As I understand it, this is what the scientists think right now....operative words "right now".
It was once thought that the universe began about 14 billion years ago due in large measure to us being unable to detect anything older than 14 billion years.
We look out and beyond that frontier there was but a void.
But then it was realized that galaxy A is "moving" (see above about space expanding) away from us at, say, 1/4 the speed of light and galaxy B is moving away from us at, say, 99/100 the speed of light.
But what about galaxy C. Well, it's moving away from us at the speed of light plus; therefore it's light will never get back to us to observe.
But more baffling (to me, anyway), if there were another astronomer right on the edge of our known universe....
He would be able to see 14 billion years out...meaning we would be right on the edge of his know universe.
But if there was an astronomer on the edge of his universe...same thing.
Therefore, you could just keep going....in all directions.....forever.
3 comments:
Thank you for the discussion. I had never heard of the possibility of parts of the universe moving away so fast that their light never reaches us. Those parts could be thought of as other universes, or we can conclude that true universe may be many times larger than the known universe.
Well, thanks to the accelerating expansion of space between all non-gravitationally-bound objects, the observable universe is actually shrinking. Eventually all non-bound systems will have no visible neighbors at all. For example, our Milky Way is part of the Local Group of 30-odd gravity-bound galaxies. At some point there will be no other galaxies visible from the vantage point of the Local Group. Of course that'll be a very long time from now, and most local stars may have burned up by such a time anyway (I don't know).
Also, mass-energy equivalence suggests an upper bound to the speed of particles. Empty space itself is often postulated to have an energy (to explain the accelerating expansion of space) but this energy never interacts with electromagnetism (only gravity). Thus the speed of light may not apply to it.
There are scores of competing theories trying to explain the accelerating expansion of space, though. The various dark energy varieties (quintessence et al) aren't a majority afaik — you've got all the brane theories about multiple heavy dimensions which contain most of the universe's mass, the string theories, m-theories, etc...
Most speculation about the OPERA neutrino results is silly. If it gets people interested in physics, fine... but we'll actually know more next year when Fermilab and others replicate the test.
Jambe, what was that second thing?
Just kidding.
As for your statement that under those circumstances the speed of light may not apply, I've never had faith in the speed of light as a constant.
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