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[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why don't antibiotics kill the good bacteria in our system?"
] | Actually, antibiotics *do* kill the bacteria naturally found in your body. Antibiotic therapy is associated with overgrowth of [*Clostridium difficile*](_URL_1_) gut flora in your bowels leading to intractable diarrhea. When this occurs, it is recommended to [change antibiotic therapy](_URL_0_). This is not a common occurrence, but when it does happen steps need to be taken to treat the side-effects of the antibiotic therapy that caused this type of diarrhea. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is the gas in giant gas clouds and nebulae dense enough that sound could travel?"
] | Not anything audible to the human ear, no. This gas is so thin that on human scales it would really just feel like a vacuum. It only really starts to act like a gas when we look on time-scales and length-scales large enough that the particles are undergoing *lots* of collisions within that time or distance. You *can* get pressure waves - sound waves, shock waves etc - but the frequency needs to be very very slow, and the wavelength needs to be very very long, enough that things start acting like a gas from that perspective. For gas clouds, we're talking years of time, and hundreds of AU of distance. Incidentally, this means that when I perform simulations of gas clouds over millions or billion of years, I really can treat them like a gas, because we're well above those scales. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are nebulae and gas clouds in space dense enough that sound could travel through them?"
] | Not any that you could hear if you were hanging out there in a spacesuit, but even in sparser regions of the interstellar medium especially energetic events like supernovae can create shockwaves that propagate for many light-years. In theory an immensely large and sensitive receiver could record these sounds, and this would be easier to do in a nebula. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why are people advised not to drink alcohol when taking antibiotics?"
] | It is never a good idea to drink while on antibiotics due to the fact that most antibiotic side effects are very similar to alcohols effects i.e. drowsiness, dizziness, nausea, and vomiting. Drinking while on antibiotics can compound on these effects making the symptoms a lot worse. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is it possible that the reason the universe is expanding is because it is still in it's acceleration phase of the big bang?"
] | Some people have postulated theories like this, but one of the biggests problems is that as far as we know, the rate of expansion of the universe is actually *accelerating*, not slowing down. Since we are not only expanding, but also show no signs of slowing down it seems unlikely that we will end in a "Big Crunch" (unless, of course, there is some hidden mechanism for reversing the rate of expansion we have not yet observed). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is it possible for a large moon have a satellite of its own?"
] | Due to the tidal effects from the host planet, orbits around a moon would not be stable in the long-term. In the short term, you can orbit a moon just like any other body, but we don't expect to find natural satellites of moons due to how brief the arrangement would be. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is it possible for the moon of one planet to have satellite of its own?"
] | Gravity does not have rules about what is allowed to orbit what. Also the phrase "moon " is just a label for a body that is orbiting something that is also orbiting a star. So yes, it is possible. Bear in mind that orbits are not stable like an eternal clockwork mechanism, so given enough time things will either collide or escape each other's gravitatonal influence. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If 1 box in 100 has a prize, I have a 1% chance of winning. But if I play it 100 times, I do not have 100% chance of winning. Why is that? And what is the actual win chance?"
] | The probability of winning at least once, P(1+), is 1 minus the probability of winning zero times, P(0). P(0) is easy enough to calculate. It's the probability of not winning 100 times sequentially. Since the probability of winning in each trial is 1%, the probability of not winning is 99%. Therefore: P(0) = 0.99 ^ 100 P(0) = 0.366032 So there's a 36.6% chance of losing 100 trials, meaning there's a 63.4% chance of winning at least once. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why does water always taste 'flat' when you leave it out overnight?"
] | Water tastes "flat" after leaving it out overnight is due to the dissolved oxygen (DO) dissipating during the course of the night. Fresh Water especially freshly poured water has a high DO that leaves water over time. Ways to counter the flat taste would to put a lid on the container and shake up the water reintroducing the water to fresh oxygen. (A interesting link for more info. [](_URL_0_) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why are dog breeds not officially different species?"
] | They are considered the same species because they can produce fertile young and have the ability to exchange genes as they have the same number of chromosomes. They also have similar immunological responses to one another. The definition for a species however is still debated and it must be remembered that classification is a human created system and nature may not always follow the rules we create for classification. Anybody please correct me if what I have said is inaccurate information. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is there a notable difference of quality of gasoline from one brand to the next?"
] | My uncle was a chemist for BP and from talking to him I was under the impression that the area you live in and their laws are far more likely to effect your gasoline quality then the brand. Just at their plant they had over 150 variations of gasoline, and they only supplied 3 or 4 states. So really if you want the best gas, look up the regulations in your town and compare them to your other local areas and see which require the least amount of "environmental additives." This is of course, assuming you want to more power/effect from your gas and not "greener" gas. You could just as easily do the opposite I suppose. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do insects sleep like mammals?"
] | Yes, insects do sleep. The problem is, its a bit trickier to study then sleep in mammals. Insects most likely undergo Torpor, or "a state of decreased physiological activity". We can assume they are in a sleep like state because they are more difficult to arouse, startle, and upon being deprived of this cycle become a lot more sluggish. Insects also have a circadian rhythm like mammals do, but it varies from insect to insect. Some insects are only active during the night, and vice versa. Related Articles: [1](_URL_0_) [2](_URL_1_) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why is the ocean so salty?"
] | You are ~~completely~~ mostly right. Salt exists in large deposits all across the globe. As water travels across the land, it picks up salt and other minerals and deposits them in the ocean. When the water evaporates from the ocean, it leaves the salt and minerals behind. Over billions of years, the oceans became salty. Good deduction on your part! Edit: See posts by others below. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If the universe is 13,8 billion years old, how can the observable universe's (aka the furthest we can see) radius be 46 billion light years of distance? (Since the light that's 46 billion light years away isn't able to travel back to us in 13,8 billion years)."
