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Friday, February 3, 2017

AskScience Panel of Scientists XVI

AskScience Panel of Scientists XVI


AskScience Panel of Scientists XVI

Posted: 02 Feb 2017 04:54 PM PST

Please read this entire post carefully and format your application appropriately.

This post is for new panelist recruitment! The previous one is here.

The panel is an informal group of redditors who are either professional scientists or those in training to become so. All panelists have at least a graduate-level familiarity within their declared field of expertise and answer questions from related areas of study. A panelist's expertise is summarized in a color-coded AskScience flair.

Membership in the panel comes with access to a panelist subreddit. It is a place for panelists to interact with each other, voice concerns to the moderators, and where the moderators make announcements to the whole panel. It's a good place to network with people who share your interests!


You are eligible to join the panel if you:

  • Are studying for at least an MSc. or equivalent degree in the sciences, AND,

  • Are able to communicate your knowledge of your field at a level accessible to various audiences.


Instructions for formatting your panelist application:

  • Choose exactly one general field from the side-bar (Physics, Engineering, Social Sciences, etc.).

  • State your specific field in one word or phrase (Neuropathology, Quantum Chemistry, etc.)

  • Succinctly describe your particular area of research in a few words (carbon nanotube dielectric properties, myelin sheath degradation in Parkinsons patients, etc.)

  • Give us a brief synopsis of your education: are you a research scientist for three decades, or a first-year Ph.D. student?

  • Provide links to comments you've made in AskScience which you feel are indicative of your scholarship. Applications will not be approved without several comments made in /r/AskScience itself.


Ideally, these comments should clearly indicate your fluency in the fundamentals of your discipline as well as your expertise. We favor comments that contain citations so we can assess its correctness without specific domain knowledge.

Here's an example application:

 Username: /u/foretopsail General field: Anthropology Specific field: Maritime Archaeology Particular areas of research include historical archaeology, archaeometry, and ship construction. Education: MA in archaeology, researcher for several years. Comments: 1, 2, 3, 4. 

Please do not give us personally identifiable information and please follow the template. We're not going to do real-life background checks - we're just asking for reddit's best behavior. However, several moderators are tasked with monitoring panelist activity, and your credentials will be checked against the academic content of your posts on a continuing basis.

You can submit your application by replying to this post.

submitted by /u/AskScienceModerator
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AskScience AMA Series: I'm Lawrence Krauss, Chair of the Board of Sponsors of the Bulletin of the Atomic Scientists, ask me anything!

Posted: 03 Feb 2017 04:00 AM PST

Lawrence Krauss, a renowned theoretical physicist, is director of the Origins Project at Arizona State University as well as the Chair of the Board of Sponsors of the Bulletin of the Atomic Scientists, who recently moved the Doomsday Clock 30 seconds closer to midnight. He is the author of more than 300 scientific publications and nine books, including the international bestsellers, A Universe from Nothing, The Physics of Star Trek, and the upcoming book The Greatest Story Ever Told--So Far. The recipient of numerous awards, Krauss is a regular columnist for newspapers and magazines, including The New Yorker, and he appears frequently on radio, television, and in feature films. Krauss lives in Portland, Oregon, and Tempe, Arizona.

Lawrence will be joining starting around 2 PM ET (19 UT).

submitted by /u/AskScienceModerator
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Do all galaxies have a very massive object at their center? If so, is it necessarily a black hole?

Posted: 03 Feb 2017 04:51 AM PST

why can't particles of zero mass be at the rest?

Posted: 02 Feb 2017 06:23 PM PST

in a book I'm reading it says the fact that a particle has zero mass means, in a way, that it cannot be at rest. why is that?

submitted by /u/throwaway_justaway
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Why is lead always the element used to protect us from radiation?

Posted: 02 Feb 2017 03:19 PM PST

To expand a bit, what properties does lead have that make it so good at protecting from radiation. How does it actually keep the radiation from touching us? What is happening at the atomic level?

submitted by /u/The_Astronautt
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Is there any evidence that pheromones play an active role for mating in humans?

