Datasets:
sentence-transformers
/
eli5

Dataset card Data Studio Files
xet
Community
question
stringlengths
19
300
answer
stringlengths
28
1.02k
What is holding carbon fiber back from being mass produced and at a low cost?
Carbon fiber is mass produced and is substantially cheaper than it was 10 or even 5 years ago. It's still not as cheap as steel or aluminum and probably never will be. Processing CF is a different story. My experience is in chopped carbon fiber added to polymers for reinforcement, so I don't know how it is used to make frames and structures. Carbon fiber has great tensile and flexural strength but is very, very brittle so sometimes it isn't a suitable material.
Why is it that when the batteries in my remote are dying, I can tap it to keep it working?
Trying to find a source, but I had an EE TA explain that bubbles formed on the cathode of the battery, impairing the battery's ability to produced sufficient power. Knocking on the battery dislodges the bubbles, giving more surface area fire the battery to react Edit : its listed under polarization _URL_0_
What specific part of cigarettes are cancerous?
There are a lot of carcinogens in cigarettes, with ~60 out of the 2000 - 4000 chemicals being known human carcinogens. The most common known carcinogens in cigarettes are: - Tar - Polycyclic aromatic hydrocarbons (e.g. naphthalene, benzopyrene) - Nicotine (this hasn't be confirmed, however there have been associated links between tumor promotion and nicotine) - Formaldehyde - Nitrosamines Of course there's a fair few others such as Polonium-210, a radioactive element (low amounts, but still enough to be carcinogenic with frequent usage). There are also other chemicals present in cigarette smoke that while might not be directly carcinogenic, could indirectly increases ones chances of cancer due to the cellular damage caused by said chemicals.
What causes lifespans to vary so widely in animals?
Metabolic theory (_URL_2_) has some interesting insights into lifespan. Some places to start reading in the literature are: _URL_1_ _URL_3_ _URL_0_
Is it possible for a moon around a planet to have it's own moon in orbit?
The magic astronomical phrase to Google here is "[Hill sphere](_URL_1_)" - that's the volume around a body where the body's gravitation dominates the gravity of whatever it's orbiting around. Anyhow, [here](_URL_0_)'s a pretty good explanation of the situation. Short answer: yup. But usually they're not very stable over long periods of time.
Does a star always have to be at the center of a solar system?
Fun fact: It's entirely possible to have a planetary only system in which there was never enough mass to form a star. Then you could have a big Jupiter of some kind at the middle being orbited by some rocky planets...all of it very cold and dark flying through the void. These would be called "sub-brown dwarf stars" or "Rogue planetary systems"
Binary stars can share an envelope, so-called contact binaries, resulting in a figure 8 object. Can planets or moons do the same?
I can offer some theory. Lets skip the explanation of how they get into these orbits and just look at the short and long term mechanics of the system. Short term: You can have binary planets at any radius apart by changing the orbital velocities, so yes a figure 8 is possible. Same for stars / moons etc Long term: Tidal forces of the sun-binary system would over long peroids slow the binary system down resulting in a collapse to a one planet system. A competing planet-planet tidal forcing effect could cause them to separate and maintain a binary orbit. These effects can be observed with the tidal locking of the moon with the earth and also the slight yearly increase in moon orbital velocity. Which effect dominates depends on orbital radii and axial rotation of planets. Can these binary planetary systems form in nature? Are there forces other than gravity that could affect this system?
Why do plants evolve to have poisonous fruit and berries? Doesn't that defeat the "purpose?"
Many poisonous fruits are only poisonous to certain animals, but not to others. As such, it functions as a selection mechanism. There might be several evolutionary benefits for the plant. Birds, for example, might spread the seeds much further than land animals. Or the digestive tract of some animals would digest the seeds along with the fruit, while that of others would not.
Why don't mosquitoes spread HIV?
So do things like Malaria and Yellow Fever need significantly less virions to start the virus in someone or how do they spread while HIV does not?
What stops mosquitoes from spreading HIV?
Unlike some other diseases such as malaria, HIV does not spread from the blood mosquitoes drink into the rest of the mosquito's body, it stays in their stomach contents and probably dies there. There is known theoretically a way a mosquito could spread HIV but it is a bit complicated and unlikely. Basically, a mosquito drinks from an HIV-positive person and shortly after lands on an HIV-negative person to bite them; the person swats the mosquito splattering the fresh HIV-positive blood from the mosquito's stomach onto their skin; they then scratch themselves so vigorously that they break the skin which allows the HIV-positive blood to touch their blood. There is not a known case of this happening so far.
If our skin cells die and regenerate so much, as well as most of the other cells in our body, why are tattoos still visible after so many decades?
Our skin has several layers, the top being composed of the epidermis (keratinized dead layers of cells) and the dermis (where your nerves, blood vessels, and epithelial progenitors are). These layers are held together and the cells are positioned by the extra cellular matrix, which is comprised of carbohydrate fibers and proteins. All tissues in your body have this as it helps organize and hold your cells in place. The ink from a tattoo is deposited below the dermis and into the extra cellular matrix. Some of it gets into cells, and when they die the ink fades. This is why tattoos will fade with time. What remains, however, is the ink that has dyed the matrix. This is also why tattoos are so hard to remove: you can't just kill the cells because the dye is not contained in any cells. It's part of the matrix surrounding your cells, so lasers are used to break down the dyes directly
What causes lightning to flash in different colors?
Lightning is just a powerful electrostatic discharge. Any colors you see are just a combination of the visible light we know and love, ROYGBIV. Depending on how far away you are from the lightning bolt it will look like different colors due to the interaction of light with the atmosphere. The closer you are the whiter it looks the further you are from the bolt the redder it looks.
If a 20 year old gets an organ transplant from a 50 year old, 30 years later is that organ functioning as if it were 80 years old or 50 years old?
