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Saturday, April 22, 2017

Is my stomach ever completely empty? And about how much fluid is in there without and food or drink?

Is my stomach ever completely empty? And about how much fluid is in there without and food or drink?


Is my stomach ever completely empty? And about how much fluid is in there without and food or drink?

Posted: 21 Apr 2017 05:55 PM PDT

I'm curious as to what the neutral stomach fullness is. Like if I don't eat or drink for about 4 hours, what is in my stomach? I'm assuming it's some kind of acid but what's the amount that would be in there? Thanks.

submitted by /u/sleepless_mc
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Why is osmium (slightly) blue?

Posted: 21 Apr 2017 05:45 PM PDT

Certain scientific papers state that osmium is a blue-coloured metal. I understand that gold and copper is distinctively coloured due to relativity (Although I am a bit hazy with copper because its nucleus is much lighter). But why is osmium blue? It is not prominently blue so I am quite certain it is not about relativity, but what could it be?

submitted by /u/Aethemeron
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What is really going on when I "sleep wrong" and wake up with a stiff neck?

Posted: 21 Apr 2017 11:52 AM PDT

Are there "quantum calculations" that can make a quantum system take as long as an average supercomputer to solve?

Posted: 21 Apr 2017 08:33 PM PDT

Also, will quantum computers make cryptocurrency obsolete? Is it possible the government already has quantum computers but hasn't revealed them to keep the advantage?

submitted by /u/1xexpertx1
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How is it possible that the strong coupling constant is greater than 1?

Posted: 21 Apr 2017 11:38 PM PDT

I can't wrap my mind around this at all. Basically for strong interactions, the more complex the interaction, the more likely it is to happen. But you can always make an interaction more complex by adding more propagators which make it more likely to happen. Doesn't this make an average strong interaction an infinite order interaction? Does is max out eventually and the probability starts to decrease?

submitted by /u/BAOUBA
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What is the difference between kinetic energy and momentum?

Posted: 21 Apr 2017 11:32 PM PDT

I appreciate they're calculated using different formulas, but I just can't visualise how they're different in my head

submitted by /u/light_dude38
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If light is a transverse wave, shouldn't all observers agree on the direction a travel for a photon?

Posted: 22 Apr 2017 01:54 AM PDT

In the classic thought experiment that illustrates time dilation, you have 2 mirrors one light second apart. Observer A says "Yup, it takes one second for the light to travel between these mirrors".

Observer B says "But wait, from my perspective, Observer A and the mirrors are traveling at .99C! It took like 1.4 seconds by my watch (because the light had to travel one light second, plus the distance that the mirrors moved in that time period), therefore time must be slower for Observer A".

My gut tells me that the Observers would NOT agree on the direction the wave was propagating, but I can't understand why. Does the wave appear to vibrate differently to the two Observers? Shouldn't they be able to agree what direction the light was vibrating in and thus be able to say what direction the light "was really going in"?

submitted by /u/nightmedic
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Is it a coincidence that the great majority of tectonic plate boundaries are in the ocean?

Posted: 21 Apr 2017 02:11 PM PDT

Seems odd I guess that there arent continents being torn in half other than a few examples of small areas like California and east Africa.

Why aren't there land equivelants to the oceanic ridges, huge mountain ranges of activity and land formation?

submitted by /u/nilhaus
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When nucleons join together to form a nucleus the total mass is greater than their individual masses (the mass defect). How is the additional mass distributed between each of the nucleons?

Posted: 21 Apr 2017 08:46 PM PDT

I understand that when nucleons join energy is converted to mass. But if an elementary proton or neutron has a fixed mass, where is this new, extra mass located? Is it divided up equally? Does it exist between the nucleons like glue? Or does it just hover randomly around the nucleus?

submitted by /u/ten_mile_river
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How entangled particles(electrons/photons) are created? And does any natural process is cosmos yield entangled particles?

Posted: 21 Apr 2017 12:13 PM PDT

How does proton-antiproton annihilation work?