] | This is a commonly asked question. [Here](_URL_0_) is the answer from the FAQs. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do some things melt, while others burn?"
] | Although there are a large number of objects that melt at a certain tenperature, there are some that don't. The latter, usually flammable objects, they are just more thermodynamically favourable to burn(oxidize) when given enough energy(heated up) then to melt. If you were to try to set alight flammable object eg. Wax in an inert atomsphere, eg. Helium, you will find that it will melt than burn. Some proteins and organic compounds decompose when heated rather than melting, is also because it is more thermodynamically favourable to decompose into simplier substance, than to melt. Edited for spelling, corrected the "all objects" part. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How can the sum of infinite rational numbers be an irrational number?"
] | One way that's helpful to think of things: The rational numbers are the numbers that can be constructed through a finite sequence of arithmetic operations (+, -, *, /) on integers (or really, just from the number 1). Any rational number has some arithmetic sequence that constructs it. Anything that can't be constructed with such a finite sequence, is defined as an irrational number. In other words, irrational numbers are those whose arithmetic construction (if it exists)^1 must be infinite. So, irrational numbers are the numbers whose arithmetic description is necessarily infinite. And an infinite sum of rational numbers is an infinite arithmetic description. Now makes sense that some of those numbers are irrational, right? tl;dr Infinity does strange things, and irrational numbers are one of those strange things. ^1 It does always exist, but you should prove that, not assume it. You can construct an infinite arithmetic sequence for any irrational by using its decimal expansion. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Plastic coke bottles (with minimal liquid residue) will, with the cap screwed on tight, develop a partial vacuum (negative pressure) inside over time. Why?"
] | Fluctuations in temperature cause changes in pressure. When the difference in pressure is positive, the air slowly escapes (I bet you don't screw the cap back as tightly when the bottle is already empty.) When the "gauge pressure" is negative, it pulls the cap closing it tighter and thus hindering the flow of air. Also the lack of internal pressure allows the bottle even out the difference by collapsing. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How do trees survive freezing temperatures? Does the water in them not freeze?"
] | water does freeze in trees, and it's a problem that trees tackle by expelling water outside their cells' walls (cells die if water freezes in them and expands enough to break the cell apart). then trees go into a hibernation mode, slowing down most processes to a bare minimum, working around the problem of water loss. conifer trees tend to be more sturdy and their cells can withstand some serious pressure from the ice crystals even if they do form inside the tree's cells or tubes. therefore, conifers generally don't "shut down" during winter completely and are built to resume operations even during short thaw periods. after all, they keep their needles (which are less prone to water loss (through evaporation/sublimation) than leaves), so they can photosynthesize, ie. create energy to keep them going throughout winter. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are pictures of Galaxies really what Galaxies look like?"
] | The diameter of a galaxy is relatively insignificant relative to its rotational period. In the case of the milky way, the galaxy rotates every 15 million years, or more, while the galaxy itself is only around 120,000 ly across, so you will have a small amount of distortion, but not enough to completely invalidate how we observe other galaxies. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why are archaea considered separate from bacteria, in terms of taxonomy/classification?"
] | They have been conclusively shown to be of distinct evolutionary lineage, which is why they are separate. For example, their flagella have completely different structures that evolved independently. (The cell wall difference is an example of that.) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Where do elements come from. Where did the planets in our solar system come from."
] | Well, our planets formed from the same gas/debris cloud that our sun did, itself a remnant of older stars which had gone super nova. Not all elements are created in [active] stars though, as stars through fusion can only create the elements up to Iron... everything else came from supernovae. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"What elements are more common to our outer solar systems planets?"
] | Science layman here, There's a lot of hydrogen and helium out there, they in themselves can produce interesting things not observed on Earth. There are gases that exist in the hydrogen-heavy gas giants like arsine, silane, and phosphine that don't occur naturally on Earth as well as some highly oxidized compounds in the top layers of Martian soil. All of these can be produced in a lab. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Does infinity have multiple values? Do all of our laws of mathematics apply when you are on an infinite level?"
] | What does it mean to "add one to" "infinity"? That notion isn't defined automatically, and the answer to your question will depend on what definitions you settle on. As other folks have already addressed, there is in fact a huge collection of infinite cardinals (to say nothing of the ordinals, which keep track of the order structure of sets and are ludicrously more numerous), so in fact you don't even get a specific quantity "infinity" to work with—you have to be more specific to even get started! |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do you see dust particles under sunlight?"
] | You see the particles in a sunbeam because they are scattering photons towards your eye. Sorry if that sounds pedantic, but I really don't know how else to say it. Dust particles have a very low [Reynolds Number](_URL_0_), which relates a particles size to the viscocity of the fluid it is in. [Stokes Law](_URL_1_) allows one to calculate settling velocities. In air there is sufficient turbulence to keep dust particles suspended for a long time, although they do settle out eventually. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How did Pangaea form before it was divided into continents?"
] | I think what you're asking here is when did the *crust* of earth form/when did plate tectonics begin? That is still debated and not my specialty, but fastparticles is currently doing an [AskScience AMA](_URL_1_) dealing with that. Pangaea was not the first supercontinent to form. Since plate tectonics has been active, we've seen evidence for [Wilson Cycles](_URL_0_). If you think about the modern plate configuration, the Americas and Europe/Africa are being "pushed" apart by the Mid-Atlantic Ridge spreading center where new oceanic crust is being formed. Oceanic crust is being consumed in subduction zones around the Pacific ring-of-fire. This is how plates are smashed together and then eventually rifted apart again in the supercontinent cycle. Google "Wilson cycles" for more reading on the topic. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Does the infinite set { 3, 3.1, 3.14, 3.141, ... } contain the whole number Pi?"
