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How did early humans develop opposable thumbs?
Evolution does not work that way. It isn't as if some creature is sitting around thinking "this mutation woukd really help us" and suddenly his kids develop the mutation. The mutation occurred randomly and the environment was so that he survived while his non-opposable thumbed brethren did not. This meant he passed on his genes **THAT OCCURED RANDOMLY**
Why are ships referred to as "her" or "she"?
Because it's mostly men who own them, they're super expensive, they cost a ton to maintain, and they're hella fun to ride.
How can acid eat through metal, but not a glass/plastic cup?
I'm not sure about the exact solution they are using, but I'm going to use aqua regia as an example. Solid metals are composed of metallic atoms arranged in a metallic lattice, with metallic bonds connecting them NOT chemical bonds. These are much weaker and can be sheared with less energy. Gold, as we know, is very unreactive to most things (one reason why it's used in coins and jewelry). However, aqua regia (3:1 mix of hydrochloric acid and nitric acid) is a special mixture that produces extremely reactive atomic oxygen. This mixture reacts with the gold and forms chloroauric acid that is soluble in water. On the other hand, glass is a very stable material and tightly bonded, which prevents most chemicals from breaking the bonds inside it and causing cracking. One exception is hydrofluoric acid, which is used to etch glass and must be stored in even more unreactive polymeric containers, like polyethenes and such.
What is an itch, why does it bother us, and how does scratching it make it go away / feel better?
Scratching an itch, releases endorphins instantly into the surround nervous system area. It provides instant gratification but ultimately makes the itch worse. Like smoking crack and getting an instant high but then coming down. I actually have no idea what I'm saying.
Why SSD is better than Hard Drive?
For one, they're faster. *Much* faster. Insanely faster. It's not even close. If you were to compare it to running, it'd be a bicycle vs a car. Additionally, SSDs can be much smaller in size, are more durable, and use less power generally. Much of this is due to physical HDDs' physical limitations. In a HDD, there are actual magnetic disks which must spin for you to read or write data, while SSDs, like their names imply, do not. While this means that, with today's disk technologies, storage space is insanely cheap with HDDs, they lose out in pretty much every other aspect to SSDs.
How do animals in eggs know when to hatch?
Genetic programming. Remember how you latched onto your mom's boob for your first meal? OF COURSE NOT. But you did, because it was genetically programmed that you had an instinctual latching-on process to get that milk into you (or, alternately, from a bottle if you weren't breast fed). Animals are the same. They bust out of the egg when their genetics tells them it's time to based on their level of development, whether or not they have a yolk sac still attached (like many fish do) or they're pretty much 100% complete and ready to go.
What are skin tags and why do we get them?
A skin tag is actually a benign tumor that usually forms where skin creases, like the neck or armpit, and sometimes the eyelids. They are almost always harmless. They're very common (moreso in women than men), and thought to be formed by skin rubbing on skin, but the exact cause is unknown. They're safe to leave and safe to have removed - they don't grow back. Be sure to consult a dermatologist for advice.
What is "Salisbury Steak" made from? And is it just a US commercially made food or does hit actually have roots in England?
Its roots are in the USA, not the UK. It's named after Dr. Salisbury who invented it in the 1800s. It's mostly ground beef but may contain some pork depending on who makes it. [Details.](_URL_0_) There is a similar food in the UK, called a *grillsteak.*
How come standard pixel widths (360p, 720p, 1080p...) correspond to the number of degrees in a/several full rotation(s) ?
It's the beauty of maths. The two aren't related besides the fact they both divide down really well. 360 divides by 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15 etc. As a percentage of these lower numbers that's way more than almost any other (this is also why a lot of people have and still do believe that base 12 counting is superior to our base 10) It's just simply that because they divide and multiply together so well they are so easy to use. Say you want to double a resolution at 360, well that's easy for any number. But say you want to shrink it to 75% size, or any other fraction.... Works super!
Why does string theory require 10 dimensions?
Yo man, I respect this subreddit, but string theory might be a little too ambitious for ELI5.
Google's new parent company Alphabet?
Alphabet is an umbrella company with Google as one of its subsidiaries. Unlike a corporate takeover, where one company purchases and generally absorbs another, Alphabet was created by Google in a bid to 'restructure' their sprawling organization.
How do movie makers hire actors to play 'ugly' roles.
Many actors of course find it insulting, but work is work, and getting acting work you gotta take what you can get, its hard.
How does lucid dreaming work? What are some of the most reliable methods to induce it, and how soon would you expect it to start 'working'?
I think some people can do it, and others simply can't do it. I've read some articles about it and a reliable method seems to be video gaming. putting yourself into some virtual reality for a long time seems to make it easier to trigger this lucid dreaming state. I've played ALOT of video games and MMO's and I'm pretty much aware in every dream I have, lucid dreaming is both a lot of fun, and a curse. It's a lot of fun to be able to control your dreams, but after a while you can start to feel "disconnected", you can experience a sorta Neo from matrix sorta feeling, if you are never able to truly dream. Anyhow - hardcore online gaming for 5-6 years should do the trick.
