ELI5: Why do you change shoes when you go Bowling?

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Two reasons. So little pebbles stuck in the soles of your shoes don’t scratch up the wood floor, and because having a little slide actually helps you bowl better.


Bowling shoes have leather soles that allow you to slide on the wooden lanes.

Most modern sneakers have rubber soles, that won’t slide. They will also scuff and damage the wood.


If you wear regular shoes you will stop short and eat shit lol there’s pads on the bottom of bowling shoes to help you slide (your feet slide when you bowl, you may not notice but it just naturally happens)


Bowling in regular sneakers is terrifying.

I tried it once after I prematurely took off my bowling shoes at the end of the game. Nope.


Fact: The need to use custom shoes at a bowling ally was a CIA invention. This is how they would track us all and locate potential troublemakers. The ‘bowling technician’ would check in your shoes and then insert the tracking device, most commonly, in the underside of the tongue. It’s still practice today, using micro trackers, most commonly by way of an aerosol can.


ELI5 What are the differences between clementines, tangerines, and other orange-like fruits?

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They are all quite closely related. All modern citrus fruits are a genetic mix of 3 original species: citrons, pomelos, and the true mandarin. Due to this close relationship, any citrus fruit can cross pollinate with any other citrus to create a different variety.


They are hybrids of different original citrus fruits. Clementines are hybrids of sweet orange and mandarin. Tangerines are hybrids of mandarin with small amounts of other species, primarily pomelo.


No one going to post that graphic that shows the relationships?


ELI5: Why do so many loading screens go to 90% really quick, then take just as long or longer to finish the last 90%?

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Here is one example:

A progress bar shows the total progress of all tasks being done. Each individual task might be different and it may not be easy to determine how long it will take (some recursive functions).

So instead of calculating the progress of each task, it will just move the progress bar forward each time one is completed. So say there are 10 tasks to do:

Task 1 of 10 complete, move the bar to 10%.
Task 2 of 10 complete, move the bar to 20%.
Task 3 of 10 complete, move the bar to 30%.

And so on. Each of those tasks can take longer than the other so the progress bar can appear to jump in some places and stop in others, instead of a smooth transition from 0% to 100%.


Sometimes progress bars are not showing an actual progress of a process. They just “programmed” to go 90% in some period of time. This period is not always the same. Sometimes progress bar moves faster or slower. When process ends, a progress bar just goes from 90% to 100%.

This is a common thing in web sites, when you need to show user that something is happening, but you don’t want to use an endless spinning loader.

Source: I’m a software engineer


Imagine garbage collectors driving round their set path. 90% of their work is grabbing all the trash and putting it in their truck. When they get back to the dump, they need to empty the truck into the trash pile.

Now imagine that while they’re dumping the trash into the trash pile, but bunch of the trash in the truck is really sticky and won’t come out easily. Now the workers need to go and scrape off all the sticky stuff and put it in the pile, which makes that last 10% of work much longer than expected.

This is very similar to when a program is finishing what it’s doing and therefore ‘dumping’ its saved data that it doesn’t need anymore. Hope I helped a bit…


I worked for a game company once that intentionally added some time to a loading screen to ensure there is enough time to read what is going on. No sense having loading screen tips that last half a second.

This was for a console and this was the only place in the game that conveying these small bits of information would fit. This was also a very light game so while it is one explanation, it is definitely not the most common.


Here’s one of the simple reason other comments have missed out.

They lie. There is no reason to trust the progress bar as accurate description of what’s happening in the system.

In an ideal progress bar, 0 to 10% should take same time as 90% to 100% by any reasonable definition of progress. Software companies lie about progress of completion to give us an illusion of completion. This happens all the time.


ELI5: What is the dark line that pregnant women get that goes from their belly button to their pubic region, why do they get it, and when/why does it disappear?

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The *linea nigra* (literally “dark line”) is an effect produced by growth hormones from the placenta. It usually fades after the baby is born.


i never developed a linea nigra in any of my pregnancies. so it’s not a universal thing. (also did not develop stretch marks, but I did develop children, so was definitely pregnant)


To add to what everyone else has said, the Linea nigra need not appear only during pregnancy. Since it’s caused by a hormone, people with hormone imbalances, or diseases like PCOS, can also get it. Also, people with darker skin (like SE Asians or Africans), are more prone to it, because their skin naturally contains more melanin. Adolescents can also get it, because of the swirl of hormones that occur during puberty.


