of the government, which is bad.
Having the military swear to the Constitution also serves another purpose, which is to separate them from the president, even though he's the commander in chief. One important move that Hitler made when he came to power was to have the military stop pledging to serve Germany and start pledging to him personally. His hope was that their loyalty to him would lead them to follow his orders even if they were harmful to the nation or its citizens.
This fear goes back at least as far as ancient Rome, when (for example) Julius Caesar was able to become emperor dictator because he had a large army of soldiers who were loyal to him personally, rather than to the Roman Republic.
Then there’s quantum entanglement, which is honestly one of the strangest things scientists have ever discovered. Imagine two particles becoming so deeply connected that no matter how far apart they are, they instantly affect each other. A simple way to picture it is like putting a left shoe in one box and a right shoe in another. If you open one box on Earth and see the left shoe, you instantly know the other box on Mars has the right one.
But quantum entanglement is even crazier because, before you look, the particles exist in multiple possible states at once. The moment one particle is measured, the other instantly “decides” its state too, even if they are separated by unimaginable distances. Scientists are still trying to fully understand how this works, and yes, it genuinely sounds like the universe is cheating its own rules.
#10
Eli5:do Donated Organs Age According To The Donor´s Age Or Do They Adapt To The Age Of The New Body?
They age according to the age of the donor. There's a lot of factors in what causes aging, but the upshot is that the organ will have experienced all of those withing the donor's body first - the cell damage due to alcohol, cr*p food, lack of exercise, age - and the donated part will continue to age from the time of donation.
However, other than normal cell aging caused by, well, age, the new body will determine how fast the new part ages. So if well taken care of once implanted in the new host, it will basically age at the rate of the recipient.
So, for example: a thirty year-old alcoholic is ended by a freak accident involving projectile waffles. How it happened doesn't matter, know only that it was batter up and the only salvageable part is the liver. Now, that liver had been soaked in alcohol, dude lived on fried bread, so it was aging fast: 1 year of age per year + 1/2 year of age to abuse, so from an aging standpoint, it was 30-years old + 15 years of damage = functionally 45 year old liver.
Now the new body it finds itself in is 25-years old, loves and cherishes that liver. It takes that liver and coddles it with clean water, veg, and a two kilometer walk every day with a dog that loves them and the world it lives in. Like, seriously, that dog is awesome and great for mental health. So the new liver continues to live one year of age per year, and no added stress and abuse, so it ages normally. The 25-year old body has a 45-year old liver, but it will continue to age normally and now that it's being treated better, might even last a little longer than expected.
Juls 34 minutes ago
It's also true that the average transplanted organ only lasts 10 - 20 years. The age of the donor organ might not be as big an issue as one thinks. A young person who receives a transplanted organ is going to need another, perhaps a third to live a natural lifespan. If they can get it, which often they cannot. Please consider having a donor card.
#11
Eli5: Why Is It, That You Can Eat A 2,000 Calorie Meal, And In Theory, You Shouldn't Need Calories Again Until The Next Day, But You Can Be Hungry Again 6-8 Hours After You Finish Eating? Is Your Body Just Not Capable Of Actually Processing That Many Calories?
Your body is like a steam engine. The fireman gets a load of coal (food) and either shovels it into the engine (your body's metabolism) or shovels it into the tender (your fat reserves).
Hunger is the fireman saying "hey, just so you know I'm not getting any coal right now... could be an issue." He doesn't care that the tender has plenty, just that no more new stuff is coming in.
#12
Eli5: How Does Your Body Burn 2000 Calories A Day, But You Have To Run A Mile To Burn 100 Extra?
You're not doing nothing. Your heart is beating, your brain is processing, your eyes and ears are collecting information, your muscle tissue is idling, awaiting command. You're maintaining a core temp of precisely 98.6F.
None of this is free, you'll consume 1500-2500 calories a day simply keeping the biological lights on.
We're highly efficient runners, and burn little energy to do so compared to many other animals.
Another concept that feels impossible is time dilation, which basically means time doesn’t move at the same speed for everyone. According to physics, time can actually slow down near extremely massive objects or when someone moves incredibly fast. Think of space like a soft mattress and a giant object like a black hole as a bowling ball sitting on it, creating a huge dip.
The closer you are to that dip, the longer time stretches. So theoretically, if you spent a short amount of time near a black hole and came back to Earth, years or even decades could have passed for everyone else while only hours passed for you. It sounds like a movie plot, but this effect has actually been scientifically proven. Even astronauts experience tiny amounts of time dilation while orbiting Earth.
#13
Eli5: Went On Vacation. Fridge Died While I Was Gone. Came Back To A Freezer Full Of Maggots. How Do Maggots Get Into A Place Like A Freezer That's Sealed Air Tight?
There was an egg on something before you even put it in there. Usually they just can't hatch because of the temp. At room temp they can hatch.
#14
Eli5: How Can Large Chains (Target, Walmart, Etc) Produce Store Brand Versions Of Nearly Every Product Imaginable While Industry Manufacturers Only Really Produce A Single Type Of Item?
Because they don't actually make it.
Costco doesn't make "Coscto Whisky" Costco has a contract with (it's not but for ease of names) Jack Daniels. And again for ease I will use "Bottles" not "Barrels"
If Jack Daniels sells their whisky for $20 a bottle, say it costs them $10 to produce. Costco says "We want to buy your whisky at $15 per bottle, but we will order 10,000 bottles. We're going to resell it as Costco Whisky"
Jack Daniels says "Sure thing, but here's an Non-Disclosure Agreement. You cannot tell anyone Costco Whisky is made by Jack Daniels."
Jack Daniels may only make $5 per bottle instead of 10 but they just sold 10,000 bottles. Costco paid $15/bottle, cost the $1/bottle to re-label it and they sell it at $18/bottle.
So it's cheaper to buy costco & they still make money. They then do this with many other products.
#15
Eli5: If Fruit Is Sweet To Encourage Animals To Eat It And Carry The Seeds Away From The Parent Tree, How Do Lemons And Limes Fit Into This Mix?
TL;DR: Because lemons and limes are crossbreeds that weren't actually a wild plant, and even if they weren't sweet, their ancestors still had sugars and that made them appealing for creatures to eat.
Most of the types of "citrus" plant that we grow and sell in produce sections now were crossbred from a mix of only a few original plants. Lemons come from "Citron", a really thick-rinded fruit with a small but sweet pulpy core, and "Bitter Orange", which is what it sounds like. Limes comes from a citrus-type tree called "Micrantha".
But even so, just because they taste sour doesn't mean that animals won't eat and spread them. A lemon DOES have sugars and, in the same way we humans like a little bitterness, animals may appreciate it too. Food doesn't have to taste sweet to be extremely healthy and an easy source of calories.
Then we have the observer effect, which almost makes the universe sound self-conscious. In the quantum world, particles behave differently when they are being observed or measured. Imagine a puppy running wildly around a backyard while no one is watching. But the second you peek outside, it freezes in one exact spot, pretending it was calm the whole time. Subatomic particles behave somewhat similarly. Before scientists measure them, they exist as waves of many possible outcomes all at once. But the moment someone tries to observe them, the particles suddenly “choose” one specific position or state. Scientists still debate exactly why this happens, but it remains one of the weirdest and most fascinating mysteries in modern physics.
#16
Eli5: Why Do Some Letters Have A Completely Different Character When Written In Uppercase (A/A, R/R, E/E, Etc), Whereas Others Simply Have A Larger Version Of Themselves (S/S, P/P, W/W, Etc)?
Because it's a shortcut, a simplified system created by scribes who had to write a lot by hand. So these scribes (some of them were monks) discovered that instead of raising the pen from the paper over and over again to write a new, separated letter, it was easier and faster to keep a continuous line that flows tying one letter to the next.
