[stevemc2]

Originally Posted by neutralino Whilst I know that some people here like talking about a "void," cosmologists do not mention such a thing (at least not in this context). Your definition of the void appears to be "non existence"-- since you admit that spacetime does not exist in the void, then there can't even be nothing there, but there is no "there." (Sorry, that sounds really philosophical, but I can't think of a way to explain it more succintly). What does "prior to the big bang" mean? How do you measure time "before the big bang" (if such a statement is even well defined!) Indeed; could you also provide some links, since I've not heard much about that? I would like to think that Prof. Kirshner would agree with me! (It looks like he's been promoted since you heard him talk! )

Neutralino,
I was not using any on-line sources but just the first book on cosmology that I grabbed last night when I was working on my reply:

The" Big Bang," 3rd Ed., Joseph Silk, Cambridge Univ. Head of Astrophysics
http://www.amazon.com/Big-Bang-Third...8587082&sr=1-3

On page 113, Silk postulations how particles may have come into being from the quantum vacuum: Prior to 1 second after the big bang, the immense gravitational forces disrupted the particle-antiparticle production/annihilation process, thereby releasing particles into the "real world."

As for quantum tunneling starting the big bang, here are some arXiv links, following a link to a lecture by Hawking in which he briefly mentions quantum tunneling at t=0. The arXiv links I'll leave off the author's names here for conciseness:

www.hawking.org.uk/lectures/quantum.html

Hawking and Hartle first proposed their tunneling theories here:
Hartle J.B. and Hawking S.W., Phys. Rev. D28, 2960 (1983).

yet, Atkatz and Pagels had a similar theory in 1982:
Atkatz, D., and Pagels, H. (1982), "Origin of the Universe as a Quantum Tunneling Event", Physical Review D 25: 2065-2073

Here are some arXiv links on the subject:

arxiv.org/abs/gr-qc/0204061 -Quantum Cosmology and Eternal Inflation

arxiv.org/abs/gr-qc/0210034 - Particle Creation in a Tunneling Universe

arxiv.org/abs/gr-qc/0206028 - Tunneling in quantum cosmology: numerical study of particle creation

http://arxiv.org/find/gr-qc/1/au:+Vi...c658ac9f0ab7bc - The Quantum Cosmology Debate


So now I've put my books aside and am researching this digression of quantum tunneling cosmogeny from my "edge of the universe" concept.
thanks
Stevemc2

[neutralino]

Thanks for the links, Steve. I'll have a thorough read of (some of) the articles, and get back to you later on today.

[stevemc2]

Originally Posted by neutralino Ok, so no, the universe is not temporally infinite, but when most cosmologists talk about the "universe being infinite" they mean to say "spatially infinite," which is something that could be true (we don't really know yet!) Whilst I know that some people here like talking about a "void," cosmologists do not mention such a thing (at least not in this context). Your definition of the void appears to be "non existence"-- since you admit that spacetime does not exist in the void, then there can't even be nothing there, but there is no "there." (Sorry, that sounds really philosophical, but I can't think of a way to explain it more succintly). What does "prior to the big bang" mean? How do you measure time "before the big bang" (if such a statement is even well defined!)

neutralino,

I divided your questions up into Points 1, 2 and 3 as follows:

POINT 1. We don't know whether the universe is spatially infinite, it could be that the universe is spatially finite & shaped like a soccer ball, per this link:

http://www.news.nationalgeographic.c...euniverse.html


POINT 2. Heinz Pagels, one of the first to hypothesize the quantum tunneling origins of the big bang, in a 1982 paper, had this to say about the void:

"Hawking and Hartle calculate the probability for the universe to emerge from a state of 'nothing,' as in Alex Vilenkin's model, to the state of 'something.'"

Pagels earlier recounts Alex Vilenkin's account of "nothing" in Vilenkin's first quantum-gravity model. (A. Vilenkin, "Creation of Universes from Nothing," Physics Letters 117B (1982)

Pagels says that in Vilenkin's early model, "nothing" does not refer to a quantum-mechanical vacuum or empty space. "'Space is still something,' Alex once remarked to me, 'and I think the universe should really begin as nothing. No space, no time-nothing.'"

"The nothingness "before" the creation of the universe is the most complete void we can imagine-no space, time or matter existed. It is a world without place, without duration or eternity, without number - it is what the mathematicians call "the empty set."

Pagels wonders what are these laws written into that void? What "tells" the void that it contains a possible universe? It would seem that even the void is subject to law, a logic that exists prior to space and time.

Like most other physicists, Pagels uses "creation" to mean the beginning to exist of something; he does not use this word in a theological sense.

Pagels ideas and quotes taken from "Perfect Symmetry: The Search for the Beginning of Time,"
Heinz Pagels (1985)

http://www.amazon.com/Perfect-Symmet...8594310&sr=1-9
(NOTE: AMAZON HAS A USED COPY OF $0.01!!!)

Thus, we have at least one cosmologist, Pagels, discussing The Void, which seems to match up with how I defined it for my thought experiement, i.e., no mass, energy, space, time, not even a vacuum with quantum jitters.

POINT 3. That's a good question, how to define (much less measure) time before the Big Bang. I'll leave it to Steven Hawking again, he proposed a concept of "imaginary time" per this link:
http://www.everythingforever.com/hawking.htm

But....he used this 'imaginary time' to argue for the universe being infinite, which means I can't throw a baseball out of it, if he's correct
Well, hopefully we can somewhere find some agreement.

As for myself and 'time', I just realized the time here is 5:00 am
so good night!!

stevemc2