question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Is X-ray crystallography is possible for metals? Or not due to absorption?</p> | g15085 | [
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<p>I never understood how the equipartition theorem was applied electromagnetic waves inside the metallic blackbody. As hyperphysics puts it (<a href="http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/mod7.html" rel="nofollow">http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/mod7.html</a>)</p>
<blockquote>
<p>T... | g15086 | [
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<p>I mean <a href="http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer" rel="nofollow">WISE</a> is monitoring near-Earth objects, but cannot see the latest Russian meteor and others. Why can it not detect small objects?</p>
<p>What is the limit of it's infrared detectors?</p> | g15087 | [
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<p>The hydrostatic paradox, states that the </p>
<blockquote>
<p>height of the water in any container is independent of the shape of
the container. </p>
</blockquote>
<p>This does make sense since it is only the height of the fluid relative to ground which determines the pressure, and it is the pressure equilibr... | g15088 | [
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<p>How can I determine the generators of the Poincare Group, $P(1,3)$ explicitly?
Here $P(1,3)$ means a matrix Lie group. </p> | g15089 | [
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<p>I was reading <a href="http://physics.stackexchange.com/q/90275/">this</a> Phys.SE question. I was unable to understand how an $SU(2)$ holonomy would produce $\mathcal{N}=2$ in four dimensions. Could anyone shed some light on this? </p> | g15090 | [
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<p>The <a href="http://en.wikipedia.org/wiki/Fahrenheit" rel="nofollow">Fahrenheit scale</a> is defined by fixed points on the scale. What interests me is the apparent arbitrary chosen numbers in these fix-points.</p>
<p>First wikipedia wites from 32 to 212. -and later in the <em>History</em> part we have from 0 to 32... | g15091 | [
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<p>Wien's fifth power law says that emissive
power is proportional to the
temperature raised to the fifth power.
On the other hand, the Stefan–Boltzmann
law says emissive power is
proportional to the temperature raised to the fourth power.
How can both of these be true?</p> | g15092 | [
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<p>Suppose that I have a monatomic gas sample consisting of $N$ atoms (e.g., $N$ argon atoms); thus there are no vibrations or rotations. How many degrees of freedom does the system have?</p>
<ul>
<li><strong>Does the system have $3N$ degrees of freedom?</strong> Each of the $N$ atoms can translate in $x$, $y$, and ... | g15093 | [
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<p>Is there a database/website which shows all comets which have passed Earth and have been viewed? Is there any country specific viewing database as well? </p>
<p>I would like to do a search on the lines of : Show me all comets were visible from India during 1950 to 1960?</p>
<p>Any searches on Google have not retur... | g15094 | [
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<p>I'm reading about giant magnetoresistance (GMR), and the most important feature of this phenomenon is the spin dependance of the electron scattering inside a magnetised lattice. However, I don't quite understand why electrons with spin parallel to the magnetisation (hence, to the majority-spin direction of the elect... | g15095 | [
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<p>I am stuck varying an action, trying to get an equation of motion. (Going from eq. 91 to eq. 92 in the image.)
This is the action </p>
<p>$$S~=~\int d^{4}x \frac{a^{2}(t)}{2}(\dot{h}^{2}-(\nabla h)^2).$$</p>
<p>And this is the solution, </p>
<p>$$\ddot{h} + 2 \frac{\dot{a}}{a}\dot{h} - \nabla^{2}h~=~0. $$</p>
<p... | g15096 | [
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<p>A bug of mass $m$ crawls out along a radial scratch of a phonographic disc rotating at $\omega$ angular velocity. It travels with constant velocity $v$ with respect to the disc.
