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Seeing the milky way in it's past

  1. Jul 30, 2010 #1
    Alright, this has been egging me for awhile now, so here it goes. If light has a finite speed, and the rate of acceleration of the expansion of the universe has sped inflation up past this finite speed, is it possible that one of the young galactic cores we observed through the deep field image is in fact the milky way as it was billions of years ago, with that light just now reaching us? And if that's possible do you think we could track, via imagery, the evolution of our galaxy?
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  3. Jul 30, 2010 #2


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    Two reasons, since we are in the milky way we have been moving with it as space expands, so the light from it has always had the same distance to travel to us. So we have always seen the center (30,000lyr away) as it was 30,000yr before NOW for all NOW

    Secondly expansion of the universe doesn't change the size of galaxies - things which are held together by gravity stay together as the universe expands.
    It's like imagining a river flowing out to sea. The river flow expands out into the ocean, but a boat that is floating down the river doesn't stretch out when it reaches the ocean - it is held together by bolts/welds etc in the same way as gravity holds a galaxy together.
  4. Jul 31, 2010 #3
    Is this related to the analogy of the expanding universe like an inflating balloon? One possible conclusion of this is if you look far enough, you will see yourself (or your galaxy) off in the distance, the line of sight wrapping all the way around the balloon and back. I believe the answer to this is "most likely not". The expansion of the universe results in a Doppler shift so high that light emitted from one side of the universe would never get to the other side. Another way to put it is the distance between opposite points increases by at least one light year every year.

    Another consequence is that if you were to take a high-relativistic space ship out to circumnavigate the universe, at one point you would realize that you could never get to your destination and you could never return home. The universe at beyond some distance behaves though it is expanding faster then the speed of light. If the acceleration of the expansion of the universe is real, someday expansion may be so high, it will rip apart stars, atoms and subatomic particles.
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