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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 down the chemicals) or bleaching it will cause the chemical dyes to break apart and lose their shape, stopping them from absorbing that light. |
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 just the candle by itself, but only because it's focused much like a lens. An easy way to think of it is that a candle in an open enclosure emits light radially, if you use mirrors you're "moving" some of the light that would have gone in other directions into the same direction, thus making it brighter! |
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 signal coming from the tip of your nose. You can sort of replicate this in a different way by rubbing on your ulnar nerve. If you flex your right arm and look down on your elbow you see two bony protrusions, one is your elbow, and the other is slightly closer to you. The ulnar nerve runs between these two bony protrusions, so if you firmly rub the area between them with one finger, you should feel a prickly sensation extending towards your little finger. |
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) -- Arsenic, Benzene, Beryllium (a toxic metal), 1,3–Butadiene (a hazardous gas), Cadmium (a toxic metal), Chromium (a metallic element), Ethylene oxide, Nickel (a metallic element), Polonium-210 (a radioactive chemical element), Vinyl chloride Most people who smoke cigarettes have nicotine addition to some degree. Don't forgot that you can practice harm reduction instead of cession. Everyone finds themselves addicted to a substance, action, or object at some point in their life. Harm reduction can be a viable alternative to quitting by minimizing the damage caused. E-cigs is a valid harm reduction technique for smoking when you don't want or can't quit. |
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 breed in large numbers which helps too, though that's not related to their lifespan (plenty of organisms which breed in large numbers have long lives). |
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 experiments have been done in labs with bacteria. This would take decades with short lived insects, and thousands of years with even the quickest reproducing mammals. Edit: spelling. |
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 composition of the outer envelope. The hydrogen in the outer envelope isn't burned, so when the supernova happens it seeds the area nearby with not only the metals in the core but with the hydrogen and helium that still make up the vast majority of the mass of the star. |
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 in items like bacon. this process is responsible for the delicious brown crispy outside on most cooked meats/high temp "dry" cooking methods. in addition proteins tend to contract into a more compact form under particular temperature conditions (eg. albumin coagulates at 115 F) and this causes some pretty dramatic changes in food as well due to them tangling amongst themselves. (eggs hardening, bacon curling). as for burned food, just don't do it. or eat it (i have heard tell that seriously burning certain foods can create nasty carcinogens) < heresay. |
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-life of about 5700 years. What this means is that there is an approximately constant fraction of the carbon in the world which is this radioactive carbon. It gets taken from the air and used in photosynthesis by plants, and so all living things should have this same fraction of 14C in them as long as they are alive and actively exchanging matter with the environment. When something dies its 14C begins to decay away and by measuring how much 14C is left in some dead thing (either by counting the decay rate with a Geiger counter or running it through a mass-spectrometer) we can measure how long ago it died. |
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 incredibly potent force, but the "rationale" behind what gets selected and what is not is not always apparent. Whenever you read stuff about "why" something evolved in humans, especially behaviors (though things like pubic hair fall under this as well), you should immediately turn your bull-shit detectors up to 11. |
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. While physically not impossible, I personally believe we will never have the technology, the resources or the manpower for such an endeavor, but for sure not in the foreseeable future. |
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 objects being greater than the speed of light with respect to each other. Crudely speaking, this is because cosmological expansion can be explained as the expansion of space itself, which does not have a "speed limit;" the speed limit only applies to things moving locally through that space. See [Davis and Lineweaver (2003)](_URL_0_) for more details on this and other common cosmological misconceptions. |
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 plenty of images on the internet of earth at night, one that nicely sums it up in my opinion: _URL_0_ |
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 panic when they hear an unfamiliar sound. Since wolves are in the elements 100% of the time, I assume pups hear the sound of a thunderstorm before that brain development cuts off, and are normalized to it. Not a zoologist or wolf expert—just have a puppy that I’ve done tons of research on so that he doesn’t panic during thunderstorms. |
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 example, [Monti (2012)](_URL_0_) ( < - pdf) which is a fairly accessible review. Edit: fixed a wrong word |
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 "stupid sleep paralysis", and finally broke myself out of it. Knowledge dispels fears. |
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 the moon's orbit too. This happens particularly if you have a large moon and a small planet. In fact, Pluto and Charon do this. So from some point on the surface of Pluto, you will see Charon always in the same spot in the sky, and vice versa from Charon. However, this doesn't give you a perpetual eclipse. The planet and the moon are locked to each other, but they're not locked to the Sun. The Sun would still move around the sky as the planet rotates (and the moon orbits), and you'd only get an eclipse when the Sun moves behind the moon. The eclipse would be longer, because the planet would be rotating slower, but you wouldn't have permanent eclipses. |
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 distinct brain centers, but occur due to a different activation pattern of basically identical centers. For example, itch processing may be characterized by weaker activation of primary and secondary somatosensory cortices but relatively stronger activation of ipsilateral motor areas and anterior cingulate compared with pain sensation. This article gives a basic idea about the differences: _URL_0_ |
