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Thursday, August 31, 2017

How will the waters actually recede from Harvey, and how do storms like these change the landscape? Will permanent rivers or lakes be made?

How will the waters actually recede from Harvey, and how do storms like these change the landscape? Will permanent rivers or lakes be made?

How will the waters actually recede from Harvey, and how do storms like these change the landscape? Will permanent rivers or lakes be made?

Posted: 30 Aug 2017 08:36 AM PDT

Does the Doppler effect have any noticeable consequences on wireless Internet connection?

Posted: 31 Aug 2017 07:22 AM PDT

Let's say I'm downloading a file and run towards my router at significant speed, will that make the file download faster, or cause errors? Does it matter whether the signal is AM or FM?

submitted by /u/sam007961
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Are there any natural instances of more than one species traveling together as a herd or pack?

Posted: 30 Aug 2017 07:46 PM PDT

Ask Anything Wednesday - Engineering, Mathematics, Computer Science

Posted: 30 Aug 2017 08:07 AM PDT

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Engineering, Mathematics, Computer Science

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions.

The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here.

Ask away!

submitted by /u/AutoModerator
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What happens when you compress water?

Posted: 30 Aug 2017 08:34 PM PDT

Since water is (one of?) the only substances that is most dense in its liquid phase, what happens when you compress water? Does it stay liquid? Turn into another, more obscure state of matter? Also related - since compression generally increases temperature, how would the temperature of compressed water change?

submitted by /u/danceswithlesbians
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A question about centrifugal force in a weightless environment?

Posted: 31 Aug 2017 03:30 AM PDT

After reading 'Rendezvous with Rama' by Arthur C Clarke, I have been stumped by a thought about centrifugal force in a weightless environment. In the book a character attempts to fly in a winged craft along the central axis of a massive closed spinning cylinder with a gaseous environment. As they go along (If I am remembering correctly) they lose power and end up being pulled down to the inside surface. So I have been thinking about what particular set of circumstances are required for the centrifugal force to act on a body.

Say for example, if I am floating in space and a completely open-ended massive spinning cylinder were to pass around me i.e., I pass through the cylinder, however I am not on the central axis but closer to the inside surface. Would I be pulled down to the surface by the centrifugal force? I am deliberately excluding the gravitational force from this thought experiment.

submitted by /u/ProblemShared
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Why does the standard deviation formula have an (n-1) instead of n?

Posted: 30 Aug 2017 04:20 PM PDT

The formula to calculate standard deviation involves adding the squares of differences between the point and mean for each data point, then dividing it by (n-1). Since standard deviation is a way to calculate spread that corresponds with mean, why isn't the sum divided by n?

submitted by /u/existentialepicure
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How does Icy-hot work?

Posted: 30 Aug 2017 08:55 PM PDT

How does icy work and why does it affect some areas when applied more than others? Also, can some areas sensitive to icy-hot become desensitized?

submitted by /u/theSpudnik
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When we pop a joint like a knuckle or our back, its a realeases air. Where does that air go?

Posted: 30 Aug 2017 03:21 PM PDT

Why shouldn't I control a parallel load register using an AND gate?

Posted: 30 Aug 2017 11:31 PM PDT

I have been taught to use a mux to control whether you load a new data value into the D-Flop or load the Flop's current output back in to the flop.

  • Why is it not better to remove the multiplexers and just have a control input ANDed with the clock and use the output signal as the clock for the flops?
  • Wouldn't doing this remove the constant reassigning of the flop's output back through the design?
submitted by /u/AsaJack
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What happens to fresh-water aquatic life during and after hurricane flooding?

Posted: 30 Aug 2017 08:17 AM PDT

Do they think "gee, this pond didn't have a house in it last I remember" or are there adaptations to survive/take advantage of the situation?

Thanks in advance

submitted by /u/iki_balam
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How do scientists fire subatomic particles at materials in their experiments?

Posted: 30 Aug 2017 06:13 PM PDT

The two that I'm thinking about right now are the Davisson-Germer experiment, where electrons were fired as I've been told, and the Rutherford Gold foil experiment, where helium nuclei were fired at gold foil.

