Timeline for To what extent does trajectory determine gravity sources?
Current License: CC BY-SA 3.0
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| Feb 9, 2013 at 5:11 | comment | added | user21349 | Or take a Newtonian spacetime with countably many identical point masses distributed on an infinite cubical lattice, all initially at rest relative to their neighbors. By symmetry, no information is recoverable from observing the motion of one such mass relative to the others. We can replace one of the masses with a test particle of negligible mass, and the test particle will still never accelerate relative to the average of the others. If the space has the topology of a torus, the number of masses can be made finite. | |
| Feb 9, 2013 at 2:10 | comment | added | Joel David Hamkins | Yes, so let's not take this answer as the end of the story. | |
| Feb 9, 2013 at 1:59 | comment | added | Abhinav Kumar | I think the question is restricting to point masses (as opposed to spread-out regions, like shells). Otherwise one could also use the same argument to replace any point mass by a ball of the same mass (as long as the trajectory does not intersect it). | |
| Feb 9, 2013 at 1:50 | history | answered | Joel David Hamkins | CC BY-SA 3.0 |