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From an article in Fermilab Today:
Our universe is as mysterious as it is vast. According to Albert Einstein's theory of general relativity, anything that accelerates creates gravitational waves, which are disturbances in the fabric of space and time that travel at the speed of light and continue infinitely into space. Scientists are trying to measure these possible sources all the way to the beginning of the universe.
The Holometer experiment, based at the Department of Energy's Fermilab, is sensitive to gravitational waves at frequencies in the range of a million cycles per second. Thus it addresses a spectrum not covered by experiments such as the Laser Interferometer Gravitational-Wave Observatory, which searches for lower-frequency waves to detect massive cosmic events such as colliding black holes and merging neutron stars.
The absence of a signal provides valuable information about our universe. Although this result does not prove whether the exotic objects exist, it has eliminated the region of the universe where they could be present.
(Score: 2) by Immerman on Saturday April 11 2015, @03:49PM
Well, I could be wrong, but I believe that current most broadly-accepted hypothesis is that space expands everywhere at a constant rate, with the apparent acceleration being due simply to the fact that with every bit of expansion there is now more space between bodies to further expand. Assuming of course that there's no force pulling them together faster than the the space between them is expanding. But the effect is so small it really only becomes noticeable at intergalactic scales. It's estimated at ~74 km/s/megaparsec, (1 parsec ~= 3 million lightyears), or in somewhat more human terms, about 8 micrometers per century per kilometer. Little enough to be completely lost in the noise of any N-body problem, even with such a weak force as gravity. I suspect it will be a *very* long time before we can formulate instruments sensitive enough to determine whether space is actually expanding within galaxies, or only in deep intergalactic space where it's relatively flat.
It is an interesting question though, and I could see an argument to be made that, at the least, the expansion of space might be effected by the energy field density in the area, in an analogue to QM's virtual particles preferentially becoming "real" in energetically favorable situations: if space is quantized, then any time you create a "bit" of space between two attracting bodies you increase the potential energy between them. Deep in intergalactic space the change in potential energy associated with a newly-formed space-bit would be much smaller, and hence it's formation would appear much more energetically favorable.
As for expanding within atoms - it wouldn't matter. The subatomic particles can only exist at certain quantized distances from each other so if, say, the space between the electrons and nucleus expanded, the electrons would simply fall down to it's stable distance, possibly emitting an extremely low energy photon completely atypical of the atom's normal emission spectra, and then everything would be normal again. (I couldn't begin the guess the actual mechanics, but that's what I assume would happen if you suddenly crammed an extra "space-bit" inside it).
It also wouldn't matter if space expanded within a planet: atoms would move slightly further away from each other, giving a little more mobility, but nothing would stop them from immediately settling back down into a tightly-packed configuration due to gravity. It might keep the planet a little more tectonically active than it would otherwise be, but the rate of expansion is so slight that nothing will ever remotely approach escape velocity.
Orbital mechanics is pretty much the only thing operating on scales of time and space where it might make a difference, but with an orbital radius of 780 million km, the distance between Jupiter and the Sun would still be expanding at a rate of only 59m/yr... okay, I'll admit that's a LOT bigger than I assumed, but I just redid the math and it seems right... Hmm. So, I naively see two possibilities: either space is not expanding within the solar system, or it *is* expanding, but the planetary orbits are actually spiraling in at the same rate - i.e. what appears to be a stable orbit would actually be unstable in Newtonian space, suggesting that the sun is actually slightly more massive than Newtonian calculations from planetary orbits would suggest. It seems like we would have noticed such a thing with our probes though, especially considering the minuscule fluctuations in Voyager's acceleration that we've been able to detect. So that would seem to suggest that space doesn't actually expand locally (or at least expands much more slowly).