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Sunday, January 24, 2016

I just dropped a can of root beer... does tapping on the lid actually fix the liquid/gas equilibrium?

I just dropped a can of root beer... does tapping on the lid actually fix the liquid/gas equilibrium?

I just dropped a can of root beer... does tapping on the lid actually fix the liquid/gas equilibrium?

Posted: 24 Jan 2016 05:55 AM PST

<!-- SC_OFF --><div class="md"><p>It seems to have worked for me in the past, but I&#39;ve heard from some people that it&#39;s just an urban legend. </p> </div><!-- SC_ON --> submitted by

why don't the stars appear red near the horizon?

Posted: 24 Jan 2016 03:03 AM PST

<!-- SC_OFF --><div class="md"><p>Since the light being scattered in the atmosphere causes sun to appear yellow/red during sunset/sunrise, why we don&#39;t see this effect for other objects, for example the moon or the stars?</p> </div><!-- SC_ON --> submitted by

What's going on with technetium?

Posted: 23 Jan 2016 05:39 AM PST

<!-- SC_OFF --><div class="md"><p>Technetium, with 43 protons/electrons, is the first element in the periodic table with <em>no</em> stable isotopes. But it&#39;s surrounded by perfectly normal elements, the next smallest completely unstable element is promethium, which is a lanthanide, and radioactive elements don&#39;t start coming with any frequency until polonium, which has nearly twice as many protons/electrons as technetium. What gives?</p> </div><!-- SC_ON --> submitted by

Why does the sound of &quot;nails on a chalkboard&quot; trigger a viscerally negative reaction in many people?

Posted: 23 Jan 2016 09:06 AM PST

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If you've lost a limb like a hand or foot, what do your muscles do when your brain sends the signal to move that limb?

Posted: 23 Jan 2016 06:53 AM PST

<!-- SC_OFF --><div class="md"><p>Obviously there&#39;s no hand to move but is there still muscle contraction? Will the &quot;stump&quot; (for lack of a better word) move slightly? Will it hurt?</p> </div><!-- SC_ON --> submitted by

Did the Zika virus mutate in South America or are people of SE Asia descent naturally not affected by microcephaly due to this virus? or are there other confounding factors?

Posted: 23 Jan 2016 03:27 PM PST

<!-- SC_OFF --><div class="md"><p>seems like Zika virus has been around for a while. why is it now a problem in Brazil but not in the past in SE Asia?</p> </div><!-- SC_ON --> submitted by

What do we know about the nocturnal behavior of northern birds in winter?

Posted: 23 Jan 2016 07:43 PM PST

<!-- SC_OFF --><div class="md"><p>My son asked and I was at a loss - I&#39;ve never seen winter birds at night. Do they have specific resting spots they return to time and time again? Do they disperse or stick together? Do they huddle? What kind of spot do they look for?</p> <p>How much are their normal winter sleep behavior affected by bird feeders?</p> </div><!-- SC_ON --> submitted by

This question is way out there, I hope it's not against any rules: We live in 4 dimensions, 3 are spatial, one is temporal. Is it possible there are other dimensions that neither? That we can not experience?

Posted: 23 Jan 2016 04:44 PM PST

<!-- SC_OFF --><div class="md"><p>This question might be very flawed to start with. Is it possible that there could be more than space -time? I&#39;m just a curious guy.</p> </div><!-- SC_ON --> submitted by

How would we perceive dilated time if it was part of our environment?

Posted: 23 Jan 2016 05:32 PM PST

<!-- SC_OFF --><div class="md"><p>Hopefully I worded that title correctly for what I&#39;m asking...</p> <p>I was reading <a href="https://www.newscientist.com/article/2073577-black-hole-sun-could-support-bizarre-life-on-orbiting-planets/">this article</a> and was thinking about it. If we were able to inhabit a planet that was close enough to a black hole for time to be dilated, how would we perceive the time? </p> <p>Let&#39;s assume that, in undilated time, we were on an identical orbital period, and rotation speed as earth. Would we perceive the passage of time as normal, but believe days to be longer, or would we perceive events as being slowed? </p> <p>Hopefully I&#39;ve asked this correctly... I&#39;m not quite a physicist, so I don&#39;t quite understand the effects, but posting and reading here has helped me learn quite a bit. </p> <p>My hypothesis: we perceive passage of time as normal, but days appear to be longer</p> </div><!-- SC_ON --> submitted by

Everyone hates mosquitoes, but would there be any negative side effects if we got rid of them all?