Posted: 02 Feb 2017 06:15 PM PST

Do our pupils dilate when we dream about light?

Posted: 02 Feb 2017 11:56 AM PST

Last night I dreamt about being in a very dark room for a long time. Eventually I walked outside and was met by this very bright daylight. It hurt my eyes, but the pain eventually disappeared, as it would in a real life situation, because of our pupils adjusting.

I found this very fascinating, because it's probably all imaginary, but it felt so real. Do our eyes react to imaginery impulses, like in this case, (bright) light in a dream?


PS: I don't know the antonym of dilating in the context of pupils, so I stuck with it in the title.

submitted by /u/TheApeirophobe
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Is our galaxy on a stable axis?

Posted: 02 Feb 2017 10:31 AM PST

Watching this video, I started to wonder, if a rotating object in zero-G is on an unstable axis, the object will rotate on a different intermediate axis to try and correct the instability.

Does the Milky Way Galaxy also rotate like this? Does a lack of rotation suggest a stable axis?

submitted by /u/truemeliorist
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If you drill a hole in a metal plate and then freeze the plate, does the hole get smaller, bigger or stays the same?

Posted: 02 Feb 2017 08:32 AM PST

Where do the electrons go in a Neutron Star?

Posted: 02 Feb 2017 11:37 AM PST

I have been reading a little bit about neutron stars and I think they are really fascinating. However, I've never understood where the electrons go when the atoms collapse into neutrons. It was explained to me that the protons in the nucleus absorb the electrons, giving the atom a neutral charge. But, neutrons are made up of 2 down quarks and an up quark without an electron in it. So what happens to the electron?

submitted by /u/floppymcschloppy
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Why is there only positive or negative electric charges?

Posted: 02 Feb 2017 05:25 PM PST

How do we know there is no "sub-negative" or "sub-positive" charges, or even a whole different set of undiscovered charge values?

submitted by /u/ExtrahCrispy
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Why do antihistamines cause drowsiness when they cross the Blood Brain Barrier?

Posted: 02 Feb 2017 05:59 PM PST

This article explains it well,

First-generation antihistamines are highly lipophilic and therefore readily cross the blood-brain barrier, contributing to adverse central nervous system effects including sedation, drowsiness, and decreased cognitive processing

but it does not specify why first-generation antihistamines cause drowsiness when they cross the BBB. What effects do these antihistamines have on the central nervous system once it crosses the barrier?

submitted by /u/kuhataparunks
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[Mathematics] Does df/dx behave like a fraction?

Posted: 02 Feb 2017 09:58 AM PST

If df/dx=2x with f=x2, is df/2x=dx? We had this question when we were doing integration with substitution. Some said no because it's an operator not a fraction but it does in fact work if you use it for integration.

submitted by /u/Tirunculus
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[Chemistry] What is smell?

Posted: 02 Feb 2017 04:20 PM PST

I know that smell is essentially molecules attaching to smell receptors in our noses(correct me if I'm wrong). So does that mean when something smells, it's "decomposing"(the source's particles escaped?)? What causes smell to originate from the source?

submitted by /u/explo_e-the-unknown
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If two astronauts are traveling half the speed of light away from each other, and looking behind them, what would they each see?

Posted: 02 Feb 2017 07:09 AM PST

How does lasing cause transitions from the metastable state when by definition the selection rules forbid it?

Posted: 02 Feb 2017 10:32 AM PST

I have a basic question about laser physics that doesn't seem to be answered in any of the standard introductory books on my shelf.

I understand that in order to create a population inversion you need to excite transitions to a metastable state, and that the lasing occurs with stimulated emission of transitions from the metastable state. However, this seems to be a contradiction in terms, which is strangely not addressed anywhere I can find online or in my textbooks! For example, in 'Modern Physics' by Thornton & Rex, they say:

"The key is that the transition from E2 to E1 must be forbidden, for example, by a Delta l = +- 1 selection rule. Then the state with energy E2 is said to be metastable."

