If all of the mass and energy in the universe was in a point smaller than the size of an electron at one time, why did it expand? Did it necessarily expand immediately on formation, or could it have remained in an initial state for some length of time until some phase threshold was reached?

  • $\begingroup$ Recommend closing because it's either a dupe or a purely metaphysical question. $\endgroup$ – Carl Witthoft Oct 7 '16 at 11:55
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    $\begingroup$ I found even earlier question, looks like it's really an appealing subject, somehow... $\endgroup$ – kubanczyk Oct 7 '16 at 12:07
  • $\begingroup$ @kubanczyk I think the second question you found is a better option for the duplicate. The first either has bad answers or answers which don't really answer the question. $\endgroup$ – zephyr Oct 7 '16 at 12:55
  • $\begingroup$ Space became available? $\endgroup$ – Wayfaring Stranger Oct 7 '16 at 14:57
  • $\begingroup$ You mean, the universe moved into a small apartment, then knocked out a wall to make a larger one? $\endgroup$ – Howard Miller Oct 7 '16 at 21:17

It's an important question, because it tells us something important about the Big Bang model. Some think that the Big Bang explains the expansion, but actually, it takes expansion as an initial condition (and it is typical of dynamical models that they require an initial condition that is outside the model) and tracks how it proceeds. We generally don't explain why our models work, we just test our models. We would need some new model to test, one that currently does not exist or is highly speculative, to be able to say why the Big Bang model works, and why the universe is expanding.

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