What are the forces (and their directions) which act on the bug?</p>
<p>I have tried thinking in this way: If I look from the point of vi... | g15097 | [
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<p>My question here is purely fundamental. I am confused with the concept in <a href="http://en.wikipedia.org/wiki/Franck%E2%80%93Condon_principle" rel="nofollow">Franck Condon (FC) principle</a> and <a href="http://en.wikipedia.org/wiki/Born%E2%80%93Oppenheimer_approximation" rel="nofollow">Born Oppenheimer (BO) appro... | g15098 | [
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<p>Based on the Bekenstein-Hawking Equation for Entropy, hasn't the relationship between quantum mechanics and gravity already been established.</p> | g15099 | [
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<p>The following passage has been extracted from Newton's book Opticks: </p>
<blockquote>
<p>...So if PR [in Fig.at the top] represent any Object without Doors, and AB be a Lens placed at a hole in
the Window-shut of a dark Chamber, whereby the Rays that come from any Point Q of that
Object are made to converg... | g15100 | [
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<p>An alternative version of this question would be: "if was to pick a star from the $10^{11}$ or so in our galaxy at random, what are the probabilities of it being various kinds of star?" (and I do mean "in our galaxy" and not "visible in the night sky").</p>
<p>There is a nice table I've seen in various places (e.g ... | g15101 | [
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<p>During a discussion on start-and-stop vehicle technology some bloke began pushing the point that re-starting the car uses stored energy from the battery, which needs to be replenished by increased fuel usage once the engine is moving. Well, this is obvious, the question is that of significance of such additional usa... | g15102 | [
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<p>The Heaviside-Feynman formula (see Feynman Lectures vol I Ch.28, vol II Ch. 21) gives the electric and magnetic fields measured at an observation point $P$ due to an arbitrarily moving charge $q$</p>
<p>$$ \mathbf{E} = -\frac{q}{4 \pi \epsilon_0} \left\{ \left[ \frac{\mathbf{\hat r}}{r^2} \right]_{ret} + \frac{[r]_... | g15103 | [
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<p>I'm aware that this is somewhat of a frequently asked question (not only here), and i've dug through respective answer for a few hours before i decided to ask here. None of those answers
helped me predict/explain my case though, so here's my problem:</p>
<p>Suppose we have this setup:
<img src="http://i.imgur.com/... | g15104 | [
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<p>I know there are zillions of questions about faster than light travel, but please hear me out. According to special relativity, it is impossible to accelerate something to the speed of light. However, we can still have objects (like photons) going at speed $c$ if they never had to accelerate in the first place, i.e.... | g15105 | [
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<p>Is it correct in saying that a particles size is it's rest energy, and that particles don't actually have size (in the way you get different size objects)?</p>
<p>What defines what sizes a particle can be? Why do particles have discrete sizes, and there's not a continuous spectrum of particles varying in size?</p>
... | g15106 | [
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<p>Since the equation of mechanics are of second order in time, we know that for $N$ degrees of freedom we have to specify $2N$ initial conditions. One of them is the initial time $t_0$ and the rest of them, $2N-1$ are initial positions and velocity. Any function of these initial condition is a constant of motion, by d... | g15107 | [
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<p>Recently I had a debate about the uncertainty principle in QFT that made me even more confused..</p>
<p>Because we use Furrier transforms in QFT we should have an analogue to the usual Heisenberg uncertainty principle in QFT between the 4-vector of space-time coordinates and the conjugate momentum, but I found no r... | g15108 | [
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<p>I have to do some calculations to get the drag from an experiment with a wake rake. In the equation I have to enter the total pressure coefficient $C_{pt}$, but in my calculations it seems to always be equal to +1. Is this correct? </p> | g15109 | [