And then a few lines later they say that the lasing transition is the stimulated emission of exactly the previous transition they just described as "forbidden." And certainly the aforementioned selection rule would prevent the stimulated emission by a photon of spin 1 angular momentum, since the metastability is due to such a transition not being possible (for example the metastable state being in the 2s state, so the only lower state is 1s, so a transition would have Delta l = 0, which is not allowed).

What am I missing?

submitted by /u/ButWhoIsCounting
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How does corking a baseball bat cause the ball to travel further when hit?

Posted: 02 Feb 2017 09:11 AM PST

Affinity chromatography or coimmunoprecipitation: When should someone use one or the other?

Posted: 02 Feb 2017 05:41 PM PST

I feel like they're both too similar. I can't really imagine a situation best suited for one, because it feels like they essentially perform the same function.  

Take the following problem, for example:

A protein called p21 is an inhibitor of cell division in human cells. Mutations that inactivate p21 are an important cause of cancer because they cause unrestrained cell division. Imagine that you are one of the first people to study p21 and you hypothesize that it inhibits cell division by binding and inhibiting cyclin-dependent kinase (CDK), which is the kinase that initiates and controls the process of cell division. What would be the easiest way to test whether p21 binds to CDK? Briefly explain how the test would be carried out.

The answer to this question is Coimmunoprecipitation, using an antibody to precepitate p21 or cdk then using Western Blotting/mass spec.  

Why can't affinity chromatography be used in this situation instead? Does anyone know any specific examples where one would be a better choice than the other?

submitted by /u/thathomelessguy
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Before it was possible to repair an ACL with surgery, were there any treatment options for those who suffered one?

Posted: 02 Feb 2017 09:18 AM PST

Could perpetual motion be created somehow in a vaccum chamber with zero gravity?

Posted: 02 Feb 2017 06:50 AM PST

I feel like without any air resistance or gravity there would be no force to slow down the perpetual motion device. Am I correct?

submitted by /u/SwiftnovaXG
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Thursday, February 2, 2017

If an astronaut travel in a spaceship near the speed of light for one year. Because of the speed, the time inside the ship has only been one hour. How much cosmic radiation has the astronaut and the ship been bombarded? Is it one year or one hour?

If an astronaut travel in a spaceship near the speed of light for one year. Because of the speed, the time inside the ship has only been one hour. How much cosmic radiation has the astronaut and the ship been bombarded? Is it one year or one hour?


If an astronaut travel in a spaceship near the speed of light for one year. Because of the speed, the time inside the ship has only been one hour. How much cosmic radiation has the astronaut and the ship been bombarded? Is it one year or one hour?

Posted: 02 Feb 2017 02:00 AM PST

Why do humans drink water differently from other animals?

Posted: 01 Feb 2017 09:12 PM PST

Of course I do not mean when we use cups or straws. What I mean is, imagine you fill your hands with water and raise it to your mouth to drink. How do you drink the water from your hands? I imagine you use your mouth to suck up the water. However when I observe my pets (cat and dog) drinking water from their bowl, they use their tongue to lap the water into their mouths. I'm not sure how other mammals do it as I have not really paid attention. I am curious why mammals would have different ways to drink water. Do other apes drink water in the same way as humans? Is the difference due to mouth/jaw physiology?

submitted by /u/MyRandomQuestions
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Would a hydrophobic surface reduce the drag of an aerodynamic object traveling in air at all?

Posted: 01 Feb 2017 08:41 PM PST

It has been shown that a superhydrophobic surface can significantly reduce the drag on an object submersed in water (not really experimentally shown on a large scale due to issues with surfactants I think). See this reference for instance:

Extraordinary drag-reducing effect of a superhydrophobic coating on a macroscopic model ship at high speed. By Hongyu Dong

I wanted to know if a drag reduction effect can still hold if we made two changes. i) the object was moved to air rather than water and ii) the surface was made to be hydrophobic rather than superhydrophobic.