] | > { 3, 3.1, 3.14, 3.141, 3.1415, ... } Does this set contain the number Pi with infinitely many digits? The way we determine the answer is "no" is by taking an element from that set and asking "does this number have an infinite number of digits?" In every case the answer is no, because the Nth number listed has just N-1 digits after the decimal point. So you pull out a number, it comes Nth in the list for some number N, thus it has N-1 digits after the decimal, thus it doesn't have infinitely many digits. This will be the logic for any possible number you find in that set. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"It seems that \"salts\" can be formed from many different combinations of elements... but do all salts actually taste salty? Or is NaCl (Sodium Chloride) the only salt that would taste \"salty\"?"
] | The receptors which trigger the sensation of salty tastes are generally detect sodium ions (Na+). Ions of elements in the first collumn of the periodic table (where also Na lies) may also taste salty. Other ionic salts such as NH4+ or Ca2+ may taste bitter. _URL_0_ |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do whales have nipples?"
] | Whale nipples are small and near the base of the tail, sort of like a very streamlined cow. [Milking a whale](_URL_0_) is possible. This requires attaching a breast pump to a whale, which is nontrivial. Whale milk is very high in fat, and is reported to taste strongly of fish. Whales are not fish - as you can clearly see they are mammals - but they eat fish or small shrimp called krill. Layman speculation: whale milk would probably make a good chowder base. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do whales have nipples?"
] | Yes, they do since they're mammals, but they seem to come out when it's time to nurse. Here's an [interesting article on whale nursing](_URL_0_) that I found for you. :) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why aren't there lunar eclipses once a month?"
] | The moon orbit is on a slightly different plane than the Earth's orbit around the sun. This means that most of the time, the moon passes above or below the Earth's shadow. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do Galaxies and Solar Systems form a 'flat' plane of matter rotating around the centre of mass, rather than a 'ball' of orbiting objects?"
] | The short answer: angular momentum. This is asked often, including at least once in the last two days. Please use a search: _URL_2_ _URL_4_ _URL_0_ _URL_1_ _URL_5_ _URL_3_ |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"When someone receives a blood transfusion or an organ transplant, what happens to the donor's DNA?"
] | > Studies have shown that donor DNA in blood transfusion recipients persists for a number of days, sometimes longer, but its presence is unlikely to alter genetic tests significantly. Red blood cells, the primary component in transfusions, have no nucleus and no DNA. _URL_0_ With organs, the doner DNA remains, as that is the organ's DNA. This doesn't change the host's DNA either, and doner DNA can be found in the host's blood for years (depends on test & organ). There is a risk the host's immune system sees the transplant as a foreign invader and tries to kill it. So testing is done to find a genetically "acceptable" organ, and there are treatments to help prevent transplant rejection. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do other animals have dominant hands/arms like humans?"
] | The short answer: [yes](_URL_0_). The effects of laterality in other animals are much milder, presumably because most animals don't rely as heavily on their hands (the most notable instance of laterality in humans) as we do. For us, laterality is obvious because our hands are specialised and used for nearly every detailed task we perform. It's more difficult, however, to observe this in dogs, since the effects are less apparent. Too, some birds have been shown to display laterality in their feet, nearly to the potency of handedness in human beings. However, it was concluded that only birds that used their feet in feeding developed any such preference. If you're still curious on the subject, try reading [this article](_URL_1_) written on it. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How was the big bang able to expand faster than the speed of light?"
] | Although there is a limt to how fast light can move there is no limit to how fast space can expand. The "stuff" from the big bang just went along for the ride. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why (physiologically) do animals poop and pee when they are scared?"
] | There is thought to be an initial shock when a threat is presented that causes disinhibition of the nervous system. Essentially, you're limbic system is constantly receiving signals to void the bowels/bladder when full. Mesocortical tracts via the frontal lobe tell your body to "hold it". However, when you get frightened, your attention (frontal lobes) allocates to the threat, leaving the limbic system alone to void the bladder/bowels. _URL_0_ |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"When you delete something off a phone or computer, where does it actually go?"
] | Data is merely a series of bits (1s and 0s) and bytes (8 bits..more efficient in a lot of ways). So...you have this device which stores that information. Well, you also have to store **where** you stored that information. Let's say that you want to store a 2MB song on an 8GB device. There are somewhere near 4,000 places it could be put. How can you tell where it is? The same way you tell where a book in a library is. You create an index. So..what you do is you store the data then you tell the device where the data is. When you "delete" the file, you are just removing the references that that space is used: the index. Whatever was written is still there until something writes over it. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Does the night air change the way we hear?"
] | I would actually assume that this is due to noise pollution. During the day there are more sounds to be heard that would cause you to not hear the trains. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Can you get sunburnt behind glass?"
] | You probably won't get burnt, but it can still cause skin cancer. Here is one study on the increased prevalence of skin cancers on the driver side of truck drivers. _URL_0_ |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is there any way to prove that space is infinite?"
