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B Big Bang expansion question

  1. Apr 6, 2017 #1
    We all know BigBang theory, which states that the universe is continuously expanding, my doubt is the term expanding, does it mean the expansion of galaxies as a whole or including the planets in it?.
  2. jcsd
  3. Apr 6, 2017 #2


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    Gold Member
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    It doesn't mean either one. Galaxies do not expand, nor do the planets. Only constructs larger than galactic clusters "expand" and by "expand" it just means they get farther apart. There are HUNDREDS (probably thousands) of threads on this there on PF. I suggest a forum search.
  4. Apr 6, 2017 #3


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    Staff: Mentor

    Expansion means that objects which are not bound strongly enough to each other, such as different galaxy clusters, gradually move apart over time. Inside of galaxy clusters, galaxies, planets, and any other 'solid' object, expansion does not occur because the forces holding these objects together is strong enough to resist expansion.
  5. Apr 6, 2017 #4
    Thanks for the link... very interesting...
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