My thinking is that if the object is traveling in air, there will still be a thin film of air pinned to the object, right? And this thin film will then help keep the surrounding flow laminar, or at least more laminar than without the hydrophobic coating. Of course, the drag might not see a significant reduction but I just want to know if it works at all.

submitted by /u/synergistali
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Why "1 + 1 = 2" ?

Posted: 31 Jan 2017 10:55 PM PST

I'm a high school teacher, I have bright and curious 15-16 years old students. One of them asked me why "1+1=2". I was thinking avout showing the whole class a proof using peano's axioms. Anyone has a better/easier way to prove this to 15-16 years old students?

Edit: Wow, thanks everyone for the great answers. I'll read them all when I come home later tonight.

submitted by /u/ehh_screw_it
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*Where* is the "hologram?"

Posted: 02 Feb 2017 06:58 AM PST

Having seen several recent news articles suggesting the first evidence seen regarding the universe as a hologram, along with older information on the theory (a lot from Susskind) I find myself still unclear on the location of information in a holographic universe.

Are they positing that it is all on an event horizon of the entire universe and completely non-local, or is it local, but all on a 2D surface at Planck scales?

submitted by /u/Hailbacchus
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How are intermontane basins formed?

Posted: 01 Feb 2017 08:24 PM PST

I understand that they are located within and in-between mountain ranges, and I've read online that the basins are often formed as a result of grabens. However, I can't figure out how the extensional forces required for graben formation could appear in such a region.

submitted by /u/geonerdSO
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Why is it that the medial branches of the dorsal rami innervate the cutaneous tissue of the upper back, but the lateral branches of the dorsal rami innervate the cutaneous tissue of the lower back?

Posted: 01 Feb 2017 08:25 PM PST

When will Alaska touch Russia, and what will happen geologically?

Posted: 01 Feb 2017 08:21 PM PST

Hello r/askscience, This is my first time asking any questions here, but I was wondering about something that Google searches failed me on, when will Alaska touch Russia. I know that it is approximately 55 miles between the tip of Alaska and Russia, but it brings up the question when will the land mass make contact? Furthermore, what will geologically happen. These areas have been separated from what I have heard since prehistoric times, so will we massive extinction of certain species since animals haven't adapted to Russian wildlife?

submitted by /u/evievi002
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How do we calculate million/billion plus half lives of elements?

Posted: 01 Feb 2017 03:37 PM PST

Why does the iron filings and bar magnets experiment result in the iron filings arranging themselves in neat lines when the magnetic field should be continuously distributed around the magnet?

Posted: 01 Feb 2017 11:53 PM PST

How does drinking water clear the bad stuff out of our bodies?

Posted: 01 Feb 2017 08:37 PM PST

Does distilled VS stilled water make a difference? How does it help our skin? Just curious how it actually works inside of our bodies. Always heard that drinking water can flush all the bad stuff out. Esp after a greasy, fat meal.

submitted by /u/Hf4444
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What happens with fat and muscle tissue when there is no food consumption?

Posted: 01 Feb 2017 07:38 PM PST

Why is it said that muscle tissue is broke down when you don't eat? Isn't the whole purpose if storing fat to use it when energy is needed?

submitted by /u/FiggerNugget
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What does the solubility of a chemical in powder form (Allopurinol) mean when I want to make solution?

Posted: 02 Feb 2017 03:04 AM PST

I am looking selleckchem.com at a powder reagent of Allopurinol. I am planning to use it for an experiment. However, the site also shows the solubility in vitro with water at 4 mg/mL (29.38 mM). If I want to make a working concentration of 10 uM (10 umol/L) in a 2 mL aliquot, how do I factor in the solubility of this reagent in water? I apologize in advance, this is all information I should probably understand. This is the link if you want to see what I mean.

http://www.selleckchem.com/products/Allopurinol(Zyloprim).html

submitted by /u/Opirr
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Does non-photonic energy count towards the total mass-energy of a system?