This system, called cursive, works great for some of the Latin letters, but not for most of them which had to be adapted. This is why A, B, E F, G, H, I, L, M, N, Q, R and sometimes S look very different in cursive from their uppercase versions.
This cursive system was later adapted by printers as the lowercase fonts.
#17
Eli5: Why Does Hearing Yourself Speak With A Few Seconds Of Delay, Completely Crash Your Brain?
We subconsciously use our own voices to make sure our mouth is making the noises we want it to. The brain can’t figure out what’s wrong but still tries to correct itself
#18
Eli5: Why Does Your Body Feel Physically Ill After Experiencing Emotional Trauma?
The limbic system is responsible for this feeling! The limbic system is the emotion and memory part of your brain, and is hugely important for how you experience and perceive things. The limbic system has a direct impact on the autonomic nervous system. If you perceive that you're in a calm situation, your limbic system will impact the rest of your brain, and thus the rest of your body, to make your body act as if it's in a calm situation. The hypothalamus is also part of the limbic system and plays a role in your body maintaining chemical balances. It is also a reason why you feel physically ill.
To give a little bit more detail on a few things:
The sympathetic portion of the autonomic nervous system is the the part of your body that makes your heart beat faster, makes you breathe faster, makes your pupils dilate, makes you sweat, and makes you stop digesting food (your blood is diverted to your muscles so you can run if needed). It is the fight of flight response in your body and has a cascade effect on the rest of your body. If your limbic system is going crazy with emotional trauma, it'll make your sympathetic nervous system ramp up as well. If you just ate and your body all of the sudden stops digesting food, you may throw up.
The limbic system (emotion and memory area of the brain) also directly impacts almost every other part of your brain. The limbic system is smack dab in the center of your brain, thus connects to everything. This is why being in a really intense situation can change how you feel physically and how you even perceive (time slowing down) a situation. One of the important parts of the limbic system is the hypothalamus.
The hypothalamus plays a huge role in maintaining your body's "natural state". If you need food, your hypothalamus is the part that makes you feel hungry. The hypothalamus is part of the limbic system, so it is under these same controls of emotion. Under a really stressful situation, your hypothalamus will react with the release of cortisol, which will affect your blood sugar and can make you feel sick.
Now, all of this kind of paints the limbic system as the bad guy, but that's not really true. The limbic system is also what integrates emotion into what we experience when something is positive. It's why your mom's cooking tastes better if you have fond memories of her. It's what makes your heart flutter when you're in love. It's what makes you remember things. Heck, it is even the reason why a truck horn can go off in the dead of night and you won't wake up, but when someone whispers your name you will.
Antimatter is another concept that sounds completely unreal. Every normal particle in the universe has an opposite version of itself called antimatter. These antimatter particles are almost identical except that their electrical charge is reversed. Now here’s the wild part: when matter and antimatter touch, they don’t simply collide or explode like in movies.
They completely erase each other in a burst of pure energy. No debris, no leftovers, just energy. It’s basically the universe’s version of hitting a giant delete button. Scientists believe antimatter existed in large amounts right after the Big Bang, and researchers are still trying to understand why our universe today is mostly made of regular matter instead.
#19
Eli5: How Can The Same Side Of The Moon Always Face Earth? Doesn't It Rotate?
It’s due to a phenomenon known as TIDAL LOCKING.
This happens when
a moon (or any celestial object) orbits another object at a close enough distance, so..
..the gravity of the “host” object is strong enough to pull one side of the moon towards it in such a way that..
...the moon rotates at the same rate as it orbits
In half a rotation, the moon would have turned 180 degrees and showed its other side. But at the same time, it went 180 degrees around the Earth, so now the other side of the earth sees the same side. Here’s a handy gif !
The one we actually see is the one on the left. The one on the right is what it would look like IF the Moon weren’t tidally locked.
Also, the “dark side” of the Moon is misleading! Both sides of the Moon can be lit up or in darkness, depending on the time of month. On a Full Moon, the face you see is bright. On a New Moon, the face you see is dark.
What most people mean by “dark side” is generally the side not facing the Earth.
(Edit: 180 degrees, forgive my 3am high a*s brain)
Edit: so here’s some extra explanations about the mechanism of tidal locking:
I actually simplified the answer a lot. It’s not about one side experiencing a stronger force, it’s about one AXIS of the Moon experiencing stronger force.
Just like how the oceans facing the Moon experience high tide as they are pulled towards it, the Earth itself is pulled towards the Moon. Thus, the Oceans on the opposite side also experience high tide.
It’s this ‘bulging’ effect that effects the spin of a body. Back when the moon was molten rock, this bulging was large enough to ‘lock’ its rotation the way it is today.
#20
Eli5: What Is The Psychology Behind Not Wanting To Perform A Task After Being Told To Do It, Even If You Were Going To Do It Anyways?
It removes the autonomous feeling from the task, resulting in the task being less rewarding, hence the lack of motivation
#21
Eli5: Why Do Traditional Cars Lack Any Decent Ability To Warn The Driver That The Battery Is Low Or About To Die?
The technical people answering are technically correct, that a voltmeter would indicate the voltage of a battery, but they’re missing what OP is after: when won’t a battery work anymore? In other words, they are wondering “why can’t I know the health of my battery?”
With car batteries (the 12V lead acid type) the voltage isn’t really a good indicator of health. An old dead battery can read ~12V just fine. It would likely power most lights and equipment, too. The real test of health comes when trying to start the engine; the “load” test. An old battery can read 12V until asked to turn the starter, then immediately drops to an unusable voltage.
The simple answer is that traditional 12V car batteries do not have the sophisticated tech to indicate their health like, say, laptop batteries. Nor is there a good way to test the health except for hooking the battery to a load, which isn’t an easy thing to build into a car’s circuitry. Basically, starting the engine IS the load test.
Edit: To all those asking why a load tester couldn’t be added into the hardware or software of a car: it could. Nearly anything is possible with time and money. But I agree with the comments from those in the industry; it comes down to three basic things:
Added cost (automotive margins are very thin)
Added complexity and engineering effort for nearly no return (exactly who would truly want this?)
Service side (auto companies do not wish customers to have to think about maintenance beyond knowing to take the vehicle in when the light turns on)
Edit 2: Since this blew up from my original simple answer, we’ve attracted the attention of my more astute engineering colleagues. It appears my answer is a little dated. The fact is that this diagnostic capability DOES exist in more modern vehicles. But just as auto companies have chosen to shroud engines in giant swaths of plastic to hide the ugly technical bits, so have they chosen to hide most of these diagnostic abilities from the consumer behind a simple light or “Service Soon” message. Good discussion!
#22
Eli5: Why Does "Hoo" Produce Cold Air But "Haa" Produces Hot Air ?
When you do a "hoo", the air is coming out from a very small opening which gives it a higher chance to mix with the air around it and cool down.
When you do a "haa", the air is coming out at a larger volume and needs more time to cool down.
Put your finger right in front your mouth when doing a "hoo" and you will sense that it's actually just as hot as a "haa", but cools much faster a few cms away.
And finally, perhaps the weirdest realization of all: almost everything around you is technically empty space. Tables, walls, chairs, your phone, your body — all of it feels solid, but atoms are actually made up of about 99.9999999% empty space. If the center of an atom were the size of a marble placed in the middle of a football stadium, the electrons would be tiny specks buzzing near the outer seats. So when you touch a table, you’re not truly “touching” it in the way you think. The electrical forces between your atoms and the table’s atoms push against each other, creating the sensation of solidity. Which means, in a very strange way, humans spend their entire lives floating microscopically above everything around them.
#23
Eli5: Why Is It That Mandarin And Cantonese Are Considered Dialects Of Chinese But Spanish, Portuguese, Italian, And French Are Considered Separate Languages And Not Dialects Of Latin?
There's a saying in linguistics: "A language is a dialect with a flag and an army."
