🚀 go-pugleaf

"Wolfgang G. Gasser" <z@z.lol.li> wrote in message 
news:epo02c$27l$1@atlas.ip-plus.net...
>:   = 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)

I didn't check in detail, but apparently you found no error.

> You write that (under ether hypothesis) the ether-length dx = 3.6 m
> of the contracted ruler corresponds to physical reality.

It just means declaring one inertial frame to be "really" at rest.

> 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.

Sure it does. In words: the proper distance of 10 m in S is measured in S' 
as spanning only 6 m.
Similarly, a proper distance of 10 m in S' is measured in S as spanning only 
6 m.
Thus a proper distance of 10