I had the linea nigra with my first pregnancy. By the time my son turned one it had faded but not completely and I found out on his first birthday I was pregnant for the second time. I thought it would come back dark since it hadn’t completely faded. Instead it continued to fade over the next couple if months completely.


Its not only pregnant women who get it, I got it during my puberty years which is like most commenters said, due to hormonal changes


ELI5: Why does does unresponsive software sometimes start working normally the second after I try to close it?

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That depends on why it’s being unresponsive.

Usually, it’s unresponsive because some process is blocked or waiting on a resource that it can’t access. When you click the close button, or when you force it to close via the task manager, you tell those processes to stop doing whatever they were doing. Since they’re no longer waiting on resources, the program becomes responsive again–but since you clicked close, it closes.


When you click the close button, it sends a high priority signal to the software to release any resources it has. One step in this is to immediately terminate whatever the program was attempting to do. Software appears to respond because it gave up whatever job it was trying to accomplish.


The software is a kid doing a really hard puzzle that he cant figure out, and is completely focused on it.

You are waiting on the kid to finish his puzzle but he just cant, so you tell him to forget the puzzle. He says oh okay, drops the puzzle and gets up to leave.


You’re clearing a stuck process by killing all processes.

Say you have 4 paper balls you’re trying drop through a tube into a basket.

1 goes through fine.

2 goes through fine.

3 gets stuck.

4 sits on top of 3.

I spray gas on the balls and light them on fire.

Ball 3 burns enough to drop through.

Ball 4 goes through fine.

Sadly, all the balls burn to ash.


Sometimes when things get unresponsive I open up task manager as sort of a threat, and just like that shit starts working again. Or maybe it just makes me feel better.


ELI5: What’s the difference between sonata, concerto, symphony etc. in classical music?

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Symphony: Full orchestra piece not centred on one instrument.

Concerto: Solo instrument accompanied by an orchestra.

Sonata: Solo instrument usually accompanied by piano (or another keyboard instrument). Can also be a solo keyboard piece.


Sonata is a musical form, meaning that the way the music is arranged is in a certain order. (Exposition, Development, Recapitulation) It’s a way for a composer to fully explore musical themes and show off their compositional skills. Sonata can also refer to a group of pieces (usually 3 movements), the 1st movement being in Sonata form, the 2nd movement usually being slower shorter piece, and the 3rd movement being in some sort of Rondo form. Throughout these 3 movements there can be re-accuring themes and harmonic progressions linking all 3 movements together.

Symphony is in reference to the full orchestra, not to be confused with symphonia which is also a musical form.

Concerto is a style of composition that involves a symphony, but emphasizes one or two specific instruments which are the “soloists”


And what about the differences between Minuette, Bolero, Requiem, Nocturne, Serenade, etc?


Sonata is a long solo. It gets performed by a soloist.

Concerto is piece for a soloist and an orchestra.

Symphony is a piece for an orchestra.


ELI5: Why is everything so much more interesting when you’re procrastinating?

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Dopamine is the main reason, we usually like scrolling on social media over studying, because dopamine works when there is expectation of something satisfiying’s about to happen. For example, dopamine is secreted when you are looking for a funny post, not when you actually find it.


I’m too lazy to describe in detail but it’s basically because your brain is wired for short term gratification. You are probably wiring your brain for these short bursts of dopamine every day without even realizing it. Checking your phone first thing in the morning, checking every notification you get, scrolling on social media endlessly. It rewires the brain to appreciate short term gratification and dopamine, making real tasks seem abysmal and boring so you’ll take anything else but the task.


Also, if it’s a real problem look into ADHD. It’s a real struggle for a lot of people. Social stigma has turned it into kind of a joke thing but if you really have it, medication can totally transform your life


Boredom is illegal to a procrastinator. If you’re bored, then you could be cleaning, etc. But if you’re never bored then there’s endless fascination to waste your concentration on.


You can think about it on multiple levels: biochemically and experientially (how it feels for you when youre living through this).

Biochemically: There are reward pathways in the brain that like short-term gratification, so you get “happy chemicals” when you do the short-term gratification which makes you feel enjoyment/reward.

Experientially: Focus is a hard thing to develop, like a muscle. When you are trying to force yourself to focus on something that isn’t easy/fun, you are constantly thinking of other things and easily taken off track. And when you impulsively click away from your target task, you get the biochemical burst of happy chemicals, since that is what your brain is used to.


eli5: Why is it that bone growth hurts (growing pains), but skin stretching doesn’t hurt (stretch marks)?

