Re: Length Contraction Fully Explained


kk wrote:
xray4abc complained:
Still I do not understand why are you focusing
on the matter of clocks.

Here's why:

Since both Lorentz's and Einstein's theories are equal
as far as the first postulate is concerned (both have
a shared one-way light law for all frames, with the
former's being c±v, and Einstein's being simply c),
we see that the second postulate is the only difference
between Lorentz and Einstein.

Here is Einstein's version of his 2nd postulate:
"Any ray of light moves in the 'stationary' system of
coordinates with the determined velocity c, whether
the ray be emitted by a stationary or by a moving body.

Hence

VELOCITY = LIGHT PATH/TIME INTERVAL

where time interval is to be taken in the sense of the
definition in § 1."

At this crucial point, it should be clear to anyone
that 50% of special relativity consists solely of
a mere definition, and a definition is not physics.

Wrong ! In short, one can not think, operate or
design any experiment, without having in mind a
model of reality, that is, using abstractions and some
postulates and/or definitions. You have to start somewhere.
You can not have, A priori, some absolute knowledge.
Even the basics of classical mechanics can be
taken ,as H. Poincare has pointed out, only as
postulates / idealized truth.

In case it is not clear, let me point it out:
The TIME portion of light's one-way speed is given
solely by definition from Einstein, and has nothing
at all to do with experiment (other than conforming
to the trivial condition that the sum of any two
one-way times must equal the round-trip time).

If we look at the definition, we see that it pertains
to at least two clocks per frame.

Here is Einstein's definition from § 1:
"We have not [yet] defined a common 'time' for [two clocks
at two points] A and B [in space], for the latter cannot
be defined at all unless we establish 'by definition' that
the 'time' required by light to travel from A to B equals
the 'time' it requires to travel from B to A."

Einstein's phase "cannot be defined at all" tells us that
he believed that there is no other solution to the two-
clock time problem.

Einstein's word "equals" tells us that he believed that
clocks are not properly related unless they have been
set manually (forced) to get the same value "c" for
light's one-way "speed" in both directions.

I would say he, simply, meant space isotropy !

These two insights provide us with the core meaning
of the second postulate, as follows:

[1] Clocks cannot be absolutely synchronized.

[2] Clocks are properly related only if they
are related per Einstein's definition.

Both of these core ingredients of the 2nd postulate are
wrong, which makes SR wrong because - as we saw above -
SR is nothing but the 2nd postulate.

Do you understand now why I am focusing on clocks?
I cannot understand why anyone would focus on
anything other than clocks as far as SR is
concerned.

--kk--

Your thread started with length contraction.
I have pointed out, that, the thing has to do more
with the limits imposed on measurements by the
limited speed of energy/action/information transmission
than with other issues.
As such, we can get not only length "contraction"
but length "dilation" too, depending on which way we
make our measurements.
The relation of time, simply
follows the relation of lengths as
they refer to the same measurements.
Do not stick too much to what Einstein has
said at a certain moment in his life, as he himself
evolved a lot along the years.
LL

.

Relevant Pages

  • Re: Length Contraction Fully Explained
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  • Re: Motion Through Space Is Meaningful
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  • Re: Light Postulate Invalidated
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  • Re: Light Postulate Invalidated
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  • Re: Light Postulate Invalidated
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