Posted: 21 Apr 2017 12:51 PM PDT

Annihilation (matter-antimatter) made me think. Electron and Positron annihilate producing 2 gamma ray photons. I thought that this concept could also be applied to proton-antiproton annihilation. However, due to the quarks,gluons a proton contains (and the anti-versions of the antiproton), I've been reading different things. Some say that the proton-antiproton annihilation produces only gamma ray photons, some say that other particles like mesons are produced. What is the correct process? (If there is a "correct" process of course)

submitted by /u/Tesmkay
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Why can't we (or don't we) connect prosthetics to the nerves of the limb it attaches to?

Posted: 21 Apr 2017 01:53 PM PDT

So to be more precise. Say someone looses their hand. The nerves controlling the muscles of the hand are still there in the arm. Thus we should be able to connect sensors to these nerves so that when the person tries to move their hand the sensors pick up the signals and send them to the prosthesis.

However I've never been able to find any prosthesis that seems to do anything like this. So my conclusion is we cannot do this. Now why is that so?

submitted by /u/plebhazard
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Is there a point in history that humans (or our genetic ancestors) became carnivorous?

Posted: 21 Apr 2017 11:07 AM PDT

Are there any remnants of planets in our solar system that existed before our sun?

Posted: 21 Apr 2017 11:37 AM PDT

How would we know, and how big can they be? How many solar births and deaths have they been through?

submitted by /u/frenzyboard
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What is the point of the Bonferroni adjustment?

Posted: 21 Apr 2017 09:17 PM PDT

Hi guys, I'm currently taking a Stats course and my professor, unfortunately, skimmed over this topic. It seems important seeing as how there are several lecture slides on it, but none of them are making sense with me. Could someone explain the Bonferroni Adjustment's purpose? Why is it useful if it makes it more difficult to reject the null hypothesis?

submitted by /u/-Narble-
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[Astronomy] If You Were In the Middle of the Boötes Void, Would You Be Able to See Yourself/Anything or Tell If You Were Moving?

Posted: 21 Apr 2017 11:31 AM PDT

I'm sitting here at my desk and have had a rush of questions about voids in space...

  1. If there's no stars within any reasonable distance - would the space around you be completely pitch black?

  2. If so, could a traveler within the void be able to tell if they were moving - if so, moving in respect to what?

  3. What would space appear to look like as you began to approach the edge of a void region from its center?

  4. Would it be small specks gradually emerging to something like the space we see from earth?

Bonus question: I know they're called black holes, but really they're black spheres right?

submitted by /u/amchaudhry
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What is most different about the English language today compared to English of George Washington's time, such as that in the Constitution and/or Declaration of Independence?

Posted: 21 Apr 2017 07:24 AM PDT

How do soundwaves react to temperature?

Posted: 21 Apr 2017 09:49 AM PDT

Imagine a room that has a microphone and a speaker. The same sound would be played in the same room. The only difference would be a different temperature. Would the microphone pick up exactly the same data?

submitted by /u/vallegs
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How do HEAT (High Explosive Anti-Tank) rounds know when they are approaching the target?

Posted: 21 Apr 2017 10:47 AM PDT

Articles about HEAT tank rounds explain in detail how they manage to penetrate the enemy tanks' armor. But, they never specify the method used to determine the distance to target (which has to be calculated precisely for the round to do its job).

So how do they do it? Do they use lasers? Radars? Simple timed fuses?

submitted by /u/ApeshitMadMuscovite
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Friday, April 21, 2017

AskScience AMA Series: We are the organizers of Celebrating Einstein, a month-long interdisciplinary science outreach event honoring Einstein's theories and achievements. Ask Us Anything!

AskScience AMA Series: We are the organizers of Celebrating Einstein, a month-long interdisciplinary science outreach event honoring Einstein's theories and achievements. Ask Us Anything!


AskScience AMA Series: We are the organizers of Celebrating Einstein, a month-long interdisciplinary science outreach event honoring Einstein's theories and achievements. Ask Us Anything!

Posted: 21 Apr 2017 04:00 AM PDT

Hi Reddit! We are some of the many organizers for Celebrating Einstein, a month-long, interdisciplinary outreach event that includes spoken lectures, danced lectures, readings, interviews with physcists, symphony performance, field trips for West Virginia schools, artistic interpretations of Einstein's theories, and more. Over 100 years ago, Einstein predicted the existence of gravitational waves, and we are just beginning to detect them now. Our goal is to communicate the beauty and significance of Einstein's theory of General Relativity, its predictions, and the recent detection of gravitational waves announced only last year with the public. Check out our website for a full list of the events we've organized, and we'd love to talk about the science, the outreach, the organization, or anything!

