CharlieM wrote:

Calilasseia:
Indeed, this expansion of the fabric of space-time is taking place inside your body as you speak. It's taking place inside the atoms of your body. The reason you don't notice it is because, on a local scale, the expansion is extremely tiny...

Maybe this site should change its name from rationalskepticism to selectiveskepticism. Am I the only one here that is skeptical of this statement. If individual atoms are still moving apart due to the same forces that caused the universe to expand in the first place, how on earth did matter manage to coalesce. The Hubble constant doesn't even apply to local groups of galaxies let alone atoms.

Local perturbations
The expansion of space is sometimes described as a force which acts to push objects apart. Though this is an accurate description of the effect of the cosmological constant, it is not an accurate picture of the phenomenon of expansion in general. For much of the universe's history the expansion has been due mainly to inertia. The matter in the very early universe was flying apart for unknown reasons (most likely as a result of cosmic inflation) and has simply continued to do so, though at an ever-decreasing rate due to the attractive effect of gravity. In addition to slowing the overall expansion, gravity causes local clumping of matter into stars and galaxies. These stars and galaxies do not subsequently expand, there being no force compelling them to do so. There is no essential difference between the inertial expansion of the universe and the inertial separation of nearby objects in a vacuum; the former is simply a large-scale extrapolation of the latter. A uniform local "explosion" of matter can be locally described by the FLRW geometry, the same geometry which describes the expansion of the universe as a whole. In particular, general relativity predicts that light will move at the speed c with respect to the local motion of the exploding matter, a phenomenon analogous to frame dragging.
This situation changes somewhat with the introduction of a cosmological constant. A cosmological constant has the effect of a repulsive force between objects which is proportional (not inversely proportional) to distance. Unlike inertia it actively "pulls" on objects which have clumped together under the influence of gravity, and even on individual atoms. However this does not cause the objects to grow steadily or to disintegrate; unless they are very weakly bound, they will simply settle into an equilibrium state which is slightly (undetectably) larger than it would otherwise have been. As the universe expands and the matter in it thins, the gravitational attraction decreases (since it is proportional to the density), while the cosmological repulsion increases; thus the ultimate fate of the ΛCDM universe is a near vacuum expanding at an ever increasing rate under the influence of the cosmological constant. However the only locally visible effect of the accelerating expansion is the disappearance (by runaway redshift) of distant galaxies; gravitationally bound objects like the Milky Way do not expand.

Calilasseia wrote:I said that the fabric of space-time expands. I didn't say anything about entities within that fabric. If there are forces present keeping compound entities held together (and last time I checked, the strong nuclear force in nuclei was pretty damn powerful), then those entities aren't going to change size, are they?

I said that the fabric of space-time expands. I didn't say anything about entities within that fabric. If there are forces present keeping compound entities held together (and last time I checked, the strong nuclear force in nuclei was pretty damn powerful), then those entities aren't going to change size, are they?

Why would dark matter collect around the galaxy? Why wouldn't it collect all through it? And if it were all through it, why wouldn't it make the galaxy just implode on itself and just like come apart?
See? It doesn't even make sense -