] | By direct observation: I'll say no. The problem is that we can only see the Observable Universe: the sphere of space whose most distant edges are as far away in lightyears as the Universe is old in years. Why? If it takes light 14.5 billion years to get here, it was created 14.5 billion years ago 14.5 billion lightyears away. That's the nature of light and the speed of light is the ultimate limit. Perhaps we will find an underlying theory in physics that will point to a limit on the total volume of the Universe including that which we cannot observe, but we still will never be able to observe the entire Universe directly, so we can't directly observe whether or not the Universe is actually infinite in volume. Not a definitive answer, but I hope it helps a bit! (B.S. Physics) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How exactly does a dog (or any other animal) \"smell fear?\""
] | > In the strictest sense, it is doubtful that animals can smell fear. Some animals have been documented to release a scent in response to stress. Such a "fear scent" may play some role in alerting a potential attacker. However, it is more likely that an animal will become aggressive towards a fearful individual as a result of a combination of multiple sensory and behavioral cues. While odor may play a significant role in attack behaviors among animals, olfactory cues probably do not function alone to incite aggression in mammals. _URL_0_ Good article on the subject with lots of references. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If all stars appear as just pinpoint sources of light, how are we able to estimate their size?"
] | Not all stars appear as pinpoints if we use a big enough telescope. We can resolve stars like [Betelgeuse](_URL_0_). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do carbonated liquids go flatter quickly in a narrower or wider glass?"
] | I would hypothesize that the wider glass would lose carbonation faster. It has a wider air-to-liquid interface area, and more internal area (more nucleation points) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"To which 'space' is space expanding?"
] | It's not expanding into anything. Rather, space is getting added between the space that already exists. The standard explanation is to imagine blowing up a balloon. The surface of the balloon gets larger and larger, but isn't expanding in to anything. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why does staring at a bright light help you sneeze?"
] | [It's called the photic sneeze reflex, it's not well understood, and only about 1/5 to 1/3 of the population has it.](_URL_0_) I know I don't. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why is Helium-3 more prevalent on the moon than it is on Earth??"
] | It gets spewed out by the sun, and when it reaches the moon it gets embedded in the soil but when it reaches the Earth it circulates through the atmosphere, moves around through geological and meteorological processes, etc and any helium in the upper layers of the soil would quickly be loosed by erosion. The main difference is that helium-3 is lighter than helium-4 (the regular kind), and also more technical differences like it's a fermion and He4 is a boson. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"where does gravity come from? Planets are round because of gravity I get that. But what makes gravity pull to the center? In other words what's at the core of planets that makes them round?"
] | Okay. You've asked two questions. Gravity is a terribly complicated subject that some people dedicate their entire lives to studying. There's a lot to it is what I'm getting at. *But* there's a very simple thing we can take from all of these smart folks' hard work to tell us why planets are round. Gravity has a really awesome property that it only cares about how far apart two things are. If you're, say, a planet in orbit a few million miles from a star, then the star is pulling on you with gravity. It doesn't matter if you're above it, below it, to the left, or to the right. You'll feel a tug based only on distance and not orientation. So, what shape looks the same no matter which way you look at it? A sphere! And that's it. Planets form into balls because gravity doesn't care if you're coming from left, right, up, or down--only how far away you are. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"are we sure all elements heavier than iron are made in supernovae?"
] | Whilst not a direct answer to your question, it is worth noting that the claim that all heavy elements are made in supernovae is wrong. See [this answer from our FAQ](_URL_0_) for some in-depth details on the main sources of heavy elements, with the s-process in particular being somewhat similar to your proposal (albeit not due to interstellar radiation). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are there any practical uses for the concept of infinity? Have any real-world applications been necessarily derived from mathematics that uses infinity?"
] | Yes. Infinity is the key ingredient to calculus. Using infinity you can define limits, and using limits you can define derivatives (rates of change) and antiderivatives/integrals (the inverse of a rate of change). Everything in science/engineering/mathematics that studies the rate at which things change (which is most of science/engineering/mathematics, and anything revolving around [differential equations](_URL_0_)) uses these concepts. Common examples in the sciences are population growth (ecology/social science), motion (physics), and probability distributions (anything with statistics). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"why is it we can see through water clearly from the outside but can't see well while opening our eyes underwater?"
] | The angle at which light bends at an interface depends on the refractive indices of both materials. This is Snell's law: sin θ_1 / sin θ_2 = n_2 / n_1. Since your eyes are designed to function in air, with a refractive index of about 1, when you immerse them in water, with a higher refractive index, light entering your eye isn't bent as much, which means it isn't focused properly. This is why you can see just fine when you put goggles on - they mean your eyes are in air, not water, so light is focused as normal. (The interface between air and water in goggles is (usually) flat, so it doesn't affect the focus of the light.) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How do we know the size of stars that are thousands of light years away?"
] | Size is usually measured by [interferometry](_URL_0_). You may know that the angular resolution (i.e. how fine the details are that it can distinguish) depends on it's size, bigger being better. By using two telescopes and interfering the light from them, you can have them act like one much larger telescope. This technique can directly measure the angular diameter of the star. As for distance, that's a bit harder. We can measure the distance to stars nearby using [parallax measurements](_URL_1_). After that, we need to use standard candles, which are objects of known brightness. If we know how bright they really are, and how bright they appear to us, we can work out how far away they are. For objects that are very distant (i.e distant galaxies), we can use cosmological redshift. This is due to light being "stretched" by the expansion of the universe, and light thats travelled further will have been stretched more. EDIT: missed out an important noun. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How do scientists estimate the distance away some stars are? How do we know there are stars millions and billions of lightyears away?"
