Timeline for Can a difference in the "speed of time" introduce acceleration?
Current License: CC BY-SA 3.0
17 events
| when toggle format | what | by | license | comment | |
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| Jun 30, 2014 at 2:27 | comment | added | Freudian Slip | @JohnRennie I've rolled back my edits and asked the revised version as a new question, in case anybody wants to take a crack at it. physics.stackexchange.com/questions/122392/… | |
| Jun 29, 2014 at 9:58 | comment | added | Valter Moretti | I also voted to reopen. | |
| Jun 29, 2014 at 9:58 | comment | added | John Rennie | @V.Moretti: I was a bit surprised the question was closed. It's a confused question but the underlying concept is interesting. Anyhow I've voted to reopen - we just need two more votes. | |
| Jun 29, 2014 at 9:54 | comment | added | Valter Moretti | It is a pity that i cannot answer. The answer is important because it reflect exactly what is going on in our actual universe! Our universe is a FLRW spacetime with (large scale) flat spatial sections! However galaxies accelerate, in this sense acceleration is due to "time curvature". | |
| Jun 29, 2014 at 7:34 | history | edited | John Rennie | CC BY-SA 3.0 |
Attempt to improve clarity
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| Jun 28, 2014 at 21:25 | comment | added | Dilaton | The OP is NOT of the mark, as what goes into the Einstein equations is curvature of spacetime and not curvature of space only. | |
| Jun 28, 2014 at 19:04 | comment | added | Freudian Slip | @JohnRennie: I realize you must be correct, my ignorance on the subject is astounding. But if something can curve space and not time, then the only thing you would need to introduce a curvature in time w/o space would be to negatively curve the space in an area. Or is that the part that isn't possible? | |
| Jun 28, 2014 at 18:53 | comment | added | John Rennie | @FreudianSlip: the local speed of light is always $c$ because spacetime is always locally flat. | |
| Jun 28, 2014 at 18:50 | comment | added | Freudian Slip | @JohnRennie: Wait, how can it curve space but not time? Wouldn't that change the local speed of light? I thought the whole reason that both time and space needed to curve were to preserve the constancy of the speed of light. | |
| Jun 27, 2014 at 0:05 | vote | accept | Freudian Slip | ||
| Jun 26, 2014 at 15:58 | comment | added | John Rennie | @FreudianSlip: gravity generally curves both time and space, but if you could come up with a gravitational field that only curved time then yes it would cause acceleration even in flat space. In other words time curvature alone can cause acceleration. The only problem is I don't know any way to curve time without curving space as well. The other way round is easy as the FLRW metric curves space but not time. | |
| Jun 26, 2014 at 14:28 | comment | added | Freudian Slip | The only condition I can think of that would cause a difference in the speed of time would be gravity, and that already introduces an acceleration. I'm just curious about whether time dilation adds any additional acceleration to a system | |
| Jun 26, 2014 at 10:07 | history | edited | John Rennie | CC BY-SA 3.0 |
Add footnote
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| Jun 26, 2014 at 10:02 | comment | added | John Rennie | @ChrisWhite: yes, true. I'll clarify my answer. | |
| Jun 26, 2014 at 9:59 | comment | added | user10851 | Flat spacetime in non-Cartesian coordinates also has nonzero Chrisoffel symbols. For example in spherical coordinates, 9 of the 64 symbols are nonzero. Not that this thwarts the argument. | |
| Jun 26, 2014 at 9:20 | history | edited | John Rennie | CC BY-SA 3.0 |
Qualification
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| Jun 26, 2014 at 8:49 | history | answered | John Rennie | CC BY-SA 3.0 |