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When colors on fabric or paper fade from sunlight, where does the color go? | When a fabric has colour it is caused by a dye or pigmentation. Colour is caused by deflecting or absorbing certain wavelengths of light. Dyes are chemical species which absorb light to provide a specific colour due to their particular structure. When exposed to chemical reactions like photodegredation (light breaking ... |
How /exactly/ is Fructose metabolized differently from Glucose? | Fructose is converted to fructose-6-phosphate, whereby it enters the normal glycolytic pathway. Glucose enters the cell, is phosophorylated to glucose-6-phosphate, which is then converted to fructose-6-phosphate. |
If i put a candle in a box, then put a candle and a mirror in another box, will the one with the mirror be brighter inside? | Yeah, as JushiBlue pointed out, it depends where you're looking. Some of the first "flashlights" (or torches you crazy Brits you) were basically this principle. Stick a candle in some type of enclosure and a bunch of reflective mirrors to focus the light outward very brightly. That outward light is much brighter than j... |
If boiling (or heating to 100ºC) kills all germs, what is the component in "gone bad" meat that can make you sick even after it is cooked. | Bacteria produce toxins, [endotoxin](_URL_1_), which is part of the bacterium, and released when the cell dies, and [exotoxin](_URL_0_), which is secreted by the cell when it is alive. Both of these can survive the boiling process. |
Assuming an infinite universe, what does it mean when cosmologists say that the early universe was a particular size? | Yeah. Usually it means that the region of the Universe which we can see today was a certain size. It's extremely difficult - often impossible - to know anything about the Universe beyond that, due to the finiteness of the speed of light. |
Why does the tip of my nose get prickly the instant before I sneeze? | Sneezing is a reflex that occurs when the sensory nerves inside your nasal cavity sense a foreign object, or irritation. These sensory nerves dont just stop in the nasal cavity, but continue onwards to innervate your nose. So when they get a stimuli, some of that stimulation could be misinterpreted by the brain as a si... |
Why can't humans hibernate? | From what I understand, [humans can](_URL_5_). It's sort of an emerging field right now, but there's a good amount of study put towards it. |
Can humans hibernate? | There has been work done involving cooling the body and infusing the blood with hydrogen sulfide to mimic the state of a hibernating mammal to induce a similar state in humans. See: _URL_0_ |
How much safer are electronic cigarettes than real ones? In what ways if any does it increase the risk of cancer or other diseases? | E-cigs are more healthy than smoking cigarettes merely by the elimination of many carcinogenic chemicals found in cigarettes. [Among the 250 known harmful chemicals in tobacco smoke, at least 69 can cause cancer. These cancer-causing chemicals include the following:](_URL_0_) (National Cancer Institute - US government... |
Do species with a shorter lifespan evolve faster than those with a longer lifespan? | Organisms with shorter lifespans will have more generations in the same period of time, so more mutations will occur in the population in the same period of time, meaning evolution will happen faster. We often use insects in labs when we want to study the evolution of traits partially for this reason; they also tend to... |
Do organisms with shorter lifespans evolve faster? | Yes. A single slightly beneficial mutation in one individual can become ubiquitous in a large population in as few as 10,000 generations. In a long lived species this could take a hundred thousand years, but in short lived microscopic species this can be less than a year. Many 10,000, 20,000, and 50,000 generation expe... |
How do Seedless Watermelons and Grapes Reproduce? | Seedless grapes and watermelons very rare in the wild. The first seedless orange came from a tree in Brazil in the 1900's that by chance didn't have seeds. Seedless oranges are genetic clones of that one. We plant them by making a cutting of the plant and planting that. |
While sleeping in a sealed room, and the oxygen was quietly being removed, would you ever wake up before you died? | You would wake up with a headache because of the low oxygen content of the room. If you could then not extract yourself from the room you'd be ready for the past tense. |