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<p>The total energy of an object comes from the time part of the four-momentum, and so isn't a Lorentz invariant. On the other hand, is the potential energy of a compressed spring a Lorentz invariant?</p> | g15110 | [
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<p>I have been reading <a href="http://pubs.rsc.org/en/Content/ArticleLanding/2012/FD/C1FD00086A" rel="nofollow">a recent paper</a>. In it, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, in which liquid resides between the parallel-plate electrodes. To simplify the situat... | g15111 | [
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<p>Intuitively, why are $\cosh(\theta) = \frac{1}{\sqrt{1-(v/c)^2}}$ and $\sinh(\theta) = \frac{v/c}{\sqrt{1-(v/c)^2}}$ true in special relativity?</p>
<p>Is there some picture I can draw in Minkowski space (or anywhere)</p>
<p><img src="http://i.stack.imgur.com/q8Gbx.png" alt="enter image description here"></p>
<p... | g15112 | [
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<p>The general group element (in the vector representation)</p>
<p>$$
\left [{ \begin{array} {c}
\bar x^1 \\
\bar x^2 \\
\bar x^3 \\
\bar t \\
1 \\
\end{array} } \right] =
\left[ {\begin{array}{ccccc}
a_{11} & a_{12} & a_{13} & V_1 & a_1\\
a_{21} & a_{22} & a_{23} & V_2 &a... | g15113 | [
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<p>Recently I get the task to build (2 + 1)-Dirac theory. I wrote corresponding Dirac equation in a form
$$
(i\sigma_{0}\partial_{0} + i\sigma_{1}\partial_{1} + i\sigma_{2}\partial_{2} - m)\Psi = 0,
$$
where
$$
\sigma_{0} = \sigma_{y}, \quad \sigma_{1} = i\sigma_{x}, \quad \sigma_{2} = i\sigma_{z}, \quad [\sigma^{\mu},... | g15114 | [
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<p>When a particle enters an excited state, the energy appears in its quantum wavefunction according to $E = h \nu$. </p>
<p>Does the $E$ in this equation also include kinetic energy, and rest mass energy? Or are they "held" somewhere else? Or are kinetic/mass energy a different framework for looking at the same ph... | g15115 | [
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0.037672288715839386,
-0.003501094179227948,
0.006038626190274954,
-0.040278416126966476,
0.017381103709340096,
0.0452493317425251,
0.0... |
<p>In derivation of the BdG mean field Hamiltonian as follows, I have a confusion here in the second step:</p>
<p>$H_{MF-eff} = \int d^{3}r\psi_{\uparrow}^{\dagger}(\mathbf{r})H_{E}(\mathbf{r})\psi_{\uparrow}(\mathbf{r})+\int d^{3}r\psi_{\downarrow}^{\dagger}(\mathbf{r})H_{E}(\mathbf{r})\psi_{\downarrow}(\mathbf{r})
... | g15116 | [
0.043868061155080795,
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0.06989235430955887,
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... |
<p>Ok, so you've basically got tensile and compression strain in a lattice mismatched material right? So as you're epitaxially layering the material, the strained material is deforming more and more "elastically" (that is, the energy is being stored in the lattice) until "plastic relaxation" which occurs when dislocati... | g15117 | [
0.05415929853916168,
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... |
<p>Can <em>any</em> antisymmetric function, i.e., a function of $N$ spatial-plus-spin variables
$\{x_i\ | \ i= 1, \ldots, N\}$ satisfying
$$ \psi(x_1,\ldots, x_i, \ldots, x_j, \ldots, x_N) = -\psi(x_1,\ldots, x_j, \ldots, x_i, \ldots, x_N)\ ,$$
always be written as a Slater-Determinant of functions ("orbitals"), <em>n... | g15118 | [
-0.018051058053970337,
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0.007137449458241463,
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0.0085680540651083,
0.0020756986923515797,
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0.003387883771210909,
0.013590372167527676,
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0.014681297354400158,
0.04343009740114212,
0.... |
<p>In chemical adsorption of H2 molecule, the distance is limited. In the physical adsorption, the distance of adsorption is limited or can be any value? Is there any correspondence to adsorption distance with the van der Waals radius of the adsorbent and adsorbate?. </p> | g15119 | [
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<p>Some researchers use Hydrogen atom termination, to model a non periodic finite sized 2D and 1D structures as periodic one. How far this approach is useful in predicting the properties of periodic systems? What are the other approaches to model a non-periodic supercell as periodic one?</p> | g15120 | [
