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Does drinking a shot of hard liquor kill the bacteria in a person's mouth?
Alcohol has very little effect on the bacteria in your mouth. Oral bacteria exist in a biofilm which acts as a barrier to alcohol which has no effect on the structure of the biofilm. There are ways to reduce oral bacteria. I work at a periodontal practice and before surgery we give our patients a dose of Amoxicillin which is an antibiotic in the penicillin group. The reason some alcohol based mouthwashes work is not due to the alcohol, but due to 'chlorhexadine'. While chlorhexadine is very effective at breaking down biofilm, it has adverse side-effects over long term use and is not recommended.
Does the gravity of the moon have noticeable effects on the planet besides ocean tides?
Tides in the solid part of Earth. Sensitive devices like the LHC [have to take this into account](_URL_0_).
Why does my eye twitch?
Same thing happened to me for 3 reasons: Excess caffeine, stress/lack of sleep, and eye strain. I cut back on caffeine and that helped, lack of sleep/stress isn't an issue for you, but the largest thing was to get reading glasses even though I see nearly 20/20. To read text on a screen or page the muscles in my eyes have to squeeze slightly to put everything in focus. This is involuntary muscle movement, but those muscles get tired and eventually cause an eye twitch (more in my left eye which has crappier vision), so prescription reading glasses make the slight adjustments (different for each eye in my case) that I need to rest those muscles. tl;dr I would guess that you are experiencing eye strain possibly exacerbated by caffeine intake.
What causes my eyelid to twitch?
I'm on my mobile right now, so I'll come back and edit in some sources later, but by and large this is a fatigue or stress response. Additionally, excessive caffeine can cause this to happen as well. It really is fascinating how sensitive our eyes are to general stress.
How and why is a RadioCarbon (14C) date calibrated?
Radiocarbon dating can date material by comparing the quantity of C14 in a sample of previously-living-but-now-nonliving matter to the concentration of C14 in the atmosphere. Though the rate of C14 decay is a constant ([though the mechanism requires some advanced physics](_URL_0_)), the amount of C14 available in the atmosphere has not been consistent over time. (In essence, the assumption of initial C14 based on today's atmosphere would be incorrect.) By calibrating, the C14 content of samples that can be accurately dated by other methods is used to build a model of what C14 content was like at a particular time. Therefore, you should expect the calibrated value to be more accurate. Source: Aitken, "Science-based Dating in Archaeology," pp. 82-85.
Why do we mostly get the flu in the fall or winter?
Because people spend more time indoor and therefore spread it more easily (for example, more touching of doorknobs) and to more people (for example, more people touching doorknobs). Flu season in the southern hemisphere is in their cold months, too.
How powerful must an asteroid be to throw the Earth into a different orbit?
Hoping this is interesting; I'm working on an analysis engine for Reddit, and it recommends these past Reddit discussions as having similar content: * [The U.S. Is Saving Nukes So It Can Blow Up Asteroids](_URL_5_) * [If a fly is hit by a train, do they feel the same force on each other? And what is that force?](_URL_5_) * [If the Earth's orbital velocity was reduced to 0, how long would it take to fall into the sun?](_URL_5_) * [Why is there a negative correlation between planet size and rotation speed?](_URL_5_) * [Is there any chance the asteroid belt in our solar system could coalesce and form a planet?](_URL_5_) This is my first post to Reddit. My goal is to turn this thing into a bot, like "Backstorybot" or "FurtherReadingBot". Let me know what you think.
Why does it appear that "all of a sudden" many people are allergic to gluten?
This will probably get buried, but read _URL_5_
What is the science behind gluten allergies and intolerance?
There's no doubt about the existence of Celiac Disease. At a ~1% rate in the general population, it is one of the most common and deadly chronic diseases. It's also extremely under-diagnosed and several studies have suggested that the failure to diagnose is because most *doctors* aren't even that well-educated about it. The controversy is about whether or not there are gluten reactions beyond Celiac Disease, and unless you get your controversial immunology news from click-bait bloggers, it's pretty clear that *something* is going on. _URL_0_
Do we sweat underwater?
Yes, you sweat under water. You won't be cooled by it though, because sweat cools you by evaporative cooling. No evaporation = no cooling.
Do Humans Sweat While They're Underwater?
As a former competitive swimmer I can definitely answer this as a "yes". Sometimes I'd sweat for nearly an hour after a workout as well as while in the pool. It really helps to have a cool pool. Most pools are kept at around 82F which is nice for just floating around. Swimmers' pools are nice around 72-73F. Water is MUCH more effective at pulling heat from a body than is air, but if you're working hard enough your muscles will still generate enough heat to start sweating.
How can the observable universe be larger than the age of the universe?
The most distant thing we can see is the Cosmic Microwave Background. The light from it traveled 13.7 billion light years to get to us. However, the matter that emitted that light is now 45 billion light years from us. This is because the metric expansion of space can result in the distance between two objects increasing at more than 299,792,458 meters per second.
Why do onions make you cry?
Growing onions absorb sulfur from the dirt surrounding them, which they incorporate into their amino acids to form amino acid sulfoxides. As an onion is cut, these sulfoxides combine with nearly released enzymes in the onion to create sulfenic acid, which is then further converted to syn-propanethial-S-oxide. Syn-propanethial-S-oxide in vapor form travels to your eyes and interacts with sensory glands there, causing irritation and the production of tears to flush out the irritant. TRPA1 is the ion channel located on the plasma membrane of many animal cells thought to be responsible for triggering the irritation response. To avoid the painful effects of cutting an onion, you can use safety glasses/goggles, ventilate the space where you are cutting, or refrigerate onions to reduce the volatility of sulfur compounds.
what causes a random shudder?