A transplanted organ will function according to the donor, so in this case it would be like an 80 year old organ. One exception to this is the liver. It had unique regenerative qualities not present in other organs. This is why it's possible to grow a full liver from a single lobe, the liver has 4 lobes I believe.
Does any organism's hair, other than humans, go white with age?
Sure, [gorillas](_URL_0_) and [golden retrievers](_URL_1_) both have fur that lightens as they age
Why acne occures mostly on facial skin?
Your genes and your hormones trigger glands in the skin to produce a hydrophobic mixture called sebum. Generally, increased excretion of sebum is associated with acne. The glands that produce sebum (called ["sebaceous"](_URL_0_) glands) are distributed all throughout the body, but are denser in areas such as the face. Thus, acne tends to be observed in the face.
What causes acne? And why is it mostly concentrated around the face and upper back?
Acne is caused by sebaceous glands producing excess sebum, which is very oily and is what causes your skin to feel oily and look shiny. It can just be from excess production or it can become trapped, causing a bump to form underneath the skin. Excess sebum production can be caused by a lot of things, like skin conditions such as sebaceous hyperplasia, or the production of dihydrotestosterone (DHT) which the body first starts producing in puberty. That’s why you start to get acne when puberty begins. It’s all about genetics, some people are genetically predisposed to excess sebum production, so it’s hard to control. Obviously these are not the only causes, but I listed a few. It’s common on the face because that’s where sebaceous glands are most highly concentrated. I’m sure it’s the same for your back, but again, it’s all about genetics.
Do dogs see other breeds as dogs like them or as a whole different species?
Unlikely, but it would be near impossible to really prove one way or the other. Important to note, though, that for dogs to see other dogs as the same species, they would have to have a concept of species, which they do not. They do have a sense of self though, and likely notice similarities with similar looking things. As an example, my greyhound won't view a German Shepard as possible prey given size and approximate look, but her interactions with pugs are a whole different story.
Do mosquitoes do anything positive for nature?
Well, like with anything, they have a place in their ecosystem. There are things that eat them, and things that compete with them for resources etc, so removing all the mosquitoes could have unpredictable effects on other species in the area. *But* my understanding is that there are lots of species of mosquito in the relevant ecosystems, and only some of those species bite humans. So if we just eliminated those specific species, some scientists think the other species would increase to make up the difference, because of the reduced competition, and the things that eat mosquitoes will just eat them instead, and no real harm would happen. There are actually some [serious attempts to do that getting going right now](_URL_0_).
We always hear about larger stars then our Sun, but what are some of the smaller stars out there and how much smaller are they?
Personally I think the best way to think about stars is in terms of their mass. (Radius can be a bit of a pain to work with. A very very rough rule of thumb though is that Rstar ~ Rsun*(Mstar/Msun) for main sequence stars. But bear in mind this is an especially bad approximation for very high mass or very low mass stars.) In terms of mass though, the typical cutoff for "how small" can they go is something on the order of .01 Msun. Anything below this rough cutoff is considered to be a brown dwarf, which is essentially a failed star. It wasn't massive enough to build enough pressure in its core to fuse hydrogen to helium, and instead fuses deuterium in small amounts. Really, they are a lot more like large Jupiters at this point. There are plenty of known brown dwarves. [Brown Dwarves](_URL_1_) And if you're interested in things that are still considered stars, but are very low mass, you can look at things like M,L,T dwarves [Dwarves](_URL_0_).
Is the sun at the same focus for all elliptical orbits?
Since an ellipse is symmetrical, there's no way to tell the difference between the two foci. If I rotate an ellipse 180 degrees, the "left" focus becomes the "right" one, but nothing has changed.
If water has a lower viscosity than oil, why does oil soak into things more quickly?
> I figured a fluid's ability to soak into things is mostly influenced by its' viscosity. Firstly, that's not entirely true. The adhesion between a fluid and the surface is arguably a greater factor. This > Why is it then that water can be wiped off with a towel while oil needs to be washed out. Contradicts this > Capillary action with oil always seems faster than with water, and oil just seems to soak into everything much more easily than water. Water can be wiped off with a towel precisely because of capillary action with water soaking into the towel.
Why does water evaporate so much quicker than oil?
All other things being equal, smaller molecules are more readily vaporized than larger ones. The water molecule (H2O) approximately 50x smaller than your average oil molecule (soybean triglyceride used as reference).
Why is New Horizons not flying closer than 7750 miles from Pluto's surface?
because 7750 miles is extremly close for a planetary flyby. there is the chance that any closer would cause the ship to go of course due to the gravity of the planet, or that a slight miscalculation would place the ship closer than expected. the windows of tolerence would then be smaler as to not allow the craft to acutally hit the surface. there may also be dust, or other debris. But one of the main reasons is that New Horizons is going really fast. it's only doing a flyby. it will not go into orbit. so if the flyby was too close you would have a very small field of view. possibly too small to do anything useful because the surface will pass the craft by so fast.
New Horizons is going to go at a distance of 12000k from Pluto from the Charon facing side. Considering that Pluto to Charon is ~18000km, doesn't that make NH closer to Charon than Pluto?
When New Horizons passes through the plane of the Pluto system it will be at Charon's distance, on the side of Pluto opposite Charon. This is the place least likely to have debris floating around. Closest approach to Pluto will actually happen about 20 minutes after New Horizons passes through the plane of the system, since New Horizons is travelling at a bit of an angle relative to the plane of the Pluto system. Check out [this graphic](_URL_0_) and the graphics on the [webpage showing the current location New Horizons](_URL_1_) to get an idea of the flyby geometry.
Why does a flame always orient itself upward?
Hot gas rises because it typically has lower density than the colder air around it. Think of the ideal gas law: PV = nRT. Increasing the temperature, you will generally increase the pressure and volume: heating a gas expands it, so it's density goes down. A flame consists of burning gas/vapor, which is hot and so less dense, so it rises like a hot air balloon.