Posted: 23 Jan 2016 01:43 PM PST

<!-- SC_OFF --><div class="md"><p>I&#39;m pretty sure most of us heard that scientists are looking into the extinction of mosquitoes by breeding the male mosquitoes to be sterile. I was just wondering would there be any negative effects of this happening or if it&#39;s all just one big positive?</p> </div><!-- SC_ON --> submitted by

Is a linearly polarized laser made up of equal parts spin up and spin down photons?

Posted: 23 Jan 2016 02:42 PM PST

<!-- SC_OFF --><div class="md"><p>Or is it composed of photons all in the same superposition of up and down? Can it be a mixture of both?</p> <p>Background: Spin in the classical picture of electromagnetism is a circulating flow of electromagnetic energy, measurable in circularly polarized light, but not in linearly polarized light. Spin in the quantum mechanical picture is a <a href="http://people.westminstercollege.edu/faculty/ccline/courses/phys425/AJP_54(6)_p500.pdf">circulating flow of energy in the wavefield of the photon</a>. An individual photon can be spin up, down, or a superposition of the two (linear polarization being a superposition in which the argument of the two complex coefficients in front of spin up and down are the same). </p> <p>Since photons are bosons, it is completely allowed for any number of them to be in the exact same state. The correspondence principle allows the interpretation of (classical) circularly polarized light as the macroscopic observation of a collection of photons all of which have the same spin (up or down).</p> <p>But it seems to me ambiguous as to how to get linearly polarized light. Either: (1) we can sum individual photons each with the same superposition, or (2) we can sum individual photons, half of which are spin up, and half of which are spin down, or (3) a mixture of (1) and (2).</p> <p>Are both (1) and (2) possible? If so, which is produced by, for instance, a diode laser? </p> <p>My intuition says both are possible, and that (1) is the natural output of a laser. However, <a href="https://en.wikipedia.org/wiki/Photon_polarization#The_nature_of_probability_in_quantum_mechanics">this discussion</a> appears to imply that (2) is not possible. Yet I can imagine combining a laser beam that is RCP (right hand circularly polarized) with one that is LCP (left). In this case, is there a substantive difference between the combined laser beam (which, statistically, is linearly polarized) and the laser beam that is &quot;naturally&quot; linearly polarized (composed of &quot;linearly polarized&quot; photons)?</p> </div><!-- SC_ON --> submitted by

Why does sweat have salts in it?

Posted: 23 Jan 2016 02:57 PM PST

<!-- SC_OFF --><div class="md"><p>Since salts are so valuable, it doesn&#39;t seem like a good idea to sweat them out. And since the point of sweating is the evaporation, is it necessary to have salts?</p> </div><!-- SC_ON --> submitted by

Do black holes have an effect on the expansion of the universe?

Posted: 23 Jan 2016 01:10 PM PST

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How come i can't drink everything that is in my cup?

Posted: 23 Jan 2016 02:27 PM PST

<!-- SC_OFF --><div class="md"><p>There&#39;s always a little drop of whatever i am drinking in my cup no matter how hard i try to drink all of it. </p> </div><!-- SC_ON --> submitted by

How can audio speakers play more than one sound at the same time?

Posted: 23 Jan 2016 07:10 AM PST

<!-- SC_OFF --><div class="md"><p>I don&#39;t really understand how a speaker can vibrate to produce 2 different (for example) songs at the same time</p> </div><!-- SC_ON --> submitted by

Can gravitation between atoms or subatomic particles be tested experimentally?

