Jonathan Manning writes:
What was there before the Big Bang, was it just gases? if so how did the gases come about?
This is how I conceptualize it. Keep in mind that these are just analogies, and not literal descriptions.
If you look at this ordinary
x/y/z graph, imagine a sphere like
this one drawn on it with the center of the sphere at the origin. The origin in this analogy represents the Big Bang singularity, and the surface of the sphere represents spacetime in the present moment. Now, imagine the sphere inflating along all the axes simultaneously and that gives you time relative to the Big Bang. In other words the radius of the sphere from the origin to the surface would be the measure of time from the Big Bang to that point. Notice that no matter what point you reference on the surface of the sphere, that point is always a positive distance from the origin or Big Bang. That is to say,
every point in spacetime lies in the future of the Big Bang. Therefore there is nothing "before" the origin.
Alternatively you can conceptualize it this way: Imagine now a different sphere like
this one. Notice that this sphere has "latitude" and "longitude" sort of mapped out on it. Let's call the
hindmost convergence of the longitudinal lines the Big Bang. It's the very faint one in the background of the sphere. Time relative to the Big Bang will thus advance from the rear of the sphere forward. You'll notice how the latitudinal circles get larger as they move away from the Big Bang. This is analagous to expanding spacetime. Now, once those circles reach the middle of the sphere, they begin to get smaller until they reach another singularity at the convergence in the foreground. This is sort of how the universe is conceptualized in a Big Bang-Big Crunch cosmology. It may be, however, that spacetime will not converge at the Big Crunch but instead continue to expand forever. If that is the case, then the universe might be more like a
cone.
Remember that each of these is just an analogy and must be in some sense incomplete since they are illustrated in three dimensions and spacetime has at least four dimensions, and it may be that the universe has many many more than those.
Hope that helped.
[This message has been edited by ::, 11-13-2003]
[This message has been edited by ::, 11-13-2003]