There was a very big thread about this very recently: _URL_0_ In short, no one is really sure!
When the tyres on a car are spinning, does the speed they are spinning at make any difference to the friction force?
If I understand you correctly: You're talking about the car apinning out; if your cars wheels spin out slowly vs spinning out fast? The truth is, tire wheels are so complex, you're probably only going to get a 100% positive answer from someone in the industry. But from what I understand, the industry is quits hush-hush about their technologies. Generally speaking, there won't be too much difference between the friction force between a slow and a fast burnout; nithing compared to the difference in force of no burnout (normal operation) and having a slow burnout. Another side fact: In normal operation of a driven tire, there is a difference in the "linear" speed of tires and the speed of the car. They are off by a factor of .1. In undruven wheels, they are expected to be the samw.
If the Moon was orbiting the Sun instead of the Earth, would it be classified as a planet or a dwarf planet ?
If it was orbiting amongst a collection of similarly sized bodied and didn't have enough mass to gravitationally affect them and toss them out of that orbit, then it would be classified as a dwarf planet. Like Pluto and Charon cannot clear out their orbit of other Kuiper Belt objects. Yes, it's a dodgy definition, but it works for the time being until there's a better one!
If contact area has no effect on friction force, why do racecars have wide wheels, and not narrow ones like on racing bicycles?
Contact area has no effect on friction force for two relatively hard surfaces. If one surface starts to 'dig in' to another surface (as asphalt digs into rubber), then the maximum frictional force does depend on surface area.
What exactly happens to fizz when you pour a soda?
That fizz is CO2 that is dissolved into the soda under high pressure during manufacturing. When you open the soda that pressure drops to ambient levels, and that CO2 is released into the air due to that pressure change. Eventually the CO2 leaves the soda and the soda 'goes flat'. The same principle is the reason that divers have to be careful when ascending. The gas that is dissolved in their blood will 'fizz' basically if they ascend and change pressures too quickly. This is known as 'the bends'.
Can (heat) burns and/or chemical burns cause skin cancer in a similar way as sunburns?
Not my area of expertise at all so I hope somebody can get into some more detail but as far as I know ionizing radiation which can be in the form of things like UV(A/B) rays or exposure to radioactive material can damage your DNA (specifically it causes a reaction between two molecules of thymine). It's that DNA damage which can cause cells to either die (most cases) or go haywire and cancerous. Heat damage is different but there is [evidence to suggest](_URL_0_) it can cause protein degradation and also DNA damage. That damage that tends to result simply in outright death rather than mutations which could cause cancer but I wouldn't say it's impossible, I just don't have that data.
What is the biggest theoretical star possible?
A strict number on the biggest mass possible for a star is a bit of a grey area but we know they can't be any size. This is, at least partly, because as a star gets heavier it gets brighter, the radiation pressure from the stars light eventually gets so much that it basically blows itself apart with its light. [The eddington luminosity](_URL_0_) is closely related to this upper limit. In addition, very massive, hot stars do not live very long massive stars may only live for millions or even hundreds of thousands of years (compared to our suns 10 billion years) before being exhausted and going supernova. The largest **known** star is about 150 times the mass of our sun although it is theorised there could have been stars around 300 times the mass of our sun in the very early universe. By comparison the milky way is 1000 billion times the mass of our sun. Even if we do not have a precise upper limit, it is somewhere in the 100's of solar masses not the 1000 billions.
What is the yield of the largest H bomb explosion possible?
Weapons designers generally consider that there is no real practical limit to the yield that could be achieved with a staged Ulam-Teller thermonuclear warhead. However, it's more destructive to use smaller warheads in a multi-warhead MIRV design that can spread out the detonations. Tsar Bomba was a three-stage design but you could add more and more stages to get higher and higher yield. Some have speculated it might be worth it to make an even bigger bomb to push away asteroids for example however.
What is the smallest possible yield of a nuclear explosion?
In principle a yield as small as you want can be made inside a nuclear reactor or carefully made bomb. For example there is the TRIGA type of reactor, in which the control rods can be completely ejected by compressed gas, making the reactor supercritical and essentially an exploding bomb. However before the chain reaction can get very far, the heating from the released energy decreases the reaction rate and fission stops. The "explosion" is just then some heating of the fuel and radiation emission, and no damage is done. [Video](_URL_0_) But this is to say that by making a bomb not go very far past critical such that it does not consume most of its fuel, one can limit the amount of energy released to any level.
How big and fast does a meteor have to be going to go through the earth?
through the center? You can't, at least not cleanly, anything of such force required would pretty much shatter the planet.
You're taken hostage, mouth gagged/taped over. You have a blocked nose due to flu, would your body fight to unblock it or would you die? (x-post /r/ShittyAskScience)
there is a fairly well tested technique for stuffed nose. - you hold your breath for ~20 seconds, rock your head back and forth slowly during that time. or try walking few steps. - then you start breathing through your nose, even if it's nigh-impossible because it's stuffy due to cold/flu/etc. - you have to disregard the feeling of slight suffocation due to inefficient air flow through the nose for at least 20 more seconds. simply keep using your nose for next 20-30 seconds. eventually your nose unblocks, due to effect of hightened amount of CO2 in the blood. it could be a similar effect with having your mouth taped over. although with a very badly stuffed nose you could actually suffocate. more info is here: _URL_0_
How do mineral deposits like veins of ore form? Why don't elements mix homogeneously in the Earth's Mantle?
