Re: Is This a Subtle but [snip]

Am Thu, 31 Jul 2008 08:08:11 -0700 schrieb Ray Vickson <RGVickson@xxxxxxx>
in 7f7a436a-bad6-419f-bdea-a2ff475d43ea@xxxxxxxxxxxxxxxxxxxxxxxxxxx:

On Jul 30, 1:14 am, The TimeLord <math-n-physics-...@xxxxxxx> wrote:
Am Tue, 29 Jul 2008 21:36:33 -0700 schrieb Shubee <e.Shu...@xxxxxxxxx>
in 42be138c-a4fe-4cad-bcbc-c7ec0402e...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx in
sci.physics.relativity:

It's not clear to me why the Lorentz transformation can't be reduced
to the Galilean transformation by resetting clocks, rescaling
distance measures and fiddling with clock rates according to the
recipe on page 11
ofhttp://www.everythingimportant.org/relativity/special.pdfand
equations (48) to (58).

How do you answer this riddle?

Shubee

Easy. The Lorentz transformation

x' = gamma (x - v t)
y' = y
z' = z
t' = gamma (t - v x / c^2)

is not the same as the Galilean transformation

x' = x - v t
y' = y
y' = z
t' = t

Simple inspection reveals that. The only way the two can ever be the
same is when v=0; but Relativity already has that built in. Rescaling x
or t will not change the underlying nature of the transformation.

Taking c = infinity will also work.

Some derivations of Lorentz from first principles (not using light
velocity, etc.) end up with a Lorentz-type transformation having a
frame-independent constant k having the dimensions of 1/(velocity)^2.
The case k < 0 leads to unphysical behaviour, so can be rejected. Of
course, k = 0 gives Galilean, while k > 0 gives actual Lorentz, which
can then be re-written using k = 1/c^2, where c is a universal speed.
Such derivations do not claim there is any physical "thing" having speed
c, but they leave open the possibility that there is such a thing. Of
course, "light" seems to fit the bill, but even if some future
experiments give varying light speeds when performed to higher accuracy
than attainable up to now, that would still not invalidate SR.

Excellent point overall. However no future experiments will find varying
light speed since under SI c is by definition 299'792'458 m/s. That sets
all derived units in accordance. So no matter what experiment you will
do, c will always be constant at exactly 299'792'458 m/s.

cf
http://physics.nist.gov/cgi-bin/cuu/Value?c

--
// The TimeLord says:
// Pogo 2.0 = We have met the aliens, and they are us!
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