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<p>I found this related question: <a href="http://physics.stackexchange.com/questions/51511/what-happens-to-5-electrons-on-a-sphere">What happens to 5 electrons on a sphere?</a></p>
<p>But this question describes the case when there can only be 5 electrons on that sphere at all times. The answer linked to the <a href=... | g10654 | [
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<p>In operator formalism, for example a 2-point time-ordered Green's function is defined as</p>
<p>$\langle\mathcal{T}\phi(x_1)\phi(x_2)\rangle_{op}=\theta(x_1-x_2)\phi(x_1)\phi(x_2)+\theta(x_2-x_1)\phi(x_2)\phi(x_1),$</p>
<p>where the subscript "op" refers to operator formalism. Now if one is to take a time derivati... | g10655 | [
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<p>My interest is purely in $\text{SO}(n)$ tensors and how one works out their irrep decomposition. For instance, for rank 2 tensors we simply split into an antisymmetric part, a traceless symmetric part and the trace. Is there a more general, recursive procedure for higher rank tensors? Even if not, what is the usual ... | g10656 | [
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<p>Would different observers agree on the age? Or is this question nonsensical? e.g. what's north of the north pole?</p>
<p>There are ways of estimating the ages of stellar bodies using various methods but is there a method for black holes? </p>
<p>My main stumbling block is the slowing down and 'stoppage' of time o... | g10657 | [
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<p>Sorry if this is a dumb question, but I'm only starting to get to grips with this quantum malarkey. Anyway...</p>
<p>Suppose I have two friends, Alice and Bob, both of whom have a random number generator. Alice's number generator will produce a number between 1 and 4, giving a probability density of:</p>
<p>A=[0.2... | g10658 | [
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<p>This is pressure in Newtonian mechanics: </p>
<p>$$P=\frac {dF}{dA}.$$
What does this mean?
(Doesn't it mean that force is a function of area?)
What type of function is force?</p> | g10659 | [
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<p>Two separate suitably short but intense <a href="http://en.wikipedia.org/wiki/Charged_particle_beam#bunch_structure" rel="nofollow">bunches</a> of <a href="http://en.wikipedia.org/wiki/Muon" rel="nofollow">muons</a>, "A" and "B", are both supposed to be constantly accelerating (in an otherwise sufficiently flat regi... | g10660 | [
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<p>What's the physical interpretation of constants in <a href="http://en.wikipedia.org/wiki/wave%27s_equation" rel="nofollow">wave equation</a> and <a href="http://en.wikipedia.org/wiki/Diffusion_equation" rel="nofollow">diffusion equation</a>?</p>
<p>$$u_{tt}=c^2u_{xx},$$</p>
<p>$$u_{t}=ku_{xx}.$$</p>
<p>Please int... | g10661 | [
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<p>My textbook gives the following explanation on how excess charges are spread over conductors:</p>
<blockquote>
<p>The excess charge on an isolated conductor moves entirely to the
conductor's surface. However, unless the conductor is spherical, the
charge does not distribute itself uniformly.</p>
</blockquote>... | g10662 | [
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<p>The following was originally given to me as a homework question at
my physics 2 course:</p>
<blockquote>
<p>Consider the following circuit</p>
<p><img src="http://i.stack.imgur.com/KntDu.jpg" alt="enter image description here"></p>
<p>The difference of potentials between the point $V_{1}$and the point
... | g10663 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/31254/can-the-lightning-be-captured-and-used-as-power-source">Can the lightning be captured and used as power source?</a> </p>
</blockquote>
<p>Each lightning contains several kilo volts of electricity.<... | g338 | [
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<p><a href="http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence" rel="nofollow">$E=mc^2$</a> is the famous mass-energy equation of Albert Einstein. I know that it tells that mass can be converted to energy and vice versa. I know that $E$ is energy, $m$ is mass of a matter and $c$ is speed of light in vacuum. <... | g1029 | [
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<p>Here we have two magnets and they are sticking to each other. What I've learned that could possibly explain it is one magnet holds positive charge and the other one holds negative. But when the eletrons travel from the negative one to the positive one in order to be equilirium (just like static electricity won't sta... | g10664 | [
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<p>I have this relative simple-looking question that I haven't been able to solve for hours now, it's one of those questions that just drive you nuts if you don't know how to do it.
