Originally posted by PinkFloyd
So when the friendly physicist said that it IS acceptable to "break" the speed of light barrier if it is SPACE itself that moves faster than light (and not light itself moving THROUGH space), then he was correct? Seemed like a pretty big loophole when it comes to breaking one of the fundamental rules (at least as I was taught), which is that NOTHING can E I'm all for sneaking in the back door and letting space expand faster than light can travel.
I think what the guy might have been talking about is this:
The universe is expanding - space itself is expanding. What does that mean? Every object is moving away from every other object. I guess it's kind of like everything in the universe is shrinking relative to the universe as a whole. Thus distances between things are constantly increasing.
Suppose light travels from point A to point B in time T. The speed of light would be equivalent to
c = (B-A)/T
Now suppose that after the light travelled, the space it had travelled expanded. B-A, the distance between the two points, increases.
Thus we could say the light travelled from point A to point B faster than the speed of light; however when it did it, it travelled shorter distance at the speed of light rather than the same distance faster than the speed of light.
I suppose one could say that the speed of light used to be greater and will be less in the future in Universe units, but then you'd also have to agree everything is shrinking.
Instead of describing it this way (which may not be 100% correct anyway) we describe it as space expanding and distances increasing - and a constant speed of light.