] | Parallax works for things close by, out to several hundred light years. Take an angular measurement in January, and another in June, and check the difference. The difference in angular position and the size of the Earth's orbit can be used to make the trigonometric calculation of distance. [See this graphic](_URL_2_). Beyond that, there are a lot of different methods, and some work better for certain distances. Type Ia supernova give off distinct [light curves](_URL_1_), and we know how much light they give off, so we can use them to figure distance. Check out the [cosmic distance ladder](_URL_0_) article for more info and examples. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"(Astronomy) If the sun will eventually turn into a red dwarf and expand, will the orbits of the planets change?"
] | Yes. The sun will lose a significant amount of mass, which will mean the planets would orbit slower and further out. But there will also be air resistance from all that solar wind, which will keep them from going out too far. They'll still orbit slower. And several of the planets will end up inside the sun, where the'll slow down and fall toward the center. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How much does a cloud weigh?"
] | > According to calculations from Peggy LeMone, senior scientist at the National Center for Atmospheric Research, a thunderstorm cloud contains approximately 275 million gallons of water. With 750,000 gallons of water going over Niagara Falls each second, it would take six minutes for an equal amount of water to go over the Falls. > So how much does a thunderstorm cloud weigh? With one gallon of water weighing 8.33 pounds, the weight of the cloud is 2.3 billion pounds, or 1.1 million tons. [Source](_URL_0_) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How much does a cloud weigh?"
] | a cubic kilometer of cumulus cloud weighs about 2.20 billion pounds. _URL_0_ |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How close does a fly have to get to the ceiling before it flips over to land?"
] | It gets close enough to grab the ceiling with its front legs. The momentum is what flips the fly over |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"During a full eclipse, the moon and sun have the same apparent size in the sky (roughly). Is this just a coincidence, or did some natural combination of factors cause the distance and size of the moon to work out that way?"
] | It's a coincidence. Both the sun and the moon vary by a few percent in apparent size, and they have a range that overlaps. Over very, very long times the sun will become bigger and the moon farther away, so eventually this will no longer be the case. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"It seems to me that maintaining orbit around the Sun requires a planet to possess a massive amount of kinetic energy. How did this happen? Why did the clouds of gas and rock that eventually coalesced into planets have so much momentum? And why was it all going the same way?"
] | Stars form out of huge gas clouds as you correctly pointed out. These gas clouds have some natural motion (swirling), this is where the initial motion comes from. As the cloud collapses to form a star, the radius of the cloud decreases. Conservation laws tell us that the angular momentum before the collapse and after the collapse must be the same. Since the radius of a collapsed cloud is so much smaller, it must spin much faster in order to have the same angular momentum. The solar system forms during the process of star collapse, so the bodies in the solar system will rotate in the same direction for the same reasons mentioned above. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why shouldn't food be frozen again after it has been thawed?"
] | Ice crystals damage cell walls much like shoving pins through a balloon. Thawing and refreezing something damages the item further, and in most cases, reduces it to just a mass of proteins with no real structure. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"When frozen foods thaw, do they spoil faster than when fresh?"
] | I can't give a yes or no answer, since it depends on the food, the way it is frozen, etc... Even when frozen, chemical reactions are still taking place, though very slowly. Fats are oxidizing (rancid), vitamins are going to break down, and food is desiccating. If the freezing process creates ice crystals, which rupture cells, the food item will probably be more vulnerable to microorganisms, and mixing the contents of all the cells and different compartments within the cells will allow things to break down more quickly. On the other hand, the desiccation of the food will reduce bacterial activity, and freezing could kill some organisms within the food. So, my best guess is that yes, food will spoil more quickly, but I can't say how much faster. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If the Solar system revolves around the galaxy, does it mean that future human beings are going to observe other nebulas in different zones of the sky?"
] | I have some questions on this. If the whole galaxy rotated at the same speed, we wouldn't see any difference, so the stars have to be going at different speeds (im aware this difference is not as significant a you would expect because of dark matter)... correct? As I understand it, the actual orbit around the galaxy is one thing, but the arms spin faster? I guess they are traveling density waves... is this correct? If so, how does the density wave work? |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"To increase power, why do gasoline engines add to the number of cylinders while diesel engines add to the size of the cylinders/engine block?"
] | Diesel engines compress the fuel air until it combusts. Petrol engines compress them less and use a spark to combust them. So in a diesel engine you get more benefit from compressing more fuel/air to combustion so bigger cylinders = more power because you get longer strokes on the piston. For petrol engines you don't want to compress so much. So bigger cylinders would give some more power but still only one stroke and you can't make the stroke a lot longer without compressing too much. So more cylinders gets you more power more efficiently. This is also why diesel engines have more torque - longer strokes on each piston - while petrol engines can go faster - more rapid strokes. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Does a tree release more Co2 when it is burned than it consumes over its lifetime?"
] | Trees get their carbon from the air, so if you burned it perfectly it would pretty much be 1:1. Any unburnt carbon after burning (ashes, etc) would mean you are pulling more out, however this goes back into ecosystem other ways. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Can trees live indefinitely or do they eventually die from \"old age\"?"
] | All living things eventually die, including trees. The oldest known tree is a bristlecone pine in California, which is 5 to 6 thousand years old. However, depending on your definition of a single individual, certain clonal species are known to be much older than this. A clonal stand of quaking aspen in Utah is considered by some to be a single individual, which is over 80,000 years old. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why are there ginger/very light brown hairs in a lot of men's beards?"
] | Beard hair is quite different to head hair; it is coarser, curlier and doesn’t fall out when we get older. Comparatively little work has been done on the genetics of human hair colour, but it is believed that in order to have a ginger beard you must be a carrier for the recessive gene on chromosome 4. With two copies of this gene you will have ginger hair all over, but with just one, the hair on your head will be brown or auburn and your beard will be ginger. – BBC Focus Magazine, #199 February 2009 Hope this answers your question, at least partially! |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why is glass so chemically stable? Why are there so few materials that cannot be handled or stored in glass?"
