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Dark energy: is it just "lost" light?

  1. Sep 23, 2014 #1
    Hello everyone, this is my first post here, and I hope I'm not asking a too "silly" question. I've already looked here and on the internet, but couldn't find a real answer to it. :)
    Here's the "silly" question. I was wondering the following, since:
    - The universe is inflating
    - The most distant objects known are ~90 billion light years away
    - The oldest signals we are able to receive are 16 light years away
    These objects cannot see each other anymore, and any particle sent to us by them right now will never reach us because it would require faster-than-light travelling. So they are just outside outside our event horizon. The same applies of course to anything that's too far away from them.
    So, I think the photons will just "keep travelling" forever, without ever reaching a destination, getting a huge redshift... forever.
    Now here's the question: being the photons energy, isn't it possible that the dark energy is just "ancient photons" being lost in the middle of nowhere?

    Thank you! :)
  2. jcsd
  3. Sep 23, 2014 #2


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    Quick point: the event horizon of the universe presently lies beyond the particle horizon (the distance that light has traveled since the big bang). This means that there is still time to receive light signals from those most distant objects.
    No, these photons are still regular old radiation. Radiation, of any wavelength, causes the universe to expand at a decelerated rate. Dark energy is something altogether different -- an exotic fluid that importantly does not dilute (or redshift) as the universe expands.
  4. Sep 24, 2014 #3


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    Or just a constant in the equations.
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