We have four organizers from the physicist/astronomer side joining us today:

  • Sarah Burke-Spolaor is a professor of astronomy at WVU. She was a postdoctoral researcher in Socorro, NM, working with the National Radio Astronomy Observatory Very Large Array. She works on electromagnetic counterparts to gravitational wave sources and fast radio bursts.
  • Kristina Islo is a graduate student in the Leonard Parker Center for Gravitation, Cosmology, and Astrophysics at the University of Wisconsin Milwaukee. As a member of the North American Nanohertz Observatory for Gravitational Waves, she studies the gravitational wave astrophysics possible with pulsar timing array experiments as well as the statistical methods used to detect signals from supermassive binary black holes.
  • Michael Lam is a postdoctoral researcher in the WVU Physics and Astronomy Department and a member of the Center for Gravitational Waves and Cosmology. He is currently working with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. His current area of research is on characterization of NANOGrav's gravitational wave detector, an array of pulsars distributed throughout the galaxy. He received his Ph.D. from Cornell University in 2016.
  • Laura Sampson is a postdoctoral researcher at Penn State University. She received her doctorate at Montana State University and worked previously at the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) at Northwestern University. She is one of only five nationwide recipients of the 2015 L'Oreal USA "For Women in Science" Fellows.

We'll be on starting at 12 PM ET (17 UT), so ask us anything!

Celebrating Einstein was originally produced by Montana State University and the eXtreme Gravity Institute. The West Virginia Celebrating Einstein event is sponsored through NSF award number 1458952, the WVU Department of Physics & Astronomy, the WVU School of Theatre & Dance, the West Virginia Space Grant Consortium, and the WVU Eberly College of Arts & Sciences.

submitted by /u/AskScienceModerator
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Why is gold soft?

Posted: 21 Apr 2017 05:11 AM PDT

Vague I know but is it because of the atomic structure? Tungsten a much much "harder" material is 5 electrons away from gold and have the same electron configuration. I noticed that the grouping on the periodic table shows similar hard/soft properties of elements by the group number. I thought this had more to do with electron structure than physical properties?

submitted by /u/hansca04
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What is difference between advection and convection?

Posted: 21 Apr 2017 01:36 AM PDT

Can light make a sound?

Posted: 21 Apr 2017 06:55 AM PDT

Is it possible to turn on a light with such intensity as to cause a vibration that could be heard? I figure light is made of particles and sound is just compressions of matter. So could light possibly make a sound?

submitted by /u/astorml
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Would shooting down a nuclear missile result in a nuclear explosion?

Posted: 20 Apr 2017 06:25 PM PDT

Regarding a successful missile defense system, intercepting a nuclear missile launch.

submitted by /u/Bcjustin
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Why does the ISS maintain a radial-in attitude?

Posted: 20 Apr 2017 11:50 AM PDT

In almost every photo of the International Space Station, you can clearly see that the cupola module is always pointing towards the earth. That means that the ISS maintains a constant attitude relative to Earth and that it's spinning at 1 rotation/orbit (90 min)

I understand that it doesn't need any energy to maintain this low angular speed, but I assume that it does create some potentially avoidable problems:

• Small centrifugal accleration on the outer most modules.

• EVA astronauts will maintain the linear velocity of the spin, thus moving away from the station after they exit.

• Docking: I just can't wrap my head around how stuff could dock to the ISS if it's spinning at 4°/min (unless it stops spinning for docking maneuvers).

So why is it spinning? Just to maintain a view for the cupola at all times? Does it stop spinning during EVAs and docking?

submitted by /u/All_HaiI_Satan
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Why don't electrons cross the plates of charged capacitors?

Posted: 20 Apr 2017 08:51 PM PDT

So I'm taking physics now and I still have trouble understanding this. If there is an electric field across the plates, why wouldn't the electrons just cross the space in between the plates instead of going the long route on the wire to the opposite plate.