Ore veins are usually hydrothermal - hot water with dissolved minerals circulates through gaps in the rock, and the minerals precipitate out. I might be answering the wrong question, but essentially the ore minerals are concentrated in veins instead of being spread evenly because they're deposited after the rock has already formed, and the fluid that deposits them is moving through weak or open spaces. Rock forming minerals don't all crystallize at the same temperature either, so magmas at different temperatures have different mineral compositions. You can sometimes get ore deposits because the ore crystallized early and sank to the bottom, but it's not as important as hydrothermal alteration. The mantle isn't homogeneous either (in general - but magma is pretty similar in hot spots across the world) but that's not the most important part when you're talking about ore deposits in particular.
Theoretically, if a rocket ship kept constant thrust on in space with unlimited fuel, will it keep accelerating indefinitely?
It would keep accelerating forever, but still never reach nor exceed c.
Are there any gas giant moons?
AFAIK there is no known case of this happening. However Just like the formation of our moon it is theoretically possible for a collision between 2 big gas giants to form 2. Had this been the case they would be treated as a double planet and not as a planet and moon system.
What effect does average length of lifespan have on the evolution of an organism over time?
A shorter lifespan gives more generations in a given period. This allows for more chances at incremental improvement in reproductive fitness. This doesn't inherently mean "faster" evolution, it only means more chances at incremental improvement in reproductive fitness. That is to say, it's possible for field mice to remain largely unchanged for tens of millions of years because they're very well adapted to their environment, while elephants might shrink, grow fur, lose their tusks, get large again and develop pointy bits on their trunks for defense. Who can accurately predict these things? Evolution is funny that way - have you seen the platypus?
Why do I get nauseated when I read in a moving vehicle?
Your eyes are telling your brain that you are sitting still, but your inner ear is telling your brain that you are moving. Your brain concludes that this sensory mismatch is caused by an ingested toxic substance and responds with nausea and vomiting.
Why do I get 'car sick' when reading a book in a moving car?
Whenever there's a disconnect between what your eyes see and what your sense of balance detects, your body is hardwired to interpret that as poisoning, hence the nausea. The trick to reading in any vehicle is to look out a window when you turn, speed up or slow down so your eyes and balance stay calibrated. When the car is moving at a constant speed, you can read without nausea.
Why are antibiotics only effective against bacteria (not viruses) and vaccines (mostly?) only effective against viruses?
There are vaccines that target bacteria. The DTaP vaccine that is on the [schedule of vaccines](_URL_1_) for children under the age of 6 works against *Corynebacterium diphtheriae*, *Clostridium tetani,* and *Bordetella pertussis.* These are three pathogenic bacteria. To answer your question, it is just easier to use antibiotics against bacteria like /u/superhelical mentioned.
Why does a mirror invert its image horizontally but not vertically?
This has to do with how we interpret the image in a mirror. When you look into a mirror and raise your right hand you think "oh, my image is raising it's left hand." But think to yourself how you determine this - In your mind you might imagine yourself rotating your body to face the same direction as your reflection. Mathematically, you have **rotated** your coordinate system while the mirror has **reflected** your coordinate system. The "backwards" discrepancy arises from the fact that rotations and reflections are mathematically different.
Why does the rate of change of temperature of food increase when heated in a microwave?
your fish at -2F would have ice in it, the phase change from solid to liquid takes a significant portion of energy.
How does carbon dating work? How do we know the half life of carbon is "X" amount of years accurately? And lastly, how are we so sure what we're using carbon dating on (Fossils, ancient artifacts, etc.) is accurately dated, especially when it gets to be millions or billions of years?
To add to Staus's answer, we can calculate the half-life of carbon based on samples of known ages, based on *other* dating methods, and then seeing how much carbon-14 is left. It follows exponential decay over time.
Does a fridge require more energy when there is something in it?
Using my uni physics class, we actually calculated this... when there is more in the fridge, there is less space to keep cool. It therefore takes less energy to run a full fridge than it does an empty one. This is assuming that the food is already cold or room temperature when you put it in the fridge. Hot food will heat up the interior of the fridge. But since for food to stay cold, the surrounding areas just need to be cold, there is the surrounding volume of the fridge minus the food volume. Long story short, more food = less volume to keep cold (items will stay cold as long as surrounding areas remain cold), less energy... BUT potentially more energy on initial placement of food items
We're on a collision course with the Andromeda Galaxy. How can this be if the universe is expanding away from a single point?
Expansion is not the universe is expanding away from a *single point* but rather, expansion is happening in all directions from the point of *any* observer and any very distant object (all distant points are expanding away from all other distant points). Expansion happens at extremely large scales and distances. At localized scales and distances gravity overcomes expansion and keeps things pretty much bound. This is why we travel with a local group of galaxies, etc... and why expansion really doesn't effect us at any personal level (our planet is not flying apart, etc). Edit: You can read more on expansion [here](_URL_0_)
Why are the world's oldest living people almost exclusively female?
Just here to point out that life expectancy for women is in general higher. And why that is, is pretty much the exact same question. But looking up, why the life expectancy of women is higher, is probably easier than your observation...
Why are most of the oldest people on this planet women?
Men work harder, more dangerous and more stressful jobs than women do on average. This drastically shortens their life span compared to women. If you go back 100 years when the average man and women were both working labour in the fields to feed their family death ages were about the same.
Why do humans and other animals have multiple eye color possibilities?
It's a mutation with no real drawbacks in terms of survival, so it has thrived amongst the "normies" within each respective species.
Is depression inherited or does life experiences affect how prone you are to depression?
It's not one or the other. Depression is caused by the combination of environmental and genetic factors, with the exact contribution of each varying from case to case. It's like not being able to walk. Maybe you can't walk because you have a genetic defect. Maybe you can't walk because your legs were broken in a car crash. Maybe you can't walk because you were born with a weak immune system, and then happened to encounter a bacteria that paralyzed you. Environment *genetics = final result.
