All Questions
Tagged with gravity general-relativity
2,007
questions
492
votes
21
answers
54k
views
How does gravity escape a black hole?
My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. I assume that the ...
- 5,039
161
votes
6
answers
55k
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Why would spacetime curvature cause gravity?
It is fine to say that for an object flying past a massive object, the spacetime is curved by the massive object, and so the object flying past follows the curved path of the geodesic, so it "appears" ...
- 1,926
132
votes
15
answers
35k
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How can anything ever fall into a black hole as seen from an outside observer?
The event horizon of a black hole is where gravity is such that not even light can escape. This is also the point I understand that according to Einstein time dilation will be infinite for a far-away-...
- 1,717
107
votes
11
answers
23k
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If gravity isn't a force, then why do we learn in school that it is?
I have studied some of Einstein's Theory of General Relativity, and I understand that it states that gravity isn't a force but rather the effects of objects curving space-time. If this is true, then ...
- 1,215
89
votes
6
answers
14k
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Why is light bent but not accelerated?
Light is bent near a mass (for example when passing close to the sun as demonstrated in the famous sun eclipse of 1919). I interpret this as an effect of gravity on the light.
However, it seems (to ...
- 1,133
87
votes
6
answers
9k
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If gravity is a pseudoforce in general relativity, then why is a graviton necessary?
As far as I’m aware, gravity in general relativity arises from the curvature of spacetime and is equivalent to an accelerated reference frame. Objects accelerating in a gravitational field are in fact ...
- 2,123
82
votes
13
answers
8k
views
Turbulent spacetime from Einstein equation?
It is well known that the fluid equations (Euler equation, Navier-Stokes, ...), being non-linear, may have highly turbulent solutions. Of course, these solutions are non-analytical. The laminar flow ...
- 7,592
81
votes
17
answers
59k
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How exactly does curved space-time describe the force of gravity?
I understand that people explain (in layman's terms at least) that the presence of mass "warps" space-time geometry, and this causes gravity. I have also of course heard the analogy of a blanket or ...
- 913
77
votes
6
answers
22k
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Does gravity CAUSE the bending of spacetime, or IS gravity the bending of spacetime?
In reading these discussions I often see these two different definitions assumed. Yet they are very different. Which is correct: Does gravity CAUSE the bending of spacetime, or IS gravity the ...
- 4,783
72
votes
6
answers
19k
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Why do we still need to think of gravity as a force?
Firstly I think shades of this question have appeared elsewhere (like here, or here). Hopefully mine is a slightly different take on it. If I'm just being thick please correct me.
We always hear ...
- 1,659
70
votes
2
answers
9k
views
Is spacetime flat inside a spherical shell?
In a perfectly symmetrical spherical hollow shell, there is a null net gravitational force according to Newton, since in his theory the force is exactly inversely proportional to the square of the ...
- 2,163
64
votes
6
answers
48k
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How exactly does gravity work?
The electromagnetic force and strong and weak forces require particles like photons and gluons. But in case of gravity there is no such particle found.
Every mass bearing object creates a ...
- 1,466
60
votes
4
answers
31k
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Does a photon exert a gravitational pull?
I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull ...
- 2,808
56
votes
3
answers
13k
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Why can't I do this to get infinite energy?
I know that I cannot do this because of conservation of energy, so I am looking for an answer as to why this will not work.
So by my understanding of Einstein's whole famous $E=mc^2$ thing it is ...
- 871
55
votes
4
answers
3k
views
GR and my journey to the centre of the Earth
[General Relativity] basically says that the reason you are sticking to the floor right now is that the shortest distance between today and tomorrow is through the center of the Earth.
I love ...
- 643