🚀 go-pugleaf

:   = harry in news:1169731394_2145@sicinfo3.epfl.ch
::  = Wolfgang G. Gasser in news:ep8ftp$48b$1@atlas.ip-plus.net

:: So S-simultaneity leads to contraction of S' wrt S (or expansion of S
:: wrt S') and S'-simultaneity to contraction of S wrt S' (or expansion
:: of S' wrt S).

: In no inertial system does any object appear to be "expanding".

Let us take a 6 m long (proper length) ruler moving at v = 0.8 c
wrt the ether, as described in your article:
http://groups.google.com/group/sci.physics.relativity/msg/9db6b5df54b79f1d
(See APPENDIX for my treatment/summary of your example)

You write that (under ether hypothesis) the ether-length dx = 3.6 m
of the contracted ruler corresponds to physical reality. Nevertheless,
you ascribe the proper length dx' = 6 m' to ruler. If we assume moving-
ruler simultaneity, i.e. dt' = 0, we get

  dx = gamma * (dx' + v*dt')  -->   dx  = gamma * dx'
                                        = (5/3) * 6 m' = 10 m

This ether distance of 10 m has a very concrete meaning. Let us assume
that along the whole length of the ruler are small flash lamps next to
each other. If they fire all at the same time (S'-simultaneity) then
the distance between the first and the last flash is 10 m in the ether.
However, the flashes do not appear at the same time: at first appears
the flash from the rear, and 80/3 ns later the last flash from the
front. During these 26.666 ns the ruler moves 6.4 m, so increasing the
distance from the contracted length of 3.6 m to the expanded of 10 m.

Let us further assume that the flash lamps fire at t' = 0 in red,
at t' = 25 ns' in blue, at t' = 50 ns' again in red, and so on.
Because the next firing always occurs, when the rear end passes the
ether position where the flash from the font end fired the last time,
this represents a measurement of ether distances using the ruler
length of 6 m'. In the ether this results in an apparent light source
moving at 0.8 c and changing after each a unity of 10 m from red to
blue or inversely.

So it should be obvious that only inasfar (i.e. S'-simultaneity) as
the ruler expands from 6 m' to 10 m wrt the ether, ether distances
can contract wrt the ruler, e.g. from 6 m to 3.6 m'.

See also:
http://groups.google.com/group/sci.physics.relativity/msg/2a0f373cafaf3b3a

Your assumptions

  - real contraction of moving objects wrt the ether
  - no (real) contraction of ether distances wrt moving objects
  - no (apparent) expansion of moving objects wrt the ether

are inconsistent with the principle of "apparent relativity" (i.e.
apparent/empirical equality of moving frames with the ether frame).
Therefore, I concluded that you and others at least sometimes confuse
"contraction of ether distances wrt moving objects" with "contraction
of these moving objects wrt to the ether". Nevertheless, the "fatal
error in LET" I'm dealing with disappears if we accept: apparent
expansion of moving objects caused by local Poincar�-simultaneity.

There is however a major empirically relevant difference between
SR and LET:

Assume a small spherical homogenous light source at the center of
a sphere with a diameter of 6 m. If the sphere is at rest in the
ether, the light intensity received from the source by the inner
surface of the sphere is obviously homogenous. Now let us assume
that the sphere moves at 0.8 c (and light propagates isotropically)
wrt the ether. Both the light source and the surrounding sphere are
contracted, resulting in analogous ellipsoids. Nevertheless, the ether
drift of -0.8 c (think about aberration) would strongly increase the
light intensity at the rear end at the expense of the front end.
(Received frequencies are the same.)

See also:
http://groups.google.com/group/sci.physics.relativity/msg/583757ad63031a21

At least in this case it is obvious, that length contraction and
time dilation are not enough to simulate the predictions of special
relativity.

Cheers, Wolfgang

________________________________________________________________________

APPENDIX:

A ruler with a rest length of 6 m passes at v = 0.8 c a rod of the
same length at rest in the ether.

The length dL' = 6 m' of the ruler is contracted by gamma in the ether:

   gamma = 1/sqrt(1-v^2/c^2) = 1/sqrt(1-0.8^2) = 5/3 = 1.666

   dL  =  dL' / gamma  =  6 m' / (5/3)  =  3.6 m

Time intervals dt' of clocks fixed on the ruler (x' = const) are
dilated/expanded wrt to the ether time:  dt = dt' * gamma

         ruler                                         --> v = 0.8c
  |--------+--------|               rod
                      |=============================|      v = 0
   < - - 3.6 m - - >   < - - - - -  6 m  - - - - - >
   < - - - - - - - - - -  10 m - - - - - - - - - - >

Clocks on both ends of the ruler are synchronized using a light signal
from the center of the ruler. In the ether system, the light signal to
the right clock (in front) needs

  1.8 m / (c-v) = 1.8 m / 0.2 c = 30 ns

and passes an ether distance of 30 ns * c = 9 m. The light signal to
the left clock (in the rear) needs only

  1.8 m / (c+v) ) 1.8 m / 1.8 c = 10/3 ns = 3.333 ns

and passes an ether distance of only 3.333 ns * c = 1 m. Thus in the
ether, the rear clock is ahead of the front clock by:

  time_offset = 30 ns - 10/3 ns = 80/3 ns = 26.666 ns

Wrt the dilated/expanded time of the moving clocks, the time offset' is
time_offset / gamma = 26.666 ns * (3/5) = 16 ns'.


 t'=0           t'=-16ns'
  |--------+--------|
                      |=============================|
Fig. 1


  t'=1ns'          t'=-15ns'
    |--------+--------|
                      |=============================|
Fig. 2

                    t'=10ns'           t'=-6ns'
                      |--------+--------|
Fig. 3                |=============================|


                                t'=16ns'           t'=0
                                  |--------+--------|
Fig. 4                |=============================|


                                                t'=25ns'             9ns'
                                                    |--------+--------|
Fig. 5                |=============================|


Let us define t' = 0 as the moment, the right clock of the ruler
passes the right end of the rod (Fig. 3). The left clock then
(ether simultaneity) indicates t' = 16 ns'.

The distance passed by the left clock of the ruler between Fig 1. and
Fig 4. is 10 m. During a movement of 10 meters a clock advances (proper
time) by

  dt' = 10 m / 0.8 c * gamma = 10 m = (0.24 m/ns) / (5/3) = 25 ns'

In order to determine the proper speed v' as measured from the moving
ruler, we can use Fig. 4 und Fig. 5. The right end of the rod passes
at t' = 0 the right clock of the ruler, and at t' = 25 ns' the left
clock. So wrt the ruler, the right rod end moves dL' = 6 m' in
dt' = 25 ns', resulting in a proper speed of v' = dL'/dt' = 0.8 c.

In order to determine length contraction of the rod at rest wrt to
the moving ruler, we can take the left ruler end of Fig. 1 and the
right ruler end of Fig. 4, both at the same local time t' = 0. The
distance between these two ends is 10 m in the ether. And because to
these 10 m corresponds a proper length of 6 m', the 6 m long rod
contracts to 6 m' * (6 m / 10 m) = 3.6 m' wrt the ruler.