] | HF is not the only chemical that etches glass. NaOH does it too. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why can some spores and bacteria survive in 100% alcohol, but not at 70% alcohol?"
] | Pure alcohol triggers defense mecanisms in bacteria that cause them to close their pores, preventing the alcohol to enter and ravage them. 70% alcohol is the "golden" ratio in the sense that it fools bacteria into thinking there's water (the remaining 30% is in fact water) so that they keep their pores open, while maintaining the highest alcohol concentration to dissolve them from the inside out. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If air is made up of 78% nitrogen and only 21% oxygen, why do all living creatures need oxygen in order to live and not nitrogen?"
] | Oxygen is much more reactive than nitrogen. You can get energy out of combining oxygen with carbon to form carbon dioxide, or by combining it with hydrogen to get water. Carbon makes for a great building block for life since it is so versatile in its bonding. Life needs a lot of complexity which carbon facilitates better than any other common element. When you have a carbon-based life form it makes sense that it'll be using carbon molecules like glucose or lipids for energy storage, as those are also carbon-based molecules. You can't combine those with Nitrogen and get energy out of the process. Just because you have a lot of something doesn't mean that it's useful. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do duster cans (keyboard cleaners, etc.) get cold when you use them upside down?"
] | When you open the valve, you are lowering the system pressure by exposing it to the atmosphere. The system balances by evaporating some of the liquid in the can to try and maintain equilibrium. This conversion takes energy out of the system, cooling it down. The same principle makes your refrigerator work in the condensation cycle. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why does wounds and skin lesions itch when they heal?"
] | Inflammatory response involves increased permeability of capillaries (to allow more immune cells to reach the vulnerable area). Pooling of fluid at the site causes the swelling you observe. This swelling pushes against the nerve endings, causing the awkward tingling sensation. So in a sense it's sort of an unavoidable side effect. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Could a right handed person be taught to use their left hand as proficiently as their right hand (and vice versa)? Or is it hardwired into our brain & unchangeable?"
] | Taught? I can't say, given the option to use your dominant hand it's extremely hard to not use it. Forced? Yes. It's been policy at various times in history and in various parts of the world to punish children that use their left had to write or draw and to force them to work right handed. While this hasn't worked out very well for many left handed people, it has been the case that left handed people have ended up being able to write and draw well with their right hand. If the creation of art through craft skills is a demonstration of proficiency then you also have examples such as [this man](_URL_0_ "Video, 48seconds, application of gold leaf") who was a right handed sculptor, jeweller, and glass blower prior to an accident which caused a brachial plexus injury that resulted in the complete loss of motor control and sensation in his right arm. He was able to retrain to become a proficient one armed left handed glass blower and teacher. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is it possible for a right handed person to become proficient or even skillful at using their left hand in areas like writing or using a mouse?"
] | I managed swap the opposite way. I grew up using my left hand for the mouse however ended up having to switch over due to a moulded tracker ball by dad bought. I eventually i got used to it and now I prefer my right hand for mouse and playing guitar however everything else is all lefthanded. I am definitely not ambidextrous but with a little time i think anyone can switch over. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is the pain in a headache actually from the brain, or does it just feel like it?"
] | Brain tissue itself has no pain receptors, so the pain from headaches comes from areas that do have pain receptors: the cranium (the periosteum of the skull), muscles, nerves, arteries and veins, subcutaneous tissues, eyes, ears, sinuses and mucous membranes. The lack of pain receptors in the brain tissue itself is what permits awake brain surgery as seen in [this video](_URL_0_). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"When I look at certain stars at night, why do some of them appear to be blinking and others don't?"
] | I think what happens is, is that light from the star refracts from particles in the atmosphere causing the light to be distorted and appears to flicker. i think this is the case because when you're on a hot day looking into the distance, the image you see seems unclear and waves almost. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"what is the smallest possible size of a planet?"
] | One of the criteria for a planet is that it's big enough that gravity pulls it into a spherical shape (hydrostatic equilibrium). Depending on what it's made of, this happens at about 200 kilometers in radius. This is known as the [potato radius](_URL_0_). |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Can't oils go stale inside of your body?"
] | Only about 1.5% of the oxygen in your blood is free, that is, not bound to hemoglobin. While heat and light definitely speed up the process, without oxygen there is no process. After digestion fats are broken down into free fatty acids (FFAs). These fatty acids are what can be oxidized and in doing so have their energy released. FFAs are transported to other body tissues via the blood by means of lipoprotein carriers such as [chylomicrons](_URL_0_). Oxidation of fatty acids is almost exclusively done in the mitochondria, and when the body wants to store fats it converts them into triacylglycerols (TAGs) and stores them in lipid droplets in adipose tissue. There isn't really much chance of oxidation or degradation of fatty acids in any of these places, as chylomicrons protect them from our bodily lipases, and adipose tissue does the same thing, while also keeping them in an anhydrous and oxygen-free environment. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why can you eat some oils, but not others?"
] | An oil is basically a liquid mass of hydrocarbons. Motor oil consists primarily of alkanes, comprising of chains of carbon with hydrogen atoms bonded to them, typically with a length around that of octane (8 carbons). Plant oils consist of triglycerides; a glyceride group with three fatty acids bound to it. The fatty acids are typically of a length of 16-18 carbon atoms and, most importantly, have a carboxylic acid in one end. The carboxylic acid is essential for digesting the oil as Coenzyme A reacts here, and during Beta oxidation the oxidation of the fatty acid will happen on the beta position of the fatty acid. This oxidation would not be possible in lieu of a carboxylic acid. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How could Mars have an oxygen rich atmosphere so long ago?"
