Re: Is there length contraction in SRT, uncle Ben?

xray4abc <lemhenyil@xxxxxxxx> wrote in message
cfdeda6f-9219-4338-9a08-13086221f8ff@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
What SRT does say about length contraction?
Consider a rod along OX axis be resting in IRF K and
moving in frame K’.
Consider 2 observers in the 2 frames, measuring the
length of the rod, setting up measurements at their will,
where they localize the endpoints in a simultaneous
manner, each in his frame.

In frame K :
Measured values are: X1, X2 in moments T1=T2
Calculated values, from Lorentz transformations are
X’1 and X’2
which give L’=L* Gamma
where L’ is the calculated length for K’
and L is the measured (and at the same time the proper) length
of the object in frame K.
As Gamma>1
We get L’>L that is : the length attributed to be valid
for frame K’ (the moving frame) IS BIGGER than the measured length
(that is the proper length)
( So far nothing new!)

Alas, you are completely wrong here.

If the rod is at rest in K (T1=T2), then it is not at rest in K',
so the value L’=L* Gamma is not the calculated length for
K’ since the times of measurement not the same and the
rod is *moving* in K'.
You don't measure the length on a moving train by subtracting
the distance to the front and the end of the train is these are
measured at different times.
If you say that the rod is at rest in K, then you must make sure
that T'1 = T'2. And *that* gives you L' = L / Gamma..

This tells you that measured length L' of a moving rod is shorter
than the "proper length"


In frame K’ :
Measured values are : X’1, X’2 in moments T’1=T’2
Calculated values, from Lorentz transformations are
X1 and X2
which give L=L’* Gamma
where L is the calculated length for K (supposed to be the proper
length)
and L’ is the measured length in K’.
As Gamma>1
we get L>L’ , that is : the length attributed to be valid
for frame K IS BIGGER than the measured length in K’ !!!!!!!!!!!!!!!

This ALSO tells you that measured length L' of a moving rod is shorter
than the "proper length"


Comments:

Do you understand your error?

Dirk Vdm

.

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