If I fell asleep in an airtight room filled with only enough oxygen to keep me alive for a few hours, would I wake up before dying? | You would wake up after your blood oxygen levels dropped below a certain point, which is what happens to people with sleep apnoea. The level required for you to lose consciousness is lower than the level which would wake you up with a start, so you would wake up, and then probably pass out quite a bit later. |
Since a star has used up its hydrogen before it goes supernova, how does the resulting gasses give birth to new stars? | A star doesn't use up all of the hydrogen in the whole star, only the material in the core can fuse. The outer layers of the star, containing most of the mass, aren't burned. Some mixing can occur by convection as the star ages, but for the most part the composition of the core will be very different than the compositi... |
Why do things taste differently when cooked or burnt? | Foodservice professional here: heating foods increases the general rate of oxidation(combustion) in the food product, this has several effects of note, not the least of which is the "Malliard browning process" which is the high temperature combination of a lipid, a protein and relatively simple starches that are common... |
How does carbon dating accurately work considering all of the molecules likely come from beyond ancient supernova? | Don't worry about supernova and the formation of the earth. Carbon dating is waaaay simpler than that. High energy cosmic rays are constantly bombarding the earth from space which convert a little bit of the Nitrogen-14 in the atmosphere into Carbon-14. That carbon-14 is radioactive and decays away slowly, with a half... |
What is the purpose of pubic hair? | Most of the hypotheses I've read have to do with social cues (signaling sexual maturity and the like) or holding on to pheromone signals (I've never seen convincing evidence of this). However, these sorts of questions are incredibly difficult to determine. Evolution is a tricky beast - natural selection is an incredibl... |
Why does sunburned skin feel warmer than usual? | Because it is. Blood has moved to it (just like any other injury) in an attempt to heal it. It also increases the temperature to acceleration the healing process (biological processes generally happen faster in the warmer environments). |
If moving above the speed of light is impossible, how will we ever get to see planets up close which are 100+ lightyears away? | We most likely won't. Planets don't emit any light, so even with super powerful telescopes this will be more than difficult. Getting there is also nothing more but a dream. Sure, like trizzwizz said, if you go sufficiently fast you can make the trip seem as short as you want, but these speeds are way beyond our reach. ... |
Will the asteroid belt eventually become a planet? | No. The current thinking is that the asteroid belt is matter that never formed a planet, but there is no mechanism that would cause it to merge into a single object. It's also worth noting that the entire asteroid belt has a mass equal to about only 4% of the mass of the Moon. |
How did we determine dogs were colorblind? | Well dogs aren't exactly colorblind. They can see colors, just not all the colors humans can. This was determined partly because of scientific research revealing dogs' eyes don't have as many cones as humans' eyes do. |
I've heard that galaxies across the universe are moving away from us at faster than the speed of light. How is this so? I thought nothing can move faster than light. | It is true that, according to special relativity, nothing can move through spacetime faster than the speed of light. However, the large-scale structure of the universe is described by general relativity, not special relativity, and in general relativity there is no prohibition on the apparent velocities of distant obje... |
Do Animals Have A Sense of Rhythm? | Some do! Check out [this article](_URL_0_). This mentions parrots and elephants specifically, but sea lions and bonobos have also been found to keep a beat. There may be other examples. |
Is glass a liquid or a solid? | Glass is glass. It is neither a crystalline solid, nor a liquid. Common SiO2 glass is an example of a *glass*: an amorphous, non-crystalline solid. |
Interstellar speaking, does our planets night side appear significantly brighter due to our artificial light ouput? | The word 'significantly' is a bit open for interpretation, but some regions of the world are certainly brighter as a result of artificial light. Most of the planet is sparsely populated (oceans, deserts, polar regions) and so most of the light output is from a relatively small fraction of the land area. There are plen... |