] | Are you asking about the creation of elemental oxygen in stars or the chemical changes that result in free diatomic oxygen gas? |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How many holes does a straw have?"
] | The word "hole" has no precise mathematical meaning. * A straw is a two-dimensional manifold (with boundary) of genus 0. For *closed* surfaces, the genus typically describes what we most often colloquially mean by "hole". So in that sense a straw has 0 holes. (This is the same reason a sphere has 0 holes.) * A straw is homeomorphic to S^(1) x [0, 1], i.e., the product of a circle and a compact interval. So its homology groups are {**Z**, **Z**, 0, 0, ... }, and so many mathematicians may just say there is 1 hole. * The boundary of a straw as a manifold is the disjoint union of two circles. So in that sense a straw has 2 holes. Take your pick, depending on your interpretation of "hole". |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are you still briefly conscious after being decapitated?"
] | Did the nazi's perform any tests regarding this subject? EDIT: Why the downvotes? This is a good and legitimate question. The nazi's both killed large numbers of people and were very scientific with all their experiments and kept meticulous records. Like it or not, we have a lot of good scientific data from them regarding some of these more gruesome topics. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Is it possible to remain conscious for a brief time after being decapitated?"
] | There is some [evidence](_URL_0_) to support that this is true. In theory, cells do not immediately run out of oxygen, nutrients, or energy so a cell can continue to function for some, very short, period of time. Decapitate a snake, and the mouth will continue to bite [video](_URL_1_). TL;DR - Yes, for a very short time. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How long could a lactating woman survive on only her own milk?"
] | She would starve to death probably more quickly than her friend joe blow who is stranded on the little ocean island with only one palm tree beside her. It takes the body energy to create milk. Energy is always lost in any energy transactions - Laws of thermo-dynamics. Thus the energy her body spent to make that milk is greater than the chemical energy contained within the milk. She will get back whatever portion of the spent energy that isn't lost if she drinks it, but energy is still lost. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If visible photons are absorbed by atoms and then re-emmited at the same wavelength, why can light not pass through dense matter?"
] | Light traveling through materials scatters. This includes air, water, glass and opaque materials. When it scatters, it is not necessarily re-emitted at the same wave length, or in the same direction. The particle that absorbed the photon may de-excite by emitting two photons with lower energies than the original. In this way, visible light is absorbed and re-emitted as heat. Alternatively, the the light may undergo a reflective scattering, where the photon is re-emitted roughly back towards the source. With transparent materials, due to the structure of the material, light has a low probability of undergoing such interactions. In opaque materials, the probability is higher. Opaque materials that are thin enough, or not *as* opaque as other materials sometimes show a glow when sufficiently bright light is shone on the opposite side - this is an indicator that light is getting through (transmission), but that there is some interference in the path of the light. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why does a room become dark when you turn off the lights?"
] | They are absorbed by the walls. If the room was covered in perfect mirrors then it would stay illuminated, but no mirror is perfect. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"After seeing several high definition photos of moons and planets, there is a large amount of visible craters. If the earth was devoid of all life, would earth's surface show just as many craters?"
] | To add to the excellent answer here: take a look at the surface of [Venus](_URL_1_) to see how active geology and a thick atmosphere can reduce the number of visible craters. Venus's surface does have craters, but they don't dominate the landscape as they do on Moon, Mars, or Mercury. (Earth's atmosphere isn't quite as good at stopping impacts as Venus's is, but you get the idea.) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do things on the stove appear to steam more when I remove them from the heat?"
] | This is a real thing. The condensation of water (which is what steam is) depends on two things in this scenario: The concentration of water in the air, and the temperature of the air. What's happening is that when your stove is still on, the air above the pot is quite warm. This prevents the water from condensing, even though the concentration of water might be quite high. When you turn the stove off, the air above the stove cools much more rapidly than the pot does. As the pot stays warm, it continues to release water (reaching the same concentration) but since the air is at a lower temperature, it cannot keep the water 'dissolved.' As a result, it condenses. This effect is also why in [steaming tea kettles](_URL_0_) there is a gap between the tip of the spout and where you can start to see the steam condense. The concentration of water close to the spout is relatively similar to the concentration a few inches/centimeters away, but the temperature is much higher closer to the spout. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How come mosquitos do not spread blood borne diseases like HIV and Hep C?"
] | Mosquitos do not inject blood when they bite. Just saliva. So for most blood borne viruses like HIV, the virus can not replicate in the mosquitos digestive system, and never makes it into its saliva. Malaria on the other hand is essentially designed for transmission by mosquitos. it grows and reproduces in the mosquitos digestive system and move into the mosquitos salivary system to be injected the next time it feeds. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How can trees die of old age, yet successive cuttings of that tree can propagate indefinitely?"
] | The reason the trees die is not because of old age, but because they outgrow their ability to successfully deliver the nutrients they need to sustain themselves because of sheer bulk. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are we smaller than atoms when compared to the milky way or observable universe?"
] | We are about ten billion times the height of an atom. The galaxy is over a billion billion times the height of us. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"If atoms are 99% 'empty space', how big would the universe be if we compressed every atom down to it's most space efficient arrangement, essentially leaving no space between particles?"