This is the scenario:</p>
<p>I have a <a href="http://2.bp.blogspot.com/_P4EHIyposmM/TImv2-brnOI/AAAAAAAAAMw/nK-NO8JUSEU/s1600/1781_PotAp... | g10665 | [
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<p>all. I have tried Googling but have had no luck. My question is simple (although, I presume the answer is not): If one knows the chemical structure of, well, a chemical, could its optical properties (such as transparency) be mathematically derived from this information alone? Perhaps I'm naive for thinking so, but I... | g10666 | [
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<p>Is the fact that weak eigenstates are not mass eigenstates completely arbitrary? Or is there a deeper reason for the existence of the PMNS and CKM matrices?</p> | g10667 | [
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<p>I remember in the high school physics, my teacher told us that the design of the plane wing is because we want the air above the wing flowing faster than the air flowing below so the pressure above and below will be different so the net force is pointing upright. I am thinking if it is possible to explain this by be... | g17 | [
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<p>I have an idea of supersymmetry in quantum mechanics, can you suggest a book on "supersymmetry in quantum field theory", which has sufficient mathematical rigour like "Peskin and Schroeder" </p> | g467 | [
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<p>I've been working my way through L. Baulieu's excellent paper [<em>Perturbative gauge theories</em>,
Physics Reports, Volume 129, Issue 1, December 1985, Pages 1-74]. Towards the end, he goes on to prove that renormalized Yang-Mills theories that are BRST invariant exhibit gauge independence and unitary. At the end... | g10668 | [
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<p>Ok so if we setup a camera before the slit we will find a single photon and will follow through accordingly, likewise by having a camera setup after the slit, we can retroactivly collapse the wave function by observation. Here is my question. If we setup the camera to record like above but NEVER EVER EVER look at th... | g10669 | [
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<p>Just out of curiosity. In the game Mass Effect, devices called mass relays contain two rotating rings, one inside of the other. See <a href="http://www.youtube.com/watch?v=qPxw5QjxhIs" rel="nofollow">http://www.youtube.com/watch?v=qPxw5QjxhIs</a> for an example, best seen around 00:10. </p>
<p>I was wondering: is t... | g10670 | [
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<p>Is there a minimal string length (maybe the <a href="http://en.wikipedia.org/wiki/Planck_lengthhttp://en.wikipedia.org/wiki/Planck_length" rel="nofollow">Planck length</a>), and is it quantized?</p>
<p>Do strings have a 0-dimensional (ie point) cross-section? </p> | g10671 | [
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<p>Just what the title states - </p>
<p>Does reversal of magnetic poles in a planet refer to the point in time when reversal is complete? </p>
<p>OR </p>
<p>Does it refer to the entire drawn out process (assuming the poles flip gradually from 0 through 180 degrees?</p> | g10672 | [
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<p>Continuing from my previous question <a href="http://physics.stackexchange.com/q/30355/5265">Is reversal of magnetic polarity in a planet an instantaneous occurence?</a></p>
<p>A change in magnetic flux is expected to generate an EMF. </p>
<p>In the case where the magnetic poles of a planet flip - What would be th... | g10673 | [
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<p>Angular momentum of an object is a physical quantity that depends on the chosen point about which to calculate the angular momentum.</p>
<p>It is often said that an object that has been thrown up in the air and is rotating, is physically rotating about the center of mass. I don't think that is what is physically ha... | g668 | [
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<p>Using a bit of classical reasoning I'm imagining black hole formation to be much like an ice skater pulling in her arms:</p>
<p><img src="http://i.stack.imgur.com/9fiOU.png" alt="skater pulls in her arms to increase angular velocity"></p>
<p>Now, the size difference between a star and its black hole can't even be ... | g10674 | [
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<p>What does exactly means "Small molecules may appear as solid, liquid, and gaseous phases without losing their molecular integrity"?, </p>
<p>I can't image how just a molecule can be a gas, liquid or solid. Or in fact the previous phrase refers to the state of aggregations of those small molecules?</p>
<p>My source... | g10675 | [