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We aren’t actually sure that that’s what causes growing pains, as an aside.

That said, I always assumed it was the muscle strains and tendon stresses as anchor points grew away from each other faster than the muscle and tendon could keep up with.


Skin is supposed to be stretchy (so we can do things like bend and breath) while bones are not


Skin stretching hurts. I was in a wheelchair for 4 months + 3 more months on crutches before I could walk again. The months of not using them plus swelling made the skin super tight on my feet, so I had to work on stretching my skin back out. Not just by moving my ankles, but moving around the skin on top of my feet too. I lost all of the extra folds of skin on the knuckles of my toes, so I had to stretch the skin on each toe back out to be able to bend them again.

Shit hurt.

Skin is pretty stretchy though. Before long it had stretched back out and doesn’t hurt anymore. I’m sure moving around for the first time as a baby hurts too, folding our knees and elbows for the first time, we just don’t remember it.


Not all bones grow at the same time or same rate. So you will go through periods where your knees literally don’t fit together or your shoulder clicks slightly out of place, etc… there’s not a ton of flexibility there. I will add however, that acne on a stretch mark does hurt really really bad though.


Growing pains happen over a much faster time frame than stretch marks do. Growing pains also involve the growth of bones, while stretch marks (usually) do not. Put these two known facts together and it’s easy to see why you hear about one more than the other. That being said, stretching, even for a moment, can hurt if pushed too far. Stretching over time can also result in pain, but it’s not a commonly reported or talked about occurrence. As said in the comments, pregnancy can result in a painful itch due to skin stretching over time, and I can personally attest to knowing a person who snapped a tendon in their foot when they stretched it to far because they over extended it during a stretch.


ELI5: How did soldiers in hot countries in middle east and India survive the heat during wars wearing a metal body armor when temperatures in these regions touched 35 degree celcius (95f) in summer days?

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Reminder: Top-level comments (direct replies to OP) are reserved for explanations. Anecdotes and off-topic comments will be removed.

You do not need to comment on how hot it gets in the Middle East. You are not the first person to do so.

You are also not the first person to remark on modern soldiers serving in the Middle East and the gear that they wear.


One of the popular theories is the surcoat, a light cotton coat worn over the armor. This would keep you a bit cooler because it would stop the (heat absorbing) metal armor from being exposed to sunlight while also shielding you from the sun, especially if it’s a lighter color. Typical Arab clothing, even in the modern day, consists of a full-length white coat for exactly this reason. If you look at historical images of Persian, Turkish, and Mamluke warriors they’re often wearing a surcoat or robe over their armor. Even more interestinglly if you look at the Bayeux tapestry, the Norman Knights are not wearing surcoats, but later depictions of English and French knights, from after the crusades, do show them wearing surcoats, suggesting it was a fashion the knights picked up in the middle east.


The thing that hurts in that area of the world is the sunlight at the time you’re describing. The cultures of that part of the world often employed cloth and chainmail as much as they could, as it is light, climate resistant, and it’s adequate protection against the weapons of the ancient era, where metal armor worn by soldiers was actually common. Now, it’s a different story because full metal armor doesn’t often see combat unless mounted to a vehicle, which means you might be cooked alive inside it, but you aren’t carrying it yourself. But essentially, ancient middle eastern armor was only metal when it was necessary because of how much of a pain in the ass it was to use. So to answer your question, they *didn’t* survive wearing full metal body armor, because it wasn’t really what they wore.

Hell, even Persia, a country that could *afford* to outfit their troops in steel, never bothered with metal armor or shields and instead used cloth and leather armor, and they used wicker-woven shields, but used metal weaponry.


It was a huge problem, the battle of Hattin was won by the Muslims in large part because they cut off the crusader’s supply of water and didn’t attack until the next day. The armor they were wearing was a huge problem and they were roundly slaughtered and lost the cool cross they were trundling along. It was after that battle that Rayanald de Chatillon was executed by Saladin for speaking out of place, and multiple massacres of Muslim civilians.

So the answer is muli-pronged. Arab armies eschewed the kind of heavy armor that was popular in Europe and earlier Grecian armies. Roman armies would wear modified armor in battle, this was true of the Eastern Roman army that was dominant long after Rome fell. Leaders needed to make sure their armies had easy access to water and to shade. If they didn’t, armies failed.