How does a flame always point upwards?
Fire warms the surrounding air. Warm air is less dense than cold air. Less dense things "float" on more dense things. The warm air rises above its surrounding cold air and drags the flame up with it. In orbit, where the effects of gravity aren't visible, [flames are spherical](_URL_0_).
Is the plane of Earth's rotation around the Sun parallel to the plane of the Sun's rotation around the center of the Milky Way?
In this [image](_URL_0_) the red line repesents the plane the planets orbit in, and the yellow line the milkyway, was made using [stellarium](_URL_1_).
Why haven't we found any meteorites older than 4.5b years old?
Actually, no. Meteorites are mostly the remnants of the molecular cloud that formed our solar system. We can use them to determine the age of the solar system, about 4.6 billion years. Small rocks like those that hit the Earth as meteorites can only form when a molecular cloud, like the one that made up the solar system, collapse under gravity. This can only happen if the cloud is very large, and thus it only happens around star forming regions. It therefore leads that all of the rocks that hit the Earth must have formed with the solar system. The chance that a rock can make it from another star all the way to us are *very* slim.
When Graphene is used in practical applications, it’s obviously not still 1 atom thick. So how is Graphene different than Graphite?
I think the difference is that graphene is a relatively large single sheet of atoms a single layer thick. Each layer is discrete and has all the properties of graphene. Graphite is made up of a ton of really tiny pieces of graphene all jumbled together so they slide around and don't do all the things graphene does when it is in contiguous pieces. I am sure a single microscopic piece of graphite would exhibit graphene properties but would be too small to do anything with.
Do the Gambler's Fallacy and Regression to the Mean concepts contradict each other?
The idea of 'regression to the mean' is that if you do more independent trials, the measured average will get closer to the expected average. So if you take your 20 flips, and then flip another 20 times, the average rate of heads over all 40 flips will usually be closer than the average over the first 20. The gambler's fallacy is basically an assumption that trials are not independent. It would correspond to a much stronger tendency toward the mean than the one found by things like the central limit theorem. _URL_0_
In statistics, how can the Gamblers Fallacy and Regression to the Mean both exist when one seems to contradict the other?
The short short answer is that regression to the mean exists (the sample mean tends to it's expected value regardless of initial starting conditions) but the sum of events does not tend to some stable value. If you start with a very luck toss of 50 heads, and then flip a fair coin 50 more times, you expect to get around 75 (i.e. 50 +50/2) heads. You don't expect to get 50 (i.e. (50+50)/2) heads
Why are there so few natural hair colours?
I think there's quite a lot of hair colors, as basically every person has a unique hair color to some degree, and it's quite a big spectrum of reds, browns, blondes, and blacks. Hair color isn't determined by just one gene, but a slew of them, and depending on the mix of genes you get from your parents you can have nearly any color on that spectrum. Ultimately though, the reason hair color is a small spectrum of reds, browns, blondes, and blacks - rather than a rainbow - is because it's determined mostly by the presence of two proteins. [Wikipedia describes it well:](_URL_0_) > Two types of pigment give hair its color: eumelanin and pheomelanin. Pheomelanin colors hair orange and yellow. All humans have some pheomelanin in their hair. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color. And if you're curious, I recommend the rest of that section of that article, because they go into a little bit of a detail about the genetics and chemistry of it.
Why are the males of some species bigger and stronger, but in other species, it's the females that are big and powerful?
There are a variety of reproductive strategies which lead to different types of sexual dimorphism. In many species, males have to fight with other males in order to establish dominance, which allows them to mate with females. Hence, there is evolutionary pressure for males to become bigger and stronger. But if we consider a spiders, for example, males do not fight with each other, they just mate at will. The female spider needs to be larger than the male because the eggs which the female will lay are much larger than the seminal fluid that the male needs to produce, and there is a biological cost to producing those eggs, which requires the female to be able to consume more food, and to hunt more effectively.
If one stops taking an SSRI for anxiety/depression, does the body recalibrate serotonin production and uptake, or does an SSRI create a form of lifelong dependency?
Everybody responds differently. Some people will have a few months of therapy and will never need SSRI's again. In this case, its reasonable to assume the brain has readjusted its neurotransmitters to whatever level allows the person to be symptom free. Other people will have multiple courses before this happens. Some will need lifelong treatment. Do not stop your SSRI because you are afraid of becoming dependent. They do not prevent your body from recalibrating neurotransmitters. You either need it for a short while, or a long while, this will depend on your body, not on stopping or starting a treatment regime.
What would Saturn's Rings actually look like?
You can see the rings even from Earth with a simple telescope; they were even noted by Galileo. They are quite visible and, though perhaps it's impossible to truly get a feel for what they'd look like up close, they definitely are visible from far enough away. Probably what the video meant is that if you were very close to a ring (VERY close) it would look not at all like a ring, but more just a bunch of rocks--the same way a farming field looks like a solid patch of color from a plane, but up close you can see even the texture of the earth.
If building large mirrors for telescopes are of such importance, why are we bothering to make them out of glass?
It's hard to point a spinning mercury mirror.
Why do insects fly so erratically?
This! The kind of question that comes to my mind every once in a while, but I never remember to look for an answer! Also, the opposite, how some insects can stay for hours or even days in the same spot, never "moving". Why? What they do?
The universe is expanding, but gravity always works, no matter the distance. So will expansion ever start reversing?
For a long time that is what peiple thought. It wass assumed that the universe would eventually collapse back into itself in an event called 'The Big Crunch'. In order to prove this theory astronomers needed to measure how the expansion of the universe has changed with time. As it turns out you can do that by looking at supernovae occuring billions of lightyears away. The measurment was made but instead of finding a universe whose expansion was slowing as they expected, what they found was that the universe was accelerating. Something is acting against gravity to push the universe apart faster and faster. This repulsive force was called dark energy and we still don't really know what it is.
