[Phys-L] Re: "moving clock runs slower" (yes)

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 10:10  -0700 9/16/05, Larry Woolf wrote:
> In your article you refer to a standard concept of a person speeding "in
> a rocket traveling slightly less than the speed of light" and say that
> "motion at such enormous speeds drastically slows the clock for the
> traveler." That reasoning, which is common, troubles me. If the traveler
> is traveling speedily with respect to an observer, then, clearly, the
> observer is traveling speedily with respect to the traveler (who is
> observing the observer). Since all motion is relative, why shouldn't the
> observer's clock slow down as observed by the traveler?
It does, and that is why I also think this sort of exposition is
confusing to the students, because it reinforces their concepts of
absolute motion rather than relative motion. Furthermore the traveler
will notice no change in any of the clocks traveling with him or her.
 From the POV of the traveler everything on the spacecraft looks
perfectly normal--and it is. It is what the traveller sees when
looking at the stay-at-home clocks that does not appear to be normal.
As you say, they will appear to be running slow, just as the
traveller's clocks, as seen from the stay-at-home POV will also
appear to be running slow.

A point all too often slopped over in the teaching of relativity.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

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