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<p>What are the differences in the types of problems Ricci/Tensor Calculus and Matrix Calculus can solve? One formulation is generally used by the physics community and the other by statisticians and engineers, but what about each of them makes them desirable for each of their fields despite what at least superficially... | g10676 | [
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<p>I'm making a table where columns are labelled with the property and the units it's measured in:</p>
<p>Length (m) |||| Force (N) |||| Safety Factor <strong>(unitless)</strong> ||| etc...</p>
<p>I'd like not to write "unitless" on several columns...and I'm quite surprised I can't seem to find a symbol for it. An... | g10677 | [
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<p>Consider a solid spherical object of uniform density that is rotating on an axis A1. Perpendicular to that axis one can draw another line that passes through the sphere. On this axis, on both sides of the sphere one attaches mass-less springs with spring constants F, and then attaches point masses of mass M to both ... | g10678 | [
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<p>A continuous charge distribution flowing as a constant current in a closed loop doesn't radiate. Is it therefore true that as you increase the number of proton bunches in the LHC, while keeping the total charge constant, the synchrotron radiation decreases?</p> | g10679 | [
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-0.04370297119021416,
0.04419410601258278,
-0.03946366161108017,
0.005688529461622238,
-0.037906911224126816,
0.06312616169452667,
-0.023818079382181168,
0.037... |
<p>What is the correct way to use the resistance and temperature correlation formula from <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html" rel="nofollow">http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.html</a>?</p>
<p>In particular, does R have to be the higher resistance and R0 th... | g10680 | [
0.04871111363172531,
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0.043235186487436295,
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0.0... |
<p>At time there are talks about <a href="http://en.wikipedia.org/wiki/Quantum_computers" rel="nofollow">quantum computers</a> and lot of talks and discussion on its exponential speed. But studying in some more details it makes reference to "Heisenberg uncertainty principle", which simply says that either position or m... | g10681 | [
0.013811876997351646,
0.08972451835870743,
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<p>I feel like the answer should be "no" since all superfluids are not strictly BEC since they can undergo a Kosterlitz–Thouless transition in 2D, for example. I believe the ideal gas isn't superfluid, but is there any experimental evidence of a BEC without superfluid properties? I've been searching with no luck.</p> | g10682 | [
0.0027528335340321064,
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<p>I came across this question in an introductory physics course awhile back and I never got over it: "A hydrogen atom has an electron in the n=5 orbit, what is the maximum number of photons that might be emitted so that it decays to the ground state (n=1)?" The answer the professor was looking for was 4 since he was p... | g10683 | [
-0.028058459982275963,
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<p>The origin of linear birefringence in crystal can be easily explained by the symmetry of the crystal. However, it seems it is hard to be applied in circular birefringence (i.e. optical activity), since there is no macroscopic symmetry in sugar solutions. </p>
<p>So I wonder how we explain the levorotatory and the d... | g10684 | [
0.007480415049940348,
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<p>If we thermally isolate a region in space, say using a hypothetical material of $0$ conductivity, and measure the region's temperature, will it be 2.7K?</p> | g10685 | [
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<p>So when people say: 'I am approaching the speed of light, and to get to 100% light I would need infinite energy' they are essentially saying that this situation is impossible?</p>
<p>I read this in Hawking's book and confused me because I assume when he says 99.9% speed of light, he means 99.9% speed of light in re... | g10686 | [
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<p>In class when we talked about the harmonic oscillator in QM we noticed that the eigenfunctions to the annihilation operator are coherent states in the sense that they have minimum uncertainty in momentum and position. My question is: What is the physical meaning behind this? Why are coherent states eigenfunctions to... | g339 | [
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<p>For example, take a water bottle. Fill it with water and then turn it upside down.