If both parties agree gerrymandering is bad and accusing the other side of the aisle, what is truly preventing gerrymandering from being outlawed?
Gerrymandering is only bad for one party, and it's great for the other. So despite both parties agreeing that it can be bad, they also know they can benefit greatly from it. The benefit for them outweighs the detriment, no matter how much they want to whine about how bad it is to appease to voters. After all, they might lose some districts if they end gerrymandering.
What exactly makes that knuckle-cracking-sound?
When you release pressure on the joint, dissolved gases in the joint fluid expand. Then they immediately dissolve again and what you're hearing is the fluids "slapping" back together. So yeah, it actually is kind of like a bubble "popping."
Why doesn't a garden-hose eventually explode even when the tap is on and the nozzle on the other end is shut-off/closed?
Your plumbing supplies water at a certain maximum pressure. That pressure is lower than the pressure required to stretch the hose. So it's less like blowing up a balloon, and more like blowing through a pinched straw. No matter how hard your lungs can blow, the straw's not going to explode.
Measles have reapeared in the USA because of anti-vaccination movements. Why should I care if I'm vaccinated, aren't I protected from it?
1. The vaccine isn't always 100% effective, and it's possible (though rare) for the vaccine to not work properly for some people. 2. Many people can't be vaccinated (allergy to the materials in the vaccination, compromised immune systems, too young to be vaccinated, etc.), and those at-risk groups rely on everyone else being vaccinated to protect them.
How does the genotyping process that 23andMe use work?
Check out Smarter Every Day's video for a behind the scenes at the factory with loads of useful info: _URL_0_
Penny stock fraud (i.e. Wolf of Wall Street)
Buying and selling penny stocks is normal. Selling penny stocks to investors and lying about what they are (eg A great opportunity, as good as a blue chip, the next Microsoft etc. etc.) is illegal. That's what the Wolf was doing.
Why do some artists sign to record labels and become famous within 6 months-a year while others sign to the same record labels and are worse-off in 6 months to a year when both artist's music/commercial potential is about the same?
> ...when both artist's music/commercial potential is about the same? This is your subjective take on the matter. Perhaps others would be inclined to agree? Besides, music trends aren't always about good sounding music but just what happens to get popular anyhow.
What became of the 'rags to riches' soccer team?
You are talking about the English team Leicester City F.C. and they are still currently at the top of the Premiere League.
Can birds fly in a moving car? If so, how?
If the acceleration of the car is zero, i.e. it is moving at a constant velocity, you might as well imagine it as being stationary. Think of an airplane cruising at 400 mph, people aren't being flung to the back of it, you can walk around, go to the bathroom, and function as if the plane isn't even moving at all. The key here is the acceleration. If you floor it in a car, you feel yourself pushing into the seat, if you brake, you fall forward. But if you're moving at a constant speed, you don't feel anything. Because the car is sealed, air resistance is not a factor, so a bird could fly just as you and I can walk on a moving train or airplane.
how does chemotherapy work without killing us?
Chemotherapy attacks rapidly dividing cells- so you're hoping cancerous cells that are wrecking havoc on your body, but unfortunately this also means it attacks other cells that normals divide rapidly like blood cells and follicle cells, which is why chemo patients often lose their hair and may require blood transfusions. Different classes of chemos attack cells in different ways, which is why some are harder on patients than others. Very simply put, it is a delicate balance between attempting to destroy as many cancer cells as you can without causing so much collateral damage within the patients body that they do actually die.
Why does water seem so cold in my mouth while i chew gum?
When you have "cool" water (say, 10C or 50F) in your mouth, it is draining heat out of your body at a certain rate. If you have ice water in your mouth (0C or 32F), it is draining heat out of your body much faster. Menthol (what makes things smell minty) is an irritant that increases blood flow. More blood flow means a faster exchange of heat. So the cool water is now draining heat out of you much faster, and your brain interprets that as meaning that you've actually got ice water in your mouth.
Why are there jokers in card decks?
The joker is still used in games like Canasta, Gin Rummy and Euchre. By removing it, those games would have to change their rules, which would annoy more people than simply leaving the cards in.
Why do stores leave some lights on even when closed?
So that if they get broken into overnight the surveillance will actually be able to show something.
Why do humans crave sugar?
Sugar, fats and starches are all high-energy food sources. During most of human evolution, we didn't have consistent access to these foods. Our bodies evolved to crave them so we would seek out energy sources (think "fuel" for our bodies). A few more berries or a handful of legumes gathered could fuel our muscles for a few more hours in a day. Today in our industrialized world, fats, refined sugars and carbs are about the cheapest foods we have access to. Since we still crave them from when they were scarce, we are now faced with the reality of overindulgence in these foods which can lead to obesity and diabetes.
The Control Group of a science experiment. How does giving a placebo to a control group do anything?
Let's say you invent a drug that prevents cancer. You have a group of people who are taking it, and another group of people who are taking a sugar pill. You're going to monitor them for 10 years and see which group has better cancer outcomes. Over the course of those 10 years, though, the city realizes that the air and water are super polluted and causing people to get cancer. So they clean it up. At the end of 10 years, both groups have gone down in cancer, but the group taking your drug went down more. Without the control group, you'd have no way of distinguishing the effects of your drug from the effects of other changes in the environment.