The field of Linguistics does not actually define what is a "language." Linguistics definitely has the concept of a dialect, and can discuss whether two groups of people speak the same dialect or different dialects. It has concepts of things like mutual intelligibility, i.e. can native speakers of two dialects understand each other. But the idea that two dialects are part of the same "language" is a question that linguistics entirely cedes to the field of politics.
So, the answer to your question: China considers itself a single political unit, and they place a high value on considering themselves unified. France, Italy, Spain, and Portugal consider themselves distinct political units from each other, and modern Italy considers itself distinct from the Roman empire.
It's also worth noting that people from different regions in Italy sometimes can't understand each other, because dialects of Italian have a very large spread. Again, they're considered the same language because Italy wants to perceive itself as a single unified cultural entity.
Were one of these regions of Italy to become independent, it's likely they would consider their dialect to a language over time, although that process would likely involve doubling-down on the regionally-distinct features of that dialect, and probably having a distinct literary tradition as well. Something like this already happened when Norway became independent of Denmark.
#24
Eli5: Why Does Making A 3 Degree Difference In Your Homes Thermostat Feel Like A Huge Change In Temperature, But Outdoors It Feels Like Nothing?
Because outside you have multiple things that affects the way the temperature feels. A slight breeze or moment in the shade will feel cooler. Humidity or the sun shining on you will make it feel warmer. Inside you don’t feel these variables nearly as often.
#25
Eli5: Why Do Some Animals (Like Spiders Or Lizards) Spend So Much Time Just Doing Nothing? What Is Happening And Why?
Most organisms are in a constant struggle for energy. Obtaining energy is dangerous, you have to leave your save burrow or go risk injury in a hunt.
That's why many organisms develop strategies for minimizing the risks they need to take. And one of the most popular strategies is simply having simple, low demand physiologies, slow metabolisms and generally low energy needs.
Warm blooded animals are fairly unique. We're like a car with the engine constantly running. That means we're ready to go from zero to a 100 right away but we're also guzzling gas constantly, even if we're standing still. That's why warm blooded animals need toc constantly eat. Some of the smaller more high energy creatures like humming birds can starve to d**th in a matter of hours.
By comparison, cold blooded animals waste zero energy on body heat. The downside is that they need to warm their bodies up with external heat like sunlight in order to get their digestive enzymes working or to get their muscles ready for fast action.
But on the upside, they need so little energy that they have to take far fewer risks than warm blooded animals. Some cold blooded animals can go up to a year or even longer without food.
The Other Guest 49 minutes ago
Just being pedantic here: "up to a year or even longer" is another way of saying "the amount of time is less than, equal to, or more than a year." It's really not very helpful.
#26
Eli5: Why Is It That You Can Keep A House Phone On It's Charging Dock For Years And It Doesn't Destroy The Battery Where As A Cellphone Will Eventually Wither Over Just A Couple Years If You Charge It For Too Long Everyday?
Edit: ELI5 version. The batteries are different types on the inside. The cell phone type gets hurt at 100% charge and the cordless house phone type lasts longer at 100%, plus the house phone type is much cheaper and easier to replace (so even if it doesn’t last super long, it’s not a big deal).
Edit2: ELI20 now features more ELI20-like-explanations In parentheses.
I've worked in the battery biz for 10 years.
Most commercial li-ion batteries don't handle high state of charge (battery % shown on your device) very well as the oxidation rate (how fast the liquid inside is getting used up) of the electrolyte is high at this state, so you lose lithium ions rapidly (battery can’t store as much charge.) This causes loss of capacity (runtime).
The internal resistance (resistance is the phenomenon that reduces battery power) of the battery goes up at the same time, and it can't charge/discharge as quickly anymore, so the end effect is it can't perform well in the device (the device needs a certain amount of power, which the battery will eventually struggle to deliver) and this actually accelerates the capacity fade even more. (Battery loss of runtime will get worse each day)
Most household phones are Ni-MH chemistry which is much lower energy density (heavier and less sexy) but handles high state of charge much better.
They used to put Ni-MH in cell phones in the mid-to-late 90s, they were big, bulky, and didn't have a lot of talk time. Li-ion was better in every way for cell phones. For household phones this isn't really a problem, and Ni-MH is much cheaper to implement, plus they are more easily customer replaceable (they don’t catch on fire, and are widely available)
You can get a much longer lifetime out of lithium-ion batteries by implementing lower maximum voltage, for example 4.1V max charging voltage instead of 4.2V. This is called derating and is used in more high-end applications like Teslas (4.1V is normal charging mode, 4.2V is "extended range" mode which you shouldn't use if you don't have to).
"Regular" lithium-ion batteries are usually charged to 4.2V and the device makers don't give a s**t about the long term longevity, they just want to advertise longer runtime on a single charge at beginning of life.
Well, whether it’s complicated science theories or just everyday things we never stop to think about, so many concepts suddenly become fascinating once they’re explained in a simple, relatable way. Honestly, sometimes the world feels a lot more mesmerizing when someone breaks it down without making our brains melt in the process. And that’s exactly what makes posts like these so fun — they remind us that learning something new doesn’t always have to feel intimidating.
Pandas, which one of these explanations completely blew your mind the most? Was there one that finally made something “click” for you after years of confusion? Let us know!
#27
Eli5: When A Baby Is Born, How Are Their Lungs Instantly Able To Breathe Air If They Haven't Been Breathing Air For 9 Months?
Alright here’s a very simple explanation. The placenta is what brings oxygen from mom to baby through baby’s umbilical cord (that’s where their belly button is) instead of through the lungs. When baby is inside mom, blood that has oxygen in it goes to the heart where it gets pumped out to the rest of the body. In you and me, there’s a little door that has a tunnel between the right side of the heart and the lungs. Our blood that needs oxygen goes through that tunnel to the lungs and then comes back through another tunnel to the left side of the heart, where it gets pumped out to the rest of the body.
In an unborn baby, the little door between the right side of the heart and lungs is closed and the pressure behind the door is very high. It’s too hard for blood to get through it, so it goes around through another secret little door to the left side of the heart. When a baby is born, there is a big shift in pressure behind that little door. When a baby takes its first breath, the secret little door slams shut. It’s kind of like when a door slams shut because of wind. When that secret little door slams shut, the pressure behind the door to the lungs gets lower, and that door gets unlocked. Now, the blood in the right side of the heart can go through that little door to the lungs where it picks up oxygen, goes to the left side of the heart, and then gets pumped through the rest of the body.
When baby is inside mom, the lungs still get a little bit of blood to them, but they aren’t the primary place where gas exchange takes place (where oxygen and carbon dioxide move in and out). They’re working on growing and producing a slippery soap-like substance called surfactant. The surfactant helps keep tiny air sacs called alveoli open and from sticking shut. The alveoli are where gas exchange takes place, otherwise known as how oxygen and carbon dioxide move in and out of your body. When the baby is born, that pressure change and sudden blood volume to the lungs and alveoli causes gas exchange to happen, and that’s how baby now breathes and gets its oxygen.
#28
Eli5: You're Not Supposed To Defrost Meats In Warm Water Due To Harmful Bacteria Growth, You're Not Supposed To Leave Food At Room Temperature For Long Without Being Refrigerated Because Of Harmful Growth But, When You Go To A Buffet, Food Can Sit Out For Hours Under Heat Lamps And Be Fine?
There's a concept in food safety called the "danger zone". It extends from about 40 F / 5 C to about 140 F / 60 C. You can keep food below the lower end of that range, or above the upper end, for a while without it going bad. The reason is that this is approximately the range of temperatures that the bacteria that cause foodborne illness can tolerate well enough to grow. They can survive in lower temps, but they won't grow or will grow very slowly, which is why you can store meat in the fridge for a few days without problems. (They'll d*e at higher temps if they're kept that hot for a while, as in sous vide cooking, but can survive brief exposure.)