Posted: 01 Feb 2017 04:58 PM PST

If I have a massive system that is just on the edge of collapsing into a black hole and I add mass, it collapses. If I shoot it with a laser, it collapses, because the photons put it over the edge as their gravitation adds to the system.

But what if I kick it and start it rotating? Does that rotational energy add to the system's mass-energy and put it over the edge? What if I linearly accelerate it? Or if I reshape it so that it is two shells, and then apply a voltage between the shells, adding energy due to capacitance? If I cooled it down, would I be taking it further from collapsing (assuming no density changes)?

If I started to create a cavity at the center of it by pushing outward, thereby increasing the gravitational potential energy of the system (and assuming no change in outer radius), would it collapse?

submitted by /u/justpassingthroo30
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Why are all ferroelectric materials also piezoelectric?

Posted: 01 Feb 2017 09:04 PM PST

I've been reading up on the piezoelectric effect which brought me to the ferroelectric effect and it said that all ferroelectric materials are also piezoelectric but I can't seem to find an explanation for why that is?

submitted by /u/usthrowaawaayy
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I just heard that it would take 4 light-years of lead to stop a neutron. This seems like it leaves out how fast the neutron is moving. How fast or why not?

Posted: 01 Feb 2017 02:58 PM PST

Were nuclear weapons a straightforward result of nuclear theory? Or was it more complicated than that?

Posted: 01 Feb 2017 01:07 PM PST

Once scientists understood how nuclear reactions occurred, were nuclear weapons an obvious/straightforward application of nuclear theory?

(Clearly there are serious practical problems in designing and testing a working mechanism, refining the material, etc, but I'm mostly asking about the initial realization of "hey, I wonder if we could make a really big bomb using this!")

Sure, anyone could plug numbers into e=mc2, but that doesn't necessarily imply you could actually use it for something.

Or to approach the same question in another way: were nuclear weapons developed independently by multiple countries, after the US demonstrated their potential? Or did they all rely on a common body of work?

submitted by /u/MegaTrain
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What is the line below the nose but above the mouth on mammals called, and what is it for?

Posted: 01 Feb 2017 01:07 PM PST

For clarification purposes: http://imgur.com/MuJfwj2

I've been googling around trying to find out what that is caled. It's seen on many mammals and seems to be a defining feature, enough so where the emoticon :3 is identified as a cat. However, unsurprisingly, looking up "what is the line below nose and above mouth called" or any permutation that makes sense yields no relevant results.

submitted by /u/Mister4Eyes
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Why can't we control our heart beat, what physically stops us from controlling those types of muscles?

Posted: 01 Feb 2017 04:41 PM PST

Why does the integral of 1/x result in a logarithm? Also, why does logarithm have base e?

Posted: 01 Feb 2017 09:52 AM PST

I think it seems too beautiful and amazing that this is just a coincidence that the integral of 1/x results in a logarithm (much less for that logarithm to have a base of one of the most useful numbers in mathematics, e) for it to just be coincidence. Can someone come up with a proof, or at least a logical argument, for why this is the case?

submitted by /u/ThePurplePancake4
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Does the intermediate axis theorem have any recapitulation in the switching of the magnetic poles of the Earth?

Posted: 01 Feb 2017 03:14 PM PST

Can a child end up with more than 50% of their genes from the father?

Posted: 01 Feb 2017 08:02 PM PST

So I got into this discussion with my SO after watching Game of Thrones

Let's say we have a husband (call him dad) and he has a child with his wife. The child (lets call him child #1 and make her a female) would have 50% of each parents genes. Now if the husband (dad) has sex with child #1 and has child #2, then child #2 would have 50% of the dad's gene and 50% of child #1 genes. But child #1 has already 50% of the dad's gene, would child #2 have 75% of the dads gene? What if this process continues many more times? Would the last child have more of the dads gene then just a half?

submitted by /u/Tunafish7428
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Does an empty refrigerator use less energy than a full refrigerator?

