Length Contraction Fully Explained

Common sense says:
Any inertially-moving rod has only two endpoints;
by not moving relative to each other, these two points
produce a single constant intrinsic rod length (even
if we are not currently able to determine said length).

Therefore, if observers in various frames find different
lengths for said rod, then this must be due to some
observer-dependent process, and _not_ to the rod itself.

Tom Roberts **agrees** by saying:
When you look at a building from directly in front,
it appears to be wider than when you look at it from
a corner. This effect does not affect the building
itself, of course, and is purely due to your point
of view. ... Similarly in SR, "length contraction"
is purely a geometrical effect, an artifact of one's
point of view ....
http://tinyurl.com/hvpej
[Roberts to Nicolaaas Vroom 3-30-06]

But what is the root physical cause of SR's
observer-dependent "length contraction"?

Tom Roberts tried to pin it down as follows:
Because the rod is moving, naturally the observer
in A must mark both ends _simultaneously_ in
frame A (which requires assistants) and then use
a meterstick at rest in frame A to measure the
length between the marks. Ultimately it is the
DIFFERENCE IN SIMULTANEITY between frames A and
B that is the source of the length contraction ....
http://tinyurl.com/hvpej
[Roberts to GSS 3-19-06]

While Roberts _believed_ he had located the root
(or ultimate) cause as being "the difference in
simultaneity," what we really need to know is
What causes this difference in simultaneity?

In other words, we need to find the physical cause
of Einstein's relativity of simultaneity.

Here is the story:

Being unable to absolutely synchronize clocks, Einstein
could not use clocks at events to correctly determine
their occurrence times, so he had to fall back on using
light signals sent from the events, merely _specifying_
that the arrival times of these signals in each frame
are to be used as the "occurrence times" of the events.

Clearly, since each frame moves _differently_ relative
to these signals, each frame's observers will see the
signals arrive differently, so we can now see that the
ultimate physical cause of the relativity of simultaneity
is simply different frame movements wrt to light signals.

Of course, if Einsteinian observers want to use _clocks_
at the events instead of using light signals from the
events, then all they have to do is make their clocks
correspond to Einstein's light-signal scheme, and this
can be done very simply by using midway-emitted light
signals to start clocks on zero.

Obviously, each frame's clocks will actually be started
differently due to the different frame motions relative
to the signals.

For example, just as in Einstein's own train/embankment
thought experiment, one frame's left clock may move
toward its approaching signal, whereas the other clock
will move away from its signal, so the clocks would not
be started truly simultaneously.

Then, if this frame's Einsteinian clocks are used to
determine the time between two absolutely simultaneous
events, then the clocks will report that the events
did not occur simultaneously.

And since events are observer-independent, this report
flatly contradicts reality, as do all other such reports
from all other Einsteinian frames' clocks (except those
from the one frame whose clocks became truly synched by
Einstein's light signals due to a lack of frame motion
either toward or away from the signals).

Given the simple fact that all but one of Einstein's
frames contains absolutely asynchronous clocks due to
absolutely different frame movements wrt the light
signals used to set Einstein's clocks, we can at last
_fully_ understand the relativistic "length contraction."

Just as Tom Roberts said, this "contraction" is merely
an artifact of Einstein's relativity of simultaneity,
which, in turn, is an artifact of Einstein's absolutely
asynchronous clocks. Einsteinian observers cannot truly
simultaneously pin down the end points of a passing rod,
so they mis-measure the rod, calling it shortened, and
each frame's observers find a different length for one
and the same passing rod, which, of course, cannot have
but one physical length, as we noted above.

BUT WHY STOP AT THE "LENGTH CONTRACTION"?

It should be crystal clear to anyone by now that thanks
to Einstein's asynchronous clocks, NONE of his two-clock
results can possibly be correct.

This means that special relativity's "time dilation,"
"momentum variance" (sometimes called "mass increase"),
"addition of velocities" (or velocity composition),
transformation equations, and light's one-way, 2-clock
speed are ALL INCORRECT.

In other words, given absolutely synchronous clocks,
exactly none of these relativistic results would occur,
including the invariance of light's one-way speed.

All of special relativity's results are due to Einstein's
use of asynchronous clocks, which, in turn, are due to
the use of a mere definition.

Clearly, a _definition_ has nothing to do with the workings
of the physical world, and cannot produce a scientific theory.

--kk--

.

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