How can we be sure of a singularity?

1. Oct 14, 2008

neonpotato

I have often been told that at the start of our "universe" (I prefer "self-contained energy system" - SCES, myself) all energy was contained in a singularity. What is the evidence for this all-containing singularity being the initiation of the big bang?

Is it not reasonable that the extremely dense core of a shrinking SCES (or universe) could have exploded with energy already in existence around it?

Any illumination would be appreciated.

Please be aware my understanding of physics is limited.

2. Oct 14, 2008

mathman

What the state of the unverse at t=0 or t<0 (big bang starts time) is an open question. There are many ideas floating around, but there is (at the moment) no way to test them.

3. Oct 14, 2008

baywax

This has puzzled me as well. My take is this. When you split a rock, you might get a few sparks, perhaps a bit of radiation and some crumbs. When you split an atom you get quite a bit more energy released than from spliting a rock. By these two examples, in tandem, I would suggest that when a sub-atomic particle (wave) is either compressed by, or forced to dispense into a "void", a great deal more energy is released than what is released by splitting an atom... in fact probably 10 to the power of 9 more energy than is released than when an atom is split.

Then again, I've been wrong before.

4. Oct 16, 2008

neonpotato

I don't follow. How is this related to my question?

5. Oct 16, 2008

marcus

check out Einstein Online, an authoritative, mainstream, up-to-date website maintained as part of the Albert Einstein Institute's public outreach program.
http://www.einstein-online.info/en/spotlights/cosmology/index.html

it's great. Atyy (who posts here sometimes) told us about it.
It has a page that discusses what you are talking about
http://www.einstein-online.info/en/spotlights/avoiding_the_big_bang/index.html
and it also has useful page regarding singularitie and the different things people mean by "big bang" which can help us avoid confusion.
http://www.einstein-online.info/en/spotlights/big_bangs/index.html

6. Oct 16, 2008

julian

Ashtekar + bojowald state

"The question of whether the universe had a beginning at a finite time in the past is now transcended'. At first, the answer seems to be no' in the sense that the quantum evolution does not stop at the big-bang. However, since space-time geometry dissolves' near the big-bang, there is no longer a notion of time, or of before' or `after' in the familiar sense. Therefore strictly, the question is no longer meaniful. The paradigm has changed and meaningful questions must noe be phrased differently, without using notions tied to classical space-times"

7. Oct 16, 2008

julian

GR is a relational theory in which you have to pick a dynamical observable to take on the role of a clock , but in the deep quantum mechaical region of the early universe there are no classical observables....

8. Oct 16, 2008

Chronos

The 'big bang' is the sound of one hand clapping [in zen speak]. Since no classical observables existed at t=0, as Julian noted, using yardsticks and clocks to describe this realm is like trying to announce a a hockey game by weight and color.

9. Oct 17, 2008

marcus

that's right! Agrees with what I've read about the computer modeling of bounce at Penn State for instance. A dynamical observable, e.g. connected to a matter field, is included and serves as clock. The model is quantum rather than classical in this case. they don't have time as such, and choose one of the physical elements in the picture to use as a clock.

Have you read much about it? You sound as if you may have. Do you have any papers you want to give links to?

10. Oct 17, 2008

baywax

I'm trying to explain my thoughts concerning what caused the big bang. So, the wave or particle I mentioned that is compressed or dispersed and out of balance with the "void" (lack of time, space) is all of what's left of the old universe or "p-brane".

Today is is evident that the universe is expanding and that objects are getting further apart. I have extrapolated this motion to a point where even sub-atomic particles have separated by great distance until space and time collapse, leaving only isolated sub-atomic particles surrounded by a void. At this point I am proposing that some sort of interaction between the sub-atomic particle and the void causes a rather large explosion and expansion. Then there is another universe developing.

Make me wrong!

11. Oct 26, 2008

julian

The note I made was cautionary - my understanding isn't detailed. Tied with the notion of time is energy - so I was unsure of the relavence of SC(Energy)S. I wish to understand these things better myself.

Something that confuses me: The results about singularity avoidance so far pertain to the kinematic level (I think) - but things can change dramatically at the physical (dynamical level). Thiemann has written a paper in which he describes the reduced pahse space quantization of GR (which explicitly operates at the physical level) and proclaims it may resolve the singularity problem dynamically. The thing is, it is an essential feature of the RPSQ that the dynamical time variable is described classically, which is at odds with what I said before!

ian

12. Oct 29, 2008

julian

I will try to bring together the list of references that contribute to my "understanding" of the issue
ian