The food at the buffet is (at least supposed to be) kept above 140 F / 60 C, so that whatever bacteria may be present can't grow effectively. The trays at a buffet usually sit above a pool of very hot water in addition to the heat lamps, which keeps them hot. (This is if the food does stay out for hours. It may simply be changed out regularly, in which case it can be kept in the danger zone.)
You can take the "keep it above the upper end of the range" principle really far, because temps above 140 F / 60 C will k*ll almost all bacteria with prolonged exposure. This is the principle behind perpetual stews, foods which were effectively cooked for years or decades.
#29
Eli5: When You Restart A PC, Does It Completely "Shut Down"? If It Does, What Tells It To Power Up Again? If It Doesn't, Why Does It Behave Like It Has Been Shut Down?
ELI5 answer When you restart a PC, it does not shut down completely.
Someone used a metaphor for a chef so I'll use that too. Shutting down completely would be like if the chef cleaned up and went home. Holding the power button down to shut down faster would be like if the chef didn't clean up and just left a mess and went home.
Restarting the computer is telling the chef to clean up everything and then set everything back up without him leaving the building. So, it's not totally "shut off" in that sense because the chef is still there to set things back up, and he knew that was the plan in advance!
#30
Eli5: I’m Told Skin-To-Skin Contact Leads To Healthier Babies, Stronger Romantic Relationshipd, Etc. But How Does Our Skin Know It’s Touching Someone Else’s Skin (As Opposed To, Say, Leather)?
Others in this thread have mentioned how difficult it is to prove the healthier babies/ stronger relationship aspect of the question.
But - your skin can tell if it's touching someone else's skin. There are an entire class of sensory receptors in the skin that respond best to soft pressure, skin temperature, slow movement touch - essentially being stroked (called Low Threshold Mechanoreceptors)
To be a bit un-ELI5 this is called affective touch and neuroscientists are only recently discovering its receptors and pathways in the nervous system. The theory goes that if the body can discriminate human contact using these receptors, it can then release the chemical oxytocin to re-enforce that personal relationship. e.g. between a new-born child and the mother holding it.
#31
Eli5: What Is The Reason That Almost Every Video Game Today Has Removed The Ability For Split Screen, Including Ones That Got Famous And Popular From Having Split Screen?
3 Main reasons:
It takes a lot of extra processing power to generate the split screen aspect.
Its development work they would rather put towards their more lucrative multiplayer (usually with microtransactions)
they sell more copies of the games to groups of friends who want to play it.
Now all of those are nonsense reasons, and I want my couch coop back, but still. I would (and do) support games with couch coop, like borderlands, lovers in a dangerous spacetime, speedrunners, etc. I recommend you do the same.
Also f Halo 5.
#32
Eli5: Why Do Blockbuster Movies Like Avatar And End Game Have There Success Measured In Terms Of Money Made Instead Of Tickets Sold, Wouldn’t That Make It Easier To Compare To Older Movies Without Accounting For Today’s Dollar vs. A Dollar 30 Years Ago?
Because a movie has yet to beat the classic Gone with the Wind adjusted for inflation, and a headline that a movie is the 17th highest grossing film adjusted for inflation is not sexy at all.
#33
Eli5: How Come All Those Atomic B*mb Tests Were Conducted During 60s In Deserts In Nevada Without Any Serious Consequences To Environment And Humans?
The simple answer is there were serious consequences to both the environment and human health. There were marked increases in cancer rates noted, not just in Nevada, but across the midwest. Test site workers and downwinders (communities down wind from the test site) sued the federal government. To date more than half a billion dollars in compensation has been paid out.
#34
Eli5: NASA Engineers Just Communicated With Voyager 1 Which Is 21 Billion Kilometers Away (And Out Of Our Solar System) And It Communicated Back. How Is This Possible?
They used a very large dish to focus the transmissions into a narrow beam. The bigger the dish, the greater the effective power. A 70M dish has a gain of around a million (depending on the frequency) .
They also used very low bit rate communications. The usable bit rate is highly dependent on signal to noise ratio.
They do use high power on the Earth side, but the spacecraft has only a few watts, and a small dish. The Earthbound receivers use ruby masters masers cooled in liquid helium to get the lowest noise.
#35
Eli5: Why Do "Bad Smells" Like Smoke And Rotting Food Linger Longer And Are Harder To Neutralize Than "Good Smells" Like Flowers Or Perfume?
They dont really; but you're keyed to be more sensitive to rotting food scents and other bad smells. Theres usually a survival reason behind it, and over time we developed a sensitivity to those scents.
Smoke is an exception; that actually does have more particles in the air that can stick to things and smell longer as a result
#36
Eli5: Why After A Good Long Cry Can't We Take A Big Deep Breath Without That Huh-Huh-Huh Tracheal Contraction?
Those "tracheal contractions" are probably either diaphragmatic or congressional intraabdominal (thanks, Swype) muscle spasms, due to the strain that had been placed on them during the crying jag.
You know how your legs get wobbly after doing a bunch of squats? Your breathing muscles get wobbly after being worked hard too.
Lukas (he/him, it/its) 52 minutes ago
Another useful comment from the thread: "When we’re stressed or upset, we produce stress hormones and our breathing becomes fast. We’re often told to “take deep breaths” to relax us. That’s why it’s a fundamental part of relaxation activities like yoga and meditation, our rate of breathing has direct effects on the chemicals we produce which determine how we feel. When most of us are asked to take a deep breath, we inhale quickly, pushing our chests out and our shoulders up. But when we do that we only fill the top parts of our lungs. What we should be doing is taking in a long and deep breath, with the aim of filling our lungs with as much air as possible. The kind of breath you’d need if you were playing a wind instrument. Air right to the bottom of the lungs, shoulders stay where they are, tummy pushes out. When we do this, we’re stretching and controlling our diaphragm, a key muscle responsible for the rate at which we’re breathing." (continued in replies)
#37
Eli5: How Can Nothing Be Faster Than Light When Speed Is Only Relative?
Wow, OP. You've asked the very same question that Einstein asked himself to come up with one of the most revolutionary ideas in physics!
You are correct that speed is relative. If I'm walking up an escalator at 2 m/s and the escalator is moving at 5m/s then my speed relative to a person standing still at the bottom of the escalator is 7 m/s, but to someone else on the escalator who is standing still and waiting patiently for the escalator to transport them to the next floor my speed is 2 m/s.
But light travels at the same speed from all perspectives. Say a spaceship is traveling at 90% the speed of light. If I shine a torch from the back of the spaceship to the front and someone on the ground can see through the spaceship's window, then the light from the torch will appear to move at the speed of light to both of us. But the escalator example would suggest that to the person on the ground, it should be traveling at 90% of the speed of light + the speed of light i.e. at 190% of the speed of light. So how can it appear to move at the speed of light to both of us? Well, if the person on the ground is looking through the window and everything in the ship (including not only the beam of light from the torch, but the people inside the ship) is moving in slow motion, then the beam of light can appear to move at the speed of light.
Mind blowing, eh? To solve the paradox, time must be relative! Time inside the ship appears to be slowed down to the person on the ground, and conversely everyone outside the ship looks like they're running around like ants to the people inside. Actually, there's a bit more to it than that, since distances are affected too. But thinking about it like this is a good starting point.
#38
Eli5: Why Is W Called "Double U" When It Is Clearly "Double V"?
When Old English was written, it used a mixture of Latin letters and older runes. One of these runes was Wynn, which was used to represent the wound that w gives today:
That runes was sometimes replaced by the combination uu - a double u - for the same sound.
In german, the letter v changed in sound to be pronounced as f in most cases (it still is). In a few cases the v-sound was retained. To distinguish these cases, scribes began to write vv for these.
When printing was developed in what is today Germany (and to some extent Italy, but that is less relevant here), the printing press manufacturers made types for the letters that they had. Since the combination vv was very common, they made a letter for it - w. In most languages letter is called "double-v".
