# Special & General Relativity

- Dependence of various physical phenomena on relative motion of the observer and the observed objects. Exp. & theo. theories of relativity
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### Relativity FAQ

Common Relativity questions, quality answers
Jul24-14 09:06 AM Greg Bernhardt
 Meta Thread / Thread Starter Last Post Replies Views Views: 5,681 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 42,794 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 42,431 If the effects of gravity are relative to an objects stress-energy-momentum tensor, is the equation: Fg = Gm1m2/r^2... Jan31-14 12:00 AM Nugatory 3 534 Hey guys, I just want to ask a quick question that confuses me a bit regarding the twin paradox. During acceleration,... Jan30-14 04:27 PM pervect 32 1,131 Hello All, would anyone know an expression for the heat capacity of an ideal gas, moving with relativistic speeds.... Jan30-14 10:30 AM Sunfire 10 463 I have a question; If two particles (let's say protons) collide at high speed, they can produce heavy particles, like... Jan29-14 08:10 PM Herbascious J 7 567 ...is the impression that "God plays dice with the universe" an illusion? If all time in the universe is already... Jan29-14 05:29 PM ZapperZ 12 929 I remember I have read somewhere that contravariant/covariant vectors correspond to polar/axial vectors in physics,... Jan29-14 02:38 PM WannabeNewton 7 812 In http://arxiv.org/abs/0808.1081 / Am.J.Phys.77:688-694,2009 Bunn and Hogg explain how cosmological redshift can be... Jan29-14 08:33 AM PAllen 13 1,110 We know the equation E=mc^2 which correlates energy to mass. If we rearrange the equation: E/m = c^2 , it turns into... Jan29-14 06:03 AM BruceW 4 391 General relativity talks about curvature of space-time due to mass. What does it actually mean by 'curve'. Is the... Jan29-14 04:55 AM nalA 24 1,388 I found a funny video on youtube, but I am not totally convinced by the argument. ... Jan28-14 05:26 PM pervect 11 597 The Michelson Moorley experiment to detect the presence of aether is the main experiment that gave rise to the theory... Jan28-14 03:58 PM Paul77 3 434 I've asked this question a few times. This time i have tiny change in the question. Instead of people I'm using... Jan28-14 03:30 PM PAllen 118 4,666 Here is another train and platform example, offered to examine ghwellsjr's view equating what you see with what is... Jan28-14 02:34 PM phyti 31 1,056 Is there a coordinate independent/geometric definition of a tensor density? Jan28-14 10:45 AM bcrowell 3 302 Due to the diffeomorphism invariance of GR ##(M, g_{ab})## and ##(M, \phi_*g_ab)## represents the same physical... Jan28-14 08:37 AM center o bass 0 273 Here's the scenerio: you have box (shape is not necessarily important, but for simplicity we'll say its a cube),... Jan28-14 08:15 AM PAllen 19 991 Yesterday, I read about Hawking's new proposal regarding the firewall paradox. A more general thought about... Jan28-14 06:09 AM PeterDonis 4 481 Hi, I would like to share you this video http://video.mit.edu/watch/michelson-interferometer-6561/ By this... Jan28-14 05:11 AM powermind 0 385 See below. I screwed up the edit and the use of tex. Jan27-14 07:20 PM TimeFall 3 301 Imagine two asteroids which are separed by 1Ly distance. They are in uniform velocity (.9c) with respect to an observe... Jan27-14 01:17 PM salvador_dali 13 611 Hi, I'm trying to write down the stress-energy tensor for a single photon in GR, but I'm running into trouble with... Jan27-14 11:44 AM bcrowell 5 463 Observers Alice and Bob are hovering far above the event horizon of a block hole. Alice stops hovering and enters... Jan27-14 09:56 AM PAllen 546 33,387 Ive Heard that things can get mass when moving in speeds Close to c. So I have question. Lets say we have to... Jan27-14 09:38 AM Drakkith 16 551 An intuitive gravity analogy that explains why the moon orbits the earth is, the earth's mass' effect on space creates... Jan27-14 05:09 AM A.T. 5 443 Hi, i'm new to this, so i'm hope this is how this works. But I had a question. I've heard that even theoretically,... Jan26-14 11:09 PM ZapperZ 18 1,005 I have heard many physicists (ex:- Michio Kaku) saying "Warp speed" from Star Trek doesn't violate any known physical... Jan26-14 05:31 PM JesseM 6 540 I had a discussion regarding the region of spacetime visible to an observer falling into aSchwarzschild black hole.... Jan26-14 03:30 PM JesseM 18 1,373 If the tangent space at p is a true vector space, then it must be that the sum of two vectors is itself a directional... Jan26-14 01:45 PM WannabeNewton 2 314 Hi all. I'm a run-of-the-mill layman—not a student. I've just developed an interest in physics lately and have been... Jan26-14 10:33 AM Incognito310 20 1,182 So I just started taking Modern Physics and we are currently discussing special relativity. And needless to say, its... Jan26-14 09:28 AM ghwellsjr 13 656 Hey everyone, for anyone who saw my thread in the chemistry section you know I'm changing my view point to that of the... Jan26-14 05:45 AM llynne 5 516 Hello, Lately I have been wondering about the implications of the speed of light being constant for all observers,... Jan26-14 02:19 AM ghwellsjr 12 560 Hello, I was reading a book about general relativity and I came across these two equations  \begin{align} ... Jan25-14 04:37 PM direct99 5 389 According to general relativity, if a remote observer monitors an object falling onto a black hole, (s)he will never... Jan25-14 03:12 PM phinds 6 380 Hi. I know that space for an object in motion will contract, relative to an observer. We generally read that space... Jan25-14 02:29 PM Mentz114 62 1,803 How do you find the inverse of metric tensor when there are off-diagonals? More specifivally, given the (Kerr)... Jan25-14 10:48 AM Nabigh R 4 569 Tensors can be of type (n, m), denoting n covariant and m contravariant indicies. Rank is a concept that comes from... Jan24-14 09:50 PM jcsd 4 331 Hi, I'm trying to understand why the metric I've seen for AdS space,... Jan24-14 11:38 AM copernicus1 0 236 From what I learned watching Brian Greene's "Fabric of the Cosmos" episode on Nova, if you look at spacetime like a... Jan23-14 08:56 PM PeterDonis 3 459 This is about Hans Ohanian, "Einstein's E = mc2 mistakes," http://arxiv.org/abs/0805.1400 , a historical paper that... Jan23-14 06:03 PM bcrowell 0 253

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