Instead of flowing steadily downward, it gulps down in parts. Why?</p> | g10687 | [
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<p>Does vacuum or outer space contain any gases? Recently i watched a video on youtube,in which NASA installs a camera on a spacecraft.The footage shows some dust particles or some matter floating over the space craft's surface and as well from the thrust.What exactly is that? If there is nothing in vacuum,how come new... | g10688 | [
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0.0008883688... |
<p>Related post <a href="http://physics.stackexchange.com/questions/55687/causality-and-quantum-field-theory">Causality and Quantum Field Theory</a></p>
<p>In Peskin and Schroeder's QFT p28, the authors tried to show causality is preserved in scalar field theory.</p>
<p>Consider commutator
$$ [ \phi(x), \phi(y) ] = D... | g10689 | [
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0.014029107987880707,
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0.03493151068687439,
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-0.... |
<p>Is it possible to have a VEV (vacuum expectation value) for tensor field? I am mainly concerned about second rank tensors. It seems it can have a VEV which will be proportional to the metric tensor (in flat space-time). Does this make any sense at all? If it does, then what are it's implications?</p> | g10690 | [
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<p>In the coordinate representation, in 1D, the wave function depends on space and time, $\Psi(x,t)$, accordingly the time dependent Schrodinger equation is </p>
<p>$$H\Psi(x,t) = i\hbar\frac{\partial}{\partial t}\Psi(x,t)$$</p>
<p>In a representation-free notations we deal instead with the ket $|\Psi\rangle = |\Psi(... | g10691 | [
0.013377324678003788,
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0.009988273493945599,
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0.036479... |
<p>Can the wave function solution to Schrodinger's Equation be interpreted as an oscillation between all possible measurements (obviously with some type of weighting that would describe the shape of the wave) in the limit that the frequency of the oscillation goes to infinity?</p>
<p>I don't see how any experiment cou... | g10692 | [
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<p>Well I had this thought experiment in which a particle observes itself, and something like the following is observed.</p>
<p>Taking in mind the uncertainty principle all particles even stopped at 0K jiggle about, but nothing stops us from going into there frame and observing from there. We do just that, we go in th... | g10693 | [
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<p>I have two questions.</p>
<p><strong>First</strong>, I understand that in a nuclear reaction
$$Q:=K_{after}-K_{before}\equiv E_{0,before}-E_{0,after} \qquad (1)$$
where $K$ is the total kinetic energy, and $E_0$ is the total rest energy.
My question is, in the reaction $^{9}Be\left(\gamma,n\right)^{8}Be$, where sho... | g10694 | [
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0.020926915109157562,
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<p>Why is light produced when an underwater bubble is collapsed with a sound wave?</p>
<p>I have come across this fact on a page (<a href="http://www.scientificamerican.com/article.cfm?id=tiny-bubbles-explain-puzz">similar to this</a>) but can't understand "Why". I'm just curious about this interesting fact. And, I wa... | g340 | [
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<p>I recently found out about sending stuff into space and using the unique zero gravity and cosmic radiation riddled environment to investigate stuff like crystal growth. Since thin film science is a hot topic still, I am wondering what can be done in space?</p>
<p>Things that come to mind, which likely have been cov... | g10695 | [
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<p>From my high school physics class I remember that there are some particles which exhibit pure alpha decay (i.e. alpha decay to there stable isotope), like Po-210, Po-211 and Bi-209.</p>
<p>What I also know is that alpha particles, due to their low speed, will be absorbed already within a few cell layers of skin ($\... | g10696 | [
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<p><a href="http://food.thefuntimesguide.com/2010/07/bamboo_cutting_board.php" rel="nofollow">http://food.thefuntimesguide.com/2010/07/bamboo_cutting_board.php</a></p>
<blockquote>
<p>Some bamboo cutting boards are glued together with adhesives that have formaldehyde in them — <strong><em>which could eventually leak... | g10697 | [
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<p>I was going through a problem in which they had given mass and speed and asked its wavelength. Now its de Broglie wavelength $h/\lambda$ and I had to find out which of them had wave nature which could be observed. I thought objects whose wavelength is greater than wavelength of light would have observable wave natur... | g10698 | [
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0.08612... |
<p>Bohr said that only certain orbits of definite energy are allowed inside the atom. He said that the electrons in their ground state do not emit radiation and that they will emit radiation when they fall from higher energy levels to lower energy levels. My question is what does orbits with definite energy mean? and w... | g341 | [
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... |
<p>Like all stars, large ones are stable as long as there is a sufficient amount of hydrogen (or helium) to fuse. This fusion process is what prevents them from collapsing in on themselves. However, once the main elements have been fused up to iron, the star becomes unstable. Eventually, it may supernova and leave a... | g10699 | [
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0.... |
<p>Suppose a particle has energy $E>V(+/-\infty)=0$, then the solutions to the Schrodinger equation outside of the potential will be $\psi(x)=Ae^{i k x}+Be^{-i k x}$.
