Re: Clock synch


"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> wrote in message
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kenseto wrote:
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> wrote in message
news:j_PDg.6702$1f6.2244@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Those two observers follow different paths through spacetime, and their
path lengths are different. For a timelike observer, elapsed proper
time
corresponds to the path length, so it is no surprise that their clocks
display different values when they rejoin, because clocks simply
indicate their elapsed proper times. <shrug>

This is nonsense.....they show different proper time because they were
running at different proper rates when they were apart.

No. If one assumes the clocks tick a different _PROPER_ rates, one does
not obtain agreement with experiment.

Sure they will agree with experiment.

When any observer in an inertial frame observes the tick rate of a
moving clock, it is observed to tick more slowly than the observer's own
clocks.

Sure...that's because they were ticking at different rates. In SR the
observed clock is predicted to be running at a slower rate. In IRT the
observed cl*** can run at a slower rate or faster rate. That's the reason
why SR is incomplete and that's the reason why SR is a subset of IRT.

When any observer in an inertial frame observes her own clock,
it is observed to tick at the same rate as her own clocks (duh!).

This is a meaningless statement.....at the same rate compare to what?

This
latter is a proper measurement, because in modern physics the word
"proper" means "in the object's instantaneously comoving inertial frame"
(or series of such frames). Note there is nothing "absolute" here,
because this applies to _ANY_ inertial frame.

Proper rate has no meaning unless you assume that the observer's clock
second has the shortest duration. But that assumption requires that the
observer to be in a state of absolute rest. Since no observer is in a state
of rest then this assumption is wrong. The valid explanation is that the
observer is also in a state of individual motion and that his clock can tick
faster or slower compared to an observed clock moving wrt him.

I repeat: the scenario I described above is directly analogous to the
fact that two sides of a triangle have a different total path length
than the other side. <shrug>


But it is not wrong to say that "their clocks tick at
different rates"

That is not wrong ONLY if you also specify how those rates are to be
measured (i.e. from which inertial frames, using what procedures).

You don't measure the rate of a moving clock. You use SR or IRT to predict
the rate of a moving clock.
In SR the rate of a moving clock is: t'=t/gamma
In IRT the rate of a moving clock is: t'=t(Faa/Fab) or t'=t(Fab/Faa)
Where Faa/Fab=gamma and Fab/Faa=1/gamma

Ken Seto


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