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Originally Posted by neutralino  Unfortunately, there is no such thing as the "edge of the universe" so the question is not defined. |
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Originally Posted by neutralino Hmm.. no-one seems to be listening to me today  . Anyway, like I said above, there is no edge/boundary to the universe. Furthermore, there cannot (by definition) by anything existing outside the universe-- by definition, the universe is all matter, energy and spacetime that exists. Thus, if you say there is some matter, or even spacetime existing outside the universe, then this is a contradiction. |
I spread out my thoughts here for clarity...
I don't understand the concept that there is no "edge/boundary" of the universe.
If space-time has been expanding since the big bang, then by inherent definition it has an outer edge of it's expansion.
To say there is no "edge of the universe," then to me that means the universe is infinite.
But, it is not infinite, but has an age of 14 - 15 billion years old.
One can calculate that the size of the universe at 1 second was about the size of the earth. So, where I am sitting now as I type, this point in space-time 1 second after the big bang was non-existent, yet to be created by the expansion of space-time. (note I am interchanging space-time as a synonynm for "universe.")
And so let's call what's on the other side of the edge "The Void."
For the sake of argument, let's define The Void as "the region empty of everything including matter, energy, space and time, and importantly, no quantum mechanical zero-point "jittery" vacuum energy of particle/anti-particle oduction/annihilation.
And, I'll concede this "edge" may also represent in a way the "edge" or boundary between physics and metaphysics, thus the question could be indeed illogical in a strictly physical sense of the word, at this point the argument could be sent out as a GOTO instruction to a metaphysics forum.
But I'll keep harping on it as follows:
So, what's on the other side, The Void?
On a similar note, prior to the big bang, was there only "The Void"
(I won't confuse things here, although I'm tempted to put in one of Hawking's arguments that the big bang arose from quantum tunneling, but that would negate my proposed definition of The Void, as the Void is completely empty, including of something to start quantum tunneling. Hawking's theory may be fruit for another thread topic....
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Well, I hope to convince neutralino, or anyone else, that the universe has "an outer edge or boundary".
Thus, to restate my argument: The universe has an edge because it has been shown by measurements of the cosmic background radiation to have arisen from the big bang around 14-15 billion years ago, and has a finite size, which is expanding (for now.) The only way there is no edge to the universe is if can be proved the universe is infinite (i.e., remember the Steady State Theory?)
Thanks to everyone for the other replies.
About 15 years ago I asked Dr. Robert Kirschner - of Harvard-Smithsonian Center for Astrophysics - this question when I was at one of his Smithsonian Institution lectures, but forgot his answer, thus I am asking it again!! Maybe I'll shoot him an email and ask him also.
Stevemc2
(I'm tempted here to add a link to the Doors' song "Break On Through to the Other Side!
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