[thedoc (OP)]

Ash Patel  asked the Naked Scientists:
   
1.       If the universe was formed by the BIG BANG, do we know where the "epicentre" is?
2.       I would have presumed that should we have had such an explosion in space, all the planets and stars in our solar system would be constantly in motion, away from the central point of the explosion why is the milky way so stable? Or is it?
3.       There are certain explosions that we "see" today that have occurred millions of years ago, even as close to the BIG BANG itself. If this is so, then were we not part of this event? I would assume that the speed of bodies or segments, or particles arising from the explosion would be much faster than the speed of light, the light (image of the explosive) then should never "catch up".
4.       Where and how did the water originate. Same problem in an explosion the water would have dispersed outward. Was there that much water?  
 
Regards
 
ASH PATEL
Johannesburg, South Africa

What do you think?

[Bill S]

By now it is well known on this forum that I am not a scientist, and that I have some odd ideas.  However, as these are some of the questions I have wrestled with over the years, I’m going to have a go, just to see how much progress I might have made.

1.  I think “epicentre” is not what you meant.  Focus is probably better.  It took me a long time to get my head round the idea that there is no point in the Universe at which the BB happened.  It happened everywhere.  Drop a spot of ink on a piece of blotting paper.   After it has spread, you can locate the centre only in relation to the paper on which the blot appears.  This could apply to the BB only if it happened in space, which it did not.  Space and time, we are assured, were created in the BB.

2.  As already mentioned, the BB must not be thought of as happening in space.  Galaxies, including the Milky Way, are extremely small parts of the Universe held together by gravity.  In fact, so are the galaxy groups, it is these groups that are moving apart.  Within the groups gravity is strong enough to counteract the spreading.

3.  Scientists tell us that there are parts of the Universe that are receding from us at such a speed that their light will never reach us.  What we have to remember is that if we see something, its light has already reached us, so we will not see things which are beyond the horizon created by the speed of light. 
As far as the relationship between what we can see, how far away it is and how fast it is receding relative to us is concerned; that is a bit complicated.  I’m still working on trying to understand that.  I would be quite happy to share the bits I think I have grasped, but I’m sure there are those who will do a much better job.

4.  Water is not something that would have existed at the time of the BB, nor for a very long time after.  Particles, atoms and molecules would have had to form first.