Re: SR cannot determine Contraction

On Feb 17, 11:55 pm, kenseto <kens...@xxxxxxxxxx> wrote:
On Feb 17, 9:30 am, "Paul B. Andersen"





<paul.b.ander...@xxxxxxxxxxxxxxx> wrote:
Peri of Pera skrev:

SR cannot determine Contraction

Lorentz proposed contraction of moving objects in a paper 'The
relative motion of the earth and the ether', Versl.Kon.Akad.Wetensch.
1, 74 in 1892 and then published the Lorentz transformation formulas
in 1899 according to which objects moving through space contract
parallel to the direction of motion and in proportion to their speed
[L'=L/sqrt(1-v^2/c^2)]. Einstein accepted the formulas but writes in
1916 (Relativity: The Special and General Theory, Chapter 16): "The
contraction of moving bodies follows from the two fundamental
principles of the theory".

The real value of v in the formula is indeterminate i.e. the real
speed of a body is unknown. However, the speed relative to other
bodies may be known. If body A moves relative to body B with a speed
of 200000km/sec, body A is seen by observers on B to contract by L/
sqrt(1-200000km/sec^2/c^2) and if body A moves at the same time
relative to body C with a speed of 100000km/sec it is seen by
observers on C to contract by L/sqrt(1-100000km/sec^2/c^2).

Conclusion: SR is useless. It does not tell us anything about the
state and condition of A, B or C but gives in every instance an
incorrect amount of the contraction of body A.
Peter Riedt

According to SR, body A doesn't contract just because it is seen:
"by observers on B to contract by L/sqrt(1-200000km/sec^2/c^2)"
and:
"by observers on C to contract by L/sqrt(1-100000km/sec^2/c^2)"

So what "incorrect amount of the contraction of body A"
are you referring to?

Your description of SR contraction is correct. SR contraction is a
perspective geometric effect....from the perspective of observer B,
A's rod is contracted by a factor of L/sqrt(1-200000km/sec^2/
c^2)"....from the persective of C, A's rod is contracted by a factor
of L/sqrt(1-100000km/sec^2/c^2)".

BTW, IRT agrees that there is no physical length contraction of a
moving rod. However, the light path length of a moving rod is changing
according the factor of 1/gamma or gamma. That means that the light
path length of a moving rod can be shorter or longer than the light
path length of the observer's rod.

OTOH, PD insisted that physicists have performed experiments that show
real physical length contraction. Can you comment on that?

Ken Seto

Ken,
Roger Penrose and James Terrell did some experiments in the 50's in
respect of contraction visibility.
Peter Riedt




In a previous posting, I wrote:
"A clock isn't affected in any way by an arbitrary
observer's motion relative to the clock.
But the clock's motion relative to the observer
will affect the observer's _observations_ of the clock."

A more general statement would be:
An object isn't affected in any way by an arbitrary
observer's motion relative to the object.
But the object's motion relative to the observer
will affect the observer's _observations_ of the object.

--
Paul

http://home.c2i.net/pb_andersen/-Hide quoted text -

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