How can one show or explain that $|B|/|A|$ gives the probability that a particle scattering off the potential is reflected?</p> | g10700 | [
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0.02587491273880005,
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<p>How can one prove that the number of images formed by two plane mirrors at right angles to each other is 3?</p>
<p>Is there a mathematical proof for the same ? </p> | g10701 | [
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0.017999744042754173,
0.0... |
<p>Where would you say I can start learning about Hamiltonians, Lagrangians ... Jacobians? and the like?</p>
<p>I was trying to read Ibach and Luth - Solid State Physics, and <a href="http://imgur.com/a/5fc56" rel="nofollow" title="Picture from "Solid State Physics" by Ibach and Luth 1991. Published by Sprin... | g10702 | [
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0.05647817999124527,
0.0918586254119873,
0.030109... |
<p>I was wondering if the good old quadratic potential was the only potential with equally spaced eigenvalues. Obviously you can construct others, such as a potential that is infinite in some places and quadratic in others, but that's only trivially different. I am not referring to equally spaced as a limiting behavior... | g10703 | [
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... |
<p>So again I have two equations:</p>
<p>$$K= \frac{1}{2} m v^2 + \frac{1}{2} I \omega^2$$</p>
<p>And</p>
<p>$$K_w = \frac{1}{2} I \omega^2 $$</p>
<p>What's the difference between these two? Thanks.</p> | g10704 | [
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0.06099537014961243,
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0.032... |
<p>In section 5.8 of Misner, Thorne, and Wheeler's "Gravitation" there is a proof that 4-momentum determined as
$$
\tag 1 p^{\mu} = \int T^{\mu 0}\,\mathrm{d}^{3}\mathbf r , \quad \partial^{\mu}T_{\mu \nu} = 0,
$$
transformed as 4-vector under the Lorentz transformation (case "c"). The authors proposed the next explan... | g10705 | [
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<p>Michio Kaku's explanation of universes in hyperspace in <a href="https://www.youtube.com/watch?v=D6XAkVA7RmY" rel="nofollow">this youtube video</a> gives a metaphor of our universe being the surface of a hyperspace bubble that's currently becoming larger. He also says these bubbles colliding would produce the creati... | g10706 | [
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0.08... |
<p>I know that displacement current is due to time-varying electric field and its not an electric current.</p>
<p>But then, is it charge that is actually being displaced?</p> | g342 | [
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-0.03768881782889366,
-0.0... |
<p>If negative mass is rotating around fixed positive mass, then what will be the nature of force and how?</p> | g343 | [
0.018152229487895966,
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<p>Usually when discussing Fermi liquid theory, it is stated that due to the quasiparticles effectively behaving like a free electron gas with effective mass, the specific heat is linear in $T$ at small temperatures.</p>
<p>However, it turns out the Helium-3 has also a dependence of type $T^3 \ln T$. I want to underst... | g10707 | [
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<p>This troubles me: We are talking about time and space being equivalent, but still only consider Spin in the $x$, $y$ or $z$-direction. What's Spin in time dimension? Is it distinction between particles and antiparticles?</p> | g10708 | [