These printing presses and the letters for them were exported everywhere, including to England. The English quickly realized that they didn't have types for all their letters, so they made do with what they had. Since English didn't have the w before printing, they simply reused that letter for the Wynn rune, which was missing. It is called "double-u" because it was also sometimes written as "uu"
Similar story for the letter Thorn, which was also missing when printing and became the "th" combination.
#39
Eli5: How, At 93 Million Miles Away, Does The Sun Feel So Warm, Yet When A Simple Cloud Passes Over It The Warmth Is Incredibly Dampened?
So when you feel the sun's warmth, you're not feeling heat coming from the sun. You're instead feeling heat created on your skin by the sun's light.
Light carries energy. Things with colour, like your skin, absorb light. When they do, the atoms that make them up get 'excited'. Depending on the atom, and what state its in, a few things can happen. If the atom is part of a molecule that energy can go to work breaking it out of the molecule. If the atom or molecule is on the surface of a solid or liquid, the energy can go towards flinging it off, into the air, turning into a gas.
If there's not enough energy to do either of those things, then the atom will just release the energy to its surroundings. Most of the time, most of the energy is released as heat. This is what you feel when the sun feels warm. Sometimes the energy can be released as light. This is how glow-in-the-dark things work.
A cloud doesn't block all the light from the sun, but it does absorb scatter a lot of it. Think of water droplets in a cloud like a million tiny disco balls. The light that gets through is either too sparce to be noticeable, or high-enough energy that it causes damage instead (ie. UV light).
#40
Eli5: When Toddlers Talk ‘Gibberish’ Are They Just Making Random Noises Or Are They Attempting To Speak An English Sentence That Just Comes Out Muddled Up?
It’s usually just them learning and playing with all the noises they are capable of vocalizing. You will also notice that pronunciation improves greatly over the next few years as they gain better coordination of their mouth and vocal muscles
#41
Eli5: Why Were Ridiculously Fast Planes Like The Sr-71 Built, And Why Hasn't It Speed Record Been Broken For 50 Years?
Before we could use satellites to take pictures from space, if we wanted to see what was going on in enemy territory, we had to take pictures from a plane.
Enemies didn't want us taking pictures so they would try to stop the plane - usually by blowing it up with missiles.
We didn't have "stealth" technology yet to keep from being seen, so if we wanted to avoid getting hit with missiles, we needed a way to avoid them. The best way we could come up with was to go so fast they couldn't catch up.
Being really high in the air helped this, because it's easier to go fast up high, and because it would take missiles so long to get up to you, you could be out of the area before they reached that height.
As a result, the SR-71 was designed to go as high and as fast as possible.
Since then, we learned to build space satellites to take our pictures, which can't be hit with missiles. We also developed "stealth" technology for planes, which keeps them from being seen on radar. This means we no longer need to develop planes for high and fast work, so the SR-71 remains the best at that.
#42
Eli5: Caffeine Has Almost No Calories, But Seems To Give Us A Burst Of Energy On Its Own. Where Does The Body Get This Energy From? Is Caffeine Forcing The Body To Use Stored Fat?
Caffeine works in two ways to make you feel that way.
First it prevents the brain from telling you that you are tired. You can think of your brain as a bunch of locked boxes with different things inside of them. Some of these boxes have things that make you happy, others make you sad. Some have things that tell you it is time to go to sleep. Caffeine jams itself into the lock on the sleepy time box so that your brain can't open it. That keeps you from feeling tired.
Caffeine also can help open the box that tells your body to go into extra energy mode. Things like your heart can work faster or slower depending on what you need. If you are sitting on the couch watching TV it's going to go slower, if you are outside working it's going to speed up. Caffeine tricks the body into thinking it needs to go into extra energy mode. Caffine doesn't create this energy, the body is just using what it has stored more quickly. Not really any different from you step on the gas in a car. You are telling it to burn more fuel and go faster.
#43
Eli5 What Is It About Grapefruit Specifically That Messes With Pretty Much Every Prescription In Existence?
Grapefruit inhibits a liver/ intestinal enzyme called CYP3A4 which is responsible for a large amount of dr*g metabolism. This can lead to either the dr*g not getting where it needs to go, or a build-up of the dr*g which can be dangerous
#44
Eli5: What Does It Mean When Scientists Say “An Eagle Can See A Rabbit In A Field From A Mile Away”. Is Their Vision Automatically More Zoomed In? Do They Have Better Than 20/20 Vision? Is Their Vision Just Clearer?
Actually, eagles can see rabbits two miles away.
Their eyes are about the same size as human eyes, so relative to their size much bigger than ours, but they have better focusing (no near- or farsightedness, constant focusign during movement) and, most importantly, they have about 5x more cells in their retina. You can think of eagles having higher resolution - where you as a human see just HD, they see more than 4K.
#45
Eli5: If The Amazon Echo Doesn’t Start Processing Audio Until You Say “Alexa”, How Does It Know When You Say It?
To put it as simply as possible, this is the process that happens:
There is a chip that is always listening in the echo. It doesn't record, doesn't transmit to Amazon.
When this chip hears the wake word (Alexa, Amazon, Echo or Computer, whatever you have set) it activates a buffer, recording a bit (less than a few seconds)
This is sent up to Amazon where their better processing (their servers are obviously more powerful than an echo) verifies the wake word was said
If the wake word wasn't said, the buffer is purged. If not, the buffer gets analyzed along with any continued speech for commands
The buffer is used so it is smooth, otherwise, you'd have to say "Alexa" wait for it to verify, with a pause, then state your command. The couple second buffer allows smoother "Alexa, turn on the lights" type commands
#46
Eli5: Why Do Alcoholics D*e When They Stop Drinking?
Alcohol is a depressant, which means it slows the activity of the brain. If someone abuses alcohol over a long period of time, their brain will adapt and create more and more sensitive reactive chemicals to try to retain normal brain function even in the presence of alcohol. This is called tolerance.
If the person were to suddenly quit drinking, the alcohol that was inhibiting brain reactions is no longer present, but the overly reactive chemicals are still there, meaning the brain is way more active than its supposed to be. This is a seizure. Think overloading a circuit with too much electricity - it burns out and misfires.
Tl:Dr: Brain becomes tolerant to alcohol and short-circuits in its absence.
#47
Eli5: Why Is It Healthy To Strain Your Heart Through Exercise, But Unhealthy To Strain It Through Stress, Caffeine, Nicotine Etc? What Is The Difference Between These Kinds Of Cardiac Strain?
Exercise is like stretching a balloon prior to blowing into it. You're maintaining its elasticity. Chronic stress on the heart is like inflating the balloon fully for a month then deflating it back down - it'll deflate down to twice the size it started, with all the elasticity gone. That is heart failure.
#48
Eli5: Why Is It Children’s Shampoo Is “Tear Free” While Regular Shampoo Burns Like All Hell In The Eyes?
Soap is a chemical with a long, and kind of clever, molecule. One end of the molecule attracts water. The other end attracts dirt, particularly oily dirt. So when you wash stuff, the oily-liking end sticks in the oily dirt and the other end gets stuck in water... and so the oily dirt gets pulled away from what you are cleaning when the water-liking end gets pulled away through scrubbing or swirling water around. So put some soap on your greasy hands, and scrub a bit, and all the greasy stuff gets lifted away.
Now there are different levels of soap out there. The CLEANING 100 soap doesn't care about gentle, it just sucks dirt up like crazy at the expense of wimpy stuff like moisture and balance. The weaker soap works, but not quite so well, but at least it doesn't damage your skin or eyes, or dry out stuff in the process.
So stronger soap chemicals are great for super greasy dirt, but the trade-off is they cause your eyes to sting when it hits them because your eyes are sensitive to super-effective soaps.