Posted: 01 Feb 2017 04:02 PM PST

After the contents of the full fridge have cooled, which one is more efficient to keep cool?

submitted by /u/ThreeFistsCompromise
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Wednesday, February 1, 2017

AskScience AMA Series: I was NASA's first "Mars Czar" and I consulted on the sci-fi adventure film THE SPACE BETWEEN US. Let's talk about interplanetary space travel and Mars colonization... AMA!

AskScience AMA Series: I was NASA's first "Mars Czar" and I consulted on the sci-fi adventure film THE SPACE BETWEEN US. Let's talk about interplanetary space travel and Mars colonization... AMA!


AskScience AMA Series: I was NASA's first "Mars Czar" and I consulted on the sci-fi adventure film THE SPACE BETWEEN US. Let's talk about interplanetary space travel and Mars colonization... AMA!

Posted: 01 Feb 2017 05:00 AM PST

Hi, I'm Scott Hubbard and I'm an adjunct professor at Stanford University in the department of aeronautics and astronautics and was at NASA for 20 years, where I was the Director of the Ames Research Center and was appointed NASA's first "Mars Czar." I was brought on board to consult on the film THE SPACE BETWEEN US, to help advise on the story's scientific accuracy. The film features many exciting elements of space exploration, including interplanetary travel, Mars colonization and questions about the effects of Mars' gravity on a developing human in a story about the first human born on the red planet. Let's chat!

Scott will be around starting at 2 PM PT (5 PM ET, 22 UT).

submitted by /u/AskScienceModerator
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Why can't we theoretically get infinite electrical power through transformers?

Posted: 01 Feb 2017 05:32 AM PST

If we can take a low voltage and turn it into a higher voltage, why can't we just keep on doing this and get more and more electrical power?

submitted by /u/blackdeath321
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Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology

Posted: 01 Feb 2017 07:05 AM PST

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Economics, Political Science, Linguistics, Anthropology

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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Is the Spring constant (K) of a spring an actual constant or is it dependent on x (stretch)?

Posted: 31 Jan 2017 09:27 PM PST

In my physics class we are doing a lab, and part of it I had to calculate the spring constant of a spring. As i increased the force acting on the spring, ie stretched it further, the calculated spring constant changed from about 4.5 down to 3.5. I believe I also did not reach the elastic limit of the spring, as we retested it and got the same results.

submitted by /u/swagruss
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Why do we perceive red as running into violet on a color wheel if their light frequencies don't similarly run into each other on the light spectrum? [neuroscience]

Posted: 31 Jan 2017 03:10 PM PST

For all other colors that bleed into each other on a color wheel, there is a corresponding "bleeding together" of frequencies on the light spectrum. Why do we perceive color in this way? Would this be the case if the visible light spectrum was a different stretch of the light spectrum, for example if we could see only between yellow and blue, or infrared and ultraviolet? Please let me know if it's unclear what I'm asking. I also was unsure whether to tag this in neuroscience, biology, or physics.

submitted by /u/sikemeay
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Whats the maximum angle light can be redirected by a gravity well?

Posted: 01 Feb 2017 06:05 AM PST

I understand that black holes, stars and any massive enough gravity well can blend light but whats the upper limit on the angle, is it possible for light to do a complete 180 and fly back towards the source?

submitted by /u/anythignrandom
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How do scientists take off particles of matter from a material for research that are as small as a micro meter or nano meter in size?

Posted: 31 Jan 2017 09:56 PM PST

How do scientists remove particles that are as small as a micro meter or nano meter from a material in order to inspect those particles? What processes or technology do scientists use to accomplish this?

I could not find this information online. Thank you very much for your assistance.

submitted by /u/Bearathor2156
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Is it possible for a person to be colorblind in only one eye?