Does increasing the volume on your iPod drain the battery any faster than having it on low volume? Will one type of speaker or headphone drain the battery any faster/slower than another?
The power consumption depends on your headphones' [impedance](_URL_1_); the lower the impedance, the more current is drawn per volt of input signal, and the louder your music sounds (at a given volume setting). Earbud-style headphones typically have an impedance of 16-32 ohms, and the output from an iPod's headphone jack is somewhere in the vicinity of 1-2 volts at full volume. Picking numbers in the middle of those ranges and applying [Ohm's law](_URL_0_) gives an estimate of ~100mW of power consumption. To put that in perspective, an iPhone 4 battery has about 5 Watt-hours of capacity, so if nothing except the headphones was powered, your battery would last around 50 hours. Of course, when you're actually listening to music, the CPU and peripherals are also being powered -- and probably using a lot more than the headphones. Don't expect to get a huge boost in your battery life by turning down the volume, but I wouldn't be surprised if the effect is measurable under controlled conditions.
Why does snow make that satisfying crunch sound after stepping on it?
There isn't much force with a falling snow flake. So when the fall and collect on the ground they are just ever so slightly laid upon each other which creates a lot of air pockets. So as you step on it you are compressing the snow forcing the air out making sound
Why does snow making a crunching noise when stepping on it?
The small crystals of ice as they compress under your shoe rub against each other or may fracture and break in and of themselves. It's that friction that causes the sound, specifically the way in which it happens, because you're applying force over a large area there's many individual squeaks or creaks from ice grains breaking apart which happen to sound like a crunch or a more high pitched sound depending on some more specific factors. You might have hear a similar sort of model of this when you bite an ice cube.
When we burn fossil fuels, aren't we just releasing carbon that was once free?
There's a few things going on here: first, we aren't even close to having the highest levels of CO2 in Earth's history. Fortunately for humans we kicked off this fossil fuel craze in an ice age, with CO2 levels and temperatures being reasonably low. Here's a [chart](_URL_1_) showing CO2 levels across the past 550 mya. Second, the carbon in the atmosphere, living things, and fossil fuels only makes up a fraction of all the carbon on Earth. [This page](_URL_0_) has a good breakdown. The _vast_ majority of all carbon is stored in rock...carbonate rocks like limestone in particular store huge amounts. This can be released into the atmosphere, and atmospheric carbon can be stored in rocks. Carbon moves around between all the different storage areas, but the main point is that carbon can move from rock > atmosphere > life > fossil fuels, meaning there can be more in fossil fuels than was ever in the atmosphere at any given time.
Hiccups, how do you stop them?
Hiccups are contractions of the diaphragm that repeat several times per minute. To my knowledge, the diaphragm spasms and all you have to do is wait. There is no cure beyond waiting.
Is eating a lot of sweet fruits (grapes/pears/nectarines/etc) the same as eating lots of sugary sweets?
Fruits have fiber, which makes them lower energy density. Energy density is significantly related to total caloric intake. Fiber also slows absorption of sugars, and blunts insulin responses, which are good things. Fruit is a better choice than fruit juices or a candy bar (which lack fiber). In general, if you make no other changes, but add 2-3 apples per day to a diet, it will lead to improved serum cholesteral and weight loss. _URL_1_ _URL_0_
What causes fermentation to stop in alcoholic beverages?
Hi, biochemist and serious hombrewer here wanting to set some things straight: Even at those high alcohol levels (15-25% seen with champagne yeasts), the yeasts don't die, they flocculate. Flocculation is the process where yeast cells aggregate, and in the context of alcohol fermentation it is a defense mechanism. Signaled by low sugar (among many other environmental conditions) they will clump together, stop fermenting, and when the clumps become too large and dense, they settle out of solution. If they died breweries/vineyard/distilleries wouldn't be able to take the settled yeast from one batch and ferment the next batch with it (in whiskey this is known as sour mashing). Additionally, with some nicer craft beers and almost all homebrew, the yeast that are still alive but haven't flocculated will be carried into the bottle to perform the process known as bottle conditioning where the beer matures and carbonates.
Why do we use gasoline in cars instead of methanol fuel?
Methanol is more costly than gasoline and is easily contaminated with water. It's less energy dense, because there are 4 hydrogen molecules and one oxygen for every carbon, while gasoline has about 2 hydrogens for every carbon, so a gallon of gasoline has twice the energy of a gallon of methanol. Methanol has to be chemically produced, while gasoline is refined from oil.
Why haven't the clouds that comprise Jupiter's atmosphere not mixed over millions of years to produce one shade of color?
Same reason that Earth's atmosphere hasn't become homogenous. Both the Earth and Jupiter have an external source of energy (the Sun) that cause continual changes to their atmospheres. On Earth, the water cycle primarily drives that; on Jupiter, we don't really know the exact details yet, but something similar certainly takes place (and hopefully Juno can give us a better understanding of this).
Why do astronauts age differently when in space?
General relativity states that the stronger an object is pulled by gravity, the slower time moves for that object. Special relativity states that the faster an object moves, the slower time moves for that object. Both phenomena will only cause differences noticeable by humans when the speed approaches the speed of light or gravity approaches that around a black hole. Astronauts in the ISS or going to the moon would only experience differences of nanoseconds. GPS satellites, however, because they have to be so accurate, are regularly adjusted because their clocks lose time compared with clocks on Earth. They are farther from Earth's gravity, which should cause them to run faster, but they're also orbiting at a high velocity, which slows time down for them more than the lower gravity speeds it up. [Source 1](_URL_0_) [Source 2](_URL_1_)
If the vacuum of space is a poor conductor of heat, how do stars give off so much of it?