What physical part of a tree absorbs Co2?
Small pore-like openings (usually found on the underside of most leaves, but not always) open and close to allow the exchange of gases (carbon dioxide in, oxygen out). These openings are called stomata, and open and close based on the amount of light they are exposed to. The process of opening and closing based on light exposure is also interesting, and has to do with small rigid structures on the inner layer of the stomas, called guard cells. These guard cells become turgid and pull apart when in contact with light, as a result of taking in water through osmosis. The opposite then happens in darkness, as water leave the guard cells, decreasing their rigidity causing them to close.
How does the flu actually kill people?
They are often at risk populations like the elderly, children, or immune-compromised. What typically kills them isn't "flu" exactly but that it causes potentially fatal situations such as pneumonia, sepsis, electrolyte imbalances triggering arrythmias or seizures, worsening existing health problems such as COPD, CHF, etc.
Do men mature slower than women, and if so why?
If we're talking in a purely physical sense, then [girls tend to enter and finish puberty earlier](_URL_0_). Mental maturity though, is quite subjective. It is hard to quantify how "mature" someone is at a given age, or compare that in a meaningful way. I have not found any studies which deal with the subject in a satisfactory manner, though I would be interested in reading one.
Compared to humans do ants have fewer cells in their bodies, or are their individual cells smaller?
insect cells are approximately the same size as human cells, and this is also true for bigger animals such as whales (all being eucaryotes, the order of magintude in size is 40 microns). The real size variation is actually more important within a given organism : you've once been a little ball of 10 microns or so cells (pluripotent stem cells within you as a blastocyst when you were hanging in your mother womb) and you have been using motor neurons (up to 2.5 meters long -while mostly being 10 microns thin tube named axons for most of this length-) to ask this question
Why is the sun extremely bright during the day, and less bright during sunset?
The atmosphere scatters a certain amount of sunlight. When the sun is near the horizon, its light is going through a geometrically thicker section of atmosphere, so more of it gets scattered before it reaches your eye. [Picture](_URL_0_)
How does a flashbang grenade produce the “flash” effect?
The flash effect uses a magnesium-based pyrotechnic that is usually encased in aluminium and uses an oxidizer for the light reaction. Oxidizers can be things like ammonium perchlorate (which is actually used in a lot of fuel propellants) or potassium nitrate (which has many, many uses that you can search up). It's actually similar to something like a firecracker or a firework, just amped up to 5 million candela.
How do flash grenades work?
Usually a reaction between a metal (e.g. Magnesium) and an oxidiser (e.g. ammonium perchlorate) . Basically a small explosion, but with the results focused on light and sound rather than concussive force. If you've ever burned magnesium in school, basically the badass version of that.
Pair Production, why is the photon consumed?
Yes, the photon is destroyed in pair production. And yes, photon-photon pair production is possible in principle.
If human-created GHG are causing global warming, how come we don’t see any ozone holes over the biggest polluting industrial centers like China, North America, Europe?
Because global warming and the ozone hole are two completely different things, caused largely by different chemicals (although there is a little overlap), and affecting different parts of the atmosphere in different ways.
Would constellations as seen from Earth be recognizable on other planets in our solar system?
The constellations would be identical on Mars. Mars is at most 2.5 AU away. The nearest star is a million AU away. There is no significant difference in perspective. The only difference would be which star is the North Star, as Mars's axis points in a different direction from Earth's.
Would constellations be visible in Venus & Mars how they are on Earth?
The distances between these planets are so small that there would be no difference in the overall all-sky map of what the constellations looked like. However, things would be rotated around, because the planets are all tilted at different angles. Most of the planets are oriented in the same vague direction, so most Northern Hemisphere constellations will still be Northern Hemisphere constellations, but they'll just be shifted around a bit. The stars won't appear to rotate around Polaris anymore - instead, they'll rotate around another point that's in-between a couple of stars. So Orion etc will still all be there, it'll just be a bit lower or higher than the same latitude on Earth, depending on the planet. Edit: Here I am ignoring the atmosphere. From the surface of Venus you can't see anything at all.
How sure are we that Type 1a supernovas are 'standard candles'?
First off, what you're referring to is chandrashekar *mass*, not limit. White dwarfs are responsible for 1a supernovae. They essentially leech off a star it's in orbit with until it gets heavy enough to go supernova. This means that the supernova always occurs at the chandrashekar mass, which means all 1a supernovae have roughly the same luminosity. Since they all have the same luminosity, if you have two 1a supernova at different distances, you can tell which is further away based on which appears to be dimmer. You don't have to worry that the dimmer appearing one is just a dimmer supernova because both supernovae have the same luminosity.
Why does Sulfur Dioxide cause a cooling effect if it is a greenhouse gas?
Sulfur dioxide injected into the atmosphere converts to sulfuric acid which then condenses to form [sulfate aerosols](_URL_1_). The aerosols are highly reflective, bouncing a portion of the incoming solar radiation directly back into space and thus increasing the earth's albedo and leading to cooling. The effect is especially strong for powerful volcanoes whose plumes reach high into the atmosphere to the stratospheric layer. Once in the stratosphere, the aerosols can persist for many years. In contrast, sulfur aerosols in the troposphere have shorter lifetimes because they are removed by rainfall. Sulfur has numerous complex interactions in the atmospheric energy balance. Sulfate aerosols also can serve as [cloud condensation nuclei](_URL_0_) thus effecting the types of clouds which form and their reflective characteristics (a cloud with lots of small droplets has different reflectance than a cloud with fewer big droplets). see also: * _URL_4_ * _URL_3_ * _URL_2_
How much fossil fuel does an electric car truly save?
