Re: SR cannot determine Contraction

On Feb 29, 10:22 am, PD <TheDraperFam...@xxxxxxxxx> wrote:
On Feb 29, 11:40 am, Dono <sa...@xxxxxxxxxxx> wrote:





On Feb 29, 8:38 am, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:

Dono wrote:
On Feb 26, 8:06 pm, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:
Dono wrote:
In other words, do you , Tom Roberts, believe that uniform relative
motion makes objects shorter?
That's your confusion. This is phrased so poorly that no answer is
possible. Your phrase "makes objects shorter" implies a change to the
object, but observations made from another frame cannot possibly affect
the object itself.

Correct. But this is exactly what the paradox states, that , from the
barn frame, the pole becomes magically shorter, by virtue of relative
motion.

You insist on using loaded words. This is not "magic", this is
GEOMETRICAL PROJECTION. When you approach a doorway with a ladder, in
some orientations the ladder fits through, and in other orientations it
doesn't. THIS IS THE SAME PHENOMENON, but it occurs in the X-T plane,
not the X-Y plane like the ladder's rotation. Relative velocity is a
(hyperbolic) ROTATION in the X-T plane.

        Actually the analogy would be better if one considered
        moving the doorway around the ladder, leaving the ladder
        fixed. But common experience does not include either
        moving doorways or poles moving at 0.8 c.

All this, while the contraction is "stressless".

Of course there is no stress -- what stress is induced in the ladder
when you rotate it? Or rather, when you look at it from another angle?

Then you are stuck with answering the following:

Would you care to show how?

-while in the proper frame S_0 :    \ Sigma (F_internal) = 0

-in a frame moving with v wrt S_0  \Sigma (F'_internal)=0 (where F'_i
is the Lorentz transformation of F_i) and that , somehow, magically,
the atom sizes or the lattice spaces between atoms have Lorentz
contracted. I think Lorentz spent a good
10 years of his life trying to prove that and it amounted to nothing.

It's not that complicated. One *measures* the rod to be of shorter
length. One *measures* the rod to have no fewer atoms strung end-to-
end -- or at least finds no evidence of some atoms being ejected from
the length.

I never said that, so please abstain from constructing strawman. Be a
little more respectful and less condescending.

One *measures* that there is no stress in the rod -- or at
least finds that there is no evidence of any stress.

How? I asked you to calculate and you are responding with prose:

Would you care to show how?


-while in the proper frame S_0 : \ Sigma (F_internal) = 0


-in a frame moving with v wrt S_0 \Sigma (F'_internal)=0 (where F'_i
is the Lorentz transformation of F_i) and , YET
the atom sizes or the lattice spaces between atoms have Lorentz
contracted. I think Lorentz spent a good
10 years of his life trying to prove that and it amounted to nothing.


I know that you can calculate very well, so , I'd appreciate some
math




One therefore
concludes that the interatomic spacing has also contracted.

Please show some calculations.
Would you care to show how?


-while in the proper frame S_0 : \ Sigma (F_internal) = 0


-in a frame moving with v wrt S_0 \Sigma (F'_internal)=0 (where F'_i
is the Lorentz transformation of F_i) and that , somehow, magically,
the atom sizes or the lattice spaces between atoms have Lorentz
contracted. I think Lorentz spent a good
10 years of his life trying to prove that and it amounted to nothing.


I know that you can calculate very well, so , I'd appreciate some
math




Then one
slaps oneself on the forehead when it occurs that there is no reason
why an atom should be any more inherently absolute in dimensions than
a rod and somehow resist the effect of contraction.

You are being condescending again. You have no proof of the above
(neither theoretical nor experimental)
Besides, some published athors will sharply disagree with you.







The whole point is the
interpretation of length contraction: real vs. imaginary. You seem to
believe it is real, Michael Janssen points the other way.

Stop using such loaded and ambiguous words -- they merely confuse you
and your reader: "real" means many different things to many different
people. Discuss MEASUREMENTS, not what someone happens to think is
"real". There is no doubt that MEASURING the length of a moving pole
will obtain a value smaller than its proper length. And if your
measurement includes rapidly opening and closing doors, the pole can fit
inside a barn that is shorter than the pole's proper length. <shrug>

All right , let's make it even less ambigous, look here:

http://en.wikipedia.org/wiki/Length_contraction#A_trigonometric_effec...

What in the Roberto Torretti statement " Relative motion will not make
a solid body shorter in the way that, say, heat
makes it larger." don't you understand, Tom?

That's right, it isn't the same process. The shortening of the rod
should in no way be confused with what happens when a rod is cooled.


So what part in what I have been telling you: " Relative motion will
not make
a solid body shorter in the way that, say, heat makes it larger."

don't you understand, Paul? I have been telling you the same exact
thing.




And that is a *measurable* result. The answer that observers in *all*
frames will agree is that, no, the barn doors will not clip the rod.
Different observers will have different accounting for *why* that is
the case, but they will all agree on that.


Not if " Relative motion will not make a solid body shorter", so you
are still short of a valid explanation in the barn frame.



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