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How can the universe be infinite, if it has a finite age?

  1. Mar 21, 2013 #1
    Morning everyone,

    I apologize for bringing up a topic that has probably been discussed to death here in the past. I've been reading the FAQ, and a few old threads about finite vs infinite universe, but I'm still struggling to grasp both of these ideas. I'd be really grateful if someone could help me better understand them, I have just a few questions.

    My first question is, how is it possible to have an infinite universe if we know it has only been around for 13.7 billion years? Is it possible that the universe had infinite spacial volume even during the Big Bang, as it was first expanding? How does this make sense? This is something that actually kept me awake last night. :shy:

    I'm also stuck on the idea of a finite universe, though this seems a bit easier to comprehend than an infinite one. I watched a YouTube video of Carl Sagan explaining a finite but boundless universe, followed by a video on how the universe is expanding. I also read an article by NASA which predicted that the universe will expand forever! Here is the link, just in case. http://www.dailymail.co.uk/sciencetech/article-1304684/Nasa-scientists-discover-Universe-expand-forever.html

    What I'd like to know is, does it even make sense to say the universe is finite, even though it is still expanding and will continue to expand forever? I have a mental picture of a sphere constantly inflating, but this is probably very wrong. I suppose while I'm at it, I'd like to throw in the question, does the universe need to be curved to be finite?

    Thanks for your time.
  2. jcsd
  3. Mar 21, 2013 #2
    Its possible that the universe was infinite at the big bang and so it will still be infinite now. When cosmologists say the universe is expanding what they mean is the distance between galaxies is growing over time; not that the universe has a certain known size which is growing over time. When they say the universe was small at the big bang they mean the "observable universe" which does have a known size and is growing over time. But we cant say that for what is beyond our horizon. The universe is bigger than what we can see, infinitely bigger? Maybe.
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