How do scientists isolate these particles and how do they store them, and how do they manipulate these particles to "fire" them at a substance? Is the way these are fired the same as just atoms of an element?

submitted by /u/ShammaLamaMu
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In a given season, do hurricanes (typhoons, etc) tend to follow a similar trajectory?

Posted: 30 Aug 2017 06:12 PM PDT

What is the average chemical composition of fossil fuels?

Posted: 31 Aug 2017 03:27 AM PDT

'Chemistry' I like to do back-of-an-envelope calculations of things related to climate science. I'm trying to estimate the amount of water produced by fossil fuel consumption, and so I'd like to see some estimate on the chemical/elemental composition of fossil fuels. For petroleum, I've found the figure 10-14% (weight) hydrogen, and for coal some 1-5%. What I am after is more of a total average over all fossil fuels, for some recent year, say after 2005.

submitted by /u/Gelnef
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In cases of broken bones, how do animals heal in the wild?

Posted: 30 Aug 2017 02:37 PM PDT

I was watching a video here in reddit earlier (link) where a Wildebeest looks like it gets its leg broken from a crocodile bite and it got me wondering: How do animals heal broken bones in the wild?

Would a case such as this result in the animal unable to walk or would it somehow naturally heal back to its original form?

submitted by /u/599080
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Do our skin cells, or liver cells, contain the genetic data for EVERYTHING in our bodies?

Posted: 30 Aug 2017 08:07 PM PDT

Do the DNA residing in the cells that live in our eyes, have genetic data that codes for how our feet should develop in humans?

submitted by /u/habibitee
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Some particularly social animals, such as whales, are known to sometimes come to humans when they need help. Do they go to animals other than humans for help? Does this get them into trouble?

Posted: 30 Aug 2017 05:34 AM PDT

How is it that, during an eclipse, the moon perfectly blocks out the sun?

Posted: 30 Aug 2017 09:56 PM PDT

The moon is considerably smaller and closer than the sun, wouldn't it kind of just be like a small speck we would see in front of the sun?

submitted by /u/Super47_
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How do they protect chemistry equipment from being eaten by whatever reaction is taking place inside?

Posted: 30 Aug 2017 09:16 PM PDT

At school I've seen my professors just pour strong acids and bases into what seem to be glass containers for experiments. Why doesn't the acid dissolve the container right away or at least start to eat away at it?

submitted by /u/its_ya_boi_dazed
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Is there 2 longest and 2 shortest days at the equator or do they differ?

Posted: 30 Aug 2017 12:24 PM PDT

How did Edwin Hubble determine Andromeda's distance from Earth?

Posted: 30 Aug 2017 10:38 AM PDT
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Wednesday, August 30, 2017

How many generations does it takes before medical history becomes irrelevant?

How many generations does it takes before medical history becomes irrelevant?

How many generations does it takes before medical history becomes irrelevant?

Posted: 29 Aug 2017 04:02 PM PDT

Why does being infected with vaccinia virus vaccine protect you from Smallpox but doesn't protect you from other "pox" such as chicken pox?

Posted: 29 Aug 2017 08:18 PM PDT

Due to my career field I was recently given the vaccinia virus because I was told it's a more "mild" form of small pox, this peaked my interest and I learned the difference between vaccinia and variola virus(small pox) but could not find an answer to my question in regards to the varicella virus (chicken pox). I probably have a misinterpretation on the correlation of the word "pox" but I'd like to know, thank you!

submitted by /u/KannonTheKid
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Why cant we use nuclear fuel until it's spent?

Posted: 30 Aug 2017 03:48 AM PDT

We use plutonium and uranium to fuel our nuclear plants. In hospitals, they're used in xray machines. At a certain point, they are considered "spent", but still contain enough energy to be considered a problem. Why can't we use them until they're gone, just like a log would be just carbon and water vapor when it's burnt out?

submitted by /u/Dringringringringrin
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How does polarization matter in Sisyphus cooling to millionths of a degree above Zero?

Posted: 29 Aug 2017 05:55 PM PDT

I was just reading about a molecule being cooled to 50/106 degrees above zero. The article referenced a higher temperature which could be obtained through Doppler cooling, but that this technique had limitations. The mechanism for Doppler cooling and it's limit makes intuitive sense to me, to the extent that I could probably calculate the limit for simple cases.

