Expert: Philip A. Stahl - 11/14/2007

Question
Hi,

Firstly I approach this question as one who has little knowledge and appalling maths, but a general interest in the world about me. Having read subjects by Tim Ferris and Bill Bryson (love his book 'A short History of nearly everything)Stephen Hawkins and the like I am greatly puzzled by many things. One thing I would like some clarification upon is this.....

My understanding is that the speed of light is an absolute and we cannot go any faster (is that correct) and were it possible to do so, we would in fact travel in time relative to any observer.
At the point of the 'Big Bang' (or whatever one wants to call it, t=0) it is believed that there was an immense flash of light accompanied by an expansion of unbelievable magnitude.
My question is how could the matter of the universe expand at a rate far far exceeding the speed of light....would this not create the paradox of the end result (the Universe) being created before the 'Big Bang' actually occuring?

Simplified explanations greatly appreciated.

Answer
Hello,

What I think you are referring to is the inflationary aspect of early cosmic expansion.

Note that this sort of thing (implying velocity of expansion > c) isn't particularly novel. In fact, a number of cosmological models posit that proper distances, i.e. between clusters of galaxies, *may increase faster than the speed of light*.

Of course, if we happen to be in such a galaxy cluster - looking out to other objects in the very early universe- this means they'll effectively be permanently sealed off from our view. Hence, no conclusions or generalizations can be made. (If you are in some light "cone" such that a cluster's velocity v < c you will not be able to see or identify clusters in light cones for which v > c. They lie beyond your observational limit)

One also needs to know what "frames of reference" are being used, and so on. I hesitate to go into any detail on this because you want it kept "simpl".  That is ok so far as it goes, but means one must exclude a lot of interesting detail to keep it so.

Let me give another example. A physicist named Alcubierre devised the basis for a "warp drive" in which the ship can travel "faster than light".

The ship is inside its own local "warp bubble" which "surfs" in between an expanding space-time on one side and a contracting space-time on the other.  The key point is that the ship can go faster than c BUT since it is at REST (within its own local warp bubble) it isn't violating any physical laws.

You can read a bit more on it here:

http://www.daviddarling.info/encyclopedia/A/Alcubdrive.html

What I am saying is that the kinematic effect of faster than light expansion in the early universe could be along similar lines. One has to know the reference frames for the galaxy clusters to establish this. (What systems are at rest, what aren't, what is being referened in motion relative to what?)

You may also wish to get hold of an excellent recent book on these issues:  'Faster Than the speed of Light' by Joao Magueijo. (2004)