Does the gut bacteria of an alcoholic differ from a non drinker? | Follow up question: Until fecal transplant becomes mainstream is there anything that can be done to repair the microbiome? I was a heavy drinker for a few years and have had to take a few courses of antibiotics. I've always suspected this as the root cause you some of my issues |
Why is the Sabatier reaction not used more to convert carbon dioxide to useful methane? | Where do you intend to get the hydrogen from? |
Do wolves panic during thunderstorms the way domesticated dogs sometimes do? | Dogs panicking during thunderstorms only primarily happens because they aren’t conditioned to the sound before formative development in the brain stops. Dog trainers can suggest playing different sounds—cars honking, trains, thunderstorms, alarms, etc.—while puppies are young so they get used to the sounds and don’t pa... |
Are there any human infections caused by plants? | The answer to your question depends on how you define plants. If you are including green algae the answer is yes. [Protothecosis](_URL_0_) is caused by an algae that has cells which lack chlorophyll and have become parasitic. |
What is the difference between being in a coma and a vegetative state? Can you be in a vegetative state but not be considered to be in a coma? | In a coma, two elements of consciousness are missing: wakefulness (responsiveness to stimulation) and awareness (of surroundings). A vegetative state is wakefulness in the absence of awareness. People in a vegetative state may open and close their eyes, but without any purposeful behavior or self-awareness. See, for ... |
What's going on during sleep paralysis? | The wiki is actually a very interesting read: _URL_0_ Myself, being aware of sleep paralysis, experienced no fear when I found myself unable to move at all and observed someone walk into my room and stare at me for a while, then sit on my chest so hard I was having difficulty breathing. The entire time I kept thinking ... |
What causes bright lights to be physically painful? | I can only offer speculation, but the size of your pupil is controlled by muscles. My guess is that the pain is from these muscles being tightened after being relaxed for a while. No research I've found suggests you have pain receptors in your eye. |
Is it likely there are planets with geostationary moons? Would they have a perpetual eclipse in one area? | Yes, we should expect this to happen. Tidal locking causes moons to reach a resonance where their rotation period is equal to their orbital period, so they've always got the same side facing the planet - our Moon does this. But a moon's gravity can also effect the planet, and cause the planet's rotation to lock into th... |
How are "itch" and "pain" perceived differently? | Both pain and itch sensation use the same pathway and are processed in the same center(primary somatosensory cortex). The scratch response and withdrawal response are also processed by the same pre-motor and supplementary cortices.The differences between pain and itch processing do not result from activation of distinc... |
Why do people with mental illness never seem to have ''positive'' hallucinations? | Those who have “positive” hallucinations may have an easier time hiding them, because their behavior may be seen as “eccentric” but on the normal side instead of “creepy,” dangerous, and weird. Basically, they’re less likely to disrupt or worry others. |
Astronomers, does the luminosity of stars change significantly over their life, specifically during their long phase as "normal" (whatever that means)? | Stars do brighten a bit over their main sequence lifetime. The Sun, for instance, would have been about three-quarters its present brightness two billion years ago. This leads to a problem called the [faint young Sun problem] (_URL_0_), where the sun's energy output at that time would have been insufficient to produce ... |
How does the mass of the star varies during its lifetime? Do stars get lighter the older they get? | I can give you part of the answer. Without anything entering the system (like meteorites) stars only ever loose mass. Each star fuses smaller elements into larger ones (Ours does Hydrogen into Helium I think). But in that fusion reaction, some mass is lost in the form of heat and light. So, the star looses mass over t... |
Do certain animals or insects have a larger range of visible light? | Quite a few animals can see into the UV range, not visible to humans (_URL_1_) Amongst others, the mantis shrimp has a spectral sensitivity extending into the UV (even if the maximum sensitivity of each of his cones is in the visible spectrum) _URL_0_ [P.S. The mantis shrimp is awesome](_URL_2_) |