Posted: 23 Jan 2016 07:31 AM PST

<!-- SC_OFF --><div class="md"><p>A quantum theory of gravity remains one of the central problems in physics today. Relativity accurately describes the macro-scale workings of the planets and celestial bodies. Quantum physics explains the inner working of atoms and fundamental particles. But to explain gravity on the subatomic scale, no theories have yet to surmise how- or if- gravity takes part at this scale. </p> <p>Gravity is observed easily every day, and can become strong enough under the correct circumstances to break apart and fuse atoms themselves inside common stars. Neutron stars and hypothesized "quark stars", at their cores, could possibly contain "quark-gluon" plasma. Yet, gravity can be easily overcome with the other 3 fundamental forces in everyday life. But at the center of stars and black holes, gravity can and does overcome the other 3 forces. </p> <p>Mass attracts to mass through gravity, and we see this at macro scales. Protons and neutrons are known to have mass. Particle accelerators routinely smash these together at high energies to produce heavier than natural elements and observe new particles. The paths the particles take are easily seen and mapped. Which brings me to my actual question.</p> <p>What if two atoms were accelerated towards each other, but offset laterally? Would the atom's individual gravity be enough to affect the path of the oncoming atom?</p> <p>The equivalent at the macro scale would be two asteroids approaching each other in straight lines, but not on a collision course. Their masses would bend each other's trajectories around each other in an easily observable way. But is this behavior observable at an atomic scale? </p> <p>Many factors would have to be accounted for. The mass of the container would generate its own gravity, along with the Earth's natural field. Microgravity would be the ideal test condition for this exercise, as then natural gravity fields would not affect the atom's paths. Tracking the path of individual atoms would of course be difficult, but this technology exists already. </p> <p>To generate a larger result it would perhaps be ideal to use one "heavy" atom, like uranium, and one "light" atom, like hydrogen. That way the hydrogen path would be severely affected by the uranium's mass. Hypothetically. Now of course if this behavior was in fact observed, the process could be repeated at the subatomic scale. For instance, one proton and one neutron. The heavier proton would deflect the neutrons path, hypothetically. That would give us an idea as to where the "graviton" or other explanation might possibly reside. Knowing the internal structures of neutrons and protons, we would know what differences lead to the different masses, and how much of a gravity field those masses produce. Which would hopefully point towards which fundamental particle either emits or is the graviton. </p> </div><!-- SC_ON --> submitted by

Why doesn't fullerene c60 conduct electricity despite the fact that it has a similar structure to graphene (which is conductive)?

Posted: 23 Jan 2016 02:01 PM PST

<!-- SC_OFF --><div class="md"><p>fullerene c60: <a href="https://upload.wikimedia.org/wikipedia/commons/4/41/C60a.png">https://upload.wikimedia.org/wikipedia/commons/4/41/C60a.png</a></p> <p>graphene: <a href="http://www.nanocarbon.cz/Images/3d_test_3_persp1.png">http://www.nanocarbon.cz/Images/3d_test_3_persp1.png</a></p> </div><!-- SC_ON --> submitted by

Are there any prion diseases known that affect only prokaryotes or specific pathogens?

Posted: 23 Jan 2016 02:13 PM PST

<!-- SC_OFF --><div class="md"><ol> <li><p>It seems to me that if we could find (or create) a prion that affects only a section of prokaryotes or pathogenic eukaryotes, this could be a powerful antibiotic that is <em>resistant to</em> antibiotic resistance. </p></li> <li><p>If resistance did develop, this could help us to understand how to treat prion diseases. </p></li> <li><p>It seems it would still be <strong>possible</strong>, but very unlikely, that prions could exist that affect only a specific virus or set of viruses as well.</p></li> <li><p>If we look at all of the known prions, from a biochemical level, do we see similarities that could lead these particular proteins to become pathogenic? </p></li> <li><p>Do we understand the mechanism of prion diseases well enough to say <strong>how</strong> a prion converts a properly folded protein into another copy of the misfolded prion? </p></li> <li><p>Lastly, do we know anything about the conditions which may promote the misfolding of a protein into a prion? This may help us to create prokaryote or pathogen-specific prions.</p></li> </ol> </div><!-- SC_ON --> submitted by

Is it a rule for gas giants to be made mostly out of hydrogen and helium?

