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Nov
18
revised Movie Interstellar - Question about Escape Velocity
added 6 characters in body
Nov
18
comment Advantage and disadvantage of weak field approximation
Linearized gravity is basically just electrodynamics with a tensor field instead of a vector field (i.e. $h_{\mu \nu}$ instead of $A_\mu$). With appropriate gauge choice the field equations reduce to a wave equation similar to Maxwell's equations for the four-potential.
Nov
18
revised Movie Interstellar - Question about Escape Velocity
added 77 characters in body
Nov
18
comment Movie Interstellar - Question about Escape Velocity
@CarlWitthoft His question is perfectly fine, and the physics here is perfectly well-defined. I don't understand your objection.
Nov
18
answered Movie Interstellar - Question about Escape Velocity
Nov
18
comment Most general second-rank symmetric tensor in Einstein theory
You could also include higher-order terms, i.e. terms like $g_{\mu \nu} R^2$, $g_{\mu \nu} R^{\alpha \beta} R_{\alpha \beta}$, etc. But once you include those you aren't talking about GR anymore.
Nov
18
comment What Would Negative Mass Do To Spacetime?
Newton's inverse-square law is equivalent to general relativity in the limit where everything is moving slowly and the gravitational field is weak. So, the first (and easiest) thing to check would be to see what happens if you plug a negative mass into Newton's gravity law. The answer, of course, is repulsive gravity. I.e. a negative mass would be repelled by ordinary matter.
Nov
17
comment Derivation of correction to canonical stress energy tensor due to addition of total divergence to Lagrangian
How about these: research.physics.illinois.edu/Publications/theses/copies/… research.physics.illinois.edu/Publications/theses/copies/…
Nov
17
comment How is strong time dilation consistent with weak tidal forces?
No problem. Don't worry about the points, they don't particularly matter to me.
Nov
17
comment How is strong time dilation consistent with weak tidal forces?
Actually (axial) tidal forces fall off as $1/r^3$ to leading order. But that just highlights your point further.
Nov
17
comment How is strong time dilation consistent with weak tidal forces?
A body in orbit doesn't feel the force of gravity, save tidal forces. That's why astronauts in the ISS are weightless! :)
Nov
17
revised Time Dilation Experiment
added 190 characters in body
Nov
17
answered Time Dilation Experiment
Nov
17
comment Time Dilation Experiment
It would help if you described what you meant by "nullify" the effects of time dilation. Relative to a stationary observer at infinity, both gravitational and velocity-related effects work to slow clocks, so there is never any sense in which they cancel each other. Or did you mean relative to a stationary observer on Earth? The latter is do-able. I'll post how below.
Nov
17
answered The virtual particles are only a fictive tool in equations? DO they exist or DON'T? And if they exist, why do we call them VIRTUAL?
Oct
23
comment Having trouble understanding some stuff about delta functions
Haha, you beat me.
Oct
23
answered Having trouble understanding some stuff about delta functions
Oct
13
answered Transformation to a uniformly rotating frame
Oct
13
comment What is $V^\mu$ if $\nabla_{\mu} V^{\mu}$=scalar?
I'm not sure what you mean. $V^\mu$ is a vector with components $V^0$, $V^1$, $V^2$, $V^3$.
Oct
11
comment Special Relativity: Finding the Euler Lagrange of a massive particle
I don't understand this. You can certainly choose $\lambda = \tau$ if you want to.