Why does my shower curtain billow inward? | It would mostly be temperature creating a convection current, the shower curtain creating a preferential one-way flap and the internal air being more humid, so it can carry more thermal energy. The typical scenario is that the inside of the shower will have rising steam, which escapes over the curtain rod, causing a pr... |
What is the purpose of vitamins in fruits and plants? How did they come to be? And why are they so good for us? | You first need to understand exactly what a vitamin *is*. A vitamin is a chemical compound that is necessary to the organism but cannot be produced by the organism, or at least not in sufficient quantities, and must be obtained through diet. So what a vitamin is to a plant can be different than what a vitamin is to a p... |
Do dogs that are used in war suffer from PTSD as well? | There was a [NY Times story](_URL_0_) on that just a day ago. |
Do I get the same nutritional value from a popcorn kernel unpopped as a popped popcorn kernel, if so, why? | Most likely - most/all of the biological compounds will not break down at the ~100-150 degrees Celsius (increased boiling point due to pressure). It may be slightly more nutritious as the protein will be denatured (protein absorption is promoted by cooking). That said, you would have to break the kernel up to get the w... |
Why do we hear a voice in our head when reading? | Another question on this topic, with which the answer might only be philosophical, I always wonderd, animals or people who would have no clue about speech or writing, how do they think? because i talk in myh ead but if you dont know the concept of langauge how do you think about stuff |
If a star emits very high radiation, higher than visible light, would it literally be invisible to the naked eye? | As an object heats up, the *peak* of its EM radiation shifts to shorter wave lengths (infrared to red to blue to ultraviolet). But a hotter body will give off more radiation at **all** wavelengths than a cooler one. So the peak shifts, which is why there are yellow stars and white stars and blue stars, but no matter ho... |
Why do we get itches that need to be scratched? | _URL_0_ But this still does not explain the function/evolutionary origin of the itch-scratch. |
When you shake up a carbonated drink, where does the pressure go once it’s ‘settled’? | The pressure forces the carbon dioxide to redissolve in the liquid of the drink, where it exists as carbonic acid (H2CO3) and bicarbonate ion (HCO3-). This is the dynamic equilibrium: H2CO3(aq) < -- > H+(aq) + HCO3-(aq) < -- > H2O(l) + CO2(g) Agitation (or heat) push this equilibrium toward gaseous CO2, and positive pr... |
Is it possible to create an electric jet engine? | A modern [jet engine](_URL_0_) is actually a compressor and turbine in one machine. The turbine harvests some of the energy from the burning fuel and uses it to power the compressor. The rest of the energy provides thrust or is lost as heat. If there is no energy input (fuel) then the turbine won't be able to generate ... |
Is it possible that there is another planet orbiting the sun at the same speed as the earth, making it impossible for us to observe? | There are two main reasons why not: Since our orbit is elliptical and not of constant speed, there would be times when we could see it. The probes we have sent to Mars and Venus and elsewhere would not have reached their targets if that hypothetical planet had a gravitational influence. |
Why do so many drugs cause "feelings of suicide" or "suicidal thoughts"? Even Anti-depression medication | From what I can remember from other times this has been asked, it's pretty much because some people are *so depressed*, they don't even want to commit suicide. An anti-depressant would give you the energy and commitment required to follow through with suicide. |
What causes the "just woke up" voice? | Opera singer here. The laryngeal folds are indeed a muscle, and therefore require that blood be flowing through them to function at full capacity. The issue is not that the muscle has tightened. Your voice is lower in the morning for effectively the same reason a professional dancer wouldn't hop out of bed and do the s... |
If I were to send a tree to mars with sufficient nutritients and water(everything it would need to grow on earth), would it be able to grow and produce oxygen? | Nasa, among other groups with space exploration in mind, are asking that question themselves: _URL_0_ It seems the biggest problem to overcome is the low atmospheric pressure, which sucks the already rare water out of plants. Nutrients don't seem to be a problem. |
