• Question: If the big bang happened and everything exploded outwards, is it possible that the opposite could happen at some point and the whole universe could implode?

    Asked by conallmolloy to Arlene, Colin, David, Eugene, Paul on 16 Nov 2012.
    • Photo: David McKeown

      David McKeown answered on 16 Nov 2012:

      Yeah there is something called the “Big crunch Theory” which is one of the theories about how the universe might end. Like you said, the universe would stop expanding and start contracting, back to a single point (and a black hole). At the moment it doesn’t look like it will happen as the universe is expanding so fast, but it is one of the possibilities.

    • Photo: Paul Higgins

      Paul Higgins answered on 18 Nov 2012:

      It is possible that the expansion of the universe continues to accelerate, as it is now (possibly leading to the big rip), or it might slow down, and eventually reverse, causing the big crunch. This depends on the density of matter and energy in the universe. If the density is large enough, gravity will eventually overcome dark energy (which causes the acceleration of expanding space) and pull everything back together until we have a “reverse big bang”. at the moment it does not look like that is going to happen, though.

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