Posted: 23 Jan 2016 03:01 AM PST

<!-- SC_OFF --><div class="md"><p>I was wondering, is it possible to form gas giant type planet with atmosphere, made of some other gas or combination of gasses? Or maybe we already have discovered some interesting exoplanet examples? </p> </div><!-- SC_ON --> submitted by

What is spin?

Posted: 23 Jan 2016 05:24 AM PST

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Why do we feel different types of pain, instead of just one generic &quot;pain&quot;?

Posted: 22 Jan 2016 11:21 PM PST

<!-- SC_OFF --><div class="md"><p>I assume the different sensory nerve are also contributing to the pain, and I can certainly see an evolutionary benefit, I&#39;m just wondering what all contributes. Also, are there different types of p-factor?</p> </div><!-- SC_ON --> submitted by
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Saturday, January 23, 2016

Jupiter is sometimes referred to as a failed star, too small to achieve nuclear fusion. If a Neptune sized planet crashed into Jupiter would it be big enough to be a star then and give us a small second star in our solar system?

Jupiter is sometimes referred to as a failed star, too small to achieve nuclear fusion. If a Neptune sized planet crashed into Jupiter would it be big enough to be a star then and give us a small second star in our solar system?

Jupiter is sometimes referred to as a failed star, too small to achieve nuclear fusion. If a Neptune sized planet crashed into Jupiter would it be big enough to be a star then and give us a small second star in our solar system?

Posted: 22 Jan 2016 08:03 PM PST

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If a photon is a &quot;particle&quot; that is all energy and without mass, is there an equivalent &quot;particle&quot; that is all mass and without energy?

Posted: 22 Jan 2016 10:28 PM PST

<!-- SC_OFF --><div class="md"><p>Moreover, is there anything about our &quot;observable universe&quot; in that our ability to &quot;observe&quot; is inherently dependent on energy, such that if a &quot;particle&quot; is all mass and <em>without</em> energy we are unable to &quot;observe&quot; it?</p> </div><!-- SC_ON --> submitted by

Spectrometry question: inverted peaks and detection in salt water?

Posted: 23 Jan 2016 04:46 AM PST

<!-- SC_OFF --><div class="md"><p>Hello askscience, I&#39;ve been having a couple problems running my substances in the spectrophotometer. I&#39;m reading <strong>dihydrostreptomycin sequisulfate</strong>, that will be used in a toxicity study. It forms nice peaks in the ultra pure water around 190-210nm, even though high concentrations don&#39;t seem to have a good correlation to concentration (I imagine it as a inverted bell), but as I&#39;ll be using low concentrations it is not a problem. When I read in the F/2 medium (made of saltwater, metals and EDTA) there&#39;s an inverted peak around 200 and several small peaks around 190nm that look like noise. I tried to change the pH and add more EDTA to chelate the metals but there&#39;s no answer. I found some articles about making a reaction to read it around 400nm, but I don&#39;t have the reagents in the lab and it would be very difficult to make it during the toxicity test. Any idea what I could do to get readable peaks?</p> </div><!-- SC_ON --> submitted by

When you hold your arms up around your head in space, do they get tired?

Posted: 22 Jan 2016 02:56 PM PST

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Will virtual particles still come into existence even after a supposed heat death of the Universe?

Posted: 22 Jan 2016 04:50 PM PST

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What happens to materials as they lose their elasticity?

Posted: 22 Jan 2016 01:12 PM PST

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Why is it that certain elements are common in asteroids, e.g. iridium, but rare on Earth?

Posted: 22 Jan 2016 08:14 AM PST

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Do wild animals get depressed or suffer from stress-related disorders in nature?

Posted: 22 Jan 2016 01:37 PM PST

<!-- SC_OFF --><div class="md"><p>If so, is their behaviour similar to human behaviour under such conditions?</p> </div><!-- SC_ON --> submitted by

What (do we think) causes Madden-Julian Oscillation?

Posted: 22 Jan 2016 10:24 AM PST

<!-- SC_OFF --><div class="md"><p>I recently learned about MJO. I can&#39;t find any information that doesn&#39;t seem to be written for PhD&#39;s on this subject. Anybody care to explain our current understanding of MJO?</p> </div><!-- SC_ON --> submitted by

A friend stated &quot;Tilt: Two charges of one Coulomb each separated by a meter would repel each other with a force of about a million tons.&quot; Is this statement true?