Why, when you cry, is your nose stimulated to run? | Tears are released from the lacrimal gland at the upper corner of your eye, and drained from the eye by the nasolacrimal duct (tear duct) in the bottom corner of the eye. It drains into your nose. |
Is glass really a liquid? | No, glass is an amorphous solid which is characterized by the molecules arrange in a liquid-like disorder, as opposed to a crystalline order. It's still rigid and has the mechanical properties of a solid though. Generally, a glass is an amorphous material which exhibits a [glass-liquid transition](_URL_0_), a reversibl... |
Why do stars and planets rotate around a single axis? Why don't any "tumble", rotating around 2 axes? | Nothing rotates around 2 axes. All three dimensional rotations, however "complex", [can be simplified to rotation around a single axis (Euler's rotation theorem](_URL_0_). The composition of two (or more) rotations is a (single) rotation. EDITED: Still learning something new every day. Although Euler's theorem is of c... |
If we all came out of Africa, does that mean the first Europeans were black? If so, why are there no longer any (native) black Europeans? | There's an evolutionary pressure for lighter skin at higher latitudes because exposure to sunlight is necessary for the production of Vitamin D. Vitamin D deficiency can cause developmental disorders like [Rickets](_URL_1_). Given enough generations, there is sufficient pressure for populations at northern latitudes to... |
How do we have images of the Milky Way Galaxy? | We don't. We have pictures of other galaxies. We know that the milky way is a spiral galaxy. So pictures of spiral galaxies stand in for the milky way. |
Is there any difference in how bright the sun appears from earth during certain parts of its orbit? | Yeah, it's about 7% brighter in January. That might be hard for humans to notice. |
Is there anywhere other than Earth in the Solar system where you could see a total solar eclipse and/or total lunar eclipse equivalent? | Such events are quite common in the outer solar system where the Sun appears to be smaller. It is possible when Amalthea, Io, Europa, Ganymede and Callisto occults the sun on Jupiter (_URL_1_), Janus, Mimas, Enceladus, Tethys, Rhea, Dione and Titan for Saturn (_URL_0_) and for many other moons on the outer planets. |
Why aren't meteors torn apart when they enter a planet's Roche Limit? | The Roche Limit is dependent on the mass of the parent body, the distance between the two bodies, and important in this case, the diameter of the affected body. Most *meteorites* (meteors are the flame trail created when passing through the atmosphere) are not large enough for the tidal forces involved to overcome the ... |
How do trees perform photosynthesis in the winter (without their leaves)? | If there are any green areas without too thick bark then perhaps they could do some there, but I think the majority just hunker down and live off the starch stores they built up over the spring/summer months. It’s probably better to jettison their leaves when the daylight hours become very short as they would probably... |
Why does wet hair behave so differently? IE. Clumping, floppiness, etc | Due to different intermolecular forces. When the hair is wet, it is coated with water, allowing hydrogen bonding and polar interactions to occur between different strands of hair. When dry, the hair (and oil coating the hair) does not have the attractive interactions. You can think of it like a bunch of towels. When t... |
What causes your hair (let's say curly, for instance) to become soft and malleable when it gets wet? | Water penetrates hair fibers and breaks some of the disulfide bonds between the fibers; this disrupts fiber structure, and they sag under gravity. Disulfide bonds reform over time and hair regains its curl — but there are chemicals that can disrupt disulfide bonds more permanently, and they are what's used in perms. [S... |
Why is bird poop white, where as almost all other poop is brown? | Most of bird poop is in fact brown(or green). The white portion you see is the urine in the form of uric acid, as birds do not urinate like mammals do. If you care to know, uric acid is used as a waste product because it is less toxic compared to ammonia(the urinary waste of fish) and Urea(mammals and amphibians) and c... |
Did trees get taller than redwoods in earths history? How big were the largest trees ever? | Don't know about the largest trees *ever*. But lepidodendron or scale trees from the carboniferous period grew to up to 30 meters. Trees were able to grew taller once they evolved stronger hardwood tissue, but even if lepidodendron were not the tallest, they were the most prolific in Earth's natural history and among t... |
