# Special & General Relativity

- Dependence of various physical phenomena on relative motion of the observer and the observed objects. Exp. & theo. theories of relativity
 Meta Thread / Thread Starter Last Post Replies Views Views: 5,005 Announcement: Follow us on social media and spread the word about PF! Jan16-12 Before posting anything, please review the Physics Forums Global Guidelines. If you are seeking help with a... Feb23-13 08:40 AM ZapperZ 1 42,756 The section of the Usenet Physics FAQ titled "Experimental Basis of Special Relativity" has been cited here many... Dec31-07 02:06 AM jtbell 0 42,395 I am trying to expand $$\varepsilon^{{abcd}} R_{{abcd}}$$ by using four identities of the Riemann curvature tensor: ... T 06:08 AM Emil 2 140 It is my understanding (perhaps I am wrong) that relativity implies that all frames of reference are equal. For... T 06:06 AM wittgenstein 5 142 Consider the following case: First frame S, which is earth. Second frame S', which is rest relative to rocket.... T 05:49 AM jartsa 8 300 a metric is also used to raise/lower indices. g_{\nu \mu } x^{\mu} = x_{\nu} g^{ \nu \mu} x_{\mu} = x^{\mu} ... T 05:07 AM ChrisVer 0 26 Hi all, this is a follow-up variant to an earlier post ... T 05:03 AM ghwellsjr 6 263 I am attempting to read my first book in QFT, and got stuck. A Lorentz transformation that preserves the Minkowski... T 04:32 AM ChrisVer 12 491 I have always been confused about time dilation in General Relativity. In the twins paradox, it is the traveling... Y 08:05 PM pervect 3 154 The Friedmann equation states that (\frac{\dot a}{a}) = \frac{8\pi G}{3} \dot \rho + \frac{1}3 \Lambda -... Y 04:18 PM PeterDonis 5 127 Is it possible to find the parametric representation X= x(y^{a}) of a surface given the components of the metric... Y 03:24 PM ChrisVer 0 89 SR directly addresses only inertial frames. Can SR be applied to analyze accelerated frames? For example, consider... Y 12:30 PM jbriggs444 12 285 relative velocity ( 1 2 3) A simple experiment can be build to demonstrate a possible contradiction between thinking theory and reality. Use... Y 11:56 AM nitsuj 53 1,463 According to SR, there is no measurement that can determine whether an object is stationary or under motion. So if two... Y 11:19 AM ghwellsjr 4 136 Can anyone answer this question? What you would see while watching a stationary clock that you are moving directly... Sep15-14 11:52 PM TumblingDice 12 380 Alright, I'm rather new to General Relativity, and I'm getting confused with four momentum. Back in SR, p^α=mU^α, but,... Sep15-14 08:55 PM Dirac271 2 177 I recently watched a video in Einstein's train though experiment. www.youtube.com/watch?v=wteiuxyqtoM From what... Sep15-14 02:51 PM Nugatory 31 1,216 Hi, I have been reading about gravitational waves for the last few days. I saw any cylindrically or spherically... Sep15-14 12:42 PM WannabeNewton 1 202 A person in the earth (stationery frame) observes the clock in the spaceship (which almost moving at the speed of... Sep15-14 08:56 AM sweet springs 4 225 On the surface of a unit sphere two cars are on the equator moving north with velocity v. Their initial separation on... Sep15-14 08:50 AM peter46464 11 446 I just recently derived the metric tensor of the 4-sphere by embedding the coordinate system within 5D spherical... Sep15-14 03:30 AM ChrisVer 5 162 As you may know, the metric tensor for 3D spherical coordinates is as follows: g11= 1 g22= r2 g33= r2sin2(θ) ... Sep15-14 01:49 AM haushofer 2 210 Rephrase from another thread I posted a while back; If you believe as masses increase in distance gravitational... Sep14-14 11:08 PM Simon Bridge 1 229 I've been starting to look at the Hilbert action derivation of Einstein's equations, and have an introductory... Sep14-14 12:34 PM Orodruin 1 154 A train (source) approaching a stationery observer, wavelength of the sound is equal to the distance between source... Sep14-14 12:24 PM jtbell 2 132 While reading Special Theory of Relativity from Feynman Lectures, I fell into the confusion about invariant speed of... Sep14-14 09:31 AM jtbell 7 300 If I understand everything correctly, space near (but outside) a mass is curved negatively, so that if I create a... Sep14-14 07:06 AM Sonderval 5 235 This has come up in enough threads now that I feel the need to give my take on it in a convenient central location, so... Sep14-14 04:41 AM martinbn 21 1,088 Bending of Light due to Gravity ( 1 2 3 ... Last) Why does light bend due to gravity? I thought hard, read a lot and I found 3 reasons I can give as the answer. But... Sep13-14 09:26 PM DaleSpam 73 1,591 Pardon my elementary questions, but: Why is it that photons can only travel at the speed of light? I know because... Sep13-14 05:33 PM Nugatory 7 238 I am not sure whether this is a 'relativity' query as it may not be concerned with the order of events nor... Sep13-14 11:37 AM DaleSpam 32 617 I thought others might be interested in an old educational paper and fim demonstrating that you can't accelerate... Sep13-14 02:32 AM bahamagreen 4 295 I wanna prove the invariance of the Klein-Gordon Lagrangian \mathcal{L}=\frac 1 2 \partial^\mu \phi \partial_\mu... Sep12-14 06:43 PM samalkhaiat 7 284 http://i57.tinypic.com/2j5n9s4.jpg We’ve all seen this little fellas up there. Two brothers, twins, in their 60’s.... Sep12-14 02:22 PM stevenhaid 4 477 I’ve just read Schutz: “Gravitation from ground up”. He says that there are 4 (not all independent) sources of... Sep12-14 08:09 AM jedishrfu 1 196 For a long time I have studied and read about whether the photon has mass. On this forum, I could find a link to a... Sep12-14 06:39 AM stevendaryl 36 936 After my recent studies of the curvature of the 2- sphere, I would like to move on to Minkowski space. However, I can... Sep12-14 06:27 AM stevendaryl 10 412 According to a quote from a past Physics Forums article, 4D spacetime can be embedded isometrically (preserving the... Sep11-14 10:08 PM PAllen 4 279 Does anyone know why we are looking for dark mater - instead of say, modifying our laws of gravity to conform with... Sep11-14 06:08 PM ohwilleke 6 283 Thought experiment: Alice, Bob, and the planet Zolan. Alice is floating in space 10 light seconds from the planet... Sep11-14 02:44 AM ghwellsjr 6 516 Objects in motion relative to an inertial frame S are measured to have contracted lengths in S in the direction of... Sep10-14 11:29 AM CKH 18 642 Hi all. New to physics forum and glad to be here. I have been referencing the site for a while now and have finally... Sep10-14 04:40 AM pervect 17 465