All Questions
385
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Does it make sense to talk about time in absence of matter? [duplicate]
The equations of general relativity should predict (although I might be wrong) that in absence of mass the spacetime is everywhere flat. That is, time is the same everywhere. However, I'm not sure ...
- 145
-3
votes
1
answer
70
views
Does quantum entanglement arise from perpendicular time vectors? [closed]
From what I understand, "quantum entanglement" is a phenomenon where certain information travels instantly between entangled particles, regardless of distance in space.
When thinking of ...
- 413
0
votes
1
answer
78
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Does time arising from entropy agree with GR?
There's a theory that the direction of time arises from entropy and the correlations (interactions) between bodies. However, I don't see how this would incorporate the effects of General Relativity, ...
- 185
1
vote
2
answers
70
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How do I interpret the time axis in a diagram with multiple light cones?
Light cones are often drawn on a spacetime diagram that has a directional time axis like the fourth one on this page:
There is a time axis, and all of the light cones are align with it because this ...
- 113
1
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0
answers
52
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Relativity explained using sound instead of light
A friend of mine asked me to explain Einstein relativity to him, and I tried to use a methaphore using sound, however for some reason it does’t quite work:
imagine there are 2 people with a clock, ...
- 111
3
votes
1
answer
122
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What is the problem with two time dimensions? [duplicate]
I am reading a book "General relativity: The theoretical minimum" by Leonard Suskind.
In page 168-169, the author explains the reason why we don't consider the case with two time dimensions ...
- 311
0
votes
2
answers
554
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Can we define time as a field? [closed]
The main objective is, can we relate time in terms of a field, I know time differs in many properties from an usual field. But I always imagine time as an forward moving field and we all know it is ...
- 47
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1
answer
176
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Can we consider that the photons that were not and will never be detected live in a zero-dimensional space? [closed]
According to Einstein’s theory of relativity, any particle traveling at the speed of light experiences no passage of time. It follows that if a photon travels through space then within any two points ...
- 115
-2
votes
2
answers
102
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Is spatial distance objective?
While reading some papers on Einstein's theory of relativity, seeing how the flow of time is not the same for everyone, a doubt occurred to me:
Let us imagine a photon moving in a well-defined space ...
1
vote
1
answer
92
views
What happens if we let time expand in the FLRW metric?
If we multiplied the time differential (dt) by a scale factor that depends on time in the FLRW metric, what would this imply on cosmology? In particular, what are its implications on the cosmological ...
- 468
8
votes
1
answer
357
views
The synchronized clocks on earth's surface: at which observer's rate are they beating?
From what I understand, the time rates (I'm not speaking about absolute times) of all clocks on earth's surface are synchronized. This means that, say, a mobile phone's clock is generally not beating ...
- 3,743
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2
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119
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Time in the Standard Model of Cosmology
Beyond a formal preference for background independence, what is stopping us from setting cosmological time as a de facto universal timeline, analogous to newtonian absolute time? General relativity ...
- 1
0
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0
answers
36
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Product of two 4 positions without writing the components
I was able to solve the first part of the following question by expanding the terms as vectors
I can't understand how to do it without expanding so I had a look at the answers.
I understand how we ...
- 13
2
votes
2
answers
293
views
Time in the negative mass Schwarzschild solution
I have read that for the Schwarzschild metric solution with $M<0$, something odd happens with the time coordinate. For the constants of motion, $dt/d\tau=e(1 - 2GM/r)^{-1}$ with $M<0$ and $e$ a ...
- 466
1
vote
0
answers
74
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Why can't the metric have more than one timelike coordinate? [duplicate]
In one of his lectures, L Susskind stated that he cannot make sense of a metric with more than one timelike dimension. I also have trouble imagining it, but is there a good mathematical or physical ...
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