I'm also confused as to why one plate is positive and the other is negative in the first place. Shouldn't the like charges want to repel each other and hence not accumulate on a plate to begin with? Apologies in advance if this is common knowledge I just always have been confused by this.

submitted by /u/stars_bitch67
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How are radio waves 1s and 0s?

Posted: 20 Apr 2017 02:37 PM PDT

Looking at wifi, how is binary transmitted via radio waves? Is there a difference in amplitude? Phase changes?

This page has some good info, just curious how wifi works specifically; visuals would be helpful if you've got em

submitted by /u/kcaselli66
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What wavelengths does sulfur emit as electrons jump between energy levels?

Posted: 20 Apr 2017 07:38 PM PDT

I know that the electrons go between the various energy levels and they emit photons at exact wavelengths, but what wavelengths does it emit? All the sources I've found have either been really inexact or super technical.

submitted by /u/Algebra-Theorem
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How do we know when the Yellowstone National Park Super volcano last erupted?

Posted: 20 Apr 2017 09:09 PM PDT

I know that scientists say that it should erupt every 600,000 years but it hasn't erupted for 640,000 years, how do we know that it erupted 640,000 years ago?

submitted by /u/vampirechick1991
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Is there uncertainty in the spins of bound electrons in orbitals?

Posted: 20 Apr 2017 03:49 PM PDT

As per the Heisenberg uncertainty, we can't know the exact spin of a particle in all directions since different spin components are non-commuting. But in such a case, why do we say that electrons in orbitals occupy strictly either spin-up or spin-down states? I realize it is possible to fully know the spin in exactly one direction, but is it not possible that the electrons in an orbital might have spins that are not exactly parallel (nor antiparallel) with each other?

submitted by /u/CallMeDoc24
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How does color index relate to a star's "Habitable Zone"?

Posted: 20 Apr 2017 10:34 AM PDT

It seems intuitive that (for a given luminosity) the hotter a star, the further out its habitable zone would be. Is this an accurate correlation?

submitted by /u/IntestinalFracking
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Why are cardiac valves from pigs not rejected by human bodies?

Posted: 20 Apr 2017 06:37 AM PDT

The problem with the body rejecting organs/tissues is huge and mostly entails the usage of pharmaceuticals preventing the rejection. Why can be transplant cardiac valves from pigs without having a rejection (in most cases)?

submitted by /u/Basti8592
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Can everything become a liquid gas or solid?

Posted: 20 Apr 2017 09:23 AM PDT

Is heat transfer through metals non-linear?

Posted: 20 Apr 2017 01:40 PM PDT

When a metal heats up from a contact with a heat source. does the rate at which that heat moves through change as temperature increases?

submitted by /u/MegaJackUniverse
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If I steep a tea bag in hot water, will it eventually reach equilibrium and stop diffusing flavor and caffeine?

Posted: 20 Apr 2017 09:07 AM PDT

How long would that take?

submitted by /u/Kenley
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When measuring radiation, what is the difference between "mrem" and "cpm" and which is more important in determining exposure?

Posted: 20 Apr 2017 08:51 AM PDT

I've noticed that most modern geiger counters can be switched from rems to sieverts to counts per minute. When attempting to measure radiation exposure for workers, which of these measurements should be used? What is the difference?

submitted by /u/CommanderCougs
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Do plants with naturally red leaves have different chemical processes for photosynthesis than green plants, or is the color difference unrelated?

Posted: 20 Apr 2017 09:49 AM PDT

Is infinity a number or concept?

Posted: 20 Apr 2017 04:08 AM PDT

How does a low atmospheric pressure affect an air flow of a vacuum pump?

Posted: 20 Apr 2017 10:42 AM PDT

My science club is planning on releasing a high-altitude balloon with a vacuum pump on board to collect some samples. The pump we're planning to use is the Boxer 3KD model. The technical data says it has a maximum free flow of 18l/min. Of course the air pressure in stratosphere is really low so I was wondering how will it affect the flow of the air in the pump? Is there any way to calculate it?

submitted by /u/ScoiaTael16
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Is the Pacific Ocean calmer than the Atlantic, and why or why not?