Why do touchscreen phones never lose calibration?
Most (if not all) phone touch screens use capacitive touch, while other things, like computer touch screens use resistive touch. I'm no expert, but you can find more information on this article: _URL_0_
Who is Guy Fawkes, why is he so important, and what is the big deal with his mask?
Guy (Guido) Fawkes planned to blow up a few very important buildings. The Gunpowder Plot, as it was known, was going to blow up the House of Lords, but he failed when someone tipped off the feds. On Nov 5 they found him with a bunch of gunpowder and and they executed him (he actually sort of executed himself, but that's another story) So on the 5th of November people let off fireworks. It's sort of a weird holiday, since they blow stuff up in honor of the fact that stuff was not blown up, but there it is. Then there was media. With movies and comics like V for Vendetta and the internet group Anonymous picking up his mask as a symbol for revolution, it became a much bigger deal than it ever was. In V's case, the mask was steeped in symbolism concerning the plot of the media (V blows up parliament and brings about social change) In Anon's case, I think it's more of an irony. No one knows who you are under a mask (being anonymous) and some trolls undoubtedly argue that they are fighting for social change.
Why do some songs on pop radio stations just now start to be played when they are months to a year old?
The record labels control when radio starts playing music. I don't listen to pop radio much, but I feel like "Take me to Church" became popular without radio, then the label released it to radio.
When you smell someone's fart, are you inhaling microscopic vaporized pieces of decal matter?
Most of what you smell is methane and other gases produced during digestion. Not fecal matter.
When a video is uploaded over and over again on youtube, what is physically happeening to make the video quality get worse each time?
Compression. A typical camera records 1080p 30fps at 17Mbps, which is just under 1GB/min. Whereas a typical bitrate on YouTube is ~3Mbps, which is < 1/5 the size. Every time you re-upload it, YouTube goes through the whole compression process again. Compression is where they take a group of similar looking colors and make them a single color (less variation means less data). So, when you re-upload it, the video already has a lot of these groups of similar colors, so it makes these groupings even larger by combining some portions from another group, and so on and so forth. [Here is an example of extreme compression](_URL_0_).
What is a covered bond? And how do they work?
Covered bonds are bonds that are secured by an underlying pool of assets, known as the cover pool. Investors buy covered bonds and so they have claim on the underlying pool. The underlying pool (typically mortgages or loans, but can also be ships, aircrafts, etc) generate cash flow, and that cash flow is passed on to the covered bond holders.
Why does gas you get in the US have so much lower octane numers than in germany?
Your octane numbers and our octane numbers don't mean the same thing. From an engineering perspective the octane number is actually a kind of hilariously arbitrary number that basically boils down a bunch of different fuel qualities, that all both individually *and* collectively control a fuel's likelihood to knock, all into a single number, and because of that the precise testing for octane numbers changes depending on the body doing the regulation. So it would be entirely possible for two utterly identical batches of fuel to get different octane ratings when tested by different countries. However, our fuels are also slightly different, as Europe is going to have a slightly different set of additives than we get in the US, but that doesn't really account for most of the difference; the differing standards do.
How did they do the dinosaur sounds for Jurassic park?
This is the first write up I found with a simple google search: _URL_0_
How can humans sense when they are being watched?
We can't. It is confirmation bias in action. Basically, you have been watched countless times. One of those times you got a funny feeling and happened to notice someone watching you. Ever since, whenever you get that feeling, you believe someone is watching you. Edit...wrong phrase.
Why do so many people get "stuck" in a retail job?
Because it's easy. Because retailers generally always need new employees. Because it's mostly mindless. Because it can be done in pretty much any small town or big city. Because it's usually "good enough" to get by. Because not changing is easier than finding a new job prospect, interviewing, and hoping that you get it over all the other applicants. Because sometimes momentum means just doing the same thing rather than actually moving forward . . .
Should I really stop drinking milk? Are Silk/Almond Milk suitable "replacements"?
> I've been seeing a lot more evidence that humans are not designed to continue to drink milk after infancy. And yet here we are, drinking milk, as impossible as a bumblebee's flight. Don't pay too much attention to this "evidence". It is true that *most* mammals stop being able to process lactose after infancy, but for the large majority of people of European descent that is not the case. Unless you yourself are actually lactose intolerant, this argument carries no weight. As to the other concerns, you can certainly look for products that are organic/non-GMO. Cows produce milk and *must* be milked, so as long as that is done humanely I don't see a moral issue there.
Why isn't everyone using hypnosis sessions or recordings to unlock languages stored in your brain, weight loss tricks, etc?
Anything can work for quitting smoking, because the trick is just to somehow convince yourself that you do not want to want to smoke anymore. A hypnosis session might work just because you think it will. Hypnosis sessions cannot give you knowledge you never had (like how to speak a language), and there are *no* clinically proven methods to achieve consistent and permanent weight loss.
How/what is starting the heart when in uterus. What initiates that very first heartbeat?