However this new record required a technique called Sisyphus cooling which I do not really understand. The wikipedia article on it wasn't terribly informative for me either. Can circularly polarized light be effective in cooling by this mechanism, or does it have to be linear?

How does light polarization effect orbital interaction? I've always assumed it was just a scalar energy involved in electron absorption of a photon.

Any direction towards further reading that would help me understand this would be appreciated.

Original article which piqued my interest: https://www.sciencenews.org/article/molecules-face-big-chill

submitted by /u/lichlord
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How Do Aircraft Rudders Work?

Posted: 29 Aug 2017 08:10 PM PDT

How does a rudder work in an aircraft as opposed to a boat? I've read aviation sites and everything is hard to understand. Wings and lift - I think I finally JUST have it. Rudders not so much. Everything in aviation slides around, the fluid friction is so low compared to water. Even a basic turn only barely makes sense.

submitted by /u/OneTimeIDidThatOnce
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Can we attach a sail of some sought to an asteroid to redirect it?

Posted: 30 Aug 2017 01:02 AM PDT

Edit: My Science teacher told me this. Apparently he has an IQ of 185, and most of the things he says make total sense, but this seems preposterous.

submitted by /u/InspireMee_
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What determines the length of the unburned wick remaining above the candlewax?

Posted: 29 Aug 2017 01:12 PM PDT

Say you're burning a candle, why is the sticking out bit of wick that specific size? Is it related to the temperature of the flame or viscosity of the molten wax or something else unrelated?

submitted by /u/L1qu1dN1trog3n
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How do we know the exact age of the earth?

Posted: 29 Aug 2017 10:24 PM PDT

When i searched online i found that the method used to calculate the age was radiometric-dating, but then we should only know that the earth is as AT LEAST as old as the oldest rock that was dated. where did the upper bound on Earth's age come from?

submitted by /u/TomiSPK
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what breakthrough has Cassini provided us with?

Posted: 29 Aug 2017 03:52 PM PDT

Could we slingshot an object around planets or the sun to get close to the speed of light?

Posted: 29 Aug 2017 07:48 PM PDT

NASA used slingshotting around earth and the moon and other planets to gain speed. If you slingshot enough times around the right planet, could an object get close to the speed of light? Or is there a limit?

submitted by /u/denmark219
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When it comes to massive projects like designing a rocket from the ground up (as SpaceX has done, for example), where does one even start?

Posted: 29 Aug 2017 04:09 PM PDT

I was just thinking about this as a recent college graduate. There are quite a few things that just completely blow my mind when it comes to the scope of a project. There are so many factors to consider, how are people able to come together to make large projects happen knowing how many things must be done, and what will happen if something is missed?

submitted by /u/TheAero1221
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How do we determine sea level?

Posted: 29 Aug 2017 09:13 AM PDT

Do we base it off of some point on land, and then depending on if it raises or lowers from that point we know if the sea is rising? And if that is how we do it, do we measure that point at high or low tide? Also, how often do we change topography maps with the new sea level?

submitted by /u/PApauper
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Why don't we drop atomic waste packaged in lead spheres into the Mariana Trench? (Or the remainders of Fukushima for example)

Posted: 29 Aug 2017 04:50 AM PDT
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Tuesday, August 29, 2017

[Computer Science] In neural networks, wouldn't a transfer function like tanh(x)+0.1x solve the problems associated with activator functions like tanh?

[Computer Science] In neural networks, wouldn't a transfer function like tanh(x)+0.1x solve the problems associated with activator functions like tanh?

[Computer Science] In neural networks, wouldn't a transfer function like tanh(x)+0.1x solve the problems associated with activator functions like tanh?

Posted: 28 Aug 2017 09:06 AM PDT

I am just starting to get into neural networks and surprised that much of it seems to be more art than science. ReLU are now standard because they work but I have not been shown an explanation why.

Sigmoid and tanh seem to no longer be in favor due to staturation killing the gradiant back propagation. Adding a small linear term should fix that issue. You lose the nice property of being bounded between -1 and 1 but ReLU already gives that up.

