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Thursday, April 13, 2017

If you run around a track twice, the first time slowly, the second time much faster so that the average for the two laps is twice the speed of the first lap. People are getting infinite speed for the second lap. Why?

If you run around a track twice, the first time slowly, the second time much faster so that the average for the two laps is twice the speed of the first lap. People are getting infinite speed for the second lap. Why?

If you run around a track twice, the first time slowly, the second time much faster so that the average for the two laps is twice the speed of the first lap. People are getting infinite speed for the second lap. Why?

Posted: 12 Apr 2017 11:42 PM PDT

This question pops up in Veritasium's new video. People are getting infinite speed for the answer.

If you run the first lap at 6 km/h and then the second lap at 18 km/h you get an average of 12 km/h. That average is 2v1 . How is this not correct?

You can also check people's answers here and the third answer to a Youtube comment here. There are also multiple answer videos that say the same thing. Help me not be confused.

submitted by /u/Mack1993
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Do all planets have a molten core? Why?

Posted: 12 Apr 2017 06:34 PM PDT

What is the difference between the Fourier series and the Fourier transform?

Posted: 12 Apr 2017 09:26 PM PDT

An alpha particle is essentially a helium nucleus; so if free electrons encountered an alpha particle, would they bond and just become helium?

Posted: 12 Apr 2017 02:58 PM PDT

Question is self-explanatory, I think.

When unstable elements decay, they can release alpha particles, which are two neutrons and two protons; a helium nucleus.

My question is would this ionizing particle become helium if it met free electrons?

submitted by /u/ArcadeIsland
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How can you derive that bound quantum systems only have discrete energies by using fundamental assumptions?

Posted: 12 Apr 2017 08:28 PM PDT

I tried to do it by using the uncertainty principle but got stuck.

If you are interested, here is what did: I saw that the collapse of the wave function that is induced by the measurement of, for example x, has a standard deviation of zero, therefore the standard deviation of the other parameter p must go to infinity. (bad math, i know)

I then checked whether the standard deviation of a sine is infinite (yes) and was only left with having to show that this is the only possible solution. However the sum of two sines als seems to be a possible solution, since that also has an infinite standard deviation. So that is a problem.

Then I realised that the fourier transformation of the collapsed wave function (dirac impulse) is not a sine, but a constant and my whole argumentation went up in smoke...

submitted by /u/physquest
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trapping a floating sphere under a stream of water

Posted: 12 Apr 2017 02:45 PM PDT

During bathtime with my infant, I've discovered that if I pour a stream of water over a floating ball, the ball is trapped under the sphere; not only this, but if I move the stream slowly, the ball follows along as though it were pulled by the stream (but of course it isn't).

I have a vague intuition as to what is happening (the ball is pushed down into the water by the stream, and the water pushes back upwards and inwards towards the ball because of its shape - when the stream moves, it pushes the ball down and away - but the water pushes it back in the opposite direction), but I'm not sure. Need official explanation please!

thanks

submitted by /u/aggasalk
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Can tattooed skin be used for a skin graft?

Posted: 12 Apr 2017 12:47 PM PDT

My own (admittedly rookie) research turned up no information. Could a section of tattooed skin be taken from a donor and grafted onto someone else like a normal skin graft? Would the ink provoke additional immune response or increase the risk of rejection?

submitted by /u/redqueenswrath
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Why do we like the taste of some foods but not others?

Posted: 12 Apr 2017 09:53 AM PDT

If two free quarks were isolated from each other at a distance, would the strong force attract them to each other?

Posted: 12 Apr 2017 10:31 AM PDT

I understand that the strong force holds quarks together, and if they are pulled apart the potential energy is enough to create two new quarks to bind to the existing quarks, so free quarks cannot be created in this manner. It is commonly said that the strong force only acts over short distances.

If two strong force sensitive particles are far away from each other, do they still interact through the strong force at all? Does the strong force really only act at short distances, or is there just no way for us to observe it acting over long distances? Do bound quarks interact with other groups of bound quarks at all through the strong force?

submitted by /u/bondiblueos9
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Why do the half lives of unstable isotopes have this distribution?

Posted: 12 Apr 2017 09:05 AM PDT

So, I recently plotted the distribution for the half lives of all the decays listed in a table of nulcides data file that I found online. (See my post on /r/dataisbeautiful ).

I was really surprised to see that the data was distributed so nicely, with two well defined peaks. It looks like half lives are (at least to a first approximation) log-normally distributed, but I don't know why that would be. Can anyone help me understand the explanation behind this?

submitted by /u/HexagonalClosePacked
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How do chip credit cards protect against static discharge?

Posted: 12 Apr 2017 09:21 PM PDT

is square root of negative one greater than zero?

Posted: 12 Apr 2017 01:34 PM PDT

Do antiparticles have the same half-lives as their matter counterparts?