In human embryos the heart begins to beat at about 22-23 days, with blood flow beginning in the 4th week when the nutritional and oxygen requirements of the growing embryo can no longer be met by diffusion from the placenta. The heart is therefore one of the earliest differentiating and functioning organs^[1](_URL_1_). The electrical stimulus that causes the [heart muscle](_URL_0_) to contract is *myogenic*, which means it arises within the heart tissue itself and doesn't require any external input.
How is body damage on a car (dents, scratches, etc) repaired?
- Most scratches can be fixed with touch-up paint. - Minor, non-creased dents can be fixed with a dent puller, basically a suction cup. - Larger dents, or creases, can be fixed with something called body puddy, or bondo-o. Essentially you fill in the dent with the puddy until it approximates the original curve of the body, sand it smooth and then paint it to match the surrounding body.
What makes hypoallergenic dogs/cats hypoallergenic?
The part that makes people allergic to cats is actually a protein (FEL D1) found in their saliva. When a cat licks herself, she deposits the protein on her skin, and when it dries off, the flakes become airborne and trigger symptoms of allergy in people. So, it's not the fur that's the issue, it's the dead skin. In short, there's no cat that's 100% hypoallergenic, they can only produce less of the protein FEL D1 than regular cats. Some cats tend to be preferred because of trial and error, and even then, some of the most likely to not cause allergies still do because maintenance is required (like bathing or brushing) to make those pets optimal.
Why is it that when I am standing I get tired easily, but when I am walking I can walk for much longer
I'm just here to say great question. But then sometimes i stand (and do something eg stand and play guitar) and its not as tiring as just standing.
Why does not every rain storm have lightning and thunder?
Lightning only occurs in high energy storms. This means they have a lot of CAPE (convective available potential energy, often weathermen will say instability). It can rain with low CAPE, but it doesn't necessarily come with lightning. High CAPE results in storms with considerably more energy. Areas like the West Coast of the US or the UK are examples of areas that consistently have enough precipitable moisture, but hardly ever experience substantial CAPE values. Areas where it is raining out West right now have CAPE values around 250 J/KG. Tomorrow the parts of the southern plains that will experience severe weather will have CAPE values of 3000 to 4500 J/KG, or more than 10 times as much energy to work with.
Batteries - Generic Vs. Name Brand
Check for an expiration date on the Kroger batteries. Sometimes the no-name batteries have been sitting in a warehouse for years before they get put on a shelf and someone buys them. From my experiences buying batteries from Amazon, I've seen the big names usually put an expiration date on the pack, as if to show they stand behind their product, while the lesser brand batteries almost never have an expiration date. They don't want you to know the batteries you're buying are probably already half dead.
Why is it when someone eats a piece of sharp cheddar cheese, they get the sensation like their forehead and cheeks are sweating?
I have never encountered this and I eat sharp cheddar often, some weeks daily. I have also never heard of anyone encountering this. If you get a flushed or sweating sensation when eating a food and it is not overly spicy then you are likely having some kind of allergic reaction or intolerance reaction and you need to get that checked out and possibly avoid that food. You can also get those reactions from being allergic to spicy foods but it is harder to tell because those reactions are normal to spicy foods even when you are not allergic.
What exactly has Hillary done over the years to not make her trustworthy? I am 17 and want to get educated for the primaries.
Not Watergate. Watergate happened in 1972 and it made Richard Nixon resign in 1974. Hillary Clinton (and Bill) was Whitewater which involved a savings and loan giving improper loans connected to real estate deals. No wrongdoing was found specifically with the Clintons there, but it centered around Bill Clinton as governor of Arkansas overstepping. As far as Benghazi, there have been 10 Republican-led investigations into her and the Obama administration on this one incident and all 10 have found no wrongdoings (It was an embassy in Libya where Americans were murdered). It's just something that her political opponents want to keep in the news in the hopes that it makes her look bad (contrast that with George W. Bush who was president during 13 embassy attacks that no one ever talks about).
If employer applications state they will not discriminate against you based on your race or gender, why do they still ask for that information?
It's usually kept separate from the application, so the recruiter doesn't read it. They will use it if someone tries to claim discrimination to prove they aren't discriminating.
Why are the cooking estimates on Frozen Foods always wrong even if you directly follow the instructions?
Cooking times vary due to the variance in appliances. However, I've noticed that with my particular oven, stovetop, and microwave, the estimated cooking times are pretty much spot-on. Perhaps you have equipment that either cooks too hot or not hot enough to match the expected cooking time. Adjust as necessary.
Why are South Koreans protesting and demanding their president resigns?
Basically, the South Korean President has admitted to being heavily influenced by a group of women who have no place in politics. They are the mostly the wives of large South Korean business-owners who have used her power to profit and further their own agendas. Tinfoil hat aside, it's more of a cult of personality that has operated in the form of a "shadow government." Citizens are quite upset because the democracy is a sham, and again, the President has admitted to it.
why is oil "slippery" ?
The defining property of oils is that they are [hydrophobic](_URL_0_). Hydrophobic molecules are non-polar. That means that the molecules don't really stick to anything. So when you push down on liquid oil, the the molecules just slide around.
How come when I log in correctly, my computer instantly let's me in, but when I type it in wrong it takes 2 seconds before telling me it was incorrect?
