RE: expansion of the universe

From: Lee Corbin (
Date: Sat Apr 19 2003 - 16:12:38 MDT

Michael writes

> Lee Corbin wrote:
> ....
> > Bertrand Russell used to say that one problem with
> > special relativity was that the other man's cigar
> > appeared to last longer than one's own. I put
> > "thinks" in quotation marks, because sometimes people
> > suppose that there is some sort of error involved, or
> > that it's subjective. No, the processes really do
> > slow down, there is no "thinks" about it, nor is
> > there anything subjective about it. There are just
> > different frames of reference, which isn't really
> > the same thing. ...
> The mutual cigar envy situation Russell described only applies while the
> smokers are moving away from one another at relativistic speed.

Michael, you probably *do* understand the physics of the
situation, but your statement is highly misleading. It
doesn't matter whether they are moving towards or away
from each other. Time dilation is controlled entirely
by the parameter v, the mutual relative velocity.

> As soon one cigar smoker changes direction (which is a
> change in velocity)

Yes; here the acceleration kicks in for a short time in the
notorious twin paradox. But the deeper truth is that the
acceleration doesn't have any direct effects itself (or
few), but rather that it puts the person undergoing the
acc into a different frame of reference. The moment that
he obtains a constant velocity, then once again his twin
ages more slowly than he (in his frame of reference).
And I emphasize again, that this is not merely appearance;
his twin really is aging more slowly, as all physical
processes occur more slowly.

> and moves back toward the other, then the second smoker,
> who is stationary relative to the first one, is seen to
> speed up enormously.

Yes, at that moment.


This archive was generated by hypermail 2.1.5 : Wed Jul 17 2013 - 04:00:42 MDT