Posted: 20 Apr 2017 07:50 AM PDT

I remember hearing as a kid that the Pacific Ocean was named such because it was more peaceful than the Atlantic. Is that true? Or is it just an odd story. Also, can one ocean be calmer than the other? I am thinking of "calmer" as being less storms, smaller waves, and other conditions that would make sailing easier on one compared to the other.

submitted by /u/wierddude88
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By what means do geneticists correlate biological data with geography?

Posted: 20 Apr 2017 10:33 AM PDT

How do geneticists connect DNA data with geographic points? How can geneticists see migration patterns and correlate them with locations on the globe?

submitted by /u/theleakyprophet
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Thursday, April 20, 2017

Would there be a benefit to putting solar panels above the atmosphere?

Would there be a benefit to putting solar panels above the atmosphere?


Would there be a benefit to putting solar panels above the atmosphere?

Posted: 19 Apr 2017 09:25 AM PDT

So to the best of my knowledge, here is my question. The energy output by the sun is decreased by traveling theough the atmosphere. Would there be any benefit to using planes or balloons to collect the energy from the sun in power cells using solar panels above the majority of the atmosphere where it could be a higher output? Or, would the energy used to get them up there outweigh the difference from placing them on the earth's surface?

submitted by /u/blizzetyblack
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How do organisms break down diatomic nitrogen?

Posted: 20 Apr 2017 05:28 AM PDT

I was watching an old SciShow episode and Hank Green said something to the effect that the N≡N triple bond is so strong, it can't usually be broken except by lightning or a comparably powerful force. Yet nitrogen is arguably one of the very most prevalent and important components of nutrition for most organisms on the planet (in my understanding?).

So how do organisms break that triple bond in order to render nitrogen reactive enough to bond with other elements?

submitted by /u/BJPenwhistle
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Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology

Posted: 19 Apr 2017 08:04 AM PDT

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology

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 is the difference between special relativity and general relativity?

Posted: 19 Apr 2017 08:06 AM PDT

Is there a rule that states that calculations of particle interactions at micro scales, by nature, cannot be scaled up into the macro-systems? Or are we just limited by our current understanding and nothing really prevents us from finding a way to scale quantum equations upwards?

Posted: 20 Apr 2017 06:32 AM PDT

[Chemistry] Can you drink Para-Water? Ortho-water? Can you breath pure Singlet Oxygen?

Posted: 20 Apr 2017 04:17 AM PDT

The spin states on the hydrogen of water can either be the same as one another or opposite to one another. Also, the spin states of Oxygen in O2 are the same way

My question is, how does this effect biochemistry? If I somehow obtained a supply of pure Para- or Ortho- Water, or filled a pure Oxygen breathing environment with Singlet Oxygen instead of Triplet Oxygen, could I safely drink said water and breath said Oxygen? What if I used air with Singlet Oxygen instead of pure Singlet Oxygen?

Also, how stable are these spin states? Would my water remain in that spin state long enough to interact with it? Would my Singlet O2 remain Singlet long enough to breath? Would it interact with my body in a way that causes injury or toxicity? Would it ignite on contact with flammable things like me?

What would happen if I tried to drink pure Ortho or pure Para water? What about breathing Pure Singlet Oxygen? Why?

submitted by /u/pds314
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When downhill snow sledding, would being heavier make you go faster (because of gravity's pull) or slower (because of friction)?

Posted: 19 Apr 2017 03:39 PM PDT

Light can be polarized, so can sound waves be polarized?

Posted: 19 Apr 2017 04:39 PM PDT

Were there any mp2 files, what about an mp5? Where does the 3 and 4 come from?

Posted: 19 Apr 2017 06:46 PM PDT

What happens to cosmic radiation and solar winds that interact with the earth's magnetosphere?

Posted: 19 Apr 2017 05:09 PM PDT

Do they bounce off? If so how do they bounce off? How do we know?

submitted by /u/Sandwich_Theorem
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Why can I hear a buzz in my earphones (which are plugged into my laptop) when I touch the Jack/plug of my speakers (which are turned off but plugged into the mains)?