Heat transfer happens through 3 primary methods: Conduction, convection and radiation. As the name implies, the property "conductivity" only applies to the first of these three methods. In space, there is no heat conduction (or convection for that matter), so we say that the conductivity of vacuum is very low (essentially 0). Stars give off their heat through the third method: radiation. Stars emit massive amounts of electromagnetic radiation (visible light, infrared, UV, etc... the spectrum depends on the temperature of the star). Radiation is also the only way for a spacecraft to shed its excess heat. Unfortunately, radiation is not very effective at doing so (but since stars are so large, they still emit a lot of heat that way), but it's the only practical solution available.
Why is it that when you have a cold, one of your nostrils is blocked, and when it finally clears, the other one blocks?
How does this change ( or does it) in people with a severe deviated septum (meaning that bit separating your nostrils is bent, most often from getting a broken nose, I'm told), to the point where you can't breathe well out of one side?
Why does wood crackle/make sounds when it burns? Is the phenomenon constant w all fires?
Especially given your username, it should be clear! 😄 A lot of the crackle of burning wood is either trapped gases (steam or combustion products) escaping confined spaces in the wood (the pops and snaps) or wood fibers snapping under the forces exerted by uneven combustion along their lengths.
If friction causes particles to heat up, why do we use fans to blow air against ourselves to cool down, and how does that work?
When you sweat in still air you form a layer of saturated vapor above the skin, which eventually reaches a vapor-liquid equilibrium, meaning you can not evaporate more sweat because the air around you can no longer absorb any more vapor. The fan blows this layer away replacing it with air that more sweat can evaporate into. The heat needed for the evaporation (turning liquid into a gas requires energy, which is provided by your body) then cools the body. Of course friction takes place, but the amount of energy exchanged via friction is neglegible against this mechanism.
If carbon dioxide is only 0.0391 percent of the atmosphere, how does it have such a big impact on climate change?
People often mistakenly conflate abundance with importance (not just with climate science, but with a lot of things). Consider this: iron makes up only about 0.006% of the mass of an average human. Yet, it is completely essential for us to live (without it the hemoglobin in our red blood cells can't transport oxygen). So any argument that something is unimportant simply because it's not abundant is not valid.
If one was in the right location in space, would it be possible to see not a sunrise, but a "galaxy-rise" with the naked eye?
Rise from what exactly? A sunrise is when the sun rises from the horizon. You can see a "milky way-rise" from earth with a clear night sky and low light pollution. Here's a beautiful video showing just that: _URL_0_
How similar are insects' muscles to ours? If an insect "worked out" would it get stronger?
Insects' muscle types differ from ours (more on that [here](_URL_0_)), but they can get stronger by using them frequently. But insects don't want extra muscle mass because they'd use more energy in flight (for the flyers).
Do insects have muscles? If so, are they structurally similar to ours, and why can some, like ants, carry so much more weight than us proportionally? If not, what to they have that acts as a muscle?
As a physicist I can only argue that all smaller animals are proportionally stronger, since muscle strength depends on the crossection of the muscle, which scales roughly with the square of the size of the animal, while weight scales roughly with the cube of the size. Hence the smaller the animal the easier it is to be stronger in relation to it's body wheight. As to how their muscles are structurally different I don't know.
What do spacecraft push upon to gain velocity?
They're pushing against the propellant which their rocket motors expel.
Spacecraft use planetary gravity assists to increase speed. But where does the energy come from? How can the Spacecraft gain velocity?
The energy comes from the planet's orbit. Since the speeds of approach and departure relative to the planet must be equal, from earth's perspective, the speed of departure includes the orbital velocity of the planet. The planet slows down very slightly.
Why do LED lights "jiggle" ?
The LEDs will be Multiplexed. Its primarily used as a way of saving I/O pins on your control circuitry. The most basic method would connect 16 LEDs as a 4x4 grid, which only needs 4+4=8 pins to control it. But doing this means that only a subset of the LEDs can be on at any one time (one row/column in this example) so each group is briefly lit in turn. when this is done fast enough your brain just sees a constant illumination, but the edges of our sight are optimised for noticing fast movement so your more likely to see the flicker when you look away. tl:dr: they are flashing to save money, you normally cant see it, but your peripheral vision sometimes can.
If water is clear and water vapor is white, why are storm clouds grey?
Water vapor is not white. Water vapor is clear. Clouds are made of small droplets of liquid water or solid ice; those small particles are what appear white. Clouds are white due to [Mie scattering](_URL_0_). Tiny particles in the air tend to make light "scatter", since there are so many small individual surfaces for light to reflect or refract off. And since Mie scattering works roughly the same on all wavelengths, the scattered light is white. Storm clouds are dark because you are underneath a very deep cloud. A lot of light has already been scattered away, so a lot less of the original sunlight is getting through, making the cloud appear grey.
Do any of the stars we can observe with tbe naked eye at night have planets orbiting them?
Yes, including Pollux, the second-brightest star in Gemini. See _URL_0_ . Stars with an apparent magnitude less than about 5 are visible to the naked eye.
What makes a plastic microwaveable or not?
Not sure about what the actual standards are for safety, but speaking very generally, plastics must meet two successive criteria to be safe to microwave: 1) the plastic has low losses in the 2.4 GHz range that the microwave operates in. Most polymers meet this criteria but because heat generation is proportional to frequency, it doesn't have to be particularly lossy to get heated. More importantly: 2) when heated excessively to the point of degradation, the plastic must not give off toxic vapors. This includes pretty much any plastic that contains plasticizers (phthalates are very common, though they're being used less in more recent years or at least being replaced by safer ones) or things like PVC that generate nasty stuff like chlorine gas when it degrades. Most microwave safe containers are made from polypropylene and sometimes polyethylene. Sometimes PET is safe, but it depends on the molecular weight and what additives are present.