Posted: 22 Jan 2016 12:15 PM PST

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What would ve happen if Russia, North America, China, Europe, Japan, Koreas were nuked? How would this affect Southern Hemisphere regions like Africa, Latin America, Australia etc.

Posted: 22 Jan 2016 09:32 PM PST

<!-- SC_OFF --><div class="md"><p>Would it be possible to still live in Southern Hemisphere?</p> </div><!-- SC_ON --> submitted by

How are snow accumulations predicted?

Posted: 22 Jan 2016 10:05 AM PST

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When pumping oil, are we leaving vast underground caverns where the oil used to be?

Posted: 22 Jan 2016 09:12 AM PST

<!-- SC_OFF --><div class="md"><p>Will this have any longstanding impacts?</p> </div><!-- SC_ON --> submitted by

Does human blood really travel 12,000 miles every day?

Posted: 22 Jan 2016 01:56 PM PST

<!-- SC_OFF --><div class="md"><p>Someone posted that on Facebook and I thought it was total bullshit. So I <a href="https://www.google.com/webhp?sourceid=chrome-instant&amp;ion=1&amp;espv=2&amp;ie=UTF-8#q=how%20far%20does%20blood%20travel%20in%20a%20day">Googled it</a> and it seems it&#39;s not bullshit? I guess my real question then would be: isn&#39;t there something more to this? That&#39;s 500 miles per hour. I can&#39;t understand how that wouldn&#39;t rip your body apart.</p> </div><!-- SC_ON --> submitted by

Does the snow in a blizzard act as a brake on the wind speed? In other words, would the wind speed be higher if it didn't have to move the mass of the snow around?

Posted: 22 Jan 2016 06:41 AM PST

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Planet orbits, can a solar system ever have 2 planets with opposing orbits?

Posted: 22 Jan 2016 10:40 AM PST

<!-- SC_OFF --><div class="md"><p>I know that planets themselves can spin in different ways (uranus spins perpendicular to all other planet rotation) but can a solarsystem that is being formed have one planet orbiting clockwise, and another planet further away orbiting counter clockwise?</p> <p>can we have a solarsystem that has all the planet orbiting in a counterclockwise orbit or is there something within the atoms and bonds that forces everything to go in 1 uniform rotation?</p> <p>sorry if i used the wrong terminology when describing my question.</p> </div><!-- SC_ON --> submitted by
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Friday, January 22, 2016

How long it will take Voyager to get to Ninth Planet?

How long it will take Voyager to get to Ninth Planet?

How long it will take Voyager to get to Ninth Planet?

Posted: 22 Jan 2016 05:35 AM PST

Eventually is there any possibility to shoot probe like Voyager in future?

submitted by vvolny
[link] [64 comments]

How is this paradox involving basic relativity principles explained?

Posted: 22 Jan 2016 06:05 AM PST

Relativity is a confusing and counter-intuitive concept to the layman, and many people only ever know that there is something called "time dilatation" and "length contration" happening, without fully comprehending (myself included). With this limited knowledge it's possible to construct paradoxes, one of which is the following:

You sit on top of a tunnel with a length of 100m. A train of 200m (when at rest) approaches this tunnel at near light speed, experiencing a length contraction of 50%, i.e. 100m. From your perspective, the train fits into the tunnel, and as soon as it enters it completely, you close the tunnel with impenetrable doors on either side with a press of a button. However, from the perspective of the train it's the tunnel that was shortened by 50% and it should have been impossible for the train (200m) to enter the now 50m long tunnel. Explain this paradox.

Hope someone can explain it in a layman-friendly way (if in any way possible) :D

And please, for the love of god, do not comment on how it's impossible for a train to be this fast, to close doors immediately, for a door to be completely impenetrable, etc. It's a gedankenexperiment and not the point of this post.

submitted by KindaOffKey
[link] [18 comments]

Can we be sure the laws of physics hold everywhere in the universe?

Posted: 22 Jan 2016 03:50 AM PST

Why is the area around where a laser has been pointed, really blurry?

