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If the universe is infinite

  1. Aug 11, 2010 #1
    If the universe is infinite (and BB theory can work with infinite and finite space equally well), then does that mean that there is an infinite number of galaxies with an infinite number of stars?

    I know we can only observe our slice of the universe that the light had time to reach us and that the universe is estimated to be 13.5 billion (or 150 billion which i saw somewhere else) years old but lets assume that the universe is finite with no boundary and it's expanding, then isn't the best thing we can do is give an ESTIMATE of how many stars and galaxies there are in the universe and how old it is based on our observable slice and keep updating the data as our instruments get stronger?

    Does that make claims such as "the universe has x amount of stars and x amount of galaxies" and "the universe is x years old" vacuous? How can we put limits on our observable piece of the universe without mentioning that perhaps on the unobservable plane there is an infinity of the same matter or at the very least, an infinity of black space with no galaxies?
    Last edited: Aug 11, 2010
  2. jcsd
  3. Aug 11, 2010 #2


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    The age of the universe is not based on how far we can look. The temperature of the microwave background as well as the universe expansion rate lead to the 13.7 billion year age.
  4. Aug 11, 2010 #3
    In order for observations to have meaning, astronomers have adopted the Cosmological principle which states that, when taken on a large enough scale, the universe is homogenous and isotropic. This means that we assume that the universe looks basically the same to all viewers regardless of position. So someone sitting 46.5 billion light years away at the edge of the observable universe should see (at this exact moment) an observable universe that appears 13.7 billion years old and 93 billion light years across.
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