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Where is the past?

  1. Feb 9, 2009 #1
    The Hubble Ultra Deep Field view, (hubblesite.org), claims to show the very early universe by virtue of it's distance. "Within a stones throw of the big bang", is the claim. And who would argue? But why this particular angle of view? Why not the opposite direction, or to the right or the left of this angle We are told, correctly, that distant views are of the past. There are more than 128,000 different angles of view. If they are all of the past, (as they must be), which way lies our origins? If this choice of angle was arbitrary, then how can it be stated with any degree of certainty that this is from whence we came, and why did it warrant a 1,000,000 second exposure?
     
  2. jcsd
  3. Feb 9, 2009 #2
    Hi Peter,

    The important thing about the hubble deep field objects is not the angle at which they are located, but rather their distance. When we say the deep field objects are "close" to the big bang, we don't mean close in location, we only mean close in time-- that is, the objects are further away in space and therefore are observed as being further back in time.

    As for the question of "which way" our origins lie-- if I understand the question you are trying to ask, then the question is moot. Big Bang theories do not place the big bang as having occured in a particular "place"-- there is not some "origin point" in space where the big bang "occurred" and where all of space is expanding away from. Rather the big bang occurred "everywhere at once"-- every single point in the universe behaves as if the whole rest of the universe is expanding away from it. So if you want to point a telescope in "the direction of" the big bang, literally any angle is as good as any other.

    As for how they did pick the particular angle of the deep field observation, wikipedia explains that the specific direction of observation for the deep field was selected entirely based on practical considerations, mostly having to do with finding a patch of sky where there were no nearby obstructions making a deep observation difficult; and that it was in fact one of twenty such acceptable patches that they identified before settling on just the one:

     
  4. Feb 9, 2009 #3
    They picked the part of the sky that they did because it appeared to be empty.

    They exposed the photo for so long because otherwise the image would have been underexposed and we wouldn't be able to see anything. Since we're looking at stuff so far away, there isn't much light so we need to expose a picture for longer.

    They aren't saying that that is the location we came from, but rather that those are the conditions our universe evolved through on it's way to the present state.
     
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