This is still very difficult to answer because "fossil fuel" encompasses a wide range of fuels, most commonly coal, natural gas, and oil. How much energy is saved depends on which source that energy comes from because each source has a different thermal efficiency (Natural Gas has an efficiency of up to 50%, while coal tends to be in the low 30s). However, when averaged across all energy production methods, it's been consistently shown the well-to-wheel efficiency of electric cars is higher than that of gasoline cars. _URL_0_
There has been an increase in electric car sales. How do we dispose of their batteries, once their lifespan ends? And would disposing batteries release less pollutants compared to gas engines?
Batteries would have to be properly disposed of and not dumped in a site, improperly disposed batteries could mix with rain water and release toxic chemicals into the soil and contaminate any nearby lakes or rivers making it more devastating than gas engines...
What non-carbon element has the most complex/interesting chemistry?
Si, Silicon has a shares a similar property to carbon: the ability for catenation form long chains also: [Silicon Biochemistry][#1] [#1]: _URL_0_
Why haven't the colors on Jupiter all mixed together yet?
The core of Jupiter is very hot. As a result, there is a significant temperature differential between the upper layers of Jupiter's atmosphere, and the lower layers. This causes convection, which moves the atmosphere around (similar to our own atmosphere regarding global wind patterns and ocean currents). Additionally, the different gasses in Jupiter's atmosphere react relatively differently to heat and pressure, and so stratify into different layers. Each of these layers has a different color and behaves differently from one another and generally won't mix without outside influence. The rotation of the planet additionally affects the structure of Jupiter's atmosphere. All of these effects constantly acting together creates the banding and storms we observe on Jupiter.
How is the universe 93 billion light-years across if it has only existed for 13.4 billion years?
The expansion of the universe is precisely the reason: it can expand so fast that galaxies can separate from each other faster than the speed of light. Take a look at this: _URL_0_
Do dogs recognize their own breed?
Dogs do not regard themselves as members of a breed. Only human beings care what breed a dog is, and breeds of dogs exist only due to the efforts of human breeders. Not only do different breeds of dogs happily mate (producing mongrel offspring) but even wolves and coyotes will breed and have produced a new canine variant called a coywolf.
If the universe were to undergo "catastrophic vacuum decay, with a bubble of the true vacuum expanding at the speed of light", would that bubble be able to reach points in space that are expanding faster than the speed of light? [Article in description]
Anything moving from a point at a constant velocity (in this case, c) cannot catch up to anything moving from that point that is moving at a rate equal to or in excess of said velocity. Not only would a metastable vacuum event fail to reach any part of space already moving away from it in excess of c, it wouldn't catch up to the light leaving the planetary system it happened in.
What is happening when I zip a file?
Here's a good example of lossless compression. _URL_0_ In this case what happens is that you analyze the uncompressed file and essentially create an encoding scheme such that from a smaller file you can recreate the original given instructions, which can be read at the header. As an extremely rudimentary example of this type of thing, let's say you have a file that contains 1000000 iterations of the number "0", nothing else. One could compress this file by turning it into something that says "when uncompressed, construct a file with 1000000 of the number "0" ". This compressed file would clearly be shorter because it doesn't have to store 1000000 characters. The reason we don't just keep everything compressed in a .zip file or something has to do with the fact that compressed files might not be as easily manipulated. For example, it would be easier to have MS Word open a .doc file than have it extract a .doc file from a .zip file.
Are the mechanisms that cause cancer mutations the same mechanisms that cause the appearance of new traits that we've evolve into?
Cancer is caused by defects in certain genes that produce tumor suppressing proteins. So when these proteins are not present, cells grow indefinitely, eventually you get cancer. Curing cancer will not have do anything to stop evolution.
How come doctors can pull people out of comas when they induce one, but it's almost impossible to pull them out if they go into a coma themselves?
A medically induced coma is simply giving a continuous controlled dose of an anesthetic. When you stop giving the anesthetic, the "coma" stops. When an individual becomes comatose for other reasons, it is usually due to severe damage to the brain or other nervous system functions. The damage usually must heal to some degree before the person becomes responsive again.
Is there any place in the solar system that one can see a moon as big as ours?
Pluto's moon, Charon, orbits at only 19500 km from Pluto. That's much closer than our Moon at 380000 km. Even if Charon is considerably smaller, it should look very big from Pluto. If I didn't mess up with the math then the angular diameter (apparent size) of Charon seen from Pluto should be 3.76 degrees. Compare this to our Moon, which is only half a degree seen from Earth.
Why does microwaving food (example: frozen curry) taste different from putting it in the oven?
Microwaves work by heating up the water in foods, not actually the foods themselves. Heat is transferred from the water to the rest of the food. This also tends to make the water expand into steam, so it gets everywhere, making everything wet. This interferes with the [Maillard reaction](_URL_0_) which is what makes roasted foods so delicious. That's why oven make things crispy browned delicious on the outside, tender on the inside (because the water turns to steam on the inside after the outside has cooked) while microwaves just leave a soggy mess.
Why aren't galaxies distorted when we look at them?
Compared with the speed of rotation, the side-to-side distance is negligible. Rotation times are measured in billions of years, whilst the diameter of your average galaxy is of the order of 100,000 light years.
Which type of commercially available milk ( 1%, 2%, whole) does human breast milk most closely resemble chemically?
[None, really.](_URL_1_) As an evasive answer, I'd say it's closest to commercially available infant formula. But, gun to my head, given the three choices you have, I'd say whole. This is only based on fat content, which is generally about 4% in both [human milk](_URL_0_) and whole milk, while 1% and 2% refer to fat content, so they have 1% and 2% respectively.
Can you be paralyzed from the legs up?
Sort of. There is a syndrome known as [Central Cord Syndrome](_URL_0_) where, because of the way the nerve fibers in the spinal cord are oriented, the upper extremities are preferentially affected more than the lower extremities. This is because the fibers that innervate the arms are oriented in the center of the spinal cord while the legs are represented more towards the outside. However, patients with CCS still have function of other muscles "above the legs", such as their facial muscles.