But other soap chemicals don't cause your eyes to sting because they're not QUITE so good at sticking to oily dirt at one end, so they're not quite so good at cleaning or wrecking the careful balance of chemistry that keeps your eyes moist and in good shape.
So we have a trade-off: oily dirt removal? Or no irritation to the eyes? Which one you want goes to which "soap" you use in your shampoo. And baby shampoo uses the second one even if it doesn't clean as good as the first, because babies generally don't stand underneath leaky car oilpans or go swimming in cold deep fryers unless you're a really bad parent.
#49
Eli5: Why Is Finding "Patient Zero" In An Epidemic So Important?
It depends on the epidemic. For rare diseases that pop up now and then, like ebola, this was important because people wanted to know where ebola was coming from. Years could pass without a single known human having it, so it was coming from the environment, likely some kind of animal. After finding out "patient zero" for ebola outbreaks, you can look at where they lived, what they did, etc. to identify likely candidates for animal hosts, and then go into the wild and collect those animals to see if they actually have the virus. If they do, then you can now warn everyone that this is how you get ebola, so they know to be cautious.
Studying diseases that can jump species barriers can also potentially teach us about which diseases might do this in the future, so we can be prepared just in case it happens.
If very little is known about the disease in question, tracing the path of transmission can tell you how the disease is spreading. Is it airborne? Does it live in the environment, or only within hosts? How long can it survive outside the host? Does it even spread from person to person, or were all those infected exposed to the same source, rather than one passing it to the other? Legionnaire's disease is like this, it DOES NOT spread from person to person, it spreads through inhaling contaminated water vapor. So if a group of people get it, we can look to see what water sources they've been near, so that we can stop any more people from being infected by that source.
Edit: For more information, I recommend this book on a cholera epidemic in London, where epidemiological techniques were first pioneered. . . by a guy named John Snow. No, really! Here's a Youtube series on the same topic.
#50
Eli5: How Can Our Brains Remember That We Forgot Something, But It Can't Remember What We Forgot?
This question asks "how is it possible?" and not "how does it work?", so I won't talk about actual brains here. But even very simple information storage and retrieval systems can be constructed so that it's obvious when information has been lost.
For example, let's say you have a book with 100 numbered pages in it.
Page 46 might be blanked out. You know that's an error, since there is no page numbered 46 after page 45, and page 47 doesn't pick up where 45 left off. Something is missing.
You don't know what was on page 46, but you can be pretty sure it's gone.
#51
Eli5 The Difference Between 4 Wheel Drive And All Wheel Drive.
4WD and AWD roughly do the same thing but in different ways, the car is proving power to all four of its wheels. The difference is how that power is divided between them. An all-wheel-drive car can allow each wheel to turn at a different rate, while a four-wheel-drive car generally has its wheel all turning at the same rate. This 4WD set up is better for offroad driving, but can cause problems in city driving, where the inside wheels need to turn slower around a corner than the outside wheels do. Because of this, a lot of 4WD cars are designed to be able to switch to rear-wheel drive when the 4WD is not needed.
#52
Eli5: Why Do Older Emulated Games Still Occasionally Slow Down When Rendering Too Many Sprites, Even Though It's Running On Hardware Thousands Of Times Faster Than What It Was Programmed On Originally?
A lot of old games are hard-coded to expect a certain processor speed. The old console had so many updates per second and the software is using that timer to control the speed of the game.
When that software is emulated that causes a problem - modern processors are a hundred times faster and will update (and play) the game 100x faster.
So the emulation community has two options:
1) completely redo the game code to accept any random update rate from a lightning-fast modern CPU
Or
2) artificiality limit the core emulation software to the original update speed of the console
Usually they go with option 2, which preserves the original code but also "preserves" any slowdowns or oddities caused by the limited resources of the original hardware.
#53
Eli5: Why Do Ships Have Circular Windows Instead Of Square Ones?
The joke answer is so that the water doesn't hit you square in the face.
The real answer is that shapes with sharp corners are structurally weak. Arcs and circles are very strong shapes. If port holes were squares, the openings would get damaged and worn out sooner.
#54
Eli5: How Do Ships Anchor Themselves In Very Deep Waters? For Example, If They Anchored In 10k Foot Deep Oceans, Do They Actually Have 10k Feet Of Anchor Chains?
The short answer is: they don’t. Ocean going vessels tend to anchor in waters 100-150 ft deep or less. You need anywhere from 2x to 6x the depth of the water in chain length (depending on wind/current) to hold fast.
#55
Eli5: Why Can't Bots Check 'I Am Not A Robot' Checkboxes?
actually, clicking the box is a rather trivial part of what those CAPTCHAs are looking for. What they're actually looking for are things like:
did the 'user' instantly move their mouse to the exact coordinates of the box, or did they traverse thru the page like a human would?
is the user scrolling to the box, or are they remotely executing javascript to trigger a scroll to the box?
how long after page load did the user find the box? Too quickly is obviously a red flag, but taking too long is also. commonly, to get around reCAPTCHA you'll need to find out 4-5 areas to click in addition to the initial click. The way that most people do this is using CAPTCHA services, which are real people solving them and returning the answer to you (i.e. for a text captcha, you'd send them the image and they'd send back the letters/numbers). The way you do this with reCAPTCHA is sending a screenshot of the computer, and you are returned the coords that you're supposed to click on to answer the question properly. [e: apparently this method is old, and a new method where the CAPTCHA is actually served up to the person within the service that will solve it for you!] However, it usually doesn't take a legitimate human 5 minutes to answer a few questions about 9 images. if you take too long, they'll make you do another image check challenge.
basically, it's really, really difficult to make a bot move the mouse, scroll, and react naturally to a page load. and even if you do manage to fool reCAPTCHA, you'll be thrown to a few image tasks which may serve to block you out from the website completely, due to the reasons mentioned above.
e: as others have mentioned, this type of stuff is only part of what reCAPTCHA relies on to determine human/non-human - particularly, your referring information & whether or not you have a logged in Google account.
e2: there are a bunch of people claiming that mouse movement tracking is impossible to do. in chrome, hit ctrl+shift+j, paste
#56
Eli5 Why Does Down Syndrome Cause An Almost Identical Face Structure No Matter The Parents Genes?
Have you ever inflated a rubber glove? With just a little air the glove looks like a hand, but the more air you add, the more it distorts as the palm fills but the fingers don't.
Down syndrome happens when a person has an extra chromosome. Everyone has two of every chromosome, which means two copies of every gene. Someone with down syndrome has three copies of a small set of genes; the third copy is on that extra chromosome. As a result, those genes get expressed too much, resulting in the familiar features that seem to hide or overshadow the features that would make them more "normal". We all have these features, but in most of us they're toned way down. Their gloves have more air in them than ours.
Edit: Many of you have correctly pointed out that DS people do not "all look the same". They have similar features explained by genetics, yes, but so do various ethnicities. Unfamiliarity can make it difficult for an "outsider" to tell the differences between individuals, but those differences are not only there, they are as stark as the differences between two random French people, or two random Han people.
#57
Eli5: Why Does A Candle Not Create Smoke When Burning But Lots Of Smoke When You Blow It Out?
When the flame is lit...that smoke is being burned. The smoke is vaporized wax. When you blow it out, the wick is still hot enough to vaporize wax, but not ignite it.
If you cool the wick like lick your finger or put in water, the wick is no longer hot enough to vaporize wax.
#58
Eli5: Why Can't We Have Supplements Or Pills For Dopamine, Oxytocin, Serotonin Or Endorphins Just Like We Have Melatonin Or Contraceptive Pills?
I don’t think the other posts are answering your question. Supplements of dopamine, serotonin, etc are not sold because those chemicals do not cross the blood-brain barrier. The blood brain barrier is essentially a filter, and it only allows specific chemicals into the brain, like glucose. So even if you took a pill that contains pure dopamine, it will not get to your brain. I think answers that say the ‘potential for a**se is too high’ are wrong, since a supplement of pure dopamine, serotonin, etc do not actually make it to the brain.
