All Questions
Tagged with spacetime general-relativity
1,867
questions
163
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9
answers
40k
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Does someone falling into a black hole see the end of the universe?
This question was prompted by Can matter really fall through an event horizon?. Notoriously, if you calculate the Schwarzschild coordinate time for anything, matter or light, to reach the event ...
- 358k
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
125
votes
6
answers
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What is known about the topological structure of spacetime?
General relativity says that spacetime is a Lorentzian 4-manifold $M$ whose metric satisfies Einstein's field equations. I have two questions:
What topological restrictions do Einstein's equations ...
- 1,734
98
votes
9
answers
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What is a manifold? [closed]
For complete dummies when it comes to space-time, what is a manifold and how can space-time be modelled using these concepts?
- 1,095
82
votes
13
answers
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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 ...
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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
77
votes
3
answers
7k
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Is there 'friction' in spacetime?
So, if all the bodies are embedded in space-time and moves through it, is there some kind of 'friction' with space time of the planets? For example, the Earth suffers friction when moving near the sun ...
- 4,747
71
votes
2
answers
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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 ...
- 2,173
68
votes
7
answers
20k
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Do photons bend spacetime or not?
I have read this question:
Electromagnetic gravity
where Safesphere says in a comment:
Actually, photons themselves don't bend spacetime. Intuitively, this is because photons can't emit ...
- 29k
59
votes
11
answers
14k
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Is spacetime wholly a mathematical construct and not a real thing? [closed]
Speaking of what I understood, spacetime is three dimensions of space and one of time. Now, if we look at general relativity, spacetime is generally reckoned as a 'fabric'. So my question is, whether ...
- 639
55
votes
4
answers
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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 ...
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48
votes
9
answers
29k
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Why is the gravitational force always attractive?
Why is the gravitational force always attractive? Is there another way to explain this without the curvature of space time?
PS: If the simple answer to this question is that mass makes space-time ...
- 1,772
47
votes
15
answers
8k
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Why does the speed of an object affect its path if gravity is warped spacetime?
I think I understand the idea of thinking about gravity not as a force pulling an object towards another object but instead a warping of space so that an object moving in a straight line ends up ...
- 579
42
votes
2
answers
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How does classical GR concept of space-time emerge from string theory?
First, I'll state some background that lead me to the question.
I was thinking about quantization of space-time on and off for a long time but I never really looked into it any deeper (mainly because ...
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