Expert: Jayendra Upadhye - 9/16/2005

Question
Hi
12.8 billion years ago a star exploded and it's light has just been seen here, fine I have no problem with that. But if the universe started 15 billion years ago then this star exploded 2.2 b years after creation.
Question One:Therefore where was our star dust or atoms when this first exploded, was we 2.2b years away and then kept ahead of it's flash by going ether, equal to or faster then the speed of light, then slowing down untill 12.8b later it's light catches-up?
I,m told we can't go faster than the speed of light, so could our stardust have seen this event twice? Could it be that if space is curved our dust was close when it first went bang, then has we moved and curved away untill we ended-up 12.8b light years across from our first observation point.
For example are we both at opposite ends of a very large S or U which is now 12.8b L/Y distance from it's ends, but closer at it's centre when it exploded?
Our stardust must have been around somewhere when this first happened because all stardust was formed at the same time after the big bang, they may have moved and been kicked about a bit since then, but they were there!
Are we in fact, not only looking back in time on the light source of that event but also from where some of our present atoms could have come from??
Not a question, just a talking point:
Blackholes kills stardust,their gravity is so powerful our known laws break down,(just as before the big bang) yet is there any evidence to suggest that they keep pace with the rest of the universe or do they stand still.If all the blackholes are left behind then maybe they all join-up to form a pre-big bang condition untill they get so big (or smaller) that something has to give and off we go again, nice thought.
All the best
bertie  

Answer
Hi Bertie..
1 - about the star that exploded 12.8 billion years ago.
let us go step by step.
assume a life span of 1 billion years for other star. (a more massive star with a shorter life).
We are at A, the other star at B
consider t0 = present time.

a) t0 - 12 billion years:- B explodes. A and B are seperated by a distance somewhat less than 12 billion years, but are receding away.
However at A, we are not still there anyway.

b) - T0 - 4.5 billion years ago:- the light from the exploding star has travelled quite a distance, but we are still far off and receding away..and the sun is just born.

c) - t0:- we are 4.5 billion years old and we look in the direction of b and "see" the star exploding 12.8 billion years ago.

considering we BOTH receded equally from each other, from the central point, we had already receded some billion light years each when the star went out! (but sun wasnt there).

by the time the light caught up with us, (recession rate is slower than speed of light), it was 12.8 billion years since the star b exploded.

IT IS KNOWN THAT INITIALLY AFTER THE BANG THE UNIVERSE EXPANDED FASTER THEN THE SPEED OF LIGHT..remember reading about that somewhere.
So 2.2 billion years ago, the universe was actually bigger than a radius of 2.2 billion light years.
It was as if the bang suddenly happened over a great volume of space! and not in a point. (inflationary phase after the event of the bang, when space time ..not matter mind you..expanded much faster than speed of light..the boundaries thus covering bigger tracts than would be possible for light.

Thus this event is easily possible where we "look back" and see the star exploding.
Know that the actual point b has meanwhile gone away even further..because life did follow its normal course after the star exploded at b 12.8 billion years ago. may be new stars weere born and died..those events will unfold for us at t0 + 1 second to t0 + forever!

2 - Dear Dear! You love to loose youself in quaint theorising dont you? :)
why should black holes be "left behind"? like any dumb star, they are subject to gravity and hubble's expansion! that is why the poor souls are even condemned to orbit "less glamorous" but more massive stars (cygnus x-1).

Havent you come across asimov's famous ideas that (the more massive the black hole, the lesser its inner density and the greater the radius of the event horizon), the universe is a colossal black hole as it satisfies all the criteria in the bracketed statement.

afterall it is REALLY REALLY MASSIVE (IT CONTAINS EVERYTHING THERE IS TO CONTAIN) and its is vacuous..and its boundaries are 15 billion light years across!

Think anout that!

Jayen