Tanh(x)+0.1x has a nice continuous derivative. 1-f(x)2 +0.1 and no need to define things piecewise. It still has a nice activation threshold but just doesn't saturate.

Sorry if this is a dumb idea. I am just trying to understand and figure someone must have tried something like this.

EDIT

Thanks for the responses. It sounds like the answer is that some of my assumptions were wrong.

  1. Looks like a continuous derivative is not that important. I wanted things to be differential everywhere and thought I had read that was desirable, but looks like that is not so important.
  2. Speed of computing the transfer function seems to be far more important than I had thought. ReLU is certainly cheaper.
  3. Things like SELU and PReLU are similar which approach it from the other angle. Making ReLU continuous rather than making something like tanh() fixing the saturation/vanishing grad issues . I am still not sure why that approach is favored but probably again for speed concerns.

I will probably end up having to just test tanh(x)+cx vs SELU, I will be surprised if the results are very different. If any of the ML experts out there want to collaborate/teach a physicist more about DNN send me a message. :) Thanks all.

submitted by /u/f4hy
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Why do sites like Google and Amazon need domain specific urls (amazon.ca google.ru) instead of .com always? Is it simply a language thing?

Posted: 28 Aug 2017 08:42 PM PDT

When was there a 'cosmic visible light' background?

Posted: 29 Aug 2017 05:18 AM PDT

Since the expansion of space causes the wavelength of cosmic microwave background to lengthen, presumably it would have covered other parts of the electromagnetic spectrum in which wavelengths are shorter. We also seem to have a pretty good idea of the rate (and rate of acceleration) at which space expands.

So at what point in the history of the universe could I look around me and see blue everywhere? Is there an equation for this? I'm not afraid of math.

submitted by /u/BrainEnema
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How has Hurricane Harvey managed to stay in the Southeastern Texas area so long when other Hurricanes crawling up the East Coast seem to go right through one place to the next at a quicker rate?

Posted: 28 Aug 2017 08:53 AM PDT

I went through Hurricane Matthew last year, and it seemed to pass through us in about half a day. Harvey seems to be in the same general area it's been for the last 2+ days.

submitted by /u/JeffTennis
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Is quantum entanglement limited to two particles?

Posted: 28 Aug 2017 09:21 AM PDT

Could two, three or millions of particles separated by space-time be "entangled"?

submitted by /u/LetsSpeakAboutIt
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When you mix two units of liquids of different temperature, and the apparent temperature changes, is this because the individual particles' energy changes, or is it just because the average of their energies changes?

Posted: 29 Aug 2017 04:49 AM PDT

Hey!

I understand that this is a simplification of actual thermodynamics, and I assume that the kinetic energy of each molecule/atom in the final liquid ends up being roughly the same over time (except for for example the well-known aspect of the warmest molecules floating to the top in most cases), but my real question is how quickly this transfer of energy between the individual particles happens. If you were able to measure the temperatures of all the individual particles at different times after mixing the liquids, would there be a period in which the particles actually retained the same temperature as they started with, and the apparent change would just be because the average temperature had changed? And if this is something that happens over time, how quickly does it happen?

submitted by /u/Hottentott14
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Does compressed air provide less buoyancy than uncompressed air?

Posted: 29 Aug 2017 04:48 AM PDT

If I held onto a balloon underwater it tries to float to the surface, but a scuba tank has way more air in it, so even though it's heavier shouldn't it still try to float to the surface far faster than a balloon?

submitted by /u/whatthehellsteve
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Why does lime juice severely burn the skin when exposed to sunlight?

Posted: 28 Aug 2017 08:14 PM PDT

What properties of a substance give it things like taste and sound?

Posted: 28 Aug 2017 06:06 PM PDT

What part of an object's atomic structure or cellular composition give it things like taste or sound (when I tap a table it sounds different than when I tap a window)?

submitted by /u/Ayaksnolkop_Ailatan
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How does Bremsstrahlung radiation work?

Posted: 28 Aug 2017 10:58 PM PDT

My understanding is that when a charged particle slows down due to an electric field it emits a photon in order to conserve energy. The example given on Wikipedia is an electron being deflected by a proton would emit a photon to conserve energy. The electron loses kinetic energy but it also gains electric potential energy so there is no energy violation. Does this imply that potential energy is not a valid energy form and can't be used for conservation of energy? Also this radiation is created in synchrotrons where the acceleration is perpendicular to the velocity. There is no change in energy on this situation so no radiation is required to conserve energy is it? Is there a gravitational equivalent of Bremsstrahlung radiation?

submitted by /u/Prowsey
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Is there a way to convert ambient heat into electricity?

Posted: 28 Aug 2017 05:49 PM PDT

Say you live in a very hot area. Is there a way to use something like solar panels to absorb the heat around your house and convert it into electricity?

submitted by /u/OK_Soda
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[Cryptology] How does the Maximum Distance Separable Matrix work?

Posted: 28 Aug 2017 09:03 PM PDT

To any cryptologists and other computer scientists out there, could you please tell me how the MDS matrix works? I honestly can't understand it. For context, I haven't really studied anything past confusion, diffusion, feistel networks, lai-massey, and sp-networks, and bitwise operations.

submitted by /u/ThomasKingofNowhere
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If Matter and Antimatter behave very, very similar, can we be sure that distant galaxies aren't made of antimatter?

Posted: 28 Aug 2017 01:04 PM PDT

To my recollection, recent tests have shown that Anti-Hydrogen reflects light very similarly to normal hydrogen.

Can we still tell them apart over astronomical distances?

submitted by /u/Ten_Tacles
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If electrons surround a nucleus in a cloud, can they collide, and if they can, what happens?

Posted: 28 Aug 2017 11:03 AM PDT

What is the current thinking on the future of uranium supply and breeder reactors?

Posted: 28 Aug 2017 11:12 AM PDT

I've seen various estimates on the future supply of Uranium, that there might be as little as 80-200 years worth left, and that there might be so much that running out won't ever be a concern. What's the current consensus on it?

Breeder reactors sound almost like a miracle technology, with the potential to extract 100 times more energy than normal reactors and massively reducing the headache of nuclear waste, but apparently 'in 2010 the International Panel on Fissile Materials said "After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries."'.

What are the drawbacks, or why are they infeasible in reality? Even if uranium is abundant, wouldn't they be worth pursuing simply because they get more value out of whatever amount is mined?

submitted by /u/daman345
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Why is element 18 more heavy than element 19?

Posted: 28 Aug 2017 10:04 AM PDT

On the periodic table, it says element 18 weighs 39.948, and that 19 only weighs 39.0983. Why isn't 19 heavier than 18? Doesn't it have 1 more proton?

submitted by /u/WashedBag
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Light & Matter vs Gravity: Gravitational Slingshot?

Posted: 28 Aug 2017 05:08 PM PDT

Under a few assumptions (some of which are inevitably going to be wrong from my unlearned point of view), it would be possible to have light photons or matter be affected by a gravitational pull such as a black hole without being pulled in completely or into orbit?

If this is so, would it be possible to "slingshot maneuver" and alter its potential energy?

Light is probably exempt from this due to its constant speed throughout a frame, but what about a body with mass? Could it speed up by slingshotting round a black hole? And if so, isn't it taking energy from said black hole?

submitted by /u/DNRTannen
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Are there any places on Earth where the gravitational force is more than other places?

Posted: 28 Aug 2017 02:53 PM PDT

What happened in a molecule when an atom decay into two smaller one ?

Posted: 28 Aug 2017 12:34 PM PDT

How has the chemical composition of air in earth's atmosphere evolved over time? If present, what were the main contributing factors?

Posted: 28 Aug 2017 01:57 PM PDT

What is the is the source/power that keeps atoms and molecules together ?

Posted: 28 Aug 2017 07:34 PM PDT

What lies beneath/behind the visible material world ?

submitted by /u/de-kandelaar
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How does chemotherapy work on a molecular level?

Posted: 28 Aug 2017 10:39 AM PDT

I don't know much about chemotherapy other than it is used to treat cancer, but I do have a high-school level background on chemistry and biology, so could someone explain what chemotherapy does, on a molecular level?

submitted by /u/MeowrCat
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