Posted: 12 Apr 2017 06:58 AM PDT

If deleted data can be retrieved, why can't we have our things in deleted state and keep much more space on hard drive disks ?

Posted: 12 Apr 2017 04:33 PM PDT

Why does scattering of light increase our visibility of it?

Posted: 12 Apr 2017 10:35 AM PDT

Sorry if the title doesn't make sense but I've been reading about why the sky is blue. I understand the fibrous concepts of scattering and what not but my question is this: If blue light is scattered the most, then wouldn't the blue light needed to observe the color be scattered and not make it to our eye? If all the other colors go "straight to our eyes" from the sky except blue, wouldn't we see white light minus the blue scattered spectrum?

submitted by /u/spork7426
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Wednesday, April 12, 2017

What is a "zip file" or "compressed file?" How does formatting it that way compress it and what is compressing?

What is a "zip file" or "compressed file?" How does formatting it that way compress it and what is compressing?

What is a "zip file" or "compressed file?" How does formatting it that way compress it and what is compressing?

Posted: 12 Apr 2017 04:35 AM PDT

I understand the basic concept. It compresses the data to use less drive space. But how does it do that? How does my folder's data become smaller? Where does the "extra" or non-compressed data go?

submitted by /u/TheRaven1
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What differentiates edible gold from the gold in my computer or a ring?

Posted: 11 Apr 2017 09:28 PM PDT

I've been watching a Youtube series called "Most Expensivest Sh*t". And in it the rapper Two Chainz basically reviews super expensive versions of everyday items. In one episode he tries a 5 dollar kernel of popcorn covered in "edible gold", what makes this gold edible and the gold you normally see inedible?

submitted by /u/Thenerdiest
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What exactly is the Navier-Stokes millennium problem trying to solve?

Posted: 11 Apr 2017 05:37 PM PDT

I just took fluid mechanics 2 and I saw that there was a millennium problem regarding the Navier-Stokes eqn. Can someone elaborate on what it involves?

submitted by /u/Dab-O-Ranch
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Why is Turner syndrome a thing when extra X chromosomes are usually inactivated anyways?

Posted: 11 Apr 2017 07:07 PM PDT

How does a DNA change appear in a trillion cells?

Posted: 12 Apr 2017 02:20 AM PDT

Methylation in epigenetics, or even a random mutation in DNA happens in one or a few cells - but how does it suddenly appear in all trillion cells, especially all the sperm cells, so that it is passed on?

submitted by /u/jnorris235
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Ask Anything Wednesday - Engineering, Mathematics, Computer Science

Posted: 12 Apr 2017 08:04 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 determines whether a spray bottle will release a stream or spray?

Posted: 11 Apr 2017 06:22 PM PDT

You can twist the nozzle on a spray bottle to change whether a stream of liquid or a spray comes out when you use it. Does that twisting action change the diameter of the orifice where the solution exits?

Additionally, is there a simple relationship describing how the orifice diameter, spray velocity, solution viscosity, etc. affects whether a stream or spray comes out?

submitted by /u/Quinos
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A conductive cable over a light-year long is connected to a positive & negative pole, how long until current flows?

Posted: 11 Apr 2017 11:12 PM PDT

Assuming an infinitely large power source for the current. What would the electrical dynamics be if a cable capable of carrying the current from the (-) end to the (+) end starting the second of creating the complete circuit?
Do these electrical dynamics breakdown at some point of scale?
At this scale could we watch the 'flow' of electricity?

submitted by /u/FunkadelicAlex
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How does an artificial neural network work? How does it "learn", "evaluate" and "use" data accordingly?

Posted: 12 Apr 2017 02:53 AM PDT

Hello,

I've recently started getting interested in Artificial Neural Networks and, even though I'm a programmer, I can't grasp how the whole process works in terms of searching, scanning and evaluating, let alone storing and using new data as new criteria.

Does anybody have experience on the matter? I've checked wikipedia and similar results for a brief introduction on ANNs, but the concept is still far for me.

Thanks, have a great day :)

submitted by /u/IAMZizzi05
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Thought experiment: You have 100 coins. Flip each one: if heads remove the coin, if tails add 100 more coins. Keep flipping until you have no coins. Will this process ever terminate?

Posted: 11 Apr 2017 01:21 PM PDT

It seems like it's never technically impossible, and it's an infinite process, which makes me think it must terminate eventually, but the process gets statistically more and more difficult to complete with each flip. What happens mathematically?

submitted by /u/Goodbye_Galaxy
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Why does derivation for the infinitely deep potential well electron energies use the standing wave on a string equation?