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<blockquote>
<p><em>A rocket is launched perpendicularly with an initial acceleration of 10 m/s<sup>2</sup>, if the fuel runs out after 1 minute, what will be the maximum height reached by the rocket?</em></p>
</blockquote> | g15121 | [
0.04046984761953354,
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0.03315415605902672,
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0.004362876061350107,
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0.02062... |
<p>When we shine line of an appropriate wavelength at a metal, e.g. gold, such that there is sufficient energy to promote an electron from the valence band to the conduction band, we'll generate with some probability a set of electron-hole pairs. We can then, to my understanding, rough approximate the electrons and ho... | g15122 | [
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<p>I remember reading something about how <a href="http://en.wikipedia.org/wiki/Iron" rel="nofollow">iron</a> was a highly stable element. Ever since then, I have looked at iron fry pans with new-found respect. However, in a recent discussion I was unable to pinpoint this 'special' quality. So what is so special about ... | g15123 | [
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<p>I would like to know the position and orientation of the Earth, relative to the sun, as a function of time. </p>
<p>I.e. select any coordinate system with the Sun at the origin so that the earth lies in the x-y coordinate plane. Provide a function which takes as input the time and produces </p>
<ol>
<li>The x-y po... | g15124 | [
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0.019059376791119576,
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0.03580945... |
<p>So we know that many people are putting hard constraints on the galactic habitability zone based on the presence of nearby <a href="http://en.wikipedia.org/wiki/Near-Earth_supernova" rel="nofollow">supernova/gamma ray bursts</a>. But if they <em>only</em> affect the ozone layer, then I doubt that it's as hard of a c... | g15125 | [
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<p>Let's say we start with the Big Bang. Every bit of matter started from this event. Therefore, given EVERY variable (every particle, movements of particles, weights, times, etc) and an INFINITE amount of time and computing power, would it be possible to predict the formation of all planets. Would it also be possible ... | g15126 | [
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... |
<p>I know that the <a href="http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation">cosmic microwave background radiation</a> (CMBR) is the leftover radiation from the <a href="http://en.wikipedia.org/wiki/Big_Bang">Big Bang</a>. Have we been able to make a concrete map of the radiation and the objects in t... | g15127 | [
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<p>This is a question from a study guide for a military officer exam:</p>
<p>I have fluid flowing through an elbow in a pipe (the elbow is in the shape of an upside down and backwards "J") and the flow goes from south to north to east. If holes are drilled at the upper left outside part of the bend and the lower right... | g15128 | [
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0.023111578077077866,
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<p>I need some clarification of what is meant when someone says "fermions cannot occupy the same quantum state". Consider two bosons:</p>
<p>$$\psi(\vec{r_1}, s_1, \vec{r_2}, s_2) = \frac{1}{\sqrt{2}} \left( \phi_A(\vec{r_1}, s_1)\phi_B(\vec{r_2}, s_2) + \phi_A(\vec{r_2}, s_2)\phi_B(\vec{r_1}, s_1) \right)$$</p>
<p>... | g15129 | [
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0.022752... |
<p>So as I understand it:
If you hit a wall at twice the speed you hit four times as hard?
I often ask people this and everyone says "at twice the speed you hit twice as hard". </p>
<p>$K=\frac{1}{2}mv^2$ is very counter intuitive. I have read an explanation that seems to say gravity is acceleration and that's where ... | g436 | [
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<p>Finding the ground state of the 3D ising model (with no magnetization) is known to be NP-complete. Just wondering what is the biggest size cubic lattice someone has found the ground state of for this model?