Is there a stable point for a solar sail balancing gravitational pull and push on the sail?
For nearly any fixed sail size, orientation and spacecraft mass, no, there is no such point. This is because both the acceleration due to the sun's gravity and the acceleration due to the sail (which is proportional to the flux of energy coming from the sun) are proportional to 1/r^2, where r is the distance to the sun. So whichever one is the largest at a given distance from the sun will be the largest at all distances from the sun. On the other hand, if your sail is in theory capable of moving you away from the sun (for an optimal orientation), you could change its orientation so that the sail sees less photons, and get the acceleration due to the sail to exactly cancel the gravitational pull of the sun. Or to get no acceleration from the sail, and let your spacecraft accelerate towards the sun.
What would happen if two gas giant type planets collided?
They would most likely merge. From the outside, the collision would look very "soupy," for lack of a better word. They would appear to behave more like a thick fluid than anything else during the collision.
Can solar systems gain escape velocity from a galaxy?
Of course! Like all objects bound by gravity, planets experience the most force from their most massive neighbours - in this case, their parent stars, hence they won’t be affected by the galactic collision unless another star happened to pass by and perturb their orbit. Since rogue stars are known and have been catalogued, such as those discovered by observing the Virgo and Fomax galactic clusters, it wouldn’t be too far-fetched to imagine that entire solar systems can be ejected, especially with higher mass stars. I don’t believe any have been observed, yet, but it’s certainly not improbable when looking at gravitational mechanics.
Why does a galaxy not form clusters of stars similar to planets?
Galaxies do form [star clusters!](_URL_2_) There are two main types, open (like the [Pleiades](_URL_0_)) and globular (like [M 68](_URL_1_)). However, these are on much smaller scales compared to the spiral arm.
After the big bang did matter spread uniformly in a sphere? If so, what made it clump together to form separate galaxies?
The big bang happened everywhere, so even while it was spread uniformly, it wasn't any shape, because it was infinite (we've measured the universe to be flat within a small error range... its possible that its closed and not infinite, but still in this case matter would have been everywhere, not in any shape). What made it clump were random quantum variations which gave certain groups motion and angular momentum different from others, which along with gravity, caused certain particles to group up. This process along with inflation actually gave physical difference distance between the groups, and expansion has kept them moving away from eachother.
If the universe is expanding, am I getting bigger too?
The space you exist in does theoretically expand, however, the chemical bonds which make up you pull you back together far more quickly than space can expand you apart. The expansion of space is only relevant on the largest of scales where there are no forces to pull bodies together. I.E intergalactic.
Why is 1080p Still the standard resolution for HD television?
It's not. HD by definition is anything with higher resolution than standard definition. 1080p just happens to be a popular one at the moment. Once costs associated with building the hardware and underlying engineering infrastructure to support higher resolutions on a large scale, we'll start to see 4k resolution proliferate through the market with even higher resolutions coming in the future.
Do computers slow over time, or is an old computer only slow due to increased software resource usage?
The CPU is clocked at the same speed, yes - assuming there have been no changes to any of the software installed on the PC, it should run at the same speed In the more general case, there are mechanisms that cause the maximum speed a CPU could run at to decrease over time - nbti is the biggest contributor and increases logarithmically over time when the device is powered. If design and test guard bands were not set strictly enough when the part was manufactured, then it's possible that it would no longer work properly at its intended condition. This would not manifest itself as the computer running slower though, just crashes
What makes a video player better than others, why do twitter videos sometimes not load while I can always watch youtube videos?
Youtube is huge with distributed servers in various data centers all over the world. When you play a video it will select the closest server near you so packets don't have to be routed all over the world to get to you. This minimizes latency and possible congestion. It's likely that Twitter doesn't have this infrastructure, or at least not near you.
When our Sun becomes a White Dwarf, Will the Planets still be held in Orbit?
The orbits of planets depend on the mass of the star, not on its size. If the star retains its mass, orbits are not affected. If the Sun somehow magically became a black hole, while keeping its mass unchanged (which is not what would happen in reality, but let's assume), then planetary orbits would not change at all. That being said, in the evolution of the Sun it will likely expand quite a lot, engulfing the interior planets, such as Mercury, Venus, perhaps the Earth too. Obviously, those planets will be destroyed in the process. Also, it's possible that the Sun may shed some fraction of its mass during its evolution, and that would affect the orbits of even more distant planets.
Why will a bottle of beer overflow when another bottle is tapped against the top of it?
This is caused by cavitation. The lower beer bottle suddenly moves downwards, but the beer stays still! Pockets of vacuum open up as the bottom glass pulls away from the beer. The pockets then close again, leaving behind a crowd of tiny bubbles. Creating tiny bubbles will have the same effect as shaking beer violently, or dropping in a Mentos. If the vacuum-collapse is too violent, the bottom of the beer bottle shatters. See [youtube, Time Warp: beer bottle ](_URL_0_)
If the singularity that existed prior to the big bang had infinite mass, wouldn't that imply the universe contains infinite matter?
Singularities (including the one that lead to the universe) don't have infinite mass, but rather infinite density. And the reason their density is infinite is because they take up essentially no space, so it's one of those divide-by-zero problems. Also, prior to the big bang the concept of "mass" didn't really have meaning. Rather, it is better to talk about "mass-energy": i.e. the raw stuff that went on to make up both energy and matter, and which can be transferred between both states via the equation E=mc^2.
Do artificial sweeteners affect health negatively?
