Navy10E writes:
However wouldn't that mean the Big Bang had to begin in a 2D enviroment?
The Big Bang Theory does not suggest that an initial universal expansion began at a 'point in space' or 'the
existential factor that existed before the Big Bang. Melchoir, I think misinterpreted it slightly. Space itself was created with the Big Bang so it actually occurred everywhere at once, not at a specific point. Along with all the matter and energy in today's Universe, space itself began with that event and has been expanding ever since.
And with your atoms query. Atoms did not actually leave the 'spot' of the big bang. They were instead made in fusion reactions in stars much later. It is believed that supernova explosions of stars send the higher elements out into space, where they later combine to form planets, etc.
The light from the big bang is in fact all around us, and is essentially uniform. This is referred to as the 'microwave background'. This light is now in the microwave frequency because the universe is cooling as it is expanding.
It is not correct to think of the big bang as having happened at a 'spot' or at some location. It was not that everything, such as your atoms, were squeezed into a little part of the universe that is the present day universe. Instead, the entire universe, occupied a very small volume. Since the big bang it has been in continual expansion. But it is actually space itself that is expanding, not objects moving through space away from some spot. A typical example of this is given by a balloon. Draw spots on an uninflated ballon, which would be like galaxies at an earlier point in the universe. Then blow up the ballon. The spots move farther apart from each other because of the streching of the material of the ballon, not because the spots are actually moving somewhere. The streching of the balloon is analagous to the expansion of space itself, and our galaxy is like a spot on the ballon.
At the beginning, the 'spot' of the Big Bang embraced the entire universe. Consequently, every point in the current universe was once at, and therefore participated in, the Big Bang.
Depending upon the phase of the expansion, the size of the universe [meaning its radius and the average distance between objects (such as galaxies)] is proportional to the 1/2 or 2/3 power of the time, while the furthest distance from which light emitted during the Big Bang can reach us [the event horizon] is proportional to the time [ct]. Therefore, as time advances, the event horizon encloses a larger and larger fraction [as well as absolute volume] of the universe. That is, the distance to the event horizon grows proportionally faster than the universe itself.
This means that, as time goes on, the event horizon continually expands to encompass new points in the universe that had, up to that time, been beyond the event horizon. Therefore, there continues to be a supply of new points whose light generated in the Big Bang is now just able to reach us.
Of course, you are correct that light already received at an earlier time from points lying closer in than the current event horizon has already passed by, never to be seen again on earth [Until, perhaps, the event horizon has grown so large that it encompasses the given point a second time. In other words, until the light emitted toward earth has travelled past the earth and made a full circuit of the universe and returned to the earth. Recall that the universe is modelled as a sphere.]
For a more detailed discussion, and a useful diagram, see:
'The First Three Minutes,' by Steven Weinberg, Bantam Books, ISBN 0-553-14131-7, pp. 36-38 (1977).
[This message has been edited by JIM, 03-13-2004]
[This message has been edited by JIM, 03-13-2004]
™ Version 4.2