This is actually a security feature - it slows down attackers. If they're trying a bunch of different passwords that might be yours (this is called a "brute force attack"), then making it take a couple of seconds to fail means it will take the attacker a ***LONG*** time to try a significant number of passwords. Then it's more likely that someone will notice what they're up to and can stop them before they actually get anything.
Why doesn't McDonald's food decompose?
It does. Those videos are very misleading, and involve fast food that appears to decompose very little only because it is kept in dry conditions (meaning that it dehydrates and essentially mummifies), and then opposed to food kept in more humid conditions that decomposes very rapidly. It's complete BS.
How do we know that ancient languages are interpreted correctly? Same for making first contact with secluded tribes. Is it based on assumption?
Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5:How do historians or linguists decode and translate an ancient language that hasn't been spoken in a long time? ](_URL_3_) ^(_23 comments_) 1. [ELI5: How do we know that our translations of hieroglyphics are correct? ](_URL_1_) ^(_ > 100 comments_) 1. [How linguists are able to translate an ancient languages? ](_URL_4_) ^(_26 comments_) 1. [How do modern humans take ancient language and figure out what it's conveying? ](_URL_0_) ^(_3 comments_) 1. [ELI5: How do we translate languages of ancient civilizations? How much of them can we translate at all? ](_URL_2_) ^(_10 comments_) 1. [ELI5: How do people decipher ancient writing systems? ](_URL_5_) ^(_5 comments_)
Why does TV shoot in 16:9 and movies shoot in 2.39:1
Former Movies theater projectionist here, Movies are shot in 1.85:1 (flat) and 2.39:1(scope/Anamorphic). During the days of actual film in movies theaters, 35mm film size was the standard in all theaters. They were marked scoped or flat which told the theater projectionist to use a standard lens for flat(16:9) or a anamorphic scope lens for the movies, this mixed with a masking system for the screen to open wider for scope movies and move inward for flat movies. So Flat movies in the theater are very close to 16:9(1.78:1) used in the home. So if tv's were actually 2.35 and TV show started to used 2.35 there would still be movies that now would display black bars and the left and right on those TV's. I would imagine if this was the case more and more movies would begin to shoot in 2.35 but in the end the film maker has an artistic choice as to what aspect ratio to shoot in
As a 27M who has smoked since the age of 16, how much of a recovery can my body make from quitting, how long will it take?
When you quit smoking, the inflammation in the airways goes down. The little hair-like projections in the airways that we call cilia begin to work again. So the lungs will get better in weeks to months. Breathing will get better. Exercise capacity will get better. Paradoxically, people find that they cough a little more right after they stop smoking, but that's natural. That's the lungs cleaning themselves out. But if you've been smoking a long time and have developed any chronic obstructive pulmonary diseases, the lungs will never totally heal, for example - Chronic bronchitis. It is an inflammation of the airway, Some of that inflammation can be reversed.
Why do we still use gunpowder in ammunition instead of other explosives that have a much greater energy to volume ratio?
No matter what explosive we use in guns, we'll still call it "gunpowder" even if it's not a powder. It's just a name that stuck. But we've actually changed the formula several times. With small arms, you actually want to limit the speed at which the agent explodes, if you can believe it. Too much energy too fast, and you have to compensate with a stronger, heavier barrel. If you can time it just right, then the explosion provides continuous pressure for the duration of the slug's trip down the barrel. Modern 'gunpowder' is designed that way. Rather than just being the simple black powder that Captain Kirk cobbled together to kill an alien lizard-man, it's now little pellets optimized for stability, timing, reduction of smoke, and power.
If human skin 'regenerates' itself within ~35 days, why don't tattoos disappear along with it?
Tattoo ink penetrates through the first layer of skin, the epidermis, into the deeper layer - the dermis. The epidermis is the layer that routinely sloughs off old skin cells. The cells of the dermis are far more stable and does not shed like the epidermis leaving the tattoo intact.
Why is it easier to balance on a moving bike than one at rest?
So, everyone so far has mentioned inertia and the gyroscopic effect. While these do have an effect, they aren't what keeps the bike from falling over. Simply put, the mass and speeds of the bike aren't enough to counter act you falling over. The true reason why you don't fall over is centrifugal force. If you were to start to lean to the left, the bike starts to take a curved path. This generates a centrifugal force which pushes the top of the bike back to being vertical(on a straight path). Here's the link to an actual [paper on this topic](_URL_0_). If you don't have a math/physics background then you can just jump to the end of it and read the first paragraph of the conclusion.
how did el Chapo and his helpers dig the hole into the prison without anyone noticing? And how did they get such a perfect accuracy on where to come up (precisely into the hidden part of his cell)?
I watched a documentary about El Chapo and the consensus seems to be that Mexico is so corrupt that he surely bought off people. It was an inside job.
What are those jets for in the sky, and why do they leave behind a trail of white behind them?