Posted: 21 Jan 2016 06:36 AM PST

I've been doing an experiment (Young's double slit experiment) and it deals with lasers. Whenever I point the laser at something, I have noticed this kind of small, red dots surrounding the point, making the region real blurred. Why does this happen?  

EDIT :- Holy crap, this post blew up! Thanks for all your answers guys, really appreciate it.

submitted by Ashen_Cyborg
[link] [107 comments]

What are symmetries?

Posted: 22 Jan 2016 05:56 AM PST

How do phospholipid bilayers interact with lipid micelles like soap?

Posted: 21 Jan 2016 06:53 PM PST

Hello all. I've been doing some research on mechanisms of transfection, one of which is lipofection. I was wondering what soap miscelles would do to the phospholipid bilayer (cell membrane) of a cell, and, if possible, why?

submitted by THE_CRUSTIEST
[link] [4 comments]

I've come up with a way to "prove" (Please note the quotation marks) that 1/0 = Aleph Null. Can anyone explain where the error(s) is?

Posted: 22 Jan 2016 01:57 AM PST

First of all, the sum of a convergent infinite series is a/(1-x) with a being the first term in the series and x being the multiplier that terms successively multiply by, e.g. a + ax1 + ax2 + ...

So, if we do 1+1+1+1+..., a is 1 and so is x, therefore we get 1/1-1, which is 1/0, therefore 1+1+1+1+... = 1/0

Since 1/0 is obviously undefined, this has to be wrong, but I don't see the problem. Can anyone please point out the error for me?

Thanks if you do.

submitted by MinimalFractal729
[link] [6 comments]

It is known that charge is always associated with mass & mass can converted into energy as E=mc2 then why do we say that charge is conserved ?

Posted: 22 Jan 2016 04:15 AM PST

Planet IX Megathread

Posted: 20 Jan 2016 03:22 PM PST

We're getting lots of questions on the latest report of evidence for a ninth planet by K. Batygin and M. Brown released today in Astronomical Journal. If you've got questions, ask away!

submitted by AskScienceModerator
[link] [2417 comments]

What is the Heisenberg Uncertainty Principle?

Posted: 21 Jan 2016 11:03 AM PST

I am an aspiring physicist but currently have little to no professional education in the subject (high school freshman). I have been trying to learn whatever I can outside of school, and I feel I know a bit about quantum mechanics from lectures by Lawrence Krauss, videos online, etc. Can someone explain what the Heisenberg Uncertainty Principle is? What does it govern on the quantum scale?

submitted by CSkinzz
[link] [35 comments]

Is there a 5th dimension? If so what is it?

Posted: 21 Jan 2016 05:49 PM PST

Just as glass allows visible light (390 to 700 nm) to pass through it, do any other materials allow only a specific range of the electromagnetic spectrum to pass through it?

Posted: 22 Jan 2016 06:21 AM PST

I have always wondered why don't we send anything to gas giants in our solar system?

Posted: 21 Jan 2016 08:02 AM PST

Are the conditions too extreme for another "curiosity" to land and explore, or do we just not know can you even land there. How about something that hits the orbit and stays there observing the planet like a satellites that observe the earth? I know the answer must be simple, but I've never heard anyone explaining this.

submitted by Pautnesis
[link] [110 comments]

Have the locations and movements of black holes ever been tracked or mapped?

Posted: 21 Jan 2016 06:54 AM PST

I am curious if known locations and movements of black holes have ever been mapped or graphed to see if there are any interesting finds about their whereabouts.

submitted by monkeymoomoo10
[link] [16 comments]

Why is NaCl used for icy roads when its enthalpy of solution is about +3.9 kJ mol-1?

Posted: 22 Jan 2016 01:32 AM PST

Would this not make NaCl lower the temperature of its surroundings? What is really happening here?

submitted by lumpyturnips
[link] [1 comment]

If I have a coin and want to prove there is a 50/50 chance for it to land either heads or tails, how many times do I need to flip it?