Well this a highly debatable question but I'm going to put it out there and say pretty much no. If you think about some of the most commonly used sweeteners like aspartame (primary sweetener in diet soft drinks (soda)), there was a few very dodgy studies done several years ago where they made a 'link' between it and cancer. Basically it turned out that they had a fed some rats the equivalent of 40 cans of diet coke everyday for a year and then one of them suddenly got cancer. And they didn't have a control group. Similar experiments were done with saccharin, all a massive over exaggeration. However, my girlfriend who is a Dental Student has told me that Xylitol which is used in sugar free chewing gum actually has anti-cariogenic properties which basically means that it reduces the rate that cavities form in your teeth.
How do artificial sweeteners work? Are there health risks associated with their use?
The YouTube user [C0nc0rdance](_URL_0_) made an excellent video on this topic. I think [this](_URL_1_) will answer all your questions.
Theoretically, could we create a telescope that allows us to see so far that we can see the Universe being created, as it happens?
Yes, and we have. Radio telescopes can see [the radiation from the Big Bang](_URL_1_) in all directions. What they're seeing though is not the moment the universe was created, but [when it became transparent](_URL_0_), which was about 380,000 years later. We cannot see any farther back than that because the Universe was full of an opaque plasma.
Why do city lights flicker from a distance?
A city is constantly heating air (from sewers, buildings etc) which is then rising up. As these streams of warmer air are rather turbulent, they change paths all the time. Hot air has lower density and thus lower refractive index than colder air, so a pocket of warmer air will slightly distort the path light takes from its source to your eye. If you were rather far away from the city lights, it's very well possible that the flickering comes from turbulent warmer regions of air between the lights and you.
Why do city lights flicker from a distance?
It's the atmosphere. Layers of air will differ in temperature, which changes the [index of refraction](_URL_2_) of light between layers. The difference in index of refraction between layers of air causes light to bend. This optical effect is why [things underwater appear to shift in location](_URL_3_). Similarly, as layers of hot air rise or layers of cool air fall, the light bends more or less as it travels between layers. This gives the appearance of flickering city lights. Turbulent air flow and temperature gradients in layers of air are also responsible for things like [mirages](_URL_0_) or [twinkling stars](_URL_1_).
Why did the Earth originally have a super-continent, Pangea?
Pangea was only the latest of a series of supercontinents that have been forming every few hundred million years for the last few billion years. We still don't totally understand some of the cyclical processes that form these supercontinents, but the short version is that ocean basins tend to keep spreading and continents tend to stick once they hit each other, so eventually they'll all clump together in one big landmass. Once they do, they'll tend to trap heat under them until a plume of magma bursts up through the crust and splits them apart.
Plants use photosynthesis to create carbohydrates and, ultimately, wood. Where does the oxygen contained in wood come from? Carbon dioxide (CO2), water (H2O) or gaseous oxygen (O2)?
Photosynthesis converts CO2 and H2O into sugars and O2. The oxygen that gets incorporated into the sugars enters the process as CO2 in the [Calvin cycle](_URL_0_).
Why aren't we mining asteroids?
The costs are still way more than the profits. Plus there's a serious risk involved, so getting investors to fund an asteroid mining mission would be tricky anyway, since there's a good chance you'd get no profit at all.
How economically/technically feasible would mining asteroids truly be? (announced by Planetary Resources)
[please join us at [/r/Futurology](/r/Futurology) for a subreddit entirely devoted to this subject](_URL_0_)
When car tires wear down on the road, does most of the rubber go into the atmosphere? Or is it still on the road?
There's this: _URL_0_ I was told in my commercial driver's course that the tire particles (not really rubber anymore) end up on the road and can cause additional slickness when it first starts to rain after a dry spell.
What causes ball sweat to smell so much different from regular sweat?
there are different types of sweat glands in different parts of the body, eccrine and apocrine glands. The eccrine glands are found in basically all skin, in the pores. This is responsible for temperature regulation, waterproofing, and other things like hormonal smells. The apocrine glands only develop in puberty and exist in areas like the armpits and genitals. This sweat is certainly more pungent because it has a different composition. _URL_0_
I know that carbon, under extreme heat and pressure, can form diamond. Is there a similar transformation with other elements?
Several substances, whether elements or complex molecules, undergo polymorphic phase changes under various temperature/pressure conditions. Water comes to mind, with a [wide variety of solid polymorphs ranging from Ice I to Ice XI](_URL_0_), each with different properties Silicon dioxide is another well known example (The Quartz/Tridymite/Cristobalite system), as is the aluminosilicate system (Andalusite, Sillimanite, Cordiérite system) and [elemental iron](_URL_1_).
[astronomy] Do the planets cause a tidal effect on the sun the same way the moon does to earth?
The planets do indeed exert a tidal force on the Sun. Similarly, the planets exert tidal forces on the Earth as well. The magnitude of this force is inversely proportional to the *cube of the distance* between the two objects. The farther away a planet is, the less intense the effect due to tidal forces. That's why the tides on the Earth due to the Moon are as large as they are. Even though the Sun is far more massive than the Moon, it's extremely far away, so the magnitude of the tidal force that it exerts is less intense. So while the Sun does feel a tidal effect from the planets, the magnitude is so small that the effect on the shape of the Sun is practically negligible.
Do any planets in the solar system, create tidal effects on the sun, similarly to the moon's effect of earth?