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 liquid water on the surface, yet the geological record shows that liquid water existed at the time. There's a more in-depth review on [arXiv] (_URL_1_). I think that the solution to the paradox involves a stronger greenhouse effect in the past, but I'm not sure. |
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 time. One thing to keep in mind, while the star is indeed loosing mass. It's volume and density change based on where in the stars lifecycle it is. Note, I am an Econ and Math major. So take all that I say with a grain of salt. I could be wrong on a point or two. |
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 pressure differential that creates an inward air current near the bottom. (Edit): I realized one other force I forgot to mention for a cold shower. The water droplets will impart momentum to the air inside the shower, which will also create some air pressure. That's probably far more significant than a humidity difference for a cold shower. |
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 person. Take vitamin C (ascorbic acid) for example. It is necessary for plant growth, but it's not a vitamin to the plant, because plants can create it through a 10-step glucose → ascorbic acid pathway. We just call it vitamin C because it's a vitamin to us. |
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 whole nutritional value from kernels. If you didn't you wouldn't get nutrition and would end up with Machinegun Anus Syndrome. |
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 how hot you get, the star will always give off visible light. Edit: Damn, I guess there's no wikibot here. Look at [this figure](_URL_0_). As the temperature moves from 3000 K to 4000 K to 5000 K, the peak moves to the left into shorter wavelengths, and more radiation is given off at *all* wavelengths, even the longer ones. |
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 pressure pushes it in the other direction, as it forces the CO2 to redissolve. |
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 enough energy to both run the compressor and provide thrust. Imagine the situation of 100% efficiency: all of the energy that gets put into the air by the compressor is regained by the turbine. In this case you have a do-nothing perpetual motion machine that will theoretically run forever but will provide no thrust. 100% efficiency is, of course, impossible. If you're thinking of simply using electricity to compress air and then release it through a nozzle, then yes. It would work, but you would be far better off just using a propeller. |
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 splits immediately-the muscles have not warmed and loosened to ideal capacity for speech. |
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 reversible process from a solid brittle state to a molten rubber like state. |
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 course true, it seems that "tumbling" is recognized by planetary scientists as referring to non-principal-axis rotation. Though the stated assumption in OP's question (that things can rotate about 2 axes) was incorrect, if you look at it as a question about non-principal-axis rotation then it makes sense. Thanks /u/conamara_chaos and /u/possiblywrong ! NEXT EDIT: OP has now clarified what he meant, rendering this answer less than useful. Y'all can stop upvoting me and upvote /u/jimbelk, /u/conamara_chaos, and /u/possiblywrong instead. |
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 develop lighter skin colors. That said, you are correct in pointing out that skin color is subject to a high degree of variation on the phenotypic (and epigenetic?) level. Because of this, most anthropologists [do not consider skin color to be a reliable indicator of genetic ancestry](_URL_0_). |
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 chemical (and gravitational) bonds the hold the meteorite together. There is at least one known case of a body breaking up before impacting a planet: the comet [Shoemaker-Levy 9](_URL_0_). I don't know exactly why it broke up, but it was made almost entirely made of ice and dust and it has for a long time been losing mass due to the sun. Both factors would weaken the comet and decrease the tidal forces needed for it to be destroyed. ~~Edit: I'm on mobile. How do I create links again?~~ Edit 2: thanks. So it's brackets-title, then parentheses-link. |
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 lose more glucose in cellular respiration than they would gain in photosynthesis, so by removing the leaves they lose a lot of respiring tissues and can survive. |
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 the towels are dry, they interact differently than when they are wet. |
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. [See here for diagrams](_URL_0_) |
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 can be excreted with less water than the other two. So while it is more energetically costly to produce, the animal saves some water that would be lost in other types of organisms. Reptiles and insects also utilize uric acid as a waste. |
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 the most consequential to humans as most of our vast coal reserves comes from their remains. |
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 around. |
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 the population to develop tolerance for lactose. Apparently Asians don't have such a tolerance due to not developing it historically. Apparently, the same applies to alcohol tolerance too, as Asians drank tea while Europeans drank alcohol to ensure that their drinks were free from dangerous bacteria. Hopefully, this source is sufficient: _URL_0_ |
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 can absorb a ton. DI resin is usually vacuum sealed and can't be exposed to air for a very long period. Activated charcoal will leach back into water if it's used way too long though. But it's not dangerous, it will just taste unfiltered. |
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 left the nest? In some cases it's just a better bet to stick with your partner (if your partner is decent). You _know_ they are capable of providing reliable care (assuming they actually are capable of that). You don't have to spend the risk or energy trying to find a new mate. |
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 oxidized from exposure to the air before they recondense. |
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 unlikely to find one that is higher in atomic number than anything we have created (118). |
