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A theory that describes how matter interacts dynamically with the geometry of space and time. It was first published by Einstein in 1915 and is currently used to study the structure and evolution of the universe, as well as having practical applications like GPS.

2
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The answer is no; you can't have both equal to 1 in the equation you gave, but you can if you introduce $R_0$, as follows. Friedmann-Lemaitre-Robertson-Walker metric is $$ { ds^2 = -c^2 dt^2 + a^2(t) …
answered Apr 23 by Andrew Steane
1
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The effective refractive index idea is not at all about electrodynamics, or dielectric constant, or anything like that. It is simply a nice way to calculate null geodesics. That is what it is, and tha …
answered Jan 3 by Andrew Steane
1
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The (completely general) formula for red shift in GR is $$ \frac{\omega_B}{\omega_A} = \frac{ p_\mu(B) v^\mu(B) }{ p_\mu(A) u^\mu(A) } $$ where $p$ is the 4-momentum of the photon traveling from A to …
answered Jan 30 by Andrew Steane
0
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The phenomenon called gravitational red shift tells you most of what you want to know. What happens is that if the camera is on a planet where one hour corresponds to 7 years on Earth, then a viewer …
answered Jun 8 by Andrew Steane
26
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The horizon that forms for a constantly accelerating frame in flat spacetime is a beautiful thing; it teaches all sorts of helpful lessons about G.R. I think the nicest way to appreciate it is to take …
answered Nov 14 '18 by Andrew Steane
4
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Yes we do really know, and the answer is that causal influences cannot travel faster than the maximum speed. Light in vacuum travels at this maximm speed, so we say that nothing can travel faster than …
answered Jun 10 by Andrew Steane
1
vote
A previous answer contains some correct statements but does not clearly answer the question IMO, so here goes. In the equation $$G^{\text{B}}_{\mu \nu} = 8 \pi \left(T^{\text{GW}}_{\mu \nu} + T^{\te …
answered Jun 14 by Andrew Steane
1
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Ben Crowell's answer is right, but I am adding a point in order to emphasize it, because this issue keeps coming up. Here is the point: The cosmological expansion is FREE FALL motion. What this mean …
answered Feb 15 by Andrew Steane
1
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This will extend the answer of Brick a little. It is possible to disturb the region of spacetime beyond the horizon of a black hole, either by sending gravitational waves into it or simply by droppin …
answered Jul 11 by Andrew Steane
0
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The way your question is phrased might be applied to something more familiar, namely electromagnetism. There you have an electromagnetic field which exerts a force on charged matter. But it does not f …
answered Apr 30 by Andrew Steane
0
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Some of your questions also arise in the case of static spacetime which is easier to understand. On the cosmic scale spacetime is not static, but I'll treat the static case first and then answer for t …
answered Mar 19 by Andrew Steane
4
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This is not a full answer, since I don't know the full answer, but it is more than a comment. My contribution is to compare your question with another, simpler one, and then come back to yours. 1. O …
answered Jan 12 by Andrew Steane
0
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Ben Crowell's answer is right. I hope I can clarify a little. If one starts from the following two assumptions: $R_{ab} = 0\;$ (i.e. field equation in vacuum) The metric can be written in the form …
answered Jul 2 by Andrew Steane
4
votes
Yes, both $r$ and $t$ in Schwarzschild coordinates have puzzling features, but perhaps $t$ more than $r$ as you say. The first part of the answer is simply to say that these are coordinates, which mea …
answered Jun 20 by Andrew Steane
1
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The answers already given are correct, but I will elaborate a little in hopes of giving some physical insight. It is a common misconception to think that zero $R_{ab}$ implies no curvature, or that z …
answered Nov 8 '18 by Andrew Steane

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