Yes, but it's very, *very* small. The reason is that while the tidal force scales linearly with the forcing body's mass, it also scales inversely as the distance *cubed*. Let's scale our units so that the **Tidal Force of the Moon on the Earth = 1**. In those relative units, the rest of the planets' tidal forces on the Sun shake out as... Planet | Planet/Moon mass ratio | Distance-to-Sun / Earth-Moon ratio| Relative Tidal Force :--|:-:|:-:|:-: Mercury|4.47|151|1.30 x 10^-6 Venus|66.3|282|2.96 x 10^-6 Earth|81.2|390|1.37 x 10^-6 Mars|8.74|593|4.19 x 10^-8 Jupiter|25800|2030|3.08 x 10^-6 Saturn|7730|3730|1.49 x 10^-7 Uranus|1180|7480|2.82 x 10^-9 Neptune|1390|11700|8.68 x 10^-10 In other words, **the largest tidal force on the Sun comes from Jupiter** (with Venus a close runner-up), and **it's 325,000x weaker than the tidal force exerted on the Earth by the Moon.**
If the moon orbits the earth, and the earth orbits the sun, what does the sun orbit?
Fundamentally, the Sun orbits the centre of the galaxy. Our galaxy - the Milky Way - is made up of hundreds of billions of stars, and these (plus interstellar gas and dark matter) provide enough mass and gravity to keep our Sun in a nice fairly-circular orbit. There *is* a supermassive black hole in the centre of the galaxy, but it's a fraction of a percent of the mass of the whole galaxy, so its gravity isn't really important until you get close to it. One more note on black holes - you can indeed have a nice stable orbit around a black hole. You have to get *really* close to a black hole for there to be any danger. In fact, a black hole has gravity as strong as any other object of the same mass. So if we replaced the Sun with a black hole with exactly the same mass, we'd still orbit around it quite happily. Have a look here: _URL_0_ for your question about the "edge of the universe"
If the Moon orbits Earth and Earth orbits the Sun, what does the Sun orbit?
The Sun orbits the galaxy. So it doesn't exactly orbit one thing, but rather the combined mass of the other stuff in the galaxy makes it follow a path that takes around 250 million years to complete one orbit. The Sun's temperature is determined by its own heat production, since any other stars are many light-years away.
Why do spirits like Whiskey give you a warming sensation when you drink them, even if they're cold?
[Alcohol causes your blood vessels to dilate, moving warm blood closer to the surface of your skin.](_URL_0_)
Why does hard liquor (whiskey in particular) make your mouth/body feel warm almost immediately?
Alcohol causes your blood vessels to dilate, which causes more blood to flow to the skin, which creates a sensation of warmth. It is "actual" warmth - with a sufficiently sensitive thermometer you can measure an increase in skin temperature - but this is achieved by redistributing the heat in your body. This can be a bad thing in cold weather, since it fights the body's normal constriction of blood vessels in the cold, and exposes more blood to environmental cooling than would otherwise be the case.
Why does the fire on a candle get extinguished if you blow on it?
Fire is a chain reaction. The reaction between the carbon in the wick/wax and the oxygen in the air creates heat, that heat give other molecules enough energy to react, which creates more heat, etc. When you blow on a candle what you are doing is blowing the hot air away from the wick, and replacing it with cool air, which cools down the wick. There is now not enough energy in the area for more reactions to occur.
Why does a candle flame go out when you blow on it?
Fire needs three things to sustain itself: fuel, oxidant, and heat. This is known as the [Fire Triangle](_URL_0_). Your candle wax is the fuel, air is the oxidant, and you provided the initial heat when you lit the candle. In order to continue burning, the fire needs all three of these things constantly. Since burning is an exothermic (heat-releasing) reaction, the heat is automatically provided once you've started it initially. This heat is constantly lost to the surrounding air, but also constantly replenished by the burning of more wax. A steady-state is reached where the temperature in the air immediately surrounding the wick is high enough to sustain the reaction, but the temperature drops off pretty quickly when you move even a cm or two away from the wick. Blowing on a candle disrupts this pocket of hot air, replacing it with cool air at a very fast rate. Too fast for the burning reaction to replenish the heat, and then the temperature drops and burning ceases.
Whats the best cure for a hangover?
Best preventative measure: take 4 advil right before you go to bed with a lot of water. ADVIL or ALEVE but not tylenol. Tylenol affects the liver, and so does alcohol, so I just try to avoid taking tylenol to give my liver a break. When you wake up, drink a sugar-free Redbull. All those B vitamins and vitamin C will help a lot. Drink more water. When your body is breaking down ethanol, the by-products can give you a raging headache. So a great idea is to have ONE drink from whatever you were drinking last night. As in one beer, or a small mixed drink. I do not rec' doing this if you need to go to work, but you are an adult and can make your own decisions. Your body will have to call up all the enzymes to break down the new ethanol and thus get rid of all the crappy by-products from the night before as well. This is why bloody mary's are so popular in the morning.
Physiologically, what is a hangover? What is the most effective hangover cure without access to hospital equipment?
It comes from all the nasty metabolites of ethanol. I'm not sure if formaldehyde is from ethanol or methanol, but I know it's one of the two. That should give you an idea of the kind of stuff we're talking about. The best cures. Activated charcoal and pedialyte (sp). In case you don't have that, burnt toast and Gatorade (or even pickle juice) will work. The charcoal and burnt toast is just carbon to absorb some of the nasty by products in your system, the Gatorade/pickle-juice is to put fluids, salts and vitamin C back into your system.
Why is the skin on the penis darker than the rest of the body?
Follow up question: other darker areas include the areolae, and the skin around the anus. Are these dark for the same reasons?
How big can a moon be to a planet before it's too big?
That depends on the amount of orbital angular momentum. If there's less than some critical amount of angular momentum (which depends on the masses of the two bodies and their radii) then the closest approach distance between the two bodies will be such that they collide. But, for any mass ratio there are orbits that the bodies can take around each other for which they don't collide. Depending on the mass ratio, the point that the two bodies orbit around (the center of mass, or "barycenter") might not be located near the center of the large body. For example, if the two bodies have equal mass then they will orbit about the point between them that is exactly the same distance from each. In our Solar System, many binary asteroids are nearly-equal-massed pairs.