dbm368</p> | g15130 | [
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... |
<p>As far as I understand, going around the critical point, it is possible to transform a liquid into a gas without seeing a phase transition.</p>
<p>Does this also mean that there is no clear separation between a gaseous phase and a supercritical fluid ? This is more or less what can be understood for the dotted line... | g15131 | [
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<p>From my previous <a href="http://physics.stackexchange.com/questions/72475/classical-theories-and-ads-cft">post</a>, I found out from the comments that there are various generalisations of <a href="http://en.wikipedia.org/w/index.php?title=AdS/CFT_correspondence&oldid=564493454" rel="nofollow">AdS/CFT</a> with d... | g15132 | [
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<p>Why do charged particles only produce magnetic fields while in motion?</p> | g346 | [
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<ul>
<li>Firstly I don't know how generic is dimensional transmutation and if it has any general model independent definition.</li>
</ul>
<p>Is dimensional transmutation in Gross-Neveau somehow fundamentally different than in say massless-scalar QED or QCD?</p>
<p>I mean in the later two cases it shows up in doing pe... | g15133 | [
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... |
<p>Sorry this question is really vague- as a result I'm very confused. Perhaps you can help me make sense of it.</p>
<p>"Radar measurements: Construct a space-time diagram of the radar tracking of an asteroid moving at speed $v$. By using the postulates of special relativity verify the expressions on (a book I do not ... | g15134 | [
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<p>I am a bit confused about the Heisenberg's Uncertainty Principle - just read about it in <em>How to Teach Physics to Your Dog</em>, by Chad Orzel. He states that the reason electrons can't be measured is because the photons used to measure electrons, collide with them causing changes in momentum and velocity.</p>
<... | g471 | [
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<p>In Le Bellac's statistical physics book he derives the Sommerfeld expansion by a contour integral.</p>
<p>The idea is to expand integrals of the type $I(\beta)\equiv \int_{0}^{\infty}d\epsilon\, \frac{\varphi'(\epsilon)}{e^{\beta(\epsilon-\mu)}+1}$. Integrate by parts and expand $\varphi(\epsilon)$</p>
<p>$$\varph... | g15135 | [
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<blockquote>
<p><img src="http://i.stack.imgur.com/Cqvd9.png" alt=""></p>
<p>The cart is rolls frictionless on the table. It has a mass of $1 kg$. Attached to it are 2 strings, that go through two frictionless sheaves. The weights have masses as in the picture.</p>
<p>a) How large is the acceleration of the... | g15136 | [
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0.00442822789773345,
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0.011... |
<p>I read some derivation related with probability amplitudes and hamiltonian matrix in some book, and have a few questions.</p>
<p>Here what the book says is.</p>
<p>We want the general solution of the pair of Hamiltonian equations,</p>
<p>$ i\hbar \frac {d{C}_{1}}{dt } = {H}_{11}{C}_{1} + {H}_{12}{C}_{2} $</p>
<... | g15137 | [
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<p>I am trying to find out the pressure at a given altitude but have been disappointed to find the following equation does not work at all: (h = height in meters)</p>
<p><img src="http://i.stack.imgur.com/ujJjV.png" alt="enter image description here"></p>
<p>Where </p>
<ul>
<li>sea level standard atmospheric pressur... | g15138 | [
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<p>I need to be able to convert an arbitrary emission spectrum in the visible spectrum range (i.e. for every wavelength between 380 and 780, I have a number between 0 and 1 that represents the "intensity" or dominance of that wavelength), and I need to be able to map any given spectrum into a particular color space (fo... | g15139 | [
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<p>How exactly do <a href="http://en.wikipedia.org/wiki/Temperature#Temperature_scales" rel="nofollow">temperature scales</a> work?</p>
<p>If my understanding is correct, the Celsius scale has two fixed points: (definitions of temperature irrespective of scale)
1. The freezing point of pure water at 1atm (labelled 0 ... | g15140 | [
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0.0316076055169105... |
<p>I'm trying to understand proper distance equation in Schwarzschild spacetime.</p>
<p>$d\sigma=\frac{dr}{\left(1-\frac{R_{S}}{r}\right)^{1/2}}$.</p>
<p>I'm sure I'm missing something really obvious here, but how do I use this to find the coordinate distance $r$
for a particular proper distance $\sigma$
. For exa... | g15141 | [
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<p>So, I have a basic, very basic, understanding of thermodynamics. I don't take it until next semester. I'm attempting to write a program which plots a temperature over time graph of a room being heated/cooled until a certain threshold is met, the users desired temperature, at which point the temperature will drop at ... | g15142 | [
