<p>Caveat: I'm not a cosmologist, so this answer may not reflect the forefront of scientific knowledge/accuracy, but I have some knowledge so thought I'd share it and hopefully someone can correct me if I'm wrong.</p>

<p>The Big Bang theory states that everything is moving away from everything else, so it must have started closer together. We know from the Cosmic Microwave Background that everything was very dense and hot and small. </p>

<p>You may have heard that the universe started in a singularity. This means one point at which all matter was in the same place. In this state, all information in matter is lost. No particle can be labelled as having a position or size or spin, because every particle is in the same state as every other particle. This means we lose all possibility of having any information about what happened before this. There are many theories of what <em>could</em> have been before this, but no matter how simple/beautiful/mathematically rigorous the theory, it is physically impossible to know anything about it so they are impossible to test. In some definitions this makes these theories not actually science, as the scientific method involves making testable predictions.</p>

CC BY-SA 3.0
2016-02-08T23:43:00.120Z
@ FJC thanks for answering. Instead of physical proof are mathematical proofs used by Astronomers to rule out possibilities? Maybe simulations on powerful supercomputers?
signsgeek
CC BY-SA 3.0
2016-02-13T23:55:17.517Z
"universe started in a singularity. This means" that's where I stopped reading... We don't know what is a singularity. Our current theories fail there; they fail to give us predictions of any future experimental results; thus current theories are scientifically useless in saying anything practical about singularity. What you say is unfalsifiable, thus it is not science at all, only an opinion or a story.
kubanczyk
CC BY-SA 3.0
2016-02-15T10:14:08.680Z
@kubanczyk If you would take the time to actually read my answer, you would see that this is essentially what I said.
FJC
CC BY-SA 3.0
2016-03-14T15:15:41.783Z
"This means one point at which all matter was in the same place." Incorrect. The Big Bang singularity is different than say, a gravitational singularity. The Big Bang is an expansion of _spacetime_ itself- all matter was not at one point in the universe, but all spacetime (that's to say, the universe itself) was infinitesimally "close" with respect to the space-time interval.
Andrew
CC BY-SA 3.0
2016-02-08T18:20:26.897Z
2016-02-08T18:20:26.897Z
FJC
<p>We don't really know what happened before the big bang, but it is logical to think that just like the the mass was released when the big bang happened, it also got crushed to that single point, and since energy can't be created or destroyed, there was also mass before the big bang. And this is also a lot similar to a black hole, leading us to think that the big bang might have been a black hole</p>

CC BY-SA 3.0
2016-02-12T19:20:11.150Z
2016-02-12T19:20:11.150Z
Vase Dodevski
<p>Does the CMB contain any clues to what caused the Big Bang? Does a mathematical model theorize it? </p>

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2016-02-06T03:50:36.830Z
I know for sure 100% that all mass definitely was as small as a little pinhole...
GambleNerd
CC BY-SA 3.0
2016-02-06T09:12:34.040Z
I won't vote-to-close yet, but please look at all the other times a similar question has been asked and try to make your question more focused. E.g. http://astronomy.stackexchange.com/questions/1484/how-do-we-know-the-big-bang-didnt-happen-in-an-existing-universe. http://astronomy.stackexchange.com/questions/13541/what-was-space-like-before-big-bang
ProfRob
CC BY-SA 3.0
2016-02-06T21:04:00.103Z
@GambleNerd Be careful with what you "know". The Big Bang didn't happen at a single point. It was the expansion of the Universe in the sense that objects moved away from each other.
Sir Cumference
<early-universe>
What happened just before the Big bang?
signsgeek
# What happened just before the Big bang?

(Asked by: username_0 on 2016-02-06)

Does the CMB contain any clues to what caused the Big Bang? Does a mathematical model theorize it?

**Tags:** early-universe

> **Comments:**
> **username_1**: I know for sure 100% that all mass definitely was as small as a little pinhole...  
> **username_2**: I won't vote-to-close yet, but please look at all the other times a similar question has been asked and try to make your question more focused. E.g. http://astronomy.stackexchange.com/questions/1484/how-do-we-know-the-big-bang-didnt-happen-in-an-existing-universe. http://astronomy.stackexchange.com/questions/13541/what-was-space-like-before-big-bang  
> **username_3**: @username_1 Be careful with what you "know". The Big Bang didn't happen at a single point. It was the expansion of the Universe in the sense that objects moved away from each other.  

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## 2 answers

### Answer by username_4 on 2016-02-08. Score: 0

Caveat: I'm not a cosmologist, so this answer may not reflect the forefront of scientific knowledge/accuracy, but I have some knowledge so thought I'd share it and hopefully someone can correct me if I'm wrong.

The Big Bang theory states that everything is moving away from everything else, so it must have started closer together. We know from the Cosmic Microwave Background that everything was very dense and hot and small.

You may have heard that the universe started in a singularity. This means one point at which all matter was in the same place. In this state, all information in matter is lost. No particle can be labelled as having a position or size or spin, because every particle is in the same state as every other particle. This means we lose all possibility of having any information about what happened before this. There are many theories of what *could* have been before this, but no matter how simple/beautiful/mathematically rigorous the theory, it is physically impossible to know anything about it so they are impossible to test. In some definitions this makes these theories not actually science, as the scientific method involves making testable predictions.

> **Comments:**
> **username_0**: @ username_4 thanks for answering. Instead of physical proof are mathematical proofs used by Astronomers to rule out possibilities? Maybe simulations on powerful supercomputers?  
> **username_5**: "universe started in a singularity. This means" that's where I stopped reading... We don't know what is a singularity. Our current theories fail there; they fail to give us predictions of any future experimental results; thus current theories are scientifically useless in saying anything practical about singularity. What you say is unfalsifiable, thus it is not science at all, only an opinion or a story.  
> **username_4**: @username_5 If you would take the time to actually read my answer, you would see that this is essentially what I said.  
> **username_6**: "This means one point at which all matter was in the same place." Incorrect. The Big Bang singularity is different than say, a gravitational singularity. The Big Bang is an expansion of _spacetime_ itself- all matter was not at one point in the universe, but all spacetime (that's to say, the universe itself) was infinitesimally "close" with respect to the space-time interval.  

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### Answer by username_7 on 2016-02-12. Score: 0

We don't really know what happened before the big bang, but it is logical to think that just like the the mass was released when the big bang happened, it also got crushed to that single point, and since energy can't be created or destroyed, there was also mass before the big bang. And this is also a lot similar to a black hole, leading us to think that the big bang might have been a black hole


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