The airplanes are for transportation of goods and people. They fly very high to reduce drag with less-dense air and to avoid other planes. The trails are kind of like little clouds made from the stuff in the air swirling around as the airplane moves through it. These are called contrails. This is kind of the same effect you get as you drag your hand through water and cause the swirling ripples. Some differences are the density of air and water, the particulates like dust and water vapor in the air, and the size and speed of the wings on the airplane. It is not chemicals or exhaust, except in the cases where that's the purpose, like in an air show or while crop-dusting. You can tell this is not what causes the contrails as those chemical trails dissipate very quickly while contrails can last for a long time.
Why have all the 'big' animals and creatures gone extinct? Megalodon, the Dire Wolf? All these creatures were huge, top of the food chain predators but now don't exist? Yet the sloth; slow, dumb and effectively defenceless has somehow managed to survive?
As per your example, a sloth survives on plants. It uses no energy because it virtually doesn't move. A sloth goes SO slow it actually can have moss grow on its fur. When predators hunt they go for sounds and sights. A piece of moss isn't that inviting. These animals survive because they're specialized to survive. I would guess that enormous apex predators are a burden on the environment and therefore when foods can't be found in enough abundance they die off (also note that most if not all extinctions for the past 10,000 years have been directly influenced by man).
What would happen if a country cut the value of its currency?
it's happened alot with countries with out of control inflation. Iran did did it. they just dropped 3 zero's. i think congo did it too. dropped like 6 zeros.
How galaxies can be hundreds of light years away, and yet we can still photograph them from earth?
First, it is important to level set on the distance. The closest galaxy to the Milky Way is the Andromeda galaxy. It is around 2.5 million light years away. A light year is the distance that light travels in a year. Since light travels at roughly 300,000,000 meters per second, a light year is a very far distance. Now to answer how galaxies such distances away can be viewed and photographed. Time. The universe has been around for billions of years and has been expanding during that time. This means that billions of years ago when the light was emitted from very distant galaxies and started making its way to Earth, it didn't have as far to travel. This is how we can see things that are farther away in light years than the age of the universe.
Can i kill someone when shooting an AK or similar in the air and the bullets drop lets say in a big crowd?
yes, but it's not the most efficient way to do it. You are much more likely to be successful if you aim directly at your target.
Why is the pain of having sore muscles somewhat enjoyable?
If I tell you that the pain you feel in your muscles after a workout is the pain of your body tearing itself down to rebuild itself better, how does that make you feel? If I tell you that the pain you feel in your muscles after a workout is your body developing cancer, how does that make you feel? And there's your answer.
Why do companies pay dividends to stockholders?
You pay dividends to make your shares attracive to own. Many people buy shares hoping they will increase in value others want an income from owning the shares in addition.
Why can't we make computers that use regular English (or just a human language at all) to do things instead of all this code like Java or C+?
Step 1: place the cup on the table Step 2: move it 1 inch to the left Did you just move the cup 1 inch to the left? Or the table? Ambiguity like that is common in "natural" languages, but is no good for a computer language. This is just one of many reasons why computers have such a hard time understanding natural languages. But people have been [working on making it happen for decades](_URL_0_).
Why do I hear so much about censorship in Australia? How did they get to be so strict about what they censor?
1. Why do you hear so much about it? Because your journalists had a slow news week. 2. How did they get to be so strict about what they censor? Honestly, age. We have a large baby boomer population that votes again and again to keep the status quo. For the longest time we weren't actually censoring video games that didn't meet our MA15+ classification but because we didn't have anything above MA15+ for video games as a whole. So they were deemed RC(refused classification) and banned from sale. It's less malicious and more carelessness on our part. We are still not quite as bad as germany or china but sensationalist media and click bait writers are fearful of both it would seem.
What is RAW picture format and why is it useful?
RAW is a direct dump of the information coming off the image sensor of your camera with no processing being done to it at all. The main benefit is that you can do a lot of image processing on RAW that you wouldn't be able to do with JPEG files. A [picture like this](_URL_0_) will show you what's capable.
If copper is self sterilizing, why doesn't every hospital make door handles, and other frequently touched objects, with it?
A couple of reasons. 1. Copper is very expensive compared to other materials. 2. Sanitizing cleaning solutions are relatively inexpensive, and even with self sterilizing surfaces, these areas would still be cleaned regularly. 3. In order to properly self sanitize, it usually takes a minimum of around 2 hours. Something like a door handle is going to be touched more often than once every two hours, so its effect isn't going to be as helpful as properly sanitizing the handle or hands. Really though, the cost is the largest reason. While KingPupPup is right in the copper oxidizes, frequently handled copper will not because the constant friction will wear away the patina.
How will Netflix use data to determine if they should do a Punisher spin off or not?
How many people watch multiple Netflix originals of other Marvel shows. If many people who watch DareDevil also watch Jessica Jones, and will also watch the upcoming Luke Cage/Iron Fist/The Defenders, that is a good indication they will also watch Punisher.
Why does the expression "... like it's going out of style" mean that you're doing it a lot? Don't people do/use things LESS as they're fading in popularity?
It's implying that they know that X will be unpopular soon so the person is basically trying to get the most out of whatever X is while its still considered acceptable.
High School student, how does college work?