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0.... |
<p>I am not sure how $QP-PQ =i\hbar$ where $P$ represent momentum and $Q$ represent position. $Q$ and $P$ are matrices. The question would be, how can $Q$ and $P$ be formulated as a matrix? Also, what is the proof of this <a href="http://en.wikipedia.org/wiki/Canonical_commutation_relation" rel="nofollow">canonical com... | g15143 | [
0.006022685207426548,
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0.08128233999013901,
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0.03603868559002876,
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-... |
<p>According to my textbook, it says that $i( LK-KL )$ represents a real quantity when $K$ and $L$ represent a real quantity. $K$ and $L$ are matrices. It says that this is because of basic rules. However, I was not able to recall my memories. Can anyone show the proof of this?</p> | g15144 | [
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<p>If someone gives me a thin film of Si, and they tell me it's (001) Si, does that mean that the (001) planes of Si are the ones making up the surface of the film?</p> | g15145 | [
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... |
<p>Just curious: is matrix picture of quantum mechnaics further used in QFT and superstring theories? It seems like not....</p> | g15146 | [
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<p>Some sunsets exhibit a phenomenon called "<a href="http://en.wikipedia.org/wiki/Green_flash">green flash</a>," where there is a quick flash of green light right as the sun is setting. I have seen this myself several times, and sort of understand it. I am a bit frustrated at my inability to explain it better to my fa... | g15147 | [
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<p>This is a basic question. Suppose that A and B are completely entangled particles and so are C and D. If B and C are antiparticles that annihilate each other will A and D be entangled as a result. It seems they should be in order to satisfy conservation laws. Also if the initial pairs were the results of pair creati... | g15148 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/14973/what-would-be-the-effects-on-theoretical-physics-if-neutrinos-go-faster-than-ligh">What would be the effects on theoretical physics if neutrinos go faster than light?</a> </p>
</blockquote>
<p>Upda... | g83 | [
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<p>I'm unable to find an answer to my questions via my searches. This questions pertains to the timeline of a star system creation.</p>
<p>My question: </p>
<p>During the creation of a star system, can satellite planets form before the star has ignited and begun to burn? </p>
<p>In more detail, I understand the basi... | g15149 | [
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<p>The Hamiltonian for graphene at $\vec{k}$ away from the $K$ point is proportional to</p>
<p>$$
\vec{\sigma} \cdot \vec{k} =\begin{pmatrix}
0 & k_x - i k_y \\
k_x + i k_y & 0 \\
\end{pmatrix}
=
k \begin{pmatrix}
0 & e^{-i \theta} \\
e^{i \theta} & 0 \\
\end{pmatrix}
$$
where $\theta=\tan^{-1}(k_y/k_x... | g15150 | [
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<p>No idea what exactly the rules are or how I should ask this question, but here's the verbatim quesiton:</p>
<p>"A Na$^{22}$ source has an activity of 100 $ \mu $C. If you handle the source, how big is the equivalent dose on your hands, if all the radiation were absorbed? Assume the volume and density to be 10 x 5 x... | g15151 | [
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<p>Having studied the topic recently I found out that simple harmonic motion can represented well with sine and cosine functions.Take for example a pendulum swing which could look like :</p>
<p><img src="http://i.stack.imgur.com/iGqpV.gif" alt="enter image description here"></p>
<p>and the equations governing the mot... | g15152 | [
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<p>An argument has been travelling in amongst my friends around this matter and after listening about it for <strong>3 whole days</strong> I decided to ask it here.</p>
<p>The Question is: Would a high atmospheric pressure slow sound that travels through it- due to there being more matter that the waves need to travel... | g15153 | [
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<p>When we have 2 sinusoidal waves with slightly different wavelengths and the same amplitude, the resulting wave has a changing amplitude (amplitude = intensity) which varies from 2*Amplitude to 0
<img src="http://i.stack.imgur.com/9Z628.png" alt="">
Suppose we have two different sources of visible light (slightly dif... | g15154 | [
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0.0... |
<p>I am currently reading the paper "Gravitation and quantum mechanics for macroscopic objects" by F. Karolyhazy (1966).</p>
<p>The author defines formally rigorous equations in order to describe the decay of the pure state $\Phi(\vec x_i)$ at $t=0$ into a mixture of states $\Phi_1(\vec x_i), \Phi_2(\vec x_i)$ with th... | g15155 | [
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<p>I'm trying to determine the amount of work required (in Joules) to create a vacuum of a certain pressure in a tube. A pneumatic cylinder will be used to remove the air from the tube to create the vacuum. </p>