Posted: 11 Apr 2017 05:57 PM PDT

In my textbook, the derivation for the infinite potential well energy formula:

E(n) = ((h2 / (8m(L2 )) *(n2 ) (1)

Is derived from considering the states of a fixed at 2 nodes:

L = (n*lambda) / 2 (2)

To derive the (1) I pasted, if we substitute lambda for the second equation into lambda = h / p we arrive at the first formula.

My question is however: this must imply that (2) is not merely used for an analogy to describe the energy states of an electron, we literally consider the wave formations of a string with two nodes and apply to the energy states of an electron. I'm new to learning this, so I'm still getting the concepts down, but how is this not only not used for analogy but actually used in the derivation? This has to do with an actual string with two nodes, not an electron pushed away with at two ends x = 0 and x = L. Could someone illuminate this logic for me?

Thanks!

submitted by /u/sangstar
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Is it possible to classically condition a function of the autonomic nervous system?

Posted: 11 Apr 2017 04:44 PM PDT

The autonomic nervous system, for those who do not know, is what controls all the involuntary functions of the body, such as breathing, digestion, etc. By classical conditioning from psychology, is it possible, or have there been any examples of, organisms having a specific function of the autonomic nervous system triggered by an neutral stimulus?

submitted by /u/B_Wilks
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How does premature birth affect development throughout life (epigenetics?)

Posted: 11 Apr 2017 09:04 PM PDT

I was born two months premature, and at face value Im a pretty normal and fit guy, though I have atrocious ADD, I've never been the quickest on my feet in a conversation, and my personality feels a bit "cold". I don't feel I have any defects, but my joints do feel a bit "loose", for lack of a better word.

I never really considered how being born premature may have affected me, but as I started studying for a human biology degree I've started to think more about the possible epigenetic factors that influence development while in the womb, and maybe the added stress at birth from being separated in an incubator. Before I simply thought it would only impact somatic development, which would eventually catch up, but now I'm wondering if it may directly affect HOX genes.

Ive not really been able to find any good literature on the subject. Does anyone possibly know how premature birth can affect gene signalling?

submitted by /u/artesen
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How can the difference between two binomial distributions not follow a known probability distribution, but the difference between two normal distributions follow a normal distribution?

Posted: 11 Apr 2017 04:51 PM PDT

Why doesn't the difference in binomial distributions follow a binomial distribution? Is it possible that the difference between binomial distributions follows a probability distribution that we just haven't discovered yet?

submitted by /u/Jdazzle217
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If we want to see things smaller than the wavelength of visible light, why can't we just make gamma ray microscopes?

Posted: 12 Apr 2017 12:01 AM PDT

I'm sure that there's a very good reason, but I don't know it.

submitted by /u/lirannl
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After learning a new language as an adult after a base language is known, what goes on in your brain as you speak the 2nd language? Does your brain translate the thoughts to the 1st language then to the 2nd language? How does this compare to learning 2 languages from birth?

Posted: 11 Apr 2017 05:58 PM PDT
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Tuesday, April 11, 2017

Does pupil constriction only happen when your eye is exposed to light in the visible spectrum?

Does pupil constriction only happen when your eye is exposed to light in the visible spectrum?

Does pupil constriction only happen when your eye is exposed to light in the visible spectrum?

Posted: 11 Apr 2017 07:27 AM PDT

How do lasers measure the temperature of stuff?

Posted: 10 Apr 2017 03:27 PM PDT

Can we say that the molecular formula of a compound shows that exact ratio of atoms of elements in it?

Posted: 11 Apr 2017 09:43 AM PDT

Why does water conduct AC better than DC?

Posted: 11 Apr 2017 06:55 AM PDT

It is a fairly common notion that AC can pass through water at lower voltage than DC can. I tried to prove this notion by passing AC and DC through some regular tap water. Link to the spreadsheet: https://gyazo.com/bc8f212d9f4575f3e35886a4effd1b85

In the graph, the blue line is DC, the yellow one is AC at 50Hz and the red one at 500Hz. The voltages are, despite the the markings in the screenshot, in millivolts.

The experiment was carried out with regular volt meters and a power supply that can output fairly decent DC and AC at different frequencies. And it shows that water does, in fact, conduct AC better than DC.

Why is that, however? Is it due to the ions, impurities, in the water or do the features of water molecules cause this? Could polarity have anything to do with this?

submitted by /u/aero_ch
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Does gravity affect sound waves (or other types of waves)?

Posted: 10 Apr 2017 04:35 PM PDT

Why does music make my hair stand on end and my skin feel all tingly?

Posted: 11 Apr 2017 08:06 AM PDT

I understand that the brain is very good at recognising patterns, and music is simply a pattern filled audio input to the brain, but why do certain solos, certain riffs, certain instruments make it feel like my heart swells, a mini burst of energy floods into my legs as I'm walking and everything goes tingly from my head and down my arms.

submitted by /u/MegaJackUniverse
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When a star explodes are the elements it has created, through nuclear reactions, distributed evenly?

