Originally posted by ImaFungi
how do you know space deforming in the way we observe it at least,, is not a result of velocity/momentum?
in other words how do you know that the space which is gravitationally indented in the vicinities of the earth- moon distance... would be deformed to
the same magnitude as if the bodies were stationarily at the earth-moon distance from one another?
That's the part in my prior post where I disclaimed other outliers such as the bodies being relativistic in some way. Momentum comes in to the
stress-energy tensor, but not enough under "normal" circumstances to be more than a unicorn poot. If the bodies are more or less at rest wrt each
other, these things don't cause measurable effects.
Same thought experiment... but perhaps adjust the ratio of distance,, and replace the earth mass bodies, with 2 atoms.... do atoms have gravity? do
atoms attract in this situation? do they attract from a force other then gravity?
Do they have gravity, yes. Do they attract in that situation, yes. Is that attraction of a magnitude that could ever be measured on an atom-by-atom
pair basis, no, because gravity is a weak force. Do they attract from a force other than gravity, absolutely, two atoms mostly interact through
electric fields when they do, with the occasional bit of magnetic field coupling.
There are a number of ways in which this can happen, either in a macroscale way (ionic or covalent bonding) or in weird minor ways (London dispersion
force, magnetic dipole-dipole interactions etc).
The weakest of these forces totally swamp out inter-atomic gravity. However, if you've got a lot of material, and a lot of time, and not much else
really disturbing the pot, then gravity will cause the material to coalesce. That's how stars are formed.
edit to add:
When you've got enough of them in one place, you obviously can observe a mass of atoms attracting another mass of atoms - which is why you have
weight. But on an atom by atom basis, it's not a big factor in how they interact.
edit on 14-11-2012 by Bedlam because: (no reason