<p>I understand the standard formula for the work to create a vacuum is: $\mathrm{pressure \; difference}... | g15156 | [
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<p>After a nuclear decay is it a necessity that the total energy of the products is more than the energy of the original particle before decaying? (NB: by 'energy' I don't intend to include mass-energy as well, unless by definition the term 'total energy' happens to include that in the realm of particle physics)</p>
<... | g15157 | [
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... |
<p>These two questions seem to be very similar, but the textbook uses a bit different methods for calculating $\Delta x$ of uncertainty principle.</p>
<p>Question A) Suppose that there is a room with the same length of its side (x-axis, y-axis, z-axis). A ball is 100g.</p>
<p>In this case, the solution says that I sh... | g15158 | [
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... |
<p>I had no problem appliying the Neothers theorem for translations to the non-relativistic Schrödinger equation</p>
<p>$\mathrm i\hbar\frac{\partial}{\partial t}\psi(\mathbf{r},t) \;=\; \left(- \frac{\hbar^2}{2m}\Delta + V(\mathbf{r},t)\right)\psi(\mathbf{r},t)$</p>
<p>$\Longrightarrow\ \mathcal{L}\left(\psi, \mathb... | g15159 | [
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0.024373725056648254,
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<p>When the red shifts of galaxies are large, why do we think that they are far away? </p>
<p>I know about Hubble's law, Tully-Fisher relation of spiral galaxies, Faber-Jackson relation of elliptical galaxies, and so on , but they seem to the empirical rules. </p>
<p>I think that the value of red shift has only the ... | g15160 | [
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... |
<p>In minimal <a href="http://en.wikipedia.org/wiki/Lambda-CDM_model" rel="nofollow">$\Lambda\mathrm{CDM}$</a>, there is a parameter labeled $\Omega_\Lambda$, and current fits place it at around $\left( \Omega_\Lambda \sim 0.73\right)$. Meanwhile, $\Lambda$ enters the Einstein field equations as an offset to the Ricci ... | g15161 | [
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<p>The question "<a href="http://space.stackexchange.com/q/868/103">Did NASA nuke Jupiter?</a>" while debunked immediately (non-fissile isotope was used) arose many what-if questions.</p>
<p>What would happen if a subcritical chunk of a fissile isotope, like Pu-239 was dumped down the atmosphere of Jupiter?</p>
<p>We... | g15162 | [
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<p>It's told in Landau - Classical Mechanics, that in the Hamiltonian method, generalized coordinates $q_j$ and generalized momenta $p_j$ are independent variables of a mechanical system. Anyway, in the case of Lagrangian method only generalized coordinates $q_j$ are independent. In this case generalized velocities are... | g15163 | [
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0.035524... |
<p>What are the major differences between <a href="http://en.wikipedia.org/wiki/Physics" rel="nofollow">physics</a> and <a href="http://en.wikipedia.org/wiki/Chemistry" rel="nofollow">chemistry</a>? I know that they both study atoms, electrons and molecules, but what makes some topics part of one and some part of anoth... | g15164 | [
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... |
<p>The de Broglie wavelength is given by</p>
<p>$$\lambda\equiv\frac{h}{mv}$$</p>
<p>Now, if we have a <em>small</em> body, it's wavelength will be large when it is in motion. Similarly, a <em>large</em> body will have small wavelength. It can be seen from the equation. First of all tell me if I am right about these ... | g15165 | [
0.032269436866045,
0.006098766811192036,
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0.015419399365782738,
0.0394360... |
<p>Maybe this is more of an Electrical Engineering question, but does anyone know why iPhones looking green/red through a linear polarizer? I find it strange that the light coming out would be polarized... I mean I guess there's no reason it shouldn't be, but what is making it polarized, moreover, what goal does it ser... | g15166 | [
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0.... |
<p>In problems about relativity we have a stationary frame S and a moving frame M and two observers initially at the same reference point. Then the two frames pass each other and we measure the distance and time with a second reference point. The two reference points are at rest in the S frame. The conclusion is that t... | g15167 | [
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0.021452... |
<p>I really don't even know how to start doing this problem.</p>
<p>I understand PV=nRT and I understand that if either T, V, or P is kept constant, then the other 2 change at the same rate, and I understand that if either T, V, or P is kept constant while the other two change, then the system experiences a change in ... | g15168 | [
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<p>I think I'm just confused, but for some reason I thought that light moving straight in one frame would have to move in the same direction in another frame. I know there are photons-but because I have not learned about them I was thinking purely from the wave model. If light has no mass, shouldn't a disturbance sent ... | g15169 | [