] | According to [Wolfram Alpha,](_URL_4_) it would form a ball roughly the size of Saturn's orbit. Of course, the ball would not be stable, but immediately collapse into a giant black hole. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why are there more blind and deaf people than people who cannot taste or smell?"
] | People with those detriments are not obvious and don't need compensating skills, so you are pretty much completely unaware of the people around you with those deficiencies. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Do other insects other than mosquitoes carry malaria?"
] | No. Only the females of some specific species of the Anopheles mosquitoes can transmit malaria(the Plasmodium parasite that infects humans). There is also variation within species. Some strains of a particular species can kill the human malarial parasite while others don't. There are other species of the Plasmodium parasite whose vectors can be other dipteran insects or other genera of mosquitoes such as Aedes, Culex or Culiseta but those don't infect humans. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"When it is said that \"The universe was smaller than an atom\" before the Big Bang, do they mean the visible universe?"
] | > which would encompass actual, physical dimensions The comparisons to a size doesn't make sense. It *didn't* encompass actual, physical dimensions. It's modelled as a dimensionless gravitational singularity with no degrees of freedom, i.e. a 'point'. Any direction was folded back into itself and it had no center nor edge. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why do so many people suffering sleep paralysis experience a threatening creature or presence?"
] | first off, questions like "why do we dream about what we dream about" do not at present have good scientific answers, aside from something general along the lines of "it has to do with memory encoding etc etc". so, there probably cannot be a very satisfying answer to this question. i did find this: [a special issue of the journal Transcultural Psychiatry] (_URL_0_) on how there are significant cultural variations in how sleep paralysis is experienced. that link is to an editorial preface to the issue; it sounds like sleep paralysis experiences are generally threatening or unpleasant and associated with some kind of seemingly supernatural oppressor, but not universally so (see the article on Chinese patients). [here is the set of articles, though i'm not sure if it's paywalled or not] (_URL_1_) |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How did ancient astronomers know that some of the star-like objects in the sky are actually planets and not other, bigger stars?"
] | So the name planet comes from the ancient greeks. It means "wandering star." They could see the planets moving through the night sky differently from the other stars. This even includes things like apparent retrograde motion. (Since we sit on Earth, and it orbits about the star at a different rate than other planets, you can imagine you see other planets moving at different rates of speed as you "catch up and/or pass it") Given that they were bright and moved in a unique manner, they took on special significance. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How did astronomers pre-dating the invention of the telescope know that planets weren't just other stars?"
] | Because of their behavior. Even without knowing that stars are distant suns and planets shine from reflected light without producing their own, there is no ambiguity that planets and stars behaviors are so different that they are completely different things, whatever those things might be. Stars are set in fixed patterns one relative to the other, they always show the same patterns. Planets, on the other hand, visibly change positions all year round, this is reflected by the very name ancient greeks gave them: *Planetai* (wanderers). This distinction was abundantly clear for millenia prior to the first telescope. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"What would happen if another star collided with our sun, assuming the other star was equal size and mass and both were traveling at the same speed?"
] | Well, for a starter, the idea of direct collision is very unlikely, but another star could be caught in the gravitational field. It would mean the two start would rotate around a middle point, get closer to each other after millions of years, until they fuses. We would end up dead, and the result could be a bigger star, a neutron star, or even a blackhole. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"How close to a parent star can a gas giant form?"
] | Not directly answering your question, but several discovered extrasolar planets are termed [Hot Jupiters](_URL_0_) since they have similar mass and compositional characteristics to Jupiter, yet orbit *very* closely to their parent star. For instance, [51 Pegasi b](_URL_1_) orbits many times closer to its parent star than Mercury does to ours. It's believed that these planets do not form at this position, but instead that they migrate from their formation position [outside the frost line](_URL_2_) to their surprisingly tight orbits. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Why does cheese break or crumble when it's cold, but gets long and stringy when it's warm?"
] | Cheese that is stringy when hot (not all of them are) acts like a synthetic polymer, e.g. chewing gum. Warm chewing gum is stringy. To remove it from a carpet, rub with an ice cube and it becomes brittle and easy to remove. This difference is due to the glass transition. This occurs at a temperature where the polymer chains slow down a lot. Below it they are brittle. Above it they are stringy. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Could a meteor have struck Earth so hard as to dislodge soil or rocks, shoot them into the atmosphere, and spread life into space?"
] | The main problem with that is that the distance between stars is mindbogglingly large. The nearest next star is at 250000 AU, compared to 40 AU for Pluto. So by the time any microbes/life would have crossed the gap, their DNA (or equivalent) would have degraded beyond repair by hard cosmic radiation. Even on Earth, which is moderately shielded against radiation, DNA/RNA [completely degrades within 3-7M years](_URL_4_), and gets fragmented beyond repair long before that. And then those fragments would still have to survive reentry on a new world. |
[
"Provided a user question, retrieve the highest voted answers on Reddit ELI5 forum",
"Are the stars we see most of the time not in the Milky Way?"
] | All the stars we see are in our galaxy, which is the Milky Way galaxy. However, the actual [_Milky Way_](_URL_0_) as known to us since antiquity is the band of stars comprising the disk of the galaxy as seen from the side. The stars we see in the sparser parts of the sky are still in that disk and still part of the Milky Way galaxy, but they're not as dense together looking, because we're seeing them against the backdrop of intergalactic space. The densest and brightest part of the _Milky Way_ band of stars is around the center of the galaxy. The main thing we see outside of our galaxy is other galaxies, so if you're looking at photos of any stars, they're in our galaxy. To me this lends a kind of 3D effect to sky photos where you can see galaxies and stars. The stars you see are close up, and the galaxies are far away. |
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