View Full Version : Quick question on inflation


§outh§tar
10-13-04, 06:52 PM
The Inflating Universe
It may be possible that space itself might have expanded faster than the horizon for a short duration before radiation and matter decoupled. In this case, physical processes within a region smaller than the horizon distance could have established thermal equilibrium. If space did indeed expand faster than the horizon, it would eventually come to surpass it in size. Since the horizon expands at the speed of light, it seems there is a paradox involved as space must violate Einstein’s theory to travel faster than the speed of light

The key point is that Einstein's theory actually says that no form of mattter or radiation can travel faster than light through space. His theory says nothing about the speed within the space which it expands.


My question:
Now if space must have grown faster than the horizon, does it not follow that whatever region this is must have initally had a velocity GREATER than the speed of light? See this analogy:

A hare and a tortoise are having a race. The hare is a little in front of the tortoise. By Einstein's theory, nothing behind the hare can exceed its speed. Now for the tortoise to overtake the hare, it must violate this principle and go at a greater velocity than the hare whilst still behind it.

Now if space was stretching within the horizon, space would have needed to expand at a GREATER velocity than the speed of light in order to overtake it and satisfy the inflationary theory, thereby violating Einstein's theory because the matter in the expanding space would be travelling faster than the speed of light. Stretching at the same velocity as the horizon was expanding would result in a directly proportional increase in velocities and therefore the "tortoise" would only be going as fast as the "hare" in front and therefore never overtake it. Stretching at a lesser velocity would mean that the "tortoise" could definitely not catch up.


Does this mean that the inflationary theory rejects the theory that nothing can travel faster than the speed of light or am I just an idiot.

Would appreciate a speedy reply, have to finish my paper soon.

thed
10-14-04, 02:02 AM
Southstar

The problem is that popular descriptions of Special Relativity say that nothing can travel faster than the speed of light (in vacuo). As always, there is a bit more to it than that.

Special Relativity only holds in inertial frames of reference (those of constant velocity with no acceleration) and providing no information (typically EM waves) is transferred. The conditions under which Inflation holds (in the first billionths of a second) are hardly an inertial frame, plus there is no information transferral.

So you are not being stupid and relativity is not violated, because it hardly holds yet.