How can the observable universe be ~ 100 billion light years in length if the universe is only ~ 14 billion years old | Observable universe is ~ 100 billion light years across. Universe is much bigger that that. It's likely that universe is infinitely large (if it is indeed flat in large scales like it seems to be). In any case, the [metric expansion of space](_URL_0_) means that universe expands in every point without stuff moving aro... |
What causes lactose intolerance? Can someone lactose intolerant become tolerant over time? | Historically the development of lactose tolerance started in Europe due to the cooler climate. Lactose was consumed in the middle east but in cheeses and sour milk drinks (you can still buy sour milk in Turkey, it's not very nice though). In europe, milk wouldn't go off as quickly and could be consumed, which caused th... |
When a water filter (e.g. Brita filter) is past its expiration date, is it just not filtering very well anymore, or is it actively making the water worse? | If it's unused and sealed properly it will be fine. If it's exposed to oxygen both activated charcoal and DI resin will exchange with oxygen and reduce the amount it will filter, thus you won't know how long until of water until it's not working well. Activated charcoal for aquarium filtering is stored a long time, it ... |
When mosquitoes suck blood, why does your skin leave a bump and not an indent? | The indent is there, just too small to see with the naked eye (usually). The bump is actually your body reacting to the mosquito saliva that she leave in you, and as a foreign entity your body fight: like a local allergic reaction. |
What are the evolutionary benefits of monogamous relationships in the wild? In other words, why do some animals pair up for life and others don't? | The main benefit is if care of offspring requires more than one parent. It's unusual but not unheard of to see monogamous pairing in species which don't provide parental care. The need for two parents to successfully raise kids can explain temporary monogamy, but what about monogamy that lasts after the offspring have ... |
What exactly composes the taste of freezer burn? Is it a chemical in the food that tastes like freezer burn? | So, you can taste the freezer burn taste in the fost that builds up in the freezer if you put a little on your tongue. This suggests the freezer burn taste is some kind volatile/aromatic in the food that tends to vaporize and recondense with the water that sublimates from food. Likely is those aromatic compounds, but o... |
If every cell in the body replaces every 7-8 years or so, then why do things like tattoos and scars never go away? | The way i understand it, when a skin cell grows old it splits itself in two, essentially replicating itself before it dies. So if the old skin cell is scar tissue or has ink embedded in it, the new one will as well. |
Would it be possible for us to find chemical elements that are not on the periodic table? | An element's identity is determined only by the number of protons it has in each atomic nucleus. Element 50 here is the same as element 50 on Zorblax. Elements with a large number of protons (above 100) are so unstable that they are not found anywhere in nature, because they have decayed too quickly. So you are unlikel... |
How much heat do the stars we see from Earth, besides the Sun, contribute to the overall temperature of the Earth? | Sun: 3.846 x 10^26 watts at 149597871000 m, 3.846 x 10^26 / (4\*pi\*149597871000^(2)) = 1368 watts per square meter The brightest star visible from Earth is Sirius. It's actually a binary pair, which in total emits 9.779 x 10^27 watts, at a distance of 81360544300000000 m, which means we receive 0.0000001176 watts per ... |
Do moons have moons? Any in our solar system? Have you detected any moons of moons in other star systems? | The closest example I can find documented are [the two co-orbital satellites of Saturn](_URL_0_). They orbit each other with a longer period than they both orbit saturn. Having said that I am sure there is some rubble orbiting many moons in the solar system. It would never be in a stable orbit and would need to be cons... |
Could bacteria ever become immune to soap | If you are talking about antibacterial soap which uses substances like Triclosan to kill microbial life, then this is already happening (leading in part to the flourishing of MRSA) and there is a backlash against the overuse of antibacterial soaps. Soap, in general, though mainly cleans object by physically removing t... |
