Why are scientists puzzled at the time of the universe that we are in?

  1. Sean Carroll and many other scientists I have heard say this same thing. Sean asks why are we born in the first 14 billion years at 13:57 . I don't understand what so interesting or peculiar about when we exist in the universe.
     
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. russ_watters

    Staff: Mentor

    Er, scientists find pretty much everything we don't know to be interesting!
     
  4. cepheid

    cepheid 5,190
    Staff Emeritus
    Science Advisor
    Gold Member

    There is the Copernican Principle that says we don't live in a special or preferred place in the universe. I.e. what we observe should be similar to what any other observer in any other location observes. Applying the same idea to time as space, you would conclude that there shouldn't be anything special about the time in the history of the universe during which we exist. However, this isn't really the case. There are some things about our epoch that would not be true of others. For example, we happen to live at a time when the matter density is comparable to the density of dark energy. This seems coincidental to cosmologists. Why should we happen to be alive at the time when these two numbers are so similar? If we had lived in the distant future, when the expansion of the universe will be totally dominated by the effects of dark energy, the expansion of the universe would be rapidly accelerating. We would living at a time when distant objects would be disappearing from view, because they woudl be expanding away from us faster than the horizon (the boundary between what we can see and what we can't). Eventually we'd reach a point where the only thing within our horizon would be our own galaxy, and we would see no evidence of the existence of any other galaxies. So cosmologists in this extremely distant future would conclude very different (and wrong) things about the nature of the universe. Lawrence Krauss was going around giving lectures about this "dismal future" a couple of years back. It seems that we indeed live at a preferred time. That is my understanding of this idea, anyway.
     
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