This was true even in WWII where a bunch of logistical resources were spent trying to get water on these arid and hot Pacific Islands. Veterans talk about the experience of being truly *thirsty* for the only time in their lives.


Chainmail is surprisingly heat resistant. There would also be frequent changing of guards so they could remove armour and helmets on breaks and get water to drink. The guards were also acclimatised and conditioned to work in these conditions.

Solid plate armour was a much more western design and occured later in the development of armour than most other types (though there are some very early examples of basic plate origin armour). This meant it was only for a relatively brief part of history that it was used. Further it was far more expensive than your average guard could afford, or that they’re lord could afford to equip them all with. Therefore only the wealthy lords (read knights) would be equipped with full plate armour. Most western troops would wear chainmail (internecting rings to form sheets that can be connected into armour that is very effective against slashes but can be pierced with thrusts or pointed weapons, giving rise to the more pointed swords and polearms) or gambesons (surprisingly effective cloth armour known to stop arrows and sword strokes).

Obviously it varies massively from time period to time period even within the realm of “medieval” and the location in question, so please take everything said with a pinch of salt with whatever you have imagining in your mind and do some research to verify what you now believe. 🙂

TL;DR – They wore cooler armour, took breaks and got used to it. Plate armour wasn’t common, long-winded explanation about western armour unrelated to the question.


ELI5: How can a psychological factor like stress cause so many physical problems like heart diseases, high blood pressure, stomach pain and so on?

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None of these responses seem at the ELI5 level. Let me try:

“Stress” is your brain thinking there is a threat and telling your body “do what you have to so you can get through *right now* and we’ll sort it out later.” So your body floods itself with chemicals that it thinks will help you overcome whatever threat the world has thrown at you – this is when people talk about “super human strength” for example.

The goal of this is to fight off a bear or out run another predator. These chemicals that get dumped into our body are highly toxic to us in the long run, but what does that matter if you die to this threat *right now*?

The issue for public health is that your brain is setup for living in the wild and doesn’t know that an unexpected meeting with your boss is not a threat to your life. So now we have a situation where we are constantly dumping toxic chemicals into our bodies for prolonged periods which causes all the problems you mentioned.


Stress *is* physical.

Oh sure it can have a psychological cause, and colloquially those might be what the word is used for, but what it actually is is a heightened state of activation of the sympathetic nervous system, the body’s fight or flight response.

High blood pressure is an intended feature of the sympathetic nervous system. It helps get blood to your muscles if you’re trying to outrun a lion.

Maintaining high blood pressure for months or years in a row isn’t great for your heart.

All the blood vessels going to your digestive system get partially shut off since really if you’re running away from a lion you don’t have time to worry about digestion right now. Do *that* for too long and your stomach lining might not be able to rebuild itself as fast as your stomach acid is dissolving it.


When you experience stress, your body will respond by preparing for danger, it is designed to do so. It is a great system for when you think a lion may be near.

Increased cortisol heigtens your alertness, adrenaline increases heartrate. You are ready for fight or flight. You’re basically a racecar in the red. Like racecars, your body is not designed to be in the red all the time. Stuff starts breaking down after a while.


Sorry, I need to ask to clarify and put in simpler terms of what people are saying:

So the “stress” or pain in my chest area is not just me imagining it, but a physical reaction? (I don’t have high blood pressure and heart diseases, yet.)

Ex. When I feel hurt emotionally/breakup, my heart hurts literally.
Ex. When I procrastinate and can’t focus on finishing schoolwork, I feel a clenching feeling in my chest.


It’s kind of an evolutionary leftover.

Your stress response is part of your fight or flight mechanism. You come under attack and your body prepares itself to fight or escape: Your heart rate picks up, you breathe harder and faster, your blood pressure increases, your blood stream is flooded with adrenaline… all the things you need to make you more alert, more resistant to pain, able to fight harder or run faster.

The problem is our fight or flight response evolved to deal with physical threats like predators. Short term crises. As cavemen we were born, we hunted and foraged for food, we reproduced and died. Our stress response was perfectly suited to that sort of lifestyle.

Today, most of our stress comes from non-physical factors, things that last way longer than it takes to stick a spear into a wolf or run like hell from a lion… and our stress response can’t tell the difference between being physically threatened and getting an unexpected bill we can’t pay, or worry about losing our job because we heard our company is downsizing.

Basically, think of your body’s stress response as gunning a car’s engine and hitting the NOS. It gives a massive increase in performance, but the engine isn’t designed to take that amount of stress for long periods of time