All Questions
92
questions
0
votes
2
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83
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How could I calculate the time it will take for light and mass to go towards a black hole and come back, to and from constant radial distances?
If you have a "perfect mirror" and a "perfect trampoline" at some constant distance outside a black hole's event horizon:
a) How would a shell observer at some distance farther ...
- 171
0
votes
1
answer
85
views
Questions about speed of gravity [duplicate]
If gravity "travels" at $c$, and the sun is travelling "forward", does it mean the planets are actually orbiting various points "behind" the center of the sun? Does it ...
1
vote
0
answers
69
views
Does squeezed light gravitate repulsively? [closed]
Since there are alternate regions of positive and negative energy densities in squeezed light, does that mean that the negative energy density parts gravitate repulsively? Since the stress energy ...
- 135
2
votes
0
answers
61
views
How much of an observer's field of view will be black upon crossing an event horizon? [closed]
The aberration of light will cause an observer to still see a black hole as "distant" when the event horizon is crossed.
This means that if the observer looks directly toward the center of ...
2
votes
0
answers
76
views
Newton-Cartan from GR
How does EFE reduce to Newton-Cartan Field Equation $R_{tt}=4\pi G \rho$ in Newtonian Limit? I understand its direct derivation from geodesics in weak field, what I am curious about is how EFE reduces ...
- 1,161
0
votes
0
answers
27
views
Black Holes and Gravity [duplicate]
We know that nothing including light can escape the gravitational pull of black hole. Now special relativity says that nothing travels faster than speed of light. Then how can effects of gravity due ...
-2
votes
3
answers
103
views
Can gravity make something faster than light? [duplicate]
Scenario,
Let's say we have complete vacuum and nothing in the universe.
If we place 2 bodies at infinite separation and have HUGE masses ($m1, m2 \sim 10^{1000}$ kg or something):
They will attract.
...
- 1
-1
votes
3
answers
197
views
How much mass is needed to make the speed of light equal to 1 mile per second?
The speed of light in special relativity is a constant, 186,000 miles per second, but in general relativity, "the speed of a light wave depends on the strength of the gravitational potential ...
- 29
0
votes
2
answers
90
views
What happens when an object being accelerated by gravity begins to approach light speed? [closed]
Imagine you have a pair of 2-dimensional circular portals, with one placed perfectly above the other (practically the same as portals in the Portal games). A spherical object is held between the ...
- 128
2
votes
1
answer
98
views
How much time does it take for the gravitons generated by a black hole singularity to travel before exerting gravity forces on other celestial bodies?
It is known to all that the travelling speed of gravitons (the propagation speed of gravitational field) is not instant. So for black holes, the gravitons (the gravitational field) generated by the ...
6
votes
0
answers
52
views
Why is the speed of gravity the same as the speed of light? [duplicate]
Why is speed of gravity the same as the speed of light, can anyone explain in simple terms?
- 199
0
votes
3
answers
86
views
How can gravity change the wavelength of a photon without the two peaks or troughs to accelerate one from the other?
How can gravity change the wavelength of a photon without the two peaks or troughs to accelerate one from the other? So is it possible that gravity accelerates light? Can the a certain wavelength ...
- 467
1
vote
1
answer
53
views
Under PPN Formalism, would the gravity of a mass double as its velocity approaches $c$?
I'm looking at the answer Michael gave to my question. Does this imply that under parameterized post-Newtonian formalism, under the $β1$ factor for kinetic energy, the gravity of a mass doubles as it ...
- 4,783
1
vote
0
answers
44
views
Speed of light in presence of gravity [duplicate]
In the special relativity it is postulated that the speed of light in vacuum is constant in all directions. This postulate is motivated by the Michelson-Morley experiment.
As far as I understand (am I ...
- 2,226
1
vote
2
answers
77
views
If a star passes near another star will that star feel gravitational influence immediately or with a delay? [duplicate]
If a star passes near another star will that star feel gravitational influence immediately or with a delay? Assuming that the distance is a large number and the stars are very massive?
- 2,255