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<ul>
<li>How Einstein's SR becomes GR?</li>
</ul>
<p>$$ds^2=dr^2-c^2dt^2,$$</p>
<p>$$ds^2=g_{\mu\nu}dx^{\mu}dx^{\nu}.$$</p>
<ul>
<li><p>When the $s$ is constant $ds^2=0$, isn't it true?</p></li>
<li><p>How to connect Einstein's SR with GR?</p></li>
<li><p>What is the GR-differential $ds^2$?</p></li>
</ul> | g10709 | [
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<p>I am not a phycisist, so please forgive my ignorance. This is related to my <a href="http://physics.stackexchange.com/questions/30894/negative-and-positive-energy-and-hawking">posts</a> and <a href="http://physics.stackexchange.com/questions/30965/naive-question-on-quantum-mechanics-and-uncertainty-principle">this</... | g10710 | [
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... |
<p>Recently I have been confused by the fact that: </p>
<p>Joseph Polchinski's name appear in FFP Physics Frontiers Prize 2013 here: <a href="https://fundamentalphysicsprize.org/laureates6" rel="nofollow">https://fundamentalphysicsprize.org/laureates6</a> </p>
<p>``<strong>Joseph Polchinski</strong> for his contribut... | g10711 | [
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<p>A car is moving at a velocity of $10 \, \text{m}/\text{s}$. After point $A$ no acceleration is provided. By simple measurement, the acceleration is found to be $-1 \, \text{m}/\text{s}^2$.</p>
<p>Using standard equations: $$v = u + at, \; v=0, \; u = 10, $$ we arrive at $t = 10 \text{s}$.</p>
<p>$$S = ut + .5 at^2... | g10712 | [
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<p>It's not homework (I'm teacher). I would like to compute sum of forces on this study :</p>
<p><img src="http://i.stack.imgur.com/2bLUJ.png" alt="enter image description here"></p>
<p>The shape is symmetrical like that I'm sure the center of gravity is in the center of the shape. I compute forces on axis X only. No... | g10713 | [
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<p>Is <a href="http://en.wikipedia.org/wiki/Loschmidt%27s_paradox" rel="nofollow">Loschmidt's paradox</a> a paradox even today? </p>
<p>In other words, is the paradox resolved or not?</p> | g344 | [
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<p>I have a question that's bugging me. Googling it only made me more confused so I really hope someone can help me clear this.</p>
<p>If a plane is flying up and down; or hovering (Like the x-wing scene from star wars for example, when yoda uses the force) does that result in constant acceleration or varied accelerat... | g10714 | [
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<p>Given the Hamiltonian for the the harmonic oscillator (HO) as
$$
\hat H=\frac{\hat P^2}{2m}+\frac{m}{2}\omega^2\hat x^2\,,
$$
the Schroedinger equation can be reduced to:
$$
\left[
\frac{d^2}{dz^2}-\left(\frac{z^2}{4}+a\right)\right]\Psi=0~,
$$
where $a=-\frac{E}{\hbar\omega}$, $z=\sqrt{\frac{2m\omega}{\hbar}}$.
Now... | g10715 | [
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<p>I have read multiple answers on StackExchange about this question, but I wasn't able to find a concrete answer. Like other questions, the reason I ask about the s-orbital is because it has a zero orbital angular momentum. But, the implication of having a zero angular momentum is unclear? Some answers discuss probabi... | g10716 | [
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<p>Suppose I have 2 fermions in a potential $V(x)$. Both particles are moving in one dimension: the $x$ axis.
