🚀 go-pugleaf

On May 7, 8:49 am, Pentcho Valev <pva...@yahoo.com> wrote:
> http://philsci-archive.pitt.edu/archive/00000960/
> Why Thought Experiments Do Not Transcend Empiricism
> John D. Norton 2002
> "(D1) In Euclidean geometry, the measured circumference of a disk is
> pi times its diameter. (Premise)
> (D2) The geometry of a non-rotating disk is Euclidean. (Premise)
> (D3) The motion of a radial element on a rotating disk is
> perpendicular to its length, so that (according to special relativity)
> the length is unaltered. (Premise)
> (D4) The motion of a circumferential element on a rotating disk is
> along its length, so that (according to special relativity) the length
> is contracted. (Premise)
> (D5) Therefore the measured circumference of a rotating disk is more
> than pi times the measured diameter. (From D2, D3, D4)
> (D6) Therefore the geometry of a rotating disk is not Euclidean. (From
> D1, D5)"
>
> Good logic? Bad logic? Does D5 follow from D4? Note that John Norton
> is the cleverest Einsteinian so if his logic (which is Divine Albert's
> logic of course) is bad, let us try to imagine the logic of much
> sillier Einsteinians.

In 1902, in "La Science et l'hypothèse", Henri Poincaré, in order to
justify non-Euclidean geometries, presented a parabole. Bidimensional
creatures live on a disk. The disk is heated under its center so that
the temperature is high at the center and decreases towards the
periphery. The creatures use rigid measuring rods in order to
determine the geometry of their world. They know nothing about the
heater and accordingly discover that the ratio of the circumference
and the diameter is greater than pi. The creatures conclude that
Euclidean geometry cannot be true on the disk.

Albert the Plagiarist (aka Divine Albert) also wanted to create a non-
Euclidean geometry but did not know that Poincare's parabole had
nothing to do with the rotating disc thought experiment. So, by
appropriating Poincare's result without much ado, Albert the
Plagiarist created a problem which is usually referred to as the
Ehrenfest paradox and has four solutions, each of them (except the
fourth) being offered as a consequence of Einstein's 1905 false light
postulate:

1. Ehrenfest: The ratio of the circumference and the diameter of the
rotating disk, as judged by a non-rotating observer, is smaller than
pi.

2. Einstein: The ratio is greater than pi.

3. M. Strauss (Int.J.Theor.Phys. 11, 107, 1974): The ratio is equal to
pi.

4. The rest of the scientific world: Who cares.

Needless to say, Ehrenfest's solution is the correct one, in the sense
that it is the only VALID consequence of Einstein's 1905 false light
postulate. Still initiated Einsteinians know that, if Einsteiniana is
to be eternal, they should explicitly worship Einstein's solution, no
matter how idiotic it is. From time to time some naive non-initiated
Einsteinian "repeats the common mistake" and refers to the truth but
initiated Einsteinians correct him immediately:

http://journals.ucfv.ca/jhb/Volume_3/Volume_3_Howard.pdf
Don Howard: "In his discussion of Einstein’s "rotating disk" thought
experiment, an important step on the road to general relativity's
implication of spatio-temporal curvature, Isaacson repeats the common
mistake of claiming that the circumference of the disk contracts,
while the diameter does not, yielding a ratio of circumference to
diameter less than π (p. 192). In fact, it is the yardstick used to
measure the circumference that contracts, yielding a circumference
seemingly larger than for the stationary disk and thus a ratio of
circumference to diameter greater than π. For a careful discussion,
see John Stachel, “The Rigidly Rotating Disk as the ‘Missing Link’ in
the History of General Relativity,” in Einstein and the History of
General Relativity, Don Howard and John Stachel, eds. (Boston:
Birkhäuser, 1989), 48-62."

Pentcho Valev
pvalev@yahoo.com