Why can we not replace nuclear "waste" aka the dirt around the uranium back into the hole that was dug? | For the posters who are confused, I believe the OP is asking about [uranium tailings](_URL_0_), a radioactive byproduct of uranium mining. It is a significant environmental issue. I don't know the answer myself, I hope an expert comes by to enlighten us. |
What can the James Webb telescope see that the Hubble can’t? | Finer and more detailed pictures. If I'm not mistaken, Hubble can only see about 10 billion light-years (ly) away, but those pictures are kinda fuzzy, we can still collect a lot of data, but JWST is going to take MUCH finer measurements, observations, and pictures. **Answer to your question starts here:** Hubble speci... |
What can the James Webb telescope see that hubble can't? | JWST will be able to see different wavelengths of light. The Hubble observes in the near ultraviolet, visible, and near infrared (0.1 to 1 μm) spectra, the JWST will observe in a lower frequency range from long-wavelength visible light through mid-infrared (0.6 to 27 μm). This will allow the JWST to observe high redsh... |
Why are the Mars Rovers so slow both physically and in processing speed? | Because the priority is high reliability rather than speed. This is also why the early [space shuttle computers](_URL_0_) used [core memory](_URL_1_). |
Why do the Mars Rovers move so slow? | I want you to imagine you have a car, which you can only control via remote, and there's a 7 minute time delay between you sending it an instruction and it performing what you want it to do. Also, you've only got a few cameras strapped to it for you to survey the area. And the area it's in is a completely unconditioned... |
What would a universe be like if it had two dimensions of time? | [Extremely unstable](_URL_2_). The predictability of physics would be very much in jeopardy, if not entirely destroyed, if there were more than two timelike dimensions. See the link for more, or (if you don't mind something a bit more technical) this [excellent paper](_URL_2_) by Max Tegmark. |
Is it possible for a universe to have more than one dimension of time? | There is a great paper that addresses the possibility of other configurations of dimensions. One the dimensionality of spacetime. By Tegmark. _URL_0_ He argues that less than 2 spatial dimensions it is too simple to have sentient observers. More than 1 time dimension makes it impossible to predict the future knowing t... |
Why can't we move our eyes independently? | In a certain sense, we can. Have you ever gone cross-eyed? Some people can even move one eye in while keeping the other eye straight. I'm sure others can do even more. But the brain prefers to use both eyes for the same image. The reason most people can cross their eyes is because the muscle on the inside of each eye (... |
Are the apparent shapes of galaxies noticably distorted by the speed of light? | According to my [calculation](_URL_0_), the difference in distance between the center and one edge of the Andromeda galaxy (one of the closest) means that we see the edges of its spirals about 2,900 years in the past relative to its center. this time scale seems almost irrelevant on a galactic level. so I would assume ... |
Is the sun capable of running on any kind of material or is it specific to hydrogen? | The sun is fusing hydrogen to helium right now and has trace amounts of other elements from the original solar nebula. In about 5 billion years so much hydrogen would have been converted to helium that hydrogen fusion will stop and the sun's helium core will collapse under gravity increasing temperature and pressure un... |
What is the fluid build-up inside a blister? | A blister is caused by shear stress that leads to the lower layers of skin, especially the [stratum lucidum](_URL_0_) and this makes a leak, which allows plasma to leak into the pocket that has now formed. This is blood plasma, but shouldn't contain blood cells. If it becomes infected it can fill with pus, or with bloo... |
why aren't there animals the size of dinosaurs anymore? | The largest known animal to ever live is the Blue Whale, which still exists. |
When our body burns fat and we lose weight where does the mass go? | You gain energy from breaking the chemical bonds. The [Citric Acid Cycle](_URL_0_) is the major energy producing pathway in your body. The end result is CO2 and reduced molecules that donate protons to the [Electron Transport Chain](_URL_1_) in your mitochondria. The mitochondria use the protons to create energy in the... |