Major- Primary area of study. Often 40-60 credits taken in this area. Minor- You've taken enough credits to have an idea of the field, but did not heavily concentrate in it. Usually 18-24 core credits. Technical School- Typically offers vocational and trade programs; mechanic, nurse, IT, etc Associates - 2 years, Bachelors - 4 years, Masters - 2 years after your bachelors. Switching schools could be due to any number of reasons - they eventually got a scholarship to a different school, were accepted to a better school their sophomore year, were failing out of first school, etc. Scholarships - talk to your school counselor. Make it a full time job applying for them your senior year of HS. It is more than possible to find enough grants and scholarships to cover your tuition, but it is often a time consuming process.
When I'm passing urine, why does it froth some of the time but not others? This is into water without any cleaning products in it.
The froth is from the amount of protein in your urine. The times you will most notice this is in the morning when the content is highest.
why is math (statistics, calculus, etc) so important for a strong programmer?
Programming is - in a sense - just applied math. Math has a strong emphasis on: - logic - developing/applying algorithms - defining stuff (classes, groups, etc) I'm not saying you can't become a great programmer without studying maths, I'm just saying since they share so many similarities it usually helps to learn both or that it is easier for you to learn the other if you find you have a talent for one of them.
Why are English words phonetically explained with strange symbols? Why not just include those symbols in the alphabet?
First, they're not an English alphabet — each symbol in IPA is meant to represent a distinct and unambiguous sound that humans make to communicate. There are *some* sounds used by humans that aren't represented in IPA yet — so, it isn't complete. Second: there are *hundreds* of symbols in IPA — far more than there are in any other phonetic alphabet. Memorising them all in order to cover cases that a student will never or rarely encounter, is pointless (even linguists don't memorise them all, that's why we have reference books). There are actually different ways to pronounce "Gabe", depending on which accent the speaker has — the "a" varies, from long (amongst minnesotans and michiganders) to the rising-to-I tone of modern Southern United States speakers (represented in your example above) to a dropping tone amongst modern Germanic speakers. IPA allows for a written description of how a word is sounded, not of the meaning of the word.
why do I run out of gas faster when the a/c is on in my car
Because you are using gas to power your car and power the motor on the air conditioner instead of just using gas to power your car.
Common Ancestor theory. Does the thought that different early life forming on different parts of the planet seperate from the first organism completely disprove this theory, or is there evidence against multiple sources lineage?
Evidence of parallel abiogenesis would damage the common ancesstor theory. The *thought* doesn't prove or disprove anything. Fossil record of life in multiple locations isn't necessarily evidence of parallel abiogenesis, as life can and does spread and become isolated. Genetic similarities provide evidence of common ancestor, even if parallel abiogenesis could be proven to have occurred, as it would simply mean the other lines died out.
How birth defects happen
There are many causes and many different situations. Some defects are chemically triggered, a perfectly normal fetus exposed to thalidomide at the wrong point in its development will turn out with a defect. Some defects are genetic, through a copying error or expression of a recessive trait a fetus will develop with a defect. The concept of "decide" and "happen" carry the connotation of understanding and thoughtful decision making that doesn't make much sense in these biologic processes.
Why did humans develop in Africa when there's so much more water/food in the Northern Hemisphere?
There may be better resources, but I thought "Guns, Germs, and Steel" (_URL_0_) had a nice explanation about how civilization came about there. Also, understand that there was an enormous amount of human history (not recorded) prior to settling down and farming. Basically, the area around Persia had a lot of the best animals and plants that were/are capable of being domesticated.
why do some sites have highly annoying add's to hinder your experience, do these sites or people that make the adds honestly believe that annoying people will increase the chances of that product being bought?
Most of these ads are not actually for the websites you see them on. The web sites displaying the ads don't really care if you buy the products being advertised. They get paid for the number of times the ad is viewed and/or the number of times someone clicks on the ad.
Can animals commit suicide ?
I've heard of two cases where they have. One was a [dolphin](_URL_1_), which stopped breathing intentionally. The other was a bear that was having its bile drained for some eastern medicine thing. Not just once, that was basically the bear's life, being a perpetually wounded source. One day, she killed her cub, then slammed her head into the bars of her cage until she died. She's not the only one, and that's not the only [method of choice](_URL_0_)... (Note that I'm not counting certain defense mechanisms, like exploding ants or some bees that die when they sting, as suicide per se.)
What is happening when my desktop tower is making (assumedly) calculating noises?
If you can hear calculating noises from your CPU, that's mighty fine hearing you have. The noise is most likely from your hard drive, moving the read/write heads back and forth on the platter.
Why can the brain recall trivial things it was exposed to once, but when intentionally trying to learn something, requires repeat exposure and concentrated effort?
It all has to do with novelty and priority. If someone says something strange, it piques your curiosity and doesn't require much effort to retain. It can potentially also threaten your existence much more than can, say, memorizing chords on the guitar. And learning a skill, you're blatantly aware of the insignificance of each little step and don't treat it with the same level of importance. It'd be "learning the guitar" that's important, not doing fingering exercises and learning sheet music, which are viewed more as obstacles to the entire skill itself. Its much easier when you regard each step as if it were the only thing you were trying to accomplish.