#59
Eli5 : How Are We Sure That We All See The Same Colors ?
Until we get full bore telepathy online, we will never know for sure. However, we are all using the same basic hardware - rods and cones, neurons, etc. So it is not unreasonable to assume that my green is the same as your green.
On the other hand, it doesn't matter how we experience things internally. What matters is that we agree that the word "green" corresponds to the same portion of the visible spectrum.
#60
Eli5: Why Is It That It Takes Few Seconds For Our Body To Decide That It's Had Enough Water Not To Be Thirsty, But Several Minutes To Recognize That No More Food Is Needed Cuz It's Not Hungry?
Sensors in your mouth, back of the throat and oesophagus can detect how much water has been consumed and report this information to the brain. Fairly shortly after drinking water, the bode will start to behave as if that water is already in the bloodstream, even if it is still somewhere in the digestive tract.
Food is a completely different story. The brain relies on stretch receptors in the stomach, hormones produced by the process of digestion, and sometimes chemicals generated by the bacteria living in the intestines. This is a much more complicated process that takes longer, which leads to a lag between actually being full, and the feeling of fullness.
#61
Eli5 Why Do People Seem To Age So Incredibly Fast After A Traumatic Experience?
Stress leads to higher cortisol with leads to ageing. This process is so strong that children who experience high levels of stress in infanthood/early childhood statistically start puberty earlier than their non-tramatised counterparts.
#62
Eli5: What Actually Happens When We Unintentionally Start To Drift Off To Sleep But Our Body Suddenly "Shocks" Us Awake?
I work in neuro and I don't know the answer to this. Scrolling through the first few top comments I'm seeing wildly different answers. Rather than further misinformation, I'll just interpret the wikipedia entry:
Looks like the reaction is not understood, but is probably the activation of the "reflex to stay upright". When your muscles relax when you fall asleep, it may accidentally be interpreted as weightlessness (falling), which may trigger the response.
So if anyone knows more than this, rather than spread dubious information, please update the wiki with your sources.
#63
Eli5: How Is Peach Flavoring So Easily Captured In Gummies, Water, Etc, When So Many Other Flavors Taste Obviously Fake?
Peaches have less chemical complexity than something like a watermelon for instance. With a peach, scientists have discovered the right set of flavor molecules, sometimes referred to as esters, that create the proper taste of a peach. I also believe the main molecular component that gives a peach its taste can be used as a food additive, like the molecule found in apples.
In contrast, the flavor molecule that makes up the most common watermelon taste; red innards, green rind, is referred to as an aldehyde, and isn't as simple. This molecule is too unstable to be made into a food additive. To top it off, watermelons (like bananas) have an incredibly rich and complex flavor profile in terms of chemical makeup. You also have far more varieties of a watermelon (also like bananas) than you do a peach, making it ever the more complicated. Unless somebody finds something that mimics the watermelon aldehyde properly, or can create a stable compound using it, you're stuck with not really watermelon flavored watermelon candy and/or treats.
#64
Eli5: Why Are So Many Electrical Plugs Designed In Such A Way That They Cover Adjacent Sockets?
Ease and durability, mostly. The part that generally covers adjacent sockets is the rectifier and transformer, the generally blocky bit that converts AC power into DC power at the proper voltage and amperage. It's better for the cable to have the mass at the end that generally doesn't move.
#65
Eli5: Why Does It Seem So Challenging Now To Send A Manned Crew To The Moon, When We Were Able To Accomplish This Over 50 Years Ago?
Space travel is always challenging, but I would argue it has more to do with motivation. After the Apollo missions, there just hasn't been a need or want to go back. We all have our sci-fi desires, but until there is money to be made (even on research), there hasn't been a point to go back. That mood encouragingly seems to be shifting and a manned mission may be on the horizon again.
#66
Eli5: What Makes A Beer Belly How It Is, Round And Hard? What Makes It Different From A Normal Stomach Or A Soft(Fat) Stomach?
If you st*b your belly with a knife, first you will cut the skin, then subcutaneous fat, then your abdominal muscles, then visceral fat, then your organs.
That means if you press your belly and feel softness, you are pressing against your subcutaneous fat. Cutaneous means skin, and subcutaneous means below the skin. If you press against your belly and feel something hard, you are pushing against your muscles.
If you have a big belly, but it's hard that means that you have a lot of visceral fat. Visceral means deep. It feels hard because you are pressing the muscle, but there's a lot of fat behind the muscle which causes your gut to bulge.
This visceral fat is very dangerous. It's right next to your organs, so it can "spill into them". You can get non-alcoholic fatty liver disease, for example. Visceral fat is the thing most associated with heart attacks, stroke, diabetes, etc. In fact, measuring your waist size is probably even better than measuring your weight or BMI.
Drinking alcohol causes beer bellies. Taking in a lot of calories causes beer bellies. And most importantly, genetics causes beer bellies. Asian people tend to store their weight in their belly, which means they can get heart attacks at far lower BMIs than other races.
Fortunately, even though visceral fat is the most dangerous kind of fat, it's the easiest to lose. Cardio like running, swimming, cycling can melt away visceral fat. It's the first kind of fat to go.
As a last thing, sometimes people say that if you have a lot of visceral fat, you are apple shaped. Your gut is big and your arms and legs are small. If you have a lot of subcutaneous fat (especially in your thighs) you are pear shaped.
#67
Eli5: Do Birds Fly For Days While Over The Ocean? How Do They Sleep?
I can actually answer this because of a podcast my 3yo son loves.
Two methods: Some birds will fly for weeks at a time non-stop, and they sleep in burst of only a couple seconds, and usually glide while doing so. They do this a few times a minute, so it builds up.
Others essentially sleep half their brain at a time, like some whales do. Like, they literally keep flying on autopilot while the left half or right half of the brain sleeps, then they switch sleeping to the other side.
Science-wise, we have NFI how animals do either of these things, but that's because we have NFI about the sleep mechanism in general.
Edit: NFI = "No fing idea". I wrote this on my phone when I woke up at 2:30am, so got lazy towards the end. Apologies for any confusion. Where I live, I think it's a normal acronym/phrase. My bad.
Edit 2: The podcast is "Imagine This" which is done by ABC Kids here in Australia. The ABC Kids Listen app has a few really good ones for young kids, from educational to fun to go-the-fuck-to-sleep. The ABC Kids Listen live streaming is geoblocked outside Australai, bit you can still download the app and listen to most podcasts anywhere in the world (according to their FAQ's). Also they have transcripts of almost all their podcasts for the deaf and hard of hearing.
#68
Eli5: Why Is Armpit Sweat Much More Pungent Than Sweat From Other Areas Of The Body, Such As Back Sweat?
Armpit sweat glands are known as apocrine sweat glands, and instead of just sweat, they also produce a mix of proteins and lipids. The bacteria on your skin love that stuff and eat it up, producing waste products in the process. It's those waste products that smell bad.
tl;dr: BO is mostly the smell of bacteria poop.
#69
Eli5: Why Are Password Managers Considered Good Security Practice When They Provide A Single Entry For An Attacker To Get All Of Your Credentials?
Because they prevent you from doing worse things- like using bad passwords because they're easier for you to remember, or reusing the same password for everything, or writing down your passwords
Edit: for those asking, writing down your password is particularly dangerous in shared spaces (like corporate offices). Imagine a scenario where a school teacher, who has access to all of the students grades and personal information, has their password written on a sticky note on their monitor
#70
Eli5 : Why Does Travelling Make You Feel So Tired When You've Just Sat There For Hours Doing Nothing?