Can plants get cancer from the sun like humans can get skin cancer? | Skin cancer is cause by damage to to our DNA by UV light, usually the UV light creates cross-links between the base pairs. Plants have a really cool enzyme called photolyase, which is light powered enzyme that breaks these cross-links and repairs the DNA. |
Why can rocket boosters have more than 100% thrust? | 100% thrust was the original specification for maximum output from the rocket. It was later determined it could handle more (up to 104% based on the original 100% definition). |
Is it possible for a propeller-driven plane to exceed the speed of sound? | A [similar question](_URL_1_) was asked a few days ago. [NACA research](_URL_0_) in the 1940s suggested that this was feasible, but as you suggested, it was discarded in favor of jet propulsion, which is a much simpler approach to the problem. The problem is that the profile of the blade required to sucessfully operate... |
Could a plane powered only by propellers (without injecting fuel into an air chamber) theoretically exceed the speed of sound? | The air reaches the propellers from the front, not the back. The propellers are moving into the air, not away from it. Even if the speed of sound was zero, once the plane starts moving it would be able to accelerate just fine by running into the air. |
Why do we chatter out teeth when we are cold? | Your body is constantly trying to maintain its core temperature. Your muscles can generate a lot of heat so when you are cold, your muscles will tense and rapidly contract and release. This used a lot of ATP (your body’s energy molecule). One of the byproducts is heat. |
Is our Solar System truly hurtling through space at an incredible speed? If so, how come we still see many stars in the same places daily if they are also hurtling through space at an incredible speed? | Let me share with you the most profound sentence anyone has ever said to me about the wonders of our observable universe and the galaxy we live in specifically:"Space is like...... really big..." If you can grasp the context of that and what comes with it, the perception of objects in space and their relativity to each... |
What is the limit to space propulsion systems? why cant a spacecraft continuously accelerate to reach enormous speeds? | The limit is that you have to carry fuel on board, and the more fuel you take (to reach a higher speed), the more fuel you have to take just to carry that extra fuel. Until like, you start getting braked by the [cosmic microwave background.](_URL_0_) |
If there is little to no friction or gravity in outer space to slow an object down, how come a space shuttle has a maximum speed? (Apparently around 28,000 kilometers per hour). Why can’t a spaceship continue to build momentum to reach up to light-speed? | In addition to the (very good) response by /u/Astrokiwi, there are all sorts of small particles scattered throughout space. At low speeds, this isn’t too much of a problem. But at high speeds, it becomes an issue. At just 1% of the speed of light, something with the mass of a baseball has kinetic energy approximately e... |
Why do I have to drink and ingest fluoride? Why can't I just buy toothpaste with fluoride in it and rub it on my teeth? Why do we have to put it in the drinking water? | There is a difference between topical fluoride found in toothpaste and rinses vs ingested fluoride in water. The object of fluoride treatment is to convert the hydroxyapetite that makes up tooth enamel to fluorapetite, which is less soluble. Topical fluoride treatments can convert some of the outermost layer to fluorap... |
Why do looking at a bright light provoke you to sneeze occasionally? | The condition is called photic sneeze reflex. From what I have read, the jury is still out on the true cause, but the best guess is that the trigeminal nerve (responsible for facial sensation and motor control) and optic nerve run close together in the head. When your optic nerve is overstimulated by the light, some of... |
Why do humans have little-to-no memories from when we are very young? Is the ability to form a memory a skill that must be learned? | Long term memory develops throughout childhood and isn't inherent upon birth. Explicit memory (memory that you are consciously aware of) is most noticeable past ages 2-3. There's a really good wiki article on this. > Declarative memory develops very rapidly throughout the first 2 years of life; infants of this age sho... |
Subsets and Splits
Random Sampled Questions
Selects 1000 random questions from the dataset that end with a question mark, providing a basic sample for review.