Then, neglecting the interaction between the particles, the spatial wave function of the system would be of the form
$$\psi_{n_{1}}(x_{1})\psi_{n_{2}}(x_{2}) $$</p>
<p>Now, if I'm considering particles with sp... | g10717 | [
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<p>I found the problem described in the attached picture on the internet. In the comment sections there were two opposing solutions. So it made me wonder which of those would be the actual solution.</p>
<p>So basically the question would be the following. Assume we would have two identical beakers, filled with the sam... | g10718 | [
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<p>Intuitively I would expect the thermal and electric conductivity to be positively related, and since electric conductivity increases with salinity, so should thermal. But according to <a href="http://web.mit.edu/seawater/Seawater_Property_Tables.pdf" rel="nofollow">this table</a> (p.10) it decreases. Why is this?</p... | g10719 | [
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0.073... |
<p>How many different types of (hypothetical) <a href="http://en.wikipedia.org/wiki/Multiverse" rel="nofollow">multiverse</a> theory exist? For example, the obvious Quantum MWI, eternal inflation, cyclic universe etc</p> | g10720 | [
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<p>I don't get a grip of what that exactly means. What IS an abstract singlet, doublet,... under $SU(N)$ or other groups?</p> | g345 | [
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<p>I have three DC circuits in my solar array. I have a three lead + ground (bare copper) tec armoured cable (#6). Why not run one circuit using the bare ground as negative? In fact, why not run three circuits and use the the bare copper as the common negative? </p> | g10721 | [
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<p>The Big Bang looks like a lower bound to the "size" of the universe in the time dimension. Could it also have an upper bound, some furthest point in time from the Big Bang?</p> | g10722 | [
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<p>Why magnetic field generates around a wire when current flow through it ?</p> | g346 | [
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0.0... |
<p>Can you help me to do this: </p>
<p>Two frames of references $S$ and $S'$ have a common origin $O$ and $S'$ rotates with constant angular velocity $\omega$ with respect to $S$.<br>
A square hoop $ABCD$ is made of fine smooth wire and has side length $2a$. The hoop is horizontal and rotating with constant angular s... | g10723 | [
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0.06904781609773636,
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<p>There is perfect parallelepipedal bar made of transparent crystal with cubic lattice floating in vacuum. Faces of parallelepiped are parallel to lattice axis. There is image, forming checkerboard pattern, each cell alternating between two distinct colors.</p>
<p>This image is projected in perpendicular on the one f... | g10724 | [
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<p>I'm asking a question that has bothered me for years and years. First of all, let me give some context. I'm a layman in physics (college educated, math major). I've read Feynman's QED cover to cover, and watched his messenger lectures. My hope is to get an answer at the "Feynman level", ideally in the crystal clear ... | g10725 | [
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<p>Why does a larger mass in a pendulum have the same period as a lighter mass? i know it has something to do with gravity and length but how can this be explained in depth? like for example the galileo's experiment where both masses were nearly the same but the lighter mass was slower (air resistance)</p> | g347 | [
0.089556023478508,
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0.02147283777... |
<p>I have watched Walter Lewin's lecture(<a href="http://www.youtube.com/watch?v=6QVbE_tU2sA" rel="nofollow">http://www.youtube.com/watch?v=6QVbE_tU2sA</a>) which was about the rainbows. But there is still a question bothering me. </p>
<p>I understood the first part of the lecture which he talked about axial symmetry... | g10726 | [
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0.030585667118430138,
0.018299... |
<p>What is meant by a local Lagrangian density? How will a
non-local Lagrangian look like and what is the problem that we do not
consider such Lagrangian densities?</p> | g10727 | [
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0.... |
<p>Is there any frequency at which cars can be charged with using wireless? Surely, wireless transmission can be safely assumed to be a form of energy transfer, and there can be charging of cars without physical electric outlets. Is there a frequency at which cars can be charged? One can see the problem of energy trans... | g10728 | [
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<p>I am studying the global causality of the spacetime. Here, I come across a problem. </p>
<p>Suppose a point $r\in \partial I^+(p)$. $I^+(p)$ is the chronological future of a different point $p$ in spacetime. Then, it is claimed that $I^+(r)\subset I^+(p)$. But why? </p>
<p>Let me first try to prove this conclusion... | g10729 | [