Former flight medic here. There is lots of data on the "stressors of flight" (many of these stressors are also present in automobiles). As the vehicle moves, the sway and direction change cause you to have to keep yourself upright. These micro movements cause your muscles to be continuously working (even if you don't realize it). The US Air Force has done studies report conistent exposure to aircraft vibrations can lead to fatuige and increased chance of health problems.
#71
Eli5: How Do Recycling Factories Deal With The Problem Of People Putting Things In The Wrong Bins?
Hi :-)
In addition to what had been said (manual sorting, or just burning it in a cogeneration plant) there are a lot of methods to sort automatically.
Magnets: Get all can lids, nails and stuff out of the garbage.
Air: Lighter stuff will be blown onto a different path. Also, electro static.
Lasers, light: By shining light or lasers on/through plastics, you can determine what plastic it is. To some extend.
Optical recognition: Especially in bottle recycling, cameras and computers will check if bottles are damaged or still contain dirt.
Soak it: Some things float or dissolve. Think paper vs plastic, wood vs metals.
Burn it: When you burn stuff, you can not only use it to heat water and drive a turbine (generate electricity). Things like metal will melt and can be retrieved later. Depending on the metal, they have different melting points and density, so this way you can seperate many different metails.
#72
Eli5: Why Are Modern Artists Able To Draw Hyper-Realistic Art Using Just A Pen/Pencil, But Artists From 100+ Years Ago Weren’t Able To?
Besides the technical issues listed here, before the advent of impressionism, realism was highly desirable in art. Take a look at, for instance Caravaggio. Although the lighting is stylised the depiction of human forms are incredibly accurate. When the Impressionist gained traction people realised that an artwork could be more than a moment captured in time and that feeling could be more important than realism. This led directly to the many forms of modern art.
So what you may be thinking is that people were unable to paint realistically but they could, they just chose not to as they explored the more abstract nature of art, and hence images such as those made by Dali, Picasso, Rothko et al.
To be clear, I'm not an artist or art historian, so I may be wildly off base here, this is just my understanding of art history from having read a handful of books.
#73
Eli5: Why Can't We Recycle Plastic In The Same Way We Do For Metal? Melt It And Remold It?
Not all plastic melts. “Thermoplastic” ones melt when heated, but “thermosetting” ones are made strong by complicated bonds that don’t break down with heat. They will catch fire first.
This is a partial answer, naturally.
#74
Eli5 What's The Difference Between The Shiny And Dull Side Of Aluminum Foil? Besides The Obvious Shiny/Dull
When they're flattening the material with rollers, it eventually gets so thin that passing it through the rollers on its own would tear the material. To solve this, they pass 2 layers through the rollers at the same time.
The shiny side of the foil is the side that was facing the rollers, and the dull side is the side that was facing the 2nd sheet.
#75
Eli5: Why Do The Oscars Tend To Favour More Critically Successful 'Artistic' Movies, Whilst The Grammy's Favour More Commercially Successful 'Mainstream' Music?
I can only try and explain from the Grammy point of view as a voting member there. Basically voting for the Grammys becomes more of a political manner in the industry than simply voting for the "best" record in each category.
The way the voting process works for the Grammys is that there are these sub-committees for each and every category. I have no idea how someone gets onto one of these sub-committees but the people on them don't seem to change much. Every year these committees convene and decide which albums out of the hundreds in each category get nominated. Then around fall of each year the rest of the voting members get sent a packet and we're allowed to cast our vote for the nominees in 5 (I think?) categories - to seemingly keep everyone from voting on every category that they couldn't have an opinion in. (Like I probably shouldn't vote for best "world music" album since I have no idea who any of the artists are there) As a side note everyone gets a free vote for some popular categories like artist of the year, album of the year, etc.
Because of these subcommittees whittling down the voting pool, by the time the vast majority of the academy gets to vote on the winners - the most "popular" artists seem to be the only choices. I think it's due to the fact that the sub-committees don't change very often and so the members on them try and pick the nominees not based on what's best but who they know who worked on the albums. It's definitely an odd way to vote and I'm not sure if the oscars are any different.
#76
Eli5: In Ancient Times And Places Where Potable Water Was Scarce And People Drank Alcoholic Beverages For Substance, How Were The People Not Dehydrated And Hung Over All The Time?
That is almost entirely a modern day myth. There were systems in place to ensure the town's water supply wasn't contaminated and drinking water in most of the world was perfectly fine. They even had a system where tanners and blacksmiths and such would be fined if their cast offs made it into the water supply and they were only allowed to operate in certain areas of town to keep the water supply clean.
The laborer's DID drink a lot of ale and beer while working but it was because the alcohol content was so low that it kept them hydrated and helped give them calories to keep up their energy. It was more like medieval Gatorade than actual alcohol as we think of it.
#77
Eli5: Why Is It Possible For People To Understand A Language But Not Speak It
Listening/hearing is a passive skill, but speaking is an active skill. A passive skill is something you are able to do without any real effort. This can include reading and learning, or listening to a language. All you do is collect the information. An active skill is something you physically have to do, which requires a bit more effort. Instead of reading a book, you have to write a book, or write a speech about what you read. Talking is an active skill. It requires thought to mouth co-ordination. Some foreign languages require sounds not pronounced in your mother language. You know what the sound sounds like, but it could be too difficult to maneuver your mouth and tongue to pronounce it. When you listen, the correct syntax and form is given to you. When you talk, you have to think of the syntax and put it into practice. In other words, when you listen, the other person does the thinking for you, but when you talk, you have to do the thinking.
I dare say that confidence also plays a role. Some people know a language, but are a bit too timid to speak it because they are afraid of sounding stupid. In that case, they avoid talking, or claim that they cannot. However, they do have a fair grasp of the language, so they understand it okay. If a person who thinks they can't talk is forced to do so, then they usually adapt and end up talking without too much issue.
#78
Eli5 - Adhd Brains Are Said To Be Constantly Searching For Dopamine - Aren't All Brains Craving Dopamine? What's The Difference?
Less ELI5, but might be interesting:
Neurotransmitters don't have a single function. There are things called neural pathways, and each neurotransmitter does different things in each pathway. The most notable pathway to be affected by ADHD is the reward pathway. It goes through lots of parts of the brain, including memory, capacity to make decisions, capacity to plan.
This pathway makes sure that if we do something good,we feel pleasure. That pleasure is then stored with the memory of the action, associated. When we try to make a decision, our brain brings back memories of things that brought us pleasure, meaning we remember things that worked, and prepares (primes) us to feel that satisfaction again.
When you have ADHD, your brain doesn't keep enough dopamine floating in that particular pathway, which means you don't feel satisfaction when doing things that would normally be rewarding. That lack of satisfaction is stored, marking the memory as unimportant. When you try to plan for something, you don't have experiences to draw on at first.
That is why ADHD causes executive disfunction, in the form of memory issues and complications with decision making.
And, of course it means that while you are doing something, your brain doesn't show you that it is an worthwhile action. That means you have to fight to stay focused, as your body tells you shouldn't. And when you do hit on a loop of reward, your brain goes "THIS MATTERS! DON'T STOP!". and breaking free to pay attention to something else becomes almost impossible.
ADHD is really interesting! If a big pain in the a*s to have.
Edit: Please keep in mind that I'm not a doctor. I'm taking some classes on the topic for an education minor, nothing to do with mental health. I'm also Autistic, so my own experience might be different from yours. Do not take my word for gospel, but only as a way to guide your own research in the future, and a way to ask good questions from your doctor.
If you want a good entry level overview on ADHD, Dr Tracey Marks has some good information on her Youtube channel on the topic. entry level being the important part.
Be well friends!
#79
Eli5: If Bacteria D*e From (For Example, Boiled Water) Where Do Their Corpses Go?
Another way that dead bacteria are a problem is when you treat tuberculosis. Live tuberculosis bacteria hide from the immune system, but dead ones don't hide well, and their insides are poisonous as well, so you start to feel really bad before feeling better.
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