All Questions
Tagged with spacetime general-relativity
1,867
questions
4
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624
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How is the complexification of spacetime justified?
As always the caveat is that I am a mathematician with very little knowledge of physics. I've started my quest for knowledge in this field, but am very very far from having a good grasp.
General ...
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20
votes
2
answers
3k
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Is spacetime simply connected?
As I've stated in a prior question of mine, I am a mathematician with very little knowledge of Physics, and I ask here things I'm curious about/things that will help me learn.
This falls into the ...
- 847
48
votes
9
answers
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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
1
vote
1
answer
244
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Can spacetime be defined by the requirement that the physical laws are simple?
When I was student I was told that time is defined by the requirement that the physical laws are simple. For example, in classical mechanics time can be defined by the requirment that the velocity of ...
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3
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What is meant when it is said that the universe is homogeneous and isotropic?
It is sometimes said that the universe is homogeneous and isotropic. What is meant by each of these descriptions? Are they mutually exclusive, or does one require the other? And what implications rise ...
- 3,439
11
votes
3
answers
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Gravitational time dilation at the earth's center
I would like to know what happens with time dilation (relative to surface) at earth's center .
There is a way to calculate it?
Is time going faster at center of earth?
I've made other questions ...
- 2,909
5
votes
1
answer
2k
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Voyager local time dilation (caused by gravity)
Voyager I, as an example, taking account gravity
and setting aside effects of speed as cause of time dilation.
If it is very far away from earth and sun,
so then there must be a difference in the ...
- 2,909
0
votes
1
answer
222
views
Is relativistic motion equivalent to fluctuating gravitational fields?
The theory of relativity makes very precise predictions about how an object's motion through space-time affects the passage of time for both the object and observers in other frames of reference.
I ...
- 109
2
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1
answer
186
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Does the recent Gravity Probe - B mission mean both the mass of an object and the spin of an object affect time?
I'm a non-engineer interested in the recent GP-B mission results: http://www.engadget.com/2011/05/06/nasa-concludes-gravity-probe-b-space-time-experiment-proves-e/#disqus_thread
Is it correct that ...
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18
votes
2
answers
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Can a non-Euclidean space be descripted through an Euclidean space of higher dimension? So why use non-Euclidean?
If you draw a big triangle in Earth 2D surface you will have an approximated spherical triangle, this will be a non euclidean geometry.
but from a 3D perspective, for example the same triangle from ...
- 2,909
5
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2
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Space-like Killing vector of Robertson-Walker metric?
In the book "Kinetic theory in the expanding Universe" (J. Bernstein, 1988, Camb. Univ. Press), it was stated that
"for nonstationary Robertson-Walker
matrixes [sic] there is no spacelike
...
- 151
5
votes
5
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2k
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How does the curvature of spacetime induce gravitational attraction?
I don't know how to ask this more clearly than in the title.
- 6,044
0
votes
3
answers
1k
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Space as "flat" plane
I was watching the documentary Carl Sagan did about gravity (I believe it's quite old though) and wondered about space being "flat" and that mass creates dents in this plane as shown at about 3 ...
- 6,927
9
votes
3
answers
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The Big Bang in an infinite universe
If the universe is spatially infinite (and assuming, if it makes a difference, that we don't have eternal inflation), what actually happened 13.7 billion years ago? Was the energy density infinite (or ...
- 3,356
6
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2
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How could spacetime become discretised at the Planck scale?
I didn't have much luck getting a response to this question before so I have tried to reword and expand it a little:
In early 2010 I attended this inaugural lecture by string theorist- Prof. ...
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