Posted: 11 Apr 2017 12:39 PM PDT

If I understand correctly all the elements we see around us were created in the nuclear reactions within stars. So when a star explodes does it send out those elements in a predictable pattern? For example, do iron atoms get shot out further than oxygen atoms? Are there distribution tables that show the likelihood of planets containing certain elements based on the distance they form from stars. If so are planets that form further out from their stars more likely to contain certain elements? Is this why Earth and Mars have so much H20 but other planets don't seem to have much H2O?

submitted by /u/x62617
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When i put a strong flashlight in my mouth my cheeks glow. What's happening? Are photons traveling through my skin?

Posted: 11 Apr 2017 06:34 AM PDT

Is chocolate actually poison to dogs? If so, why?

Posted: 11 Apr 2017 10:12 AM PDT

Growing up we're always taught the chocolate is just about the worst thing you can feed to a dog. However, my dog (a roughly 8 year old black lab mix) has gotten into her fair share of chocolate in her days. She has never once gotten sick from it.

Somebody please explain to me if this chocolate rule is just a myth or if there are exceptions. What reason do we have to believe that chocolate causes dogs harm in the first place?

submitted by /u/Z-Fishizzle
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In fusion reactors, how do they use magnets to control the heat?

Posted: 11 Apr 2017 12:08 PM PDT

Can electrical circuits make noise?

Posted: 10 Apr 2017 09:08 PM PDT

My laptop (UX305C) doesn't use a fan nor a mechanical hard drive, but I hear a very soft kind of zzz - zz -zzz noise in especially quiet environments. What might be the cause of this?

Edit: sorry, the title should say "sound."

submitted by /u/Senrinn
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Isn't convection just conduction through a fluid medium?

Posted: 11 Apr 2017 07:29 AM PDT

Title says it all really. I was told there were three methods of heat transfer: conduction, radiation and convection.

It seems to me convection is just a convenient way to model heat transfer and fluid mechanics, but the actual heat energy must be transferring via conduction and radiation.

submitted by /u/APleasantLumberjack
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Why do electrons come in pairs?

Posted: 11 Apr 2017 01:19 PM PDT

A lot of chemistry talks about bonding pairs, lone pairs etc., but is there a specific reason why they don't come in threes or more? Also I have read about electron spin, but I'm still rather unsure about what that actually means.

submitted by /u/xkimlam
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Is it possible to measure magnetic field strength? What is it measured in?

Posted: 11 Apr 2017 01:47 AM PDT

Title. Is there a name for magnetic field strength (like how current is measured in amps)?

Bonus: what is the average strength of an audio cassette tape? Hard drive? Loud speaker magnet?

submitted by /u/crazyman50000
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Can one use microwaves from satellites to melt the iron core of mars in an attempt to reactivate the magnetic field?

Posted: 11 Apr 2017 12:45 AM PDT

Sorry, im not a very educated man when it comes to physics. Im guessing the mantle is too thick and it would need too much energy but in theory, can this work?

submitted by /u/etinbs
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Why can't cars reach 300mph?

Posted: 11 Apr 2017 07:05 AM PDT

I read that the Bugatti Chiron has an engine powerful enough to do so but it can't? Why is this?

submitted by /u/tenletters124
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Can someone explain the solution of the Monty Hall problem?

Posted: 11 Apr 2017 10:43 AM PDT

Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

PS The answer is- Switch

submitted by /u/meethil9
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What natural phenomenon used to occur back in prehistoric times that we wouldn't see now?

Posted: 10 Apr 2017 09:43 AM PDT

[Computing] Does streaming a YouTube video use the same amount of cell data as downloading the entire thing?

Posted: 10 Apr 2017 12:05 PM PDT

Title. For example if I streamed a normal YouTube video, would I use more or less data streaming it compared to downloading it with say: YouTube Red?

submitted by /u/HPA_m33k
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When you heat an unstable isotope, does it decrease its half-life time and does the opposite happen when you cool it?

Posted: 10 Apr 2017 03:20 PM PDT

What geological processes formed Vulcan Point Island in the Philippines?

Posted: 11 Apr 2017 05:37 AM PDT

Are there any species that have more than 2 genders? If so, how would reproduction work for them?

Posted: 10 Apr 2017 05:22 PM PDT

Why doesn't the phase of the moon change when it's in the sky overnight?

Posted: 11 Apr 2017 05:47 AM PDT

As the moon orbits around the Earth, and the Earth rotates on it's axis, why doesn't the moon's phase change (ex: go from full to crescent) when in the sky overnight?

submitted by /u/adamarchitect
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Has an animal ever evolved some kind of wheel-like feature for efficient transportation?

Posted: 10 Apr 2017 12:18 PM PDT
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