0.09191777557134628,
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0.04676150903105736,
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-0.00... |
<p>One often comes across news articles that claim that an earthquake shifted the earth's axis.</p>
<blockquote>
<p><a href="http://news.google.com/?q=earthquake%20shifted%20OR%20shifts%20earth%27s%20axis">http://news.google.com/?q=earthquake%20shifted%20OR%20shifts%20earth%27s%20axis</a></p>
</blockquote>
<p>If yo... | g10730 | [
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... |
<p>I've read a few other posts, and none seem to give me an answer that satisfies my curiosity. Thus far I've only been studying time independent QM, so I'm not even sure how wave functions evolve over time for microscopic things, let alone macroscopic things. However, what mandates that events that expect to happen ac... | g10731 | [
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<p>This may be a very simple question but somehow I can't seems to solve it. For the sake of completness, I will use the same original question I am working on.</p>
<p><strong>Question:</strong> The density of ice is $917 kg/m^3 $ and the density of seawater is $1020 kg/m^3$. If a piece of ice with dimensions $ 1m $ x... | g10732 | [
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<p>The Japanese tsunami, moving at about 700 km/h, affected areas as distant as Chile's coast, 20 hours after the earthquake. How does the Coriolis force affect tsunami? Also, I saw an image of a boat caught within a large whirlpool. Is the whirlpool's rotation due to Coriolis force?</p> | g10733 | [
-0.004144543781876564,
0.041829176247119904,
0.004472497850656509,
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0.052451375871896744,
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0.0005643402691930532,
0.01441816333681345,
-0.... |
<p>Does anyone know a reference or a paper which discusses string theory correction to Friedmann equations?</p> | g10734 | [
0.035871218889951706,
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0.008383671753108501,
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0.03625183179974556,
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0.023006625473499298,
0.03224434703588486,
0.05... |
<p>In the Debye-Scherrer procedure a sample of crystalline powder is hit by a beam of monochromatic photons. The diffracted photons are measured with a detector. We have constructive interference of the photons if the Bragg conditions are met.
In my lecture notes it says that there are always crystalline planes oriente... | g10735 | [
0.0371243916451931,
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0.002426530234515667,
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0.0055486843921244144,
-0... |
<p>Isn't this statement regarding projectile motion wrong?</p>
<blockquote>
<p><em>If a body is thrown at an angle to the horizontal with initial velocity $u$, then displacement of body as a function of time is $\vec{s}=\vec{u}t+\frac12\vec{g}t^2$. (Air drag is neglected)</em></p>
</blockquote>
<p>How can it be cor... | g10736 | [
0.0786217525601387,
0.025088327005505562,
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0.04542503505945206,
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0.033210862427949905,
0.07345534861087799,
-0.030... |
<p>Given a many body spin system, a collection of N spin-1/2 particles, under the interaction of the twisting Hamiltonian:
$$H_{int} = \sum_{i,j=1}^Na_{i,j}\sigma_{z,i}\sigma_{z,j}= A J_{z}^{2}$$
assume all $a_{i,j}$ are equal and define:
$$\mathbf{J} = \sum_{n=1}^{N} \mathbf{\sigma}_{n}$$
the collective spin operator,... | g10737 | [
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0.044701702892780304,
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0.017588261514902115,
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0.03468421846628189,
0.008410255424678326,
-0.0176373403519392,
0.022763224318623543,
0.021663818508386612,
-0.02... |
<p>Consider a point mass $A$ with mass $m$ in empty space. The point mass $A$ does not have a velocity and does not rotate.
Since gravity is symmetric for nonmoving objects, the spacetime curvature around $A$ is also symmetric.</p>
<p>So at a distance $d$ from the point mass $A$ how strong is the curvature $C$ ?</p>
... | g10738 | [
-0.005927518010139465,
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0.023829614743590355,
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0.009971288032829762,
0.01803039200603962,
-... |
<p>How can we get the mass of an uncharged proton, i.e. how varies the mass of the charged proton if i remove the electric charge?</p>
<p>For the isotopic spin theory neutron and proton have the same mass and it is possible to distinguish that particles only for the different values of the third component of the isoto... | g10739 | [
0.0372481606900692,
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0.0017385127721354365,
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0.09742970019578934,
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0.02446812391281128,
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-0.010566980578005314,
0.0093870609998703,
0.016400... |
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