Why is the US president elected to a 4 year term, but members of the senate get unlimited 6 year terms?
It is worth pointing out that the 2-4-6 year term system (House of Representatives, President, Senators) was put in place to prevent what the Founding Fathers feared most: tyranny. On any given election cycle, only 1/3 of the Senate is up for re-election so that one botched/rigged election cannot completely take over the Senate. Rotating congress(wo)men and presidents in and out in different intervals assured relatively smooth transitions of power and guarded against radical change in direction of the country. Presidential term limit is a new thing. Basically: politicians got scared when FDR was elected to four consecutive terms.
how does nonsurgical cool sculpting work to reduce fat?
Basically they freeze your fat cells to death, nothing really more complicated than that. The dead cells are then absorbed by your body. Viola, less fat. Calling it "nonsurgical" I think is a bit of a stretch. "Non-invasive" certainly, but it is an hour long medical procedure during which a local anesthetic is necessary. It's technical name is Cryolipolysis (literally frozen fat cell destruction); you can read more about it on the [wikipedia page](_URL_0_) if you're interested.
apparently you cant die from holding your breath, explain
If you're able to hold your breath long enough, you pass out and then involuntary breathing begins.
Why do my eyes hurt after looking at a screen too long?
This is due to how the human eye focuses. It doesn't work like a camera wich gets set to a focus distance and then stays there. Breaking it down to eli5 level: If the responsible muscles rest, your focus is on the *very distant* setting. Looking at very close things is muscle exercise, and while your eye muscles can pretty much work constantly (in contrast to your leg muscles for example), the can't, just like other muscles can not, maintain a specific position for very long without hurting.
Why can't people drink the water in Mexico but fruit that was grown in Mexico and watered with non filtered water is ok to eat?
The water is a problem because of bacteria. Bacteria will not survive being absorbed by the roots of a plant and turned into fruit. Water sprayed on the surface of fruit could potentially be a problem, but the bacteria that live in water wouldn't survive long out in the air and sun.
Why do you get so hungry when you are high?
In your body you have an Endocannabinoid system which has a role in appetite, pain-sensation, mood, and memory. It's suggested that THC the psycoactive compound in cannabis activates a receptor called CB1 which directly increases appetite when fired.
what happens to credit card debt when people die?
The balance will be taken from the estate of the deceased. If the estate does not have enough to cover the balance, the debt is written off as a loss. I have heard anecdotes of debt collectors chasing after descendants for the debt, but unless they have signed as legally obligated to paying it, there is no legal standing for them to repay it.
If we have never seen or been to the planet's core. How do we know what it looks like or how it works?
We used a lot different methods. The waves of the earthquakes act differently when moving through different materials. Measuring large earthquakes allowed us to get a good idea of what was going on in the earth just passed the mantle. The rest was speculation constructed from what we knew of the outer layers of the earths core and from the fact that we have a magnetic field means, that our core has to be solid iron turning in liquid iron. By the power of earths magnetic field we can get a relative idea of the size and concentration of the core and from the local asteroids and judging by what should have been available around the time earth was formed, we could conclude as to what it's composition should be. There is more, but that should give you an idea of how we can figure stuff out without needing to actually see it.
While watching late-night TV, I see ads for buying gold and silver. Why should/shouldn't I do that? What's the deal?
Generally, commodities like gold and silver can be a less volatile market than stocks or currency. However, most of these commercials are scams. Especially for buying coins. The amount of gold they have in them is tiny. like less than $1 worth of gold in a coin that costs $20.
How does a can of whipped cream work?
Liquid cream is held in the can along with nitrous oxide, under pressure. This pressure keeps the nitrous oxide liquid too. When you press the nozzle, it releases the pressure. This causes the nitrous oxide to boil - turn into a gas - which has the dual effect of both aerating the cream and pushing it out of the can. This is why the can gets cold (as with all aerosols) - when the pressure drops, the temperature drops.
How do we take photos of the universe that aren't from Earth's perspective
The photos either are taken from our perspective or are artist renderings based on data we've collected.
How does exercise benefit a human physiologically?
A lot of hormonal stuff happens that I don't know enough about to explain, but basically, you damage your body and your body goes "well shit, I gotta be stronger if this is gonna keep happening." So then it gets stronger. Note that if you do the same exercises forever, you won't keep getting stronger, you'll just maintain that level of strength... Your body is already used to it. If you DON'T exercise, your body goes "Oh I don't need all this muscle anymore, I can get weaker!" And you get weaker.
Why is an introductory class to something referred to as '101'?
Because in American colleges, every course is given a 3 digit number. The first digit represents the year that most students are expected to take the course. Most of the first classes an American college student will encounter is Whatever 101.
Why are gas prices so high even though the US is producing the most it has in over two decades?
That's a loaded question, but on an ELI5 level: Higher domestic production is just one small piece of the supply and demand curves that dictate gas pricing. Other factors, particularly supply of imported crude (which accounts for a very large percentage - 40-70% depeneding on who you want to cite - of petroleum product in the US), rapidly increasing global demand and a complicated regulatory system all contribute to pump (ha!) the price higher. Also worth noting that gas in the US is still cheaper by volume than most of the world.