Do two different animal populations of the same species speak the same "language" if they develop separately from each other? If not would they change over time?
One species which became two separate isolated populations may or may not genetically diverge in such a manner. Two ant populations may or may not developed new or change chemical signals in relation to the original population. There is nothing in evolution to say that something must happen. It is interesting to note that emotional language is still intact between primates (us and the apes). Reading facial expression, identifying distress etc. _URL_1_ _URL_0_
What animals can humans get sick/get sick from? (such as transmitting a cold) What about their/our immune systems is similar that allows the sickness to be transmitted?
It should come as no surprise that many diseases which cross the species barrier to infect humans (the term is zoonotic) disproportionately come from animals that have a history of domestication. some of the better known examples: Influenza from birds(chickens)/pigs, tuberculosis from cows, several groups of intestinal parasites. It isn't so much the similarity of our immune system that accounts for this. Rather, over several thousands years in close proximity between species, many of these pathogens have been able to "feel" their way into infectious niches. That is what evolution is all about - seeking and exploiting opportunities in the environment that favor survival.
How common are illnesses such as the cold or the flu in other animals? and if they aren't common, why?
Flu is very common in waterfowl. It doesn’t make them sick, however. Generally people don’t get sick from the flu virus types that infect birds, but pigs can get both. And if a pig gets both, their cells can be infected by both viruses, both adding stuff into the cell’s DNA. Then a new virus emerges. This is why most epidemic versions of influenza have strain names of Asian cities. Asia is one place where ducks and pigs are often raised in close proximity.
Some of you might this this is a stupid question, but are nebulas and supernovas in space actually colored so brilliantly?
Get a telescope, even just a moderately sized one, and look at Orion's Nebula. It's a noticeably vibrant blue-violet. Most pictures of those things are false-color, to make it easier to identify the various gasses and elements in a structure. eg., making all hydrogen blue. But that certainly doesn't mean that they're merely black to the human eye. Many of them are bright and colorful, because of stars or even radiation emissions similar to neon lights. There are a few dark (black) nebulae though that can only be seen as shadows in front of someghing brighter.
How come photons are not affected by gravity?
They are affected by gravity. However, you don't see the beam from your flashlight bending down, for example, because the effect is far too weak. We can, though, measure the deflection of a beam of light when it passes by a large astronomical object, such as a star.
How do astronomers estimate the age of distant planets and stars?
A newer technique, that hasn’t been mentioned yet, uses asteroseismology to “see into” the cores of stars, which can tell you the age. It’s similar to how we use seismology to understand the Earth’s core. One advantage is that individual stars can be aged, not just clusters. Both the CoRoT and Kepler missions have done this. _URL_2_
Will a new planet eventually form in our solar system's asteroid belt?
No. Also the mass of all the asteroids together is [about 4% of the mass of the Moon](_URL_0_) - pretty small.
How close can we fly a spacecraft to the Sun? Any reason to send a craft right at the Sun?
In principle, we can launch a spacecraft that will impact the sun, but I don't see why it would be worth the expense of doing so. If we were going to get a probe close to the sun, we'd likely use gravity assists to do the hard part of the work. This means it would take a long time to get the probe where it's going, the probe's perihelion can be as low as we wish, and it's aphelion would at minimum be close to mercury's orbit. As for building a probe that can survive being close to the sun, the side of the probe facing the sun would need to be shiny and thermally conductive. Perhaps a gold coated sheet of tungsten or silver, connected to radiators in the shade of the craft by heat pipes. The side in the shade should be as black as possible to increase emissivity, and be shaped in a cone that closely matches the shadow of the reflective part.
How close could we send an unmanned spacecraft to the sun ?
We could make one crash into the Sun if we really wanted to do that. Basically, if you can send something out of the solar system, you can also crash it into the Sun. But of course it's a bit pointless to send anything into the Sun. Orbiting the Sun at a close distance is considerably harder to do. [Solar Probe Plus](_URL_1_) is a planned probe that would orbit the Sun and at the closest point come to 0.034 AU of the Sun (8.5 solar radii or about 1/8 of the radius of Mercury's orbit). The orbit would be fairly eccentric, at the furthest point it would be around Mercury's orbit. So I'd say that technologically we're capable of at the very least that. With more resources put into it, I'm sure we'd be able to get a closer orbit. At the moment, the record holder for the closest probe to the Sun is [Helios 2](_URL_0_), launched in 1976. It got to within 0.29 AU of the Sun, slightly closer than the closest point of Mercury's orbit. The furthest point of Helios' orbit was roughly Earth's orbit.
If you built a telescope in space, that had track a fixed point to view, similar to the Kepler, and did this for years, or even decades, of an exposure, could you see objects back to the edge of the big bang?
Not all the way back to the big bang, no. The universe was opaque to photons until around ~300,000 years after the big bang (this is when the [Cosmic Microwave Background](_URL_0_) was produced). We cannot see past this point. One problem with looking back further is that the older the photon, the more it has been redshifted due to the expansion of the universe, which means you need to use infrared or radio telescopes. That's not impossible to do, it just requires different kinds of telescopes. Infrared, for example, is a bit tricky as the telescope needs to be cooled down, which is actually moderately hard to do in space (the sun tends to warm things up a lot).
How did we discover that stars were really distant suns?
Conveniently enough, the current issue of Scientific American has an article titled [The Case against Copernicus](_URL_0_) that is relevant to your question. It describes the history of scientific evidence against the Copernican model, including the use of parallax and measuring the apparent diameters of the stars to arrive at incorrect distances and sizes of the stars. One interesting note there was that astronomers of the era didn't realize that the atmosphere made stars appear larger in the sky than they actually were, and so they came to the conclusion that the Copernican model was flawed as the lack of parallax indicating they were extremely far away combined with the over-estimate of diameter required the stars to be outrageously huge. It's a good read, I recommend it.
