All Questions
Tagged with speed-of-light general-relativity
292
questions
2
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1
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161
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When you are in a gravitational field, do object far away get physically closer to you as you get closer to the mass?
An observer A is close to a black hole and an observer B one light year away. They are both remaining at constant radial distance from the black hole. A is at 2 Rs away from the center of the black ...
- 171
1
vote
2
answers
126
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If the speed of causality changes, could you go FTL?
In the middle of some research, I reached a sort of confusion that I’d like to sort out. In flat space FTL is impossible, because in a Minkowski metric,
$$\mathrm{d}s^2=c^2 \mathrm{d}t^2-\mathrm{d}x^2-...
- 689
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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
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1
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85
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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 ...
4
votes
3
answers
1k
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Is the meter relative to time?
Is the meter relative when we are near the speed of light?
I was reading a physics book and I found that the meter is the length that light travels for an amount of time, so since time is relative ...
5
votes
1
answer
90
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Would the effective speed of an Alcubierre drive be limited by the propagation speed of gravity?
The idea of a warp drive is to "expand space behind the ship and contract it in front"- in this way reaching a target destination faster than one could conventionally. However, the actual ...
- 87
6
votes
2
answers
182
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General relativity vs newtonian mechanics [duplicate]
My high school textbook briefly touched the topic of black holes, and this is how it defined them:
"Consider a spherical body of mass $M$ and radius $R $. Suppose,due to some reason the volume ...
- 294
1
vote
0
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69
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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
3
votes
4
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835
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Gravitational Time Dilation and the Apparent Speed of Light
It has been proven that time far away from Earth is faster than time on the surface of Earth, due to gravitational time dilation. (GPS satellites take gravitational time dilation to account.)
Would ...
- 141
3
votes
1
answer
109
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Spacetime that allows matter to rotate faster-than-light
Is there a solution to Einstein's equations which allows:
the object to be rotating at sub-light speed when viewed from within itself.
for a distant observer the object to rotate at superluminal ...
- 131
2
votes
0
answers
61
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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 ...
0
votes
1
answer
76
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Is it more accurate to say space in a weaker gravitational field is contracted, or that time is faster?
Little thought experiment. An observer places a mirror and a clock 1 lightyear away from a black hole. He then goes in the black hole's gravitational field at a point where he sees the clock tick at 2 ...
- 171
-4
votes
1
answer
109
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What would happen if the aether did exist and there was no such thing as relativity? [closed]
I'm curious as to the purpose of relativity and why the universe would function this way as opposed to a universe with an aether. So what would be different if we had an aether?
- 361
2
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0
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76
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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
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What could a year long journey look like, while traveling near the speed of light, through the lens of that telescope?
Hypothetically speaking if you had a satellite going near the speed of light in a straight line towards an exoplanet light years away and that satellite had a telescope pointed at the surface of an ...
