<p>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.</p>

CC BY-SA 3.0
2016-10-07T14:46:59.423Z
2016-10-07T14:46:59.423Z
Ken G
<p>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?</p>

CC BY-SA 3.0
2016-10-07T11:55:20.573Z
Recommend closing because it's either a dupe or a purely metaphysical question.
Carl Witthoft
CC BY-SA 3.0
2016-10-07T12:07:08.200Z
I found [even earlier question](http://astronomy.stackexchange.com/questions/7863/why-did-the-big-bang-not-just-produce-a-big-black-hole), looks like it's really an appealing subject, somehow...
kubanczyk
CC BY-SA 3.0
2016-10-07T12:55:50.337Z
@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.
zephyr
CC BY-SA 3.0
2016-10-07T14:57:08.737Z
Space became available?
Wayfaring Stranger
CC BY-SA 3.0
2016-10-07T21:17:43.267Z
You mean, the universe moved into a small apartment, then knocked out a wall to make a larger one?
Howard Miller
<black-hole><cosmology><singularity>
Why Did The Universe Expand?
Howard Miller
# Why Did The Universe Expand?

(Asked by: username_0 on 2016-10-07)

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?

**Tags:** black-hole, cosmology, singularity

> **Comments:**
> **username_1**: Recommend closing because it's either a dupe or a purely metaphysical question.  
> **username_2**: I found [even earlier question](http://astronomy.stackexchange.com/questions/7863/why-did-the-big-bang-not-just-produce-a-big-black-hole), looks like it's really an appealing subject, somehow...  
> **username_3**: @username_2 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.  
> **username_4**: Space became available?  
> **username_0**: You mean, the universe moved into a small apartment, then knocked out a wall to make a larger one?  

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## 1 answers

### Answer by username_5 on 2016-10-07. Score: 0

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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