Why don't humans have 'mating seasons' like most other animals?
Well, this question will only garner speculative answers as no one knows. Animals usually have mating seasons so that when the offspring's born it will have an abundant supply of nourishment (either directly or indirectly, e.g feeding off the milk the mother sustains through feeding). For example, elk and deer have their mating season during the autumn months and give birth around spring time when plants begin to grow. This leads to good foraging opportunities for the mother to nourish her young as well as there still being enough plants for the calf to start feeding on during weaning. It has been theorized that humans don't require this sort of "offspring timing" to coincide with food availability because we **always** have food available. However, most infants are born in the summer months. If this is some remnant of a mating season to give birth around the wet season in Africa, I'm skeptical of, but who knows.
Why do animals have mating seasons, and why don’t humans?
Because you don't want to have a child in October and raise it through the winter when there's less food. Since humans spend 18 years as a dependant it doesn't matter what time of year u have them as they are going to see a winter as an infant
Why is hair growth more dense in certain areas of the body?
HEY GUYS I know it's fun to speculate about evolutionary just-so stories, but /r/askscience isn't the place for that - please don't post an answer unless there is actually scientific evidence that it *is* true, not just a lack of evidence that it *couldn't* be true. Tangential information about hair that is scientifically accurate is okay, though of course the top priority is to answer the question - and it's very possible that science has not solved this one yet.
Are Photons matter? And do they have mass? How much mass do they have relative to electrons? Does a photon with more energy have more mass? How do we calculate the amount of mass tiny particles have?
Photons do not have mass. They are generally not considered matter (which isn't a very precisely defined term itself), but in some scenarios they can behave like matter. For example, if you have a hot reflective box of mirrors, inside you can get what is called a photon gas.
Which are the least abundant elements on the periodic table and why are they the least abundant?
A general trend is that the heavier an element is, the lower the abundance. In addition, elements with an even atomic number are more abundant, I believe due to the fact that most heavier elements are formed through fusion of an atom with a helium nucleus. Plutonium-244 is the least abundant primordial element (on earth), because its half life is short compared to the age of earth, but just barely long enough that some can still exist. [Here](_URL_0_) is a chart. Lithium, Beryllium, and Boron are all far less common than one would expect from this simplistic rule of thumb, because they are hard to form from helium-4 nuclei. For example, the only stable form of beryllium is Be-9. Most beryllium produced in stars is Be-8, formed from two heliums. This isotope is very unstable, with a half-life of 6.7(17)×10^−17 s.
Why did the Romans (?) name Jupiter after Zeus if with the naked eye, Venus looks to be the biggest planet?
"But since they call Jupiter king of all, who will not laugh to see his star so far surpassed in brilliancy by the star of Venus? . . . They answer that it only appears so because it is higher up and much farther away from the earth. If, therefore, its greater dignity has deserved a higher place, why is Saturn higher in the heavens that Jupiter?" -St. Augustine Obviously this is several hundred years later, but maybe they understood it's relative distance from earth and deduced it was actually larger...?
Does pollen carry or assist the spread of illness?
Pollen can act as a significant vector for viruses (_URL_0_ you can only see the abstract, but that's enough to know that pollen is a viral vector), however pollen doesn't actually increase the amount of pathogenic particles leaving someone with a transferable disease unless they are allergic.
Do any animals laugh?
Laughter can be induced in great apes by introducing incongruity. For example, wearing a banana on your head, instead of consuming it as a food item, will elicit laughter in Chimpanzees (Pan troglodytes.)
There has been a lot of anti-ADHD rhetoric going around lately. Do we have proof that ADHD (especially in adults) is actually a disorder? Or are people like me truly just lazy, awful people?
ADHD is listed on the [DSM](_URL_1_), which means that it is considered a real clinical disease at the moment. However, that does not mean it will always be so (homosexuality was listed on the DSM in the past). But given what we know about ADHD, it is likely a 'real disease'. For example, there is a significant genetic component, with greater concordance between monozygotic vs dizygotic twins. A number of genes have been implicated, but no single key regulator has been found. There are some neuroimaging findings (average brain volume smaller in some areas), but we don't use it for diagnosis - it's entirely a clinical diagnosis based on the signs and symptoms. With that said, it's also possible that ADHD is overdiagnosed in some circles (though there are [data](_URL_2_) suggesting that [this is actually a misconception](_URL_0_)).
Why is language gender a thing in some languages but not others?
When it comes to Indo-European languages, they preserved the proto-Indo-European gender system. Not perfectly though, animate vs neuter is the distinction I hear about in PIE, but most old Indo-European languages use a three gender (masculine, feminine, neuter) difference. Spanish and all Romance languages lost the neuter during Vulgar Latin. With English, gender was lost somewhere in Middle or Early Modern. Gender systems are used to "connect" words. For example, Spanish uses gender to "link" nouns to the adjectives that modify them. Slavic languages (Polish in particular) take this a step further and have a past tense that requires the person, number, and subject's gender. I have not heard of a language where the older form had no gender and some change occurred which added a gender system. It is possible, I just have not heard of a real world example. Also, would this not be better as a post on r/asklinguistics or r/linguistics?
Given the amount of refining that goes into granulated sugar, is there really much difference between organic and non-organic?
It depends on where you buy the food. The term "organic" is a regulated term, so whether it has any meaning at all depends on local laws. [_URL_5_](_URL_5_) [_URL_6_](_URL_0_) Organic labeling standards do not just cover the chemical contents of the final product as they are delivered to the consumer, they also mandate agricultural and production standards such as sustainable farming practices and animal welfare practices. For example: Organic labeling soil fertility management requirements in the USA: [_URL_1_](_URL_2_) Organic labeling animal living space requirements in the USA: [_URL_4_](_URL_3_) So the label "organic" may mean something significant about the way food was produced, even if the end product delivered to the consumer is chemically identical to the non-organic counterpart.
