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Universe Expanding

  1. Apr 18, 2013 #1
    Hey i am new to the forum but i have done some studying and im trying to wrap my head around something but im not sure if im quite getting it i was hoping if someone could direct me to some reading or books, and so here it is, i was recently explained to that as the universe is expanding everything in it expands with it like a graph being stretched but for example the stars are on the points in the graph now, but does that mean that the stars and galaxies don't move beyond these points but i know thats not true is it? or is it moving in sync with the points on the graph, or am i just looking at this the wrong way?
  2. jcsd
  3. Apr 18, 2013 #2


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    Gold Member

    Perhaps this will help:

  4. Apr 18, 2013 #3
    Phinds balloon analogy is a good one.
    On the descriptive you gave above. I would like to clarify you graph analogy. Think of those points on the graph as coordinates. The coordinates do not change. The space between coordinates expand evenly in all directions. Expansion does not provide inertia or motion to those coordinates Individual stars and galaxies maintain their normal velocities. That graph example only represents expansion which has nothing to do with inertia.
    One other note expansion is easily overpowered by gravity. Such as galaxy clusters. So we usually state that expansion does not occur in gravitationally bound regions.
  5. Apr 18, 2013 #4
    Thank you for your response and the great read so lets say the pennies are expanding on the surface of the ballon they dont change mass or velocity am i correct? but now this leads me to ask how do the galaxies move? is it from the momentum of each others gravity?
  6. Apr 18, 2013 #5
    This is where i become less read but im going to try to use common sense, if the universe is expanding then the volume in it must be decreasing unless new matter is being created.Is there a particular reason why the universe is expanding? at this point i feel like i can find the answer somewhere in the forums, rendering this post useless i suppose my question is why is the universe expanding and would there be a way to ride the expansion sort of like an ocean wave or to accelerate it?
  7. Apr 18, 2013 #6
    FAQs is a good place to start.
    The FAQ subforum has some good articles.

    Also this site has a decent tutorial as well


    In your questions above switch
    volume with density. The link I provided along with the PF FAQ subforum will provide those answers.
  8. Apr 18, 2013 #7
    Thank you
  9. Apr 18, 2013 #8
  10. Apr 29, 2013 #9
    Thank you man your a very helpful person it is greatly appreciated
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