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 square meter. The total is more difficult, but we can approximate it using the table here: _URL_0_ This is a slightly different concept but it should be close. Sirius is magnitude -1.47, so magnitude 0 is approximately 0.0000001176 / 2.512^1.47 = 0.00000003037 w/m^2. The weighted sum of that table (2.5 * 1 + 1.0 * 3 + 0.4 * 11 + ...) comes out to 113.3, so the total power received by all non-sun stars of magnitude 10 or brighter is 0.000003441 w/m^(2). |
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 constantly refreshed from nearby ring systems, as around Saturn. |
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 the majority of physical material from the surface of what is being washed. Since this is a physical process, not a biochemical one, no resistance could really be selected for, so it will still work no matter how bacteria evolve and adapt. |
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 specializes in taking visible light observations, or pictures if you will, although it has tools to measure in other wavelengths, whereas JWST is going to specialize in longer wavelengths like infrared due to the expansion of the universe redshifting wavelengths from so far away. This will allow us to see what the universe might've been like when it was just a wee baby and starting to create galaxies |
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 redshift objects that are too old and too distant for the Hubble and other earlier instruments to observe. In addition, and most exciting to me is that the JWST will be able to measure the atmospheres of Exoplanets. So if we see a planet that has a very similar atmosphere as ours, then that's strong evidence that it may harbor life. |
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 off-road surface. And in the back of the car you've got $2,500,000,000 worth of breakable glass. And you really really want the thing to still be working in 10 years time. So hopefully that explains the caution aspect. Also, you're trying to move about one ton of material with a 110 watt power supply. |
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 the current conditions (ultrahyperbolic) and therefore impossible for science to exist, or really it is useless to learn anything since you can't make predictions. |
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 (closest to the nose) is much stronger than the other ones. These inner muscles are capable of overpowering the others so that we can converge our gaze and focus up really close on images. We simply have no need to separate our eyes outward (whatever the opposite of cross-eyed is), so we never really developed this ability. Whatever image we're trying to see in that way would be better observed with both eyes anyway. Hope this helps. |
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 there is little warping from the width of the galaxy |
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 until helium can fuse to carbon. The higher temperature causes the outer layers to expand into a red giant. The sun is not massive enough to fuse carbon. So, a star the size of our sun can't run on carbon or heavier elements. More massive stars will fuse carbon and with sufficient mass all the way to iron. At which point the core collapses to a neutron star or black hole, typically with a super nova. Since, iron has the lowest energy per nucleon element no energy can be produced by fission or fusion, so clearly the Sun cannot run on any material because it clearly cannot run on iron. |
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 blood (then it becomes a blood blister.) The body will form new cells under the damaged area, and the swelling will subside, and the plasma is reabsorbed in time. Generally treatment of a blister is to cover and leave it alone, should it not resolve on it's own we may consider an incision and drainage, but this should be done with sterile technique, as you can easily cause an infection here that can rapidly lead to sepsis given the right conditions. |
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 form of ATP, which is basically the energetic form of currency your body uses. This regenerates the molecules in their oxidized state, so they can be re-used to donate protons again. As for where the mass goes? Well, the H+ given to the Electron Transport Chain comes from the long carbon chains consisting of a bunch of CH2 molecules strung together. We lose the H's, so what are we left with? Carbon. When we breathe in O2, we make CO2 using the carbon we're left with, and breathe out the carbon molecules into the air as CO2. That's why you breathe in O2 and breathe out CO2. |
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 above Mach .9 is significantly different from the designs used to operate below that speed. Beyond Mach .9, the propeller blades must become significantly shorter and thinner and the blade angle must be decreased compared to blades used on slower aircraft. |
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 other in regards to velocity and distance becomes easy to grasp. |
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 equivalent to [exploding 150 tons of TNT.](_URL_0_) While not all of that will necessarily be transferred on impact, you still end up with a sizable hole in you spaceship. Less of a physical limitation than a practical one, but it does tie in the the idea of friction. |
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 fluorapetite and consequently a lifetime of treatment with topical products is of benefit in prevention of dental caries. Ingested fluoride absorbed into the blood is utilized during growth and development converting a percentage of the entire mass of enamel to fluorapetite rather than just the surface layer as with a topical. This makes for a tooth much more resistant to decay, but it is only of benefit during growth and development. Thus once all the permanent dentition enamel has finished developing, I'm guessing at an average age of 12-13 yrs, ingested fluoride is no longer of value for tooth enamel formation. |
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 the signal bleeds over to the trigeminal nerve causing you to sneeze. Quick [SciAm](_URL_0_) article about it. |
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 show evidence of cognitive development in many ways (e.g., increased attention, language acquisition, increasing knowledge). There is a difference in the brain development of explicit and implicit memory in infants. Implicit memory is controlled by an early-developing memory system in the brain that is present very early on, and can be explained by the early maturation of striatum, cerebellum, and brain stem, which are all involved in implicit learning and memory. _URL_0_ |