Re: Clock synch


"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> schreef in bericht
news:MATBg.2947$1f6.2824@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Nicolaas Vroom wrote:
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> schreef in bericht
news:Z3SAg.3029$kO3.2790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
There is no "time dilation", in the sense of a clock physically ticking
slower, or in the sense of "time moving slower". There is no
"shortening/elongating", in the sense of a given object physically
getting shorter or longer.

The effects called "time dilation" and "length contraction" in SR are
not physical effects, and are due to different measurement procedures
used by differently moving observers.

That means, if I understand you correct, that an observer at rest
(not using a moving clock)
can never detect any effect in which "length contraction" is
involved ?

Not at all. An observer can detect length contraction by performing an
appropriate measurement that projects the proper length of a moving object
onto her own spatial coordinates. It's just that no such measurement has
been carried out to the requisite accuracy, basically because it is
infeasible to measure this accurately enough with existing technology.

Measuring time dilation is MUCH easier.


That means you agree with me that in the train experiment
(described in the text:
http://users.pandora.be/nicvroom/simultaneity.jpg
copied from the book:
"Understanding Einstein's Relativity"
by Ray d'Inverno )
when neither the proper length of the train
(= length of train at v= 0)
nor the difference between the Firing Devices is changed,
that Observer A (standing near the track)
will NOT see the light flashes simultaneous ?


Tom Roberts


.

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