Posted: 19 Apr 2017 04:20 PM PDT

I don't know if jack is the right word - the bit that I'd usually plug into my laptop..

submitted by /u/yslk
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Is the term "frequency" meaningless for a square wave because it consists of nearly infinite harmonics of some fundamental sinusoidal frequency?

Posted: 20 Apr 2017 04:09 AM PDT

Can we find the frequency of a square wave?

submitted by /u/shank9717
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Could redox reactions happen using positions?

Posted: 19 Apr 2017 08:26 PM PDT

I know gaining an electron would be reduction, and losing an electron would be oxidation.

However, could these redox reactions take place using positions instead? If so, would the rules swap, making oxidation be gaining a positron?

submitted by /u/ProjectCyan
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What is the gauge group associated with the graviton, if the graviton turns out to exist?

Posted: 19 Apr 2017 07:47 PM PDT

I understand that the gauge symmetry almost completely specifies the nature of the force it applies to, for example U(1) must behave like electromagnetism, up to the coupling constant. I have also read that, if there is a massless spin-2 boson, it must carry a force identical to gravity. So what Lie group leads to the force of gravity? Or am I wrong about something I've said here?

submitted by /u/EnshaednK
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Is Centrifugal Force a significant factor in the apparent gravity felt on Earth?

Posted: 19 Apr 2017 01:58 PM PDT

Does Centrifugal Force contribute at all to alleviate the felt force of Gravity on Earth? For example, if the Earth stopped spinning suddenly would it feel like everything just became heavier because there would no longer be the Centrifugal Force pulling us outwards? Would that answer be the same on a celestial body that is significantly larger or smaller than earth? Or on one that spins much faster?

submitted by /u/LateNightPhilosopher
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Long after humanity disappears from the planet, what will be the last remaining sign we were ever on Earth?

Posted: 19 Apr 2017 05:31 AM PDT

What makes spring springy?

Posted: 19 Apr 2017 07:14 PM PDT

Well what does make spring come back to their original form and why if you extend too much it'll lose some 'springiness'?

submitted by /u/darazeway
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Does negative mass from an engineered dispersion relation count as negative mass in the stress-energy tensor of general relativity?

Posted: 19 Apr 2017 02:59 PM PDT

Recently a group reported a negative effective mass in the paper Negative mass hydrodynamics in a spin-orbit–coupled Bose-Einstein condensate.

As I understand it, this negative mass comes from the equation, derived from the dispersion relation, m = 1/k_ex * 1/(∂²ω/∂k²).

They showed that this negative mass exhibits many unusual phenomena, including accelerating in the opposite direction of applied force and "the breaking of parity and of Galilean covariance."

My question is: does this negative mass appear or count as negative mass in the stress-energy tensor of general relativity?

(And of particular interest, as it relates to the creating an energy-density lower than the vacuum for a hypothetical Alcubierre drive?)

submitted by /u/science1482181229
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What is the difference between a surfactant, a wetting agent, and an emulsifier? Are they all the same thing?

Posted: 19 Apr 2017 06:39 PM PDT

I hear all three terms used, for example the hydroponic stores always talk about using a wetting agent but it seems similar to when the cannabis cookbook guys talk about using lecitithin as an emulsifier. And sometimes people call it a surfactant also.

submitted by /u/cant20
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Why are so many transiction metal compounds good heterogeneous catalysts?

Posted: 19 Apr 2017 04:07 PM PDT

How does a source of light, with finite surface area, send light in infinite directions?

Posted: 19 Apr 2017 05:03 PM PDT

The sun for example (albeit very large) will send light in all directions even though it's only got a limited about of surface (surface is probably the wrong word) to send light from. How?

submitted by /u/brad5995
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What is the difference between the specific entropy given in steam tables (s) and the specific entropy given in ideal gas tables (s_0)?

Posted: 19 Apr 2017 04:55 PM PDT

Why is there a nonzero vacuum permittivity?

Posted: 19 Apr 2017 04:24 PM PDT

To my understanding, the propagation of electric fields through a vacuum (and indeed through all matter) has a limiting factor, the constant of nature known as vacuum permittivity (=~8.85x10-12 Fm-1). My question is what is the physical reason for this constant/effect? Is it a result of light having a top speed?

submitted by /u/CameronBerry96
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