Big Bang

[Billy_Dean]

Originally posted by Jems@14 November 2003 - 05:32
The universe isn't supposed to be expanding into anything, rather, space is stretching. You can imagine a universe with an infinite spacial dimensions, but where every point is moving away from every other point. There is no 'border'. Otherwise, we would have the very odd situation of being at the exact centre of an expanding universe. There is no real centre.

Also, the big bang did not necessarily need a cause. While you may think of everything as being cause and effect, and of exactness of position, speed, time etc, the universe does not really work this way. It is impossible to determine anythings exact speed or position, and not everything has a cause. It seems that the laws of quantuam mechanics were operating before the big bang, this would allow for space and matter to appear from nowhere. Space is not just nothing, a container. It is something more tangible. At a quantum level it is actually 'frothy'.

Release your mind from its prison of the 'realities' of everyday life

Something had to set the big bang off, it had no reason to just happen. If all the energy presently in the universe came from the first singularity, it must have had a cause. As for space stretching, what space? The universe? Where does infinity come into this? The universe is a finite size, "space" outside the universe is not, or there would be nowhere to expand into.

[ilw]

I think the big bang theory is by far the best so far, for me the most convincing evidence is that if you look at the speed and direction of the galaxies visible to us you can see that they would have occupied the same space 15 billion years ago. Using other measures theres evidence that 15 billion years is roughtly the age of the universe, so it seems logical to assume it all came from one point. Theres also evidence that the early stages had to be really hot.
Personally thats enough evidence for me to believe in a big explosion, of course it doesn't answer the questions of what came before


How can an infinite universe have a beginning in time?

In general relativity, a universe with an infinite spatial extent today ( something you can establish experimentally) must also have had an infinite spatial extent at its instant of 'birth'. But you don't have to throw one infinity at another to, relativistically, make sense out of this as we might want to do not knowing intuitively what infinity is all about. An infinite universe can have an origin at a finite moment in the past because, in general relativity, one can have a 'singularity' condition in which the volume of 3-d space vanishes at a finite moment in the past, so that even if the 3-d space was still infinite at that moment, the separations between nearby and distant points reached a limit of zero separation at the same time. Rather than having to drag this moment into the eternal past to 'logically' solve the problem ( which would not work physically), you can solve the problem at the instant of creation, and place this instant at a finite time in the past. This is the unique solution offered by general relativity for a 'problem' that had bedeviled philosphers since the time of Saint Augustine.

If space and gas started everything going, where did these things come from?

We know that 'space' and 'gas' are two very different things, but long ago they were actually one and the same. Because Einstein's general theory of relativity works so well, we have to accept for now its description of space and time as only aspects of the gravitational field of everything in the universe...gas...energy...matter...light. Near the Big Bang, gravity amplified itself by feeding off of its own energy in a complex and brief state, which ended in this gravitational energy producing the first generations of particles and anti-particles. These later decayed into, not only the familiar electrons and quarks, but also into the particles of light and the essences of the other fundamental forces in existence today. Mathematically we can describe much of this transformation, because many of its key ingredients have been seen by physicists already, at their laboratories. But the earliest conditions have yet to be artificially re-created so that we can thoroughly test our best theories.

So, gas was once part of space; space remains indistinct from gravity, and so everything we see around us was once part of the invisible field we call gravity...which flashed into existence billions of years ago.

Clear as mud.
http://image.gsfc.nasa.gov/poetry/ask/acosmbb.html