# Origin of dimensions

1. Aug 4, 2014

### DiracPool

I've been reviewing the timeline of the big bang...

http://en.wikipedia.org/wiki/Chronology_of_the_universe
http://en.wikipedia.org/wiki/Graphical_timeline_of_the_Big_Bang

...and wasn't able to find an answer to a question I have.

That question is, is there any evidence that the spatial and time dimensions unfolded in any certain order, or, as the saying goes, "did all 4 dimensions just spring forth simultaneously and fully formed from the head of Zeus?"

For example, I typically think of "time" as the 4th dimension, which implies a sense of seriation. I think of it as coming last. I think of the first dimension as coming first, the second second, the third third, and the fourth time. I think of these dimensions as "evolving" out of one another. Maybe I think that way because that is really how we learn these things. We typically model systems when we learn them in one dimension, using ODE's, and then only invoke the Laplacian, reluctantly, when we need to or want to step up our game, so to speak.

But the origin of the universe? I was looking into the Hartle-Hawking state: http://en.wikipedia.org/wiki/Hartle–Hawking_state

What does that mean? "Time diverged from the three state dimension?" From what I understand, all we know is that the whole thing got kicked at 10^-43 seconds, the so-called, "Planck time." So it seems to me that the "Time" dimension had to have come first, OR, all 4 dimensions must have come into existence simultaneously. Does anyone have some insight on this?

2. Aug 4, 2014

### Chronos

The Hartle-Hawking state suggests spatial dimensions preceded time in the very early universe. In that sense, the universe had no 'beginning'. Under Hartle-Hawking, all three spatial dimensions emerged simultaneously followed by the emergence of time. It is motivated by, and believed to be a solution to the Wheeler-Dewitt equation.

3. Aug 4, 2014

### DiracPool

This is all I know of the Wheeler-Dewitt equation...

That doesn't seem to give any indication of why a time dimension suddenly appeared or evolved. What caused that?

And what about the spatial dimensions pre-time? Were there just 3 dimensions sitting there? For how long? (I guess that question isn't relevant) And why 3 dimensions? Doesn't it make sense that we had to start with one? Then two, then three?