Posted: 22 Jan 2016 06:53 AM PST

And if I can't prove it, how certain could I be?

submitted by Maoatu
[link] [1 comment]

Inputting "1.6*10^13 m/s" into WolframAlpha shows that the "upper limit on the speed of quantum information" is 54000 c. What is this about?

Posted: 22 Jan 2016 05:51 AM PST

Are there any primes or classes of primes, for example large Mersenne primes, which are not normal numbers?

Posted: 21 Jan 2016 06:21 PM PST

Why do deep sea fish have such odd features such as transparency and bioluminescence?

Posted: 21 Jan 2016 06:34 AM PST

Why did evolution decide that these fish should have eyes that look up directly out of their transparent heads, for example?

submitted by Rednaxila
[link] [9 comments]

Does special relativity preclude multiple time dimensions?

Posted: 21 Jan 2016 05:07 PM PST

Could objects have multiple futures and multiple pasts? I was just wondering if anything in special relativity actually precludes this from being the case. I realize that even if not, it is still an unfalsifiable position for now.

submitted by butWhoWasBee
[link] [9 comments]

Why does cream/milk make coffee lighter, but sugar doesnt?

Posted: 22 Jan 2016 03:43 AM PST

Why does the sound from rocket launches tend to change suddenly at a certain altitude?

Posted: 21 Jan 2016 06:43 AM PST

After watching numerous videos of rocket launches, from huge launches like the Space Shuttle or Saturn V, to big rockets like the Delta IV or Titan IV, to smaller rockets like the Atlas V, I've noticed something about the sound of the launch that is the same in almost every single video. At first the sound begins as a deep roar. As the rocket rises, the sound begins to "destabilize", and at a certain altitude the sound very suddenly becomes significantly more thunderous and crackly. I am aware of where the crackling noise itself comes from, but I've never quite understood exactly why the sound evolves the way it does. Does it have something to do with how the jet is aimed at the microphone? Or does it involve the sound having less interaction with the ground as the rocket rises? Or perhaps the decrease in atmospheric density with altitude changes the sound of the jet? All of these? None of them? I'm really quite curious about this, because it seems so universal. Here are some examples of what I am talking about:

Apollo 11 Tracking Camera The sound starts off as a deep roar and begins crackling very suddenly at 36 seconds in.

STS-92 Launch The sound from the solid rocket boosters arrives at 9:20, and becomes significantly more ferocious at 9:31.

Last Titan IV Launch The sound from the boosters arrives at around 20 seconds and becomes much more prominent at 40 seconds. The people present comment on it.

Orion EFT-1 Delta IV Heavy The sound begins with a rather ominous "Vwoomp", then continues rumbling heavily before very suddenly transitioning to a crackling noise at around 1:00.

These are only a few examples, but like I said, I've seen the same thing in practically every launch video I've ever watched.

submitted by LunarDelta
[link] [10 comments]

About the 7 base SI units: "7 is the number of physical quantities that are independent from one another. It comes from the fact that the number of quantities in physics is higher by 7 to the number of determination equations (definition equations and natural laws)." -- Can someone explain this?

Posted: 21 Jan 2016 08:42 AM PST

Side question: How is the Candela Cd not kg m2 s-3, since it is a measure of luminous power (W) per solid angle (dimensionless)?

Edit: Thank for the insightful inputs. I took that course for granted, but after going through the lectures again, and having passed the exam, I am now fully convinced that these guys have absolutely no idea what they are talking about. I did learn a lot from you guys so thanks again.

submitted by RegencyAndCo
[link] [12 comments]

Is it possible to have a satellite orbit earth but keep its camera focused on Mars, without using active controls?

Posted: 21 Jan 2016 10:48 PM PST

I.e. a specific angular velocity, attitude, and orbit that would allow this. Is there only one unique solution?

submitted by Arthur___Dent
[link] [7 comments]

If you had one molecule of water, how would you determine its state?

Posted: 21 Jan 2016 04:51 AM PST

I guess if you had it in a vacuum, it'd have to be a gas, right? Because of the pressure. But let's say it's at an unknown temperature and pressure and there is no other matter around for it to interact with (like air). Is it a solid, liquid, or gas, and how do you tell?

submitted by fir1st
[link] [16 comments]
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