If Earth is experiencing a constant (small) force due to solar wind, why doesn't our orbit slowly get larger?
The earth also experiences a constant force due to the sun's gravity, but you don't ask why the orbit doesn't slowly get smaller. The effect of the solar wind is to reduce the force of gravity between the Earth and the sun by a tiny amount, which makes the Earth's orbit very slightly bigger than it would otherwise be. To really change the orbit of an object, a force needs to be applied in the direction of motion.
The difference between shampoo/conditioner/liquid body wash?
Conditioner contains fatty acids, glossers, sunscreen, anti-static, and many other compounds to keep your hair well protected. Shampoo contains compounds to remove excess oils, sweat, dandruff and dirt away from your hair and scalp. Body wash is a mixture of water and detergent with fragrance added. It's more basic than shampoo as to not irritate the skin, but will strip all of the oils out of hair.
Is brown rice really a more "healthy" choice than white rice?
Brown rice naturally has more nutrients like vitamin B and iron, but when making "enriched" white rice they usually add them back in. Still, white rice usually doesn't have any magnesium. Also, there's twice as much fiber in brown rice, which is a significant amount considering its health benefits. Also, brown rice contains bran oil not present in white rice, which has been shown to help lower cholesterol.
Why did Eurasian diseases not transfer to all of North America when the Vikings made contact, instead devastating the Americas post-Columbus?
So, the vikings got to North America in an expedition from Greenland, which was itself an expedition from Iceland, which was itself colonized from Scandanavia. Epidemic diseases don't persist well in small populations, and Greenland was a small, isolated population colonized from a fairly small, fairly isolated population. So probably no epidemic diseases managed to hop from island to island to island the few times the connection was made. It's not a straightforward X percent of contact. You could have one guy wash ashore freshly dead of smallpox and that could do the trick, or you could have a fair amount of contact provided no one carrying the disease happened to get by (long travel times and intermediate steps in the chain make transmission less likely). But the nature of the Norse contact just didn't allow anything too nasty to take the jump.
Why does getting water up your nose burn?
Water is hypotonic relative to the contents of your cells (meaning it has less dissolved stuff). Due to osmosis, this will cause your cells to swell and potentially burst. The painful sensation comes from osmotic stress on the cells inside your nose. Neti-pots use saline instead of water for this reason.
How does turning on AC help defog car window?
When the AC cools the air, the moisture that is in the air is condensed, so that the air is dry. The dry air from the AC can then take up water from the window (evaporation), as the air is not yet saturated with water vapour. e. To also add, the AC generally has to be used in conjunction with the dehumidifier, as the dry air can be heated so that it can take up more water before reaching saturation.
How does turning on AC with heat actually help to defog a car windshield?
AC is not just cooling; > Air conditioning (often referred to as AC, A/C, or air con) is the process of removing heat and **moisture** from the interior of an occupied space, to improve the comfort of occupants. [Wiki](_URL_0_) The ac condenser coil is before the heater, the incoming air passes over the cold coil and water vapour in the air condenses. The air is then dryer than it otherwise would've been before heading to the heater. The air may not be quite as hot had the ac been off but it is dryer, which improves defogging. Dehumidification before heating the standard approach for HVAC systems.
How come we can remember sights and sounds more vividly than tastes and smells?
There is no more vivid recall or association than smell.
Why can't we remember smells as well as sights?
Smell is the strongest sense that brings you memories. Even more than sight of music. A smell harks back to our primitive times when it was a more advanced sense and we used it more. Some don't understand this but once you get a familiar smell you have not smelled in a very long time your memories come flooding back in her vivid much more vivid than driving by a place and seeing or hearing a song. It's a trip.
Is there any truth to the British Lung Foundation's claim that cannabis cigarettes increase the risk of lung cancer 20 times more than tobacco cigarettes?
There is a link between marijuana use and schizophrenia. There is some controversy as to whether there truly is a causation or if there is just a correlation. _URL_1_ _URL_3_ A marijuana cigarette has "a higher respiratory burden" than a regular cigarette, but also keep in mind the quantity of each that is generally smoked over a period of time. This study also notes the increased inhalation associated with marijuana use. _URL_0_ Marijuana use shows no increase in lung, head, or neck cancers. Marijuana can cause respiratory problems. _URL_2_
How do scientists measure how many light-years away a star is?
The Cosmic Distance Ladder (or how to tell distance in space): 0) Radar - good for < 1 light hour away 1) Trigonometric Parallax - accurate up to ~200pc (look up the HIPPARCOS mission) 2) Moving Cluster method - ~140pc (so basically on works for the nearest clusters; the Hyades and the Pleides) 3) Statistical and Secular Parallax - ~ 500 pc 4) Main Sequence fitting - up to 10 kpc 5) Variable stars (Period Luminosity Relationships) RR Lyrae - 200 kpc Cepheids - 1 Mpc 6) Novae - 1 Mpc 7) Luminosity Functions (of planetary nebulae and globular clusters) - 10 Mpc 8) Baade-Weselink Method - 30 Mpc 9) Surface Brightness fluctuations - 100 Mpc 10) Galactic Kinematics (Tully-Fischer or Faber-Jackson relations) - 200 Mpc 11) Supernova Type 1a (Standard Candles) ~ 1 Gpc 12) Sunyaev-Zel'dolvich method 13) Gravitational Lensing (time delays) 14) Hubble Law - 100 Mpc and up
How do scientists calculate that a star is xy billion light years away?
I've already seen the answers posted but I wanted to post these Khan Academy videos that I found helpful when learning about this topic. This is about calculating stellar distance using [parallax](_URL_1_). And this one explains [red and blue shifts](_URL_0_). I could write a long block comment but I feel Sal at Khan Academy does a better job of explaining than I can, also you might find some other cool cosmology/astrology videos you want to watch.