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0.022338557988405228,
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0.0035697421990334988,
0.014914... |
<p>The ideal blackbody radiation curve (unlike the quantized emission seen from atomic spectra), is continuous over all frequencies. Many objects approximate ideal blackbodies and have radiation curves very similar in shape and continuity to that of an ideal blackbody (often minus some emission and absorption lines fr... | g802 | [
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... |
<p>The classic example of an indeterministic system is a radioactive isotope, e.g. the one that kills Schrödinger's cat.</p>
<p>I get there are arguments against hidden variables in quantum mechanics, but how could they be so sure, back in the twenties, that the strong nuclear forces involved in radioactivity were not... | g15170 | [
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<p>I'm in a group trying to design an underwater optical communication system for a capstone project. For this system we are planning on using multiple high powered LEDs passing through a lens system, and a photodiode with a collector lens at the other end of the system.</p>
<ul>
<li>So far we have been trying to make... | g15171 | [
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0.01626966893672943,
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0.04436647519469261,
... |
<p>Let an object of mass $m$ and volume $v$ be dropped in water from height $h$, and $a$ be the amplitude of the wave generated. What is the relation between $a$ and $h$. How many waves are generated? What is the relation between the amplitudes of successive waves? Does it depend on the shape of the particle?</p>
<p>A... | g15172 | [
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0.014945534989237785,
0.036476511508226395,
0.061... |
<p>Looking for some information on how light and xrays interact with phosphorous, or what might cause the following:</p>
<p>Scenario</p>
<p>A focus beam of light is directed at a phosphor plate at the same time as an xray beam. Afterwards a 'shadow' is observed where the focus beam was located on the plate.</p>
<p>Q... | g15173 | [
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0.009171525947749615,
0.07201402634382248,
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-0.... |
<p>e.g.</p>
<p>If I had two bottles one with Vodka in and one with Water in (both the same glass bottle spec/size)</p>
<p>If I then put these two bottles in a freezer would the surface temperature of the bottle be the same or different?</p>
<p>Thanks</p> | g15174 | [
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0.010547634214162827,
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-0.01805... |
<p>I know the LHC people are publishing new limits every now and then, but as a non-expert in reading experimental papers (yet), I was wondering if there's a friendly website that collects and presents the limits in a readable and accessible way for non-experts? </p> | g15175 | [
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0.016975082457065582,
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0.03382139652967453,
0.06230210140347481,
-0.01890498399734497,
0.006456934381276369,
0.0261747... |
<p>Could someone please explain why if the time-independent heat equation can, via changing of variables, take the form of Bessel's equation that the $\sqrt\lambda$ should take the values of the zeros of $J_0$ from <a href="http://www.maths.usyd.edu.au/u/UG/IM/MATH2965/r/NOTES-Week-5.pdf" rel="nofollow">slides 20-21 of... | g15176 | [
0.04417017474770546,
-0.04058950021862984,
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-0.05789119750261307,
0.01940152607858181,
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0.03603446111083031,
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0.02465140074491501,
-0.035746652632951736,
0.08024372905492783,
0.018768014386296272,
0.00732... |
<p>Not sure if this is the right place to post, but how is it possible to have laws of a theory?</p>
<p>A theory is not able to be a law, since it's just an explanation that can always be disproven. So how is there a law of a theory?</p> | g394 | [
0.000619264377746731,
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0.0... |
<p>I left out the remnants of my Long Island Iced Tea. This was a mixture of various liquors, lemon juice, Splenda, and water from the melted ice. It was left on my kitchen counter for several days:</p>
<p><img src="http://i.stack.imgur.com/l1t2T.jpg" alt="enter image description here"></p>
<p>You'll notice the bot... | g15177 | [
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0.019... |
<p>We are working on a science project and try to engineer a power plant of a new kind. It is called Air HES (air hydroelectric station). The idea is described on <a href="http://airhes.com/" rel="nofollow">our website.</a></p>
<p>Do you think it is possible to create such power plant? We already consulted some scient... | g15178 | [
-0.021161232143640518,
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0.03249184414744377,
0.01706196367740631,
0.013944... |
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