🚀 go-pugleaf

On Sep 3, 11:22 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote in
sci.physics.relativity:
> Note also that "length contraction" is misnamed, and no object's length actually
> contracts, only MEASUREMENTS of length do so. But don't think it is purely
> measurements -- because the underlying effect is a geometric projection, it can
> have physical consequences (e.g. the kinematics of high-energy collisions and
> interactions).
>
> Tom Roberts

Bravo, Honest Roberts! When your brothers Einsteinians teach that the
80m pole remains inside the 40m barn IN A COMPRESSED STATE, they mean
just this: the pole is not contracted at all - the underlying effect
is a geometrical projection with physical consequences:

http://math.ucr.edu/home/baez/physics/Relativity/SR/barn_pole.html
"These are the props. You own a barn, 40m long, with automatic doors
at either end, that can be opened and closed simultaneously by a
switch. You also have a pole, 80m long, which of course won't fit in
the barn. Now someone takes the pole and tries to run (at nearly the
speed of light) through the barn with the pole horizontal. Special
Relativity (SR) says that a moving object is contracted in the
direction of motion: this is called the Lorentz Contraction. So, if
the pole is set in motion lengthwise, then it will contract in the
reference frame of a stationary observer.....So, as the pole passes
through the barn, there is an instant when it is completely within the
barn. At that instant, you close both doors simultaneously, with your
switch. Of course, you open them again pretty quickly, but at least
momentarily you had the contracted pole shut up in your barn. The
runner emerges from the far door unscathed.....If the doors are kept
shut the rod will obviously smash into the barn door at one end. If
the door withstands this the leading end of the rod will come to rest
in the frame of reference of the stationary observer. There can be no
such thing as a rigid rod in relativity so the trailing end will not
stop immediately and the rod will be compressed beyond the amount it
was Lorentz contracted. If it does not explode under the strain and it
is sufficiently elastic it will come to rest and start to spring back
to its natural shape but since it is too big for the barn the other
end is now going to crash into the back door and the rod will be
trapped IN A COMPRESSED STATE inside the barn."

Pentcho Valev
pvalev@yahoo.com