#1 Eli5: Why Do You Need A Master's Degree To Become A Librarian, Especially When The Median Salary Is Barely Above $50,000?

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.
#2 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?

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.
#3 Eli5: If Ants Love Sugar, And Bees Make Honey, Why Aren’t Bee Hives Constantly Attacked By Ants?

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 Can People Walk Many Miles Without Discomfort, But When They Stand For More Than 15 Minutes Or So, They Get Uncomfortable?

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.
#5 Eli5: Why Do Ships Have Circular Windows Instead Of Square Ones?

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.
#6 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?

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: How Come All Those Atomic B*mb Tests Were Conducted During 60s In Deserts In Nevada Without Any Serious Consequences To Environment And Humans?

#8 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?

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.
#9 Eli5: How Come You Can Be Falling Asleep Watching TV, Then Wide Awake When You Go To Bed Five Minutes Later?

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.
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: When A Baby Is Born, How Are Their Lungs Instantly Able To Breathe Air If They Haven't Been Breathing Air For 9 Months?

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.
#11 Eli5: Why Do Alcoholics D*e When They Stop Drinking?

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.
#12 Eli5: Why Can't We Have Supplements Or Pills For Dopamine, Oxytocin, Serotonin Or Endorphins Just Like We Have Melatonin Or Contraceptive Pills?

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 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?

It's a trade off between needing to find a variety of food and not needing the cellular machines to make more stuff.
#14 Eli5: Why Is W Called "Double U" When It Is Clearly "Double V"?

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.
#15 Why Is 12 Hour Time Even Taught? Wouldn’t It Just Be Easier To Remember 13:00 Instead Of 1:00pm?

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.
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: 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?

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.
#17 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?

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.
#18 Eli5 What Is It About Grapefruit Specifically That Messes With Pretty Much Every Prescription In Existence?

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: Why Is Finding "Patient Zero" In An Epidemic So Important?

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.
#20 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?

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.


