1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Center vs edge of universe

  1. Dec 26, 2011 #1
    If we are not located at the center of the universe, then when we look out into space are we not sometimes looking towards the center of the universe and at other times towards maybe the edge of the universe. Assume the universe is finite- since we put an age on it, and the fact that it is expanding. Then why can,t we aim our telescopes towards the edge of the universe, if there is one. The hubble deep field pictures supposedly took in photons that had traveled for some 13 + billions years to get to the telescope, what does that mean? Thirteen billion years for the center of the universe, across the diameter, what?
    Also if we could aim a telescope at the edge, would we maybe detect photons that have only traveled a max of a billion years to reacher the telescopes detectors.

    This was filled with assumptions, but i think I got the question across.
  2. jcsd
  3. Dec 26, 2011 #2


    User Avatar
    Gold Member

    It is not known whether or not the universe is infinite or finite but it is well known that there is no center and there is no edge. This can be with EITHER finite or infinite.

    This question comes up here a couple of times a week, so a forum search will give you a ton of information.
  4. Dec 27, 2011 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    As Phinds said it is unknown whether the universe is finite or infinite in size. However, it is known that if it is indeed finite, the size is bigger than we can observe. This is because every direction we look simply looks the same as the one before it. IE we can look just as far in every direction.

    The photons from the Hubble Deep Field and Ultra Deep Field have been travelling for a time period of 13 billion years or so. They have been in transit for that long just to get to us.

    IF there is an edge, it is further than the current estimated distance of 40+ billion light years, which is the distance from us here on Earth to the furthest we can see. Distance in cosmology is...different...than what you and I deal with here on Earth thanks to the expansion of the Universe. The photons that reached the Hubble Space Telescope travelled for 13 billion years, yet the galaxies they were emitted from are MUCH further away now, as expansion has moved them away from us over time.
  5. Dec 29, 2011 #4
    thats pretty cool thanks
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook