Turn on thread page Beta

cosmology: evidence for a finite universe?? watch

    • Thread Starter
    Offline

    2
    ReputationRep:
    what evidence is there to show that the universe is finite??
    • Thread Starter
    Offline

    2
    ReputationRep:
    any ideas? HELP!
    Offline

    2
    ReputationRep:
    As the universe is expanding, can be shown by red shift, the universe must be finite or else it would not actually be expanding as it was already infinitely large
    Offline

    14
    ReputationRep:
    that doesn't seem logical to me, you seem to assume that galaxies within an infinite universe cannot get any further apart. by this logic there should be no seperation at all between galaxies. similar to saying assume infinity + 5 = infinity, therefore 5 = 0 and we have a contradiction: "infinity does not exist"

    I think one argument is that if there were an infinite amount of stars, the sky would be white at night because any black body in space that gets in the way of the Earth and the infinite stars emitting radiation towards the Earth will absorb it and emit it again in every direction, so overall the Earth would see radiation from every fdirection... unfortunately I can't rmemeber the name and may have explained it rather poorly
    Offline

    12
    ReputationRep:
    No evidence I think . In theory, Universe can be Big Crunch
    Offline

    14
    ReputationRep:
    I also believe that the expansion of space at the current time is greater than the speed of light, so the light from stars travelling towards us is actually moving away from us because the distance it must travel is increasing faster than the light is travelling (like those travelators on gladiators!).. the unvierse is 150bn ly across and only 13.7 bn years old, how would this be possible if expansion was not faster than the speed of light?

    so this would seem to provide an explanation for why the sky is not white.
    Offline

    2
    ReputationRep:
    Just because space is infinite it wouldn't have to have an infinite amount of mass so the white sky idea is wrong. Also I never said that the galaxies can't get further away in space in an infinite univerves, just that space itself would not expand, red shift does not show the movement of galaxies as such but the stretching of space
    Offline

    14
    ReputationRep:
    recessional redshift does show their recessional velocities though.. and if space is infinite, what prevents it from expanding?

    maybe the big bang provides evidence that it is not infinite. I don't know where they plucked the figure of 150bn ly from as the diameter of the universe but thats probably come from some evidence that it's not infinitely large
    Offline

    13
    ReputationRep:
    (Original post by mik1w)
    the unvierse is 150bn ly across and only 13.7 bn years old, how would this be possible if expansion was not faster than the speed of light?
    Because the rate of expansion may have been non uniform, and greater than it is now (it may have been greater than the speed of light at some point). But anyway, this is irrelevant to the original question.
    Offline

    2
    ReputationRep:
    Basaically because there was a big bang a finite time ago and space expands at a finite speed universe = finite. Don't worry about the argument i used before it is a very complicated one which is difficult to simplify but it does hold true.
    Offline

    14
    ReputationRep:
    you could try to explain the complicated version to me if you like...

    this time you are assuming that nothing existed before the big bang
    Offline

    2
    ReputationRep:
    Well of course i never did assme that anything existed before the big bang, because even if it did it would have no observable influence on our lives. Try reading a brief history of time for the more complicated version
    Offline

    14
    ReputationRep:
    (Original post by rpotter)
    Well of course i never did assme that anything existed before the big bang, because even if it did it would have no observable influence on our lives.
    What difference does that make?
    So what if we can or can't observe it, that's like saying "the universe is finite because we can't see the rest of it if it were infinite"...
    Offline

    2
    ReputationRep:
    No, all i'm saying is that there was nothing before the big bang, the universe is not contained by something but contains itself. I never said that because we can't see the infinite parts it is finite stop misrepresenting what i am saying
    Offline

    14
    ReputationRep:
    "because even if it did it would have no observable influence on our lives"
    Then what did you mean by this?

    And how do you know there was nothing before the big bang if we can't observe it?
    Offline

    2
    ReputationRep:
    Since time began at the big bang there was nothing before the big bang because time didn't exist, and so 'before' has no meaning. Even if something did exist before, whatever that means, there is no way that we could observe it because it would have happened 'before' time began so would not really exist
    Offline

    14
    ReputationRep:
    Where are oyu getting this from?
    Is there any evidence of time not existing before the big bang?
    And how can something happen "'before' time began"?
    Offline

    8
    ReputationRep:
    (Original post by mik1w)
    Where are oyu getting this from?
    Is there any evidence of time not existing before the big bang?
    And how can something happen "'before' time began"?
    Better yet...is there any evidence that there was anything? If something was there already, it must have been push out of where the big bang occured. But if it has been push out, it no longer is anywhere which can interact with us. Hence if it can not interact with us, how can we make measurements to work out its existance?
    Offline

    0
    ReputationRep:
    We dont know if the universe will
    a- stop expanding and stay like that
    b- continue expanding
    c- collapse to a big crunch.
    Offline

    2
    ReputationRep:
    When I talk about 'before' the big bang, i purposely put it in apostrophes to show that it doesn't really have a meaning in this context. Time began at the big bang:

    'According to the many experts however, space didn't exist prior to the Big Bang. Back in the late '60s and early '70s, when men first walked upon the moon, "three British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose turned their attention to the Theory of Relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein's Theory of General Relativity to include measurements of time and space.1, 2 According to their calculations, time and space had a finite beginning that corresponded to the origin of matter and energy."3 The singularity didn't appear in space; rather, space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing. So where and in what did the singularity appear if not in space? We don't know. We don't know where it came from, why it's here, or even where it is. All we really know is that we are inside of it and at one time it didn't exist and neither did we.' The above quote is from www.big-bang-theory.com

    Belive me now
 
 
 
Turn on thread page Beta
Updated: July 16, 2005
The home of Results and Clearing

1,012

people online now

1,567,000

students helped last year

University open days

  1. Keele University
    General Open Day Undergraduate
    Sun, 19 Aug '18
  2. University of Melbourne
    Open Day Undergraduate
    Sun, 19 Aug '18
  3. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
Poll
A-level students - how do you feel about your results?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.