Posted: 31 Jan 2017 09:53 AM PST

Something like the heterochromia mutation?

submitted by /u/thebrandedman
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What is the speed of sound in a neutron star?

Posted: 31 Jan 2017 12:02 PM PST

Before mining happened on earth, which natural resources would be visible from the surface?

Posted: 01 Feb 2017 02:40 AM PST

I imagine the easiest bits were mined first. Would there have been mountains literally glistening with gold and diamonds just 10,000 years ago?

submitted by /u/breathing_normally
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Is there difference between 2G, 3G, and 4G in terms of power consumption?

Posted: 01 Feb 2017 02:33 AM PST

Do all three standards consume the same amount of power if we assume that it takes all three standards 5 minutes to download a 1MB file?

submitted by /u/q1029384756
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Are lasers required to produce collimated light?

Posted: 01 Feb 2017 06:13 AM PST

I was reading the wikipedia article on laser diodes which says:

Due to diffraction, the beam diverges (expands) rapidly after leaving the chip, typically at 30 degrees vertically by 10 degrees laterally. A lens must be used in order to form a collimated beam like that produced by a laser pointer. If a circular beam is required,

If the beam produced by a laser diode diverges and needs to be corrected with a lens anyways, do we need a laser diode at all? Could a regular LED or any other light source be used instead?

submitted by /u/gburdell4u53
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When talking about the age of the universe, which reference frame are scientists using?

Posted: 31 Jan 2017 06:49 PM PST

I understand that, the stronger the gravitational field the slower time would pass - wouldn't it mean that the early (more dense)universe had a slower clock overall? When the number 13.8 Billion years is mentioned, which reference frame has experienced all this time?

submitted by /u/paskal91
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Is there an animal/organism that does not sleep? Does it have the capacity for learning and memory?

Posted: 31 Jan 2017 08:05 AM PST

One of the hypotheses for the function of sleep is to strengthen previously learned information and filter out 'irrelevant' or 'useless' information learned during waking.

Are there any organisms that do not show classically defined 'sleep'?

Sleep I will define as a state of immobility, reduced responsiveness to external stimuli, and is homeostatically controlled.

submitted by /u/DarwinDanger
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Why does hearing dimish when we yawn?

Posted: 31 Jan 2017 11:34 AM PST

As you approach the speed of light, does the CMB in front of you get blueshifted?

Posted: 31 Jan 2017 05:48 PM PST

And similarly redshifted behind you?

submitted by /u/FTLSquid
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If a neutron is made of 3 quarks, each with spin +1/2, why does a neutron only have a spin of +1/2?

Posted: 31 Jan 2017 08:30 PM PST

Is this to do with the Pauli Exclusion Principle as it relates to quarks?

submitted by /u/CallMeDoc24
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What's happening in their brain when someone with dyslexia mixes up letters?

Posted: 31 Jan 2017 12:49 PM PST

As the light of more stars reaches the earth, will the night sky become brighter and brighter over time?

Posted: 31 Jan 2017 11:53 AM PST

Looking forward billions of years, if someone was able to look up at the night sky from earth (lets assume its still here), will there be some point in the future where the night sky is saturated with light?

submitted by /u/clorisland
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Where does it hail the most? What causes it to hail there more than anywhere else?

Posted: 31 Jan 2017 11:49 AM PST

I was driving to school today and we got hail today for the first time I can remember in years. It snows yearly where I live

submitted by /u/FloofyRabbit
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Is there a maximum "brightness"?

Posted: 31 Jan 2017 04:36 PM PST

Would a situation be possible where some surface would be entirely "covered" in photons whereas no more photons could physically fit there?

submitted by /u/Opqwer
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When a geographically isolated population becomes reproductively isolated from previously interbreeding populations, what exactly changes to make them incapable of interbreeding?

Posted: 31 Jan 2017 10:36 AM PST