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Space expansion on smaller scales

  1. Jun 27, 2010 #1
    Space is expanding. This is evident from the redshift of distant objects.

    My question is what effect does it have on smaller scales? Since the expansion of space carries objects along with it (necessary for the objects to be farther) wouldn't the expansion within galaxies slowly pull them apart? wouldnt the expansion on planets exert a minute outward pressure? on smaller objects?

    Of course due to the small distances involved (since the stretching of space is cumulative over distance i.e. that unit of length expands x, as does the next one) and the large timescales required, these effects would be miniscule, but they would be present, right?

    Or is the fact that the galaxies are moving with the expansion not due to causation but due to a root common cause: i.e. space is expanding, but it does not carry objects with it. The reason galaxies move along with the expanding space is only due to their initial outward momentum from the big bang.

    Which (if either) seems to be the correct model as to our current understanding? I'm a little bit confused...
  2. jcsd
  3. Jun 27, 2010 #2
    You should do a search..this has been discussed many,many times. Or search Hubble expansion...here or Wikipedia.

    The gravity holding galaxies together prevents expansion within galaxies....the universe expands only over vast intergalatic distances...adjacent galaxies are essentially not affected.....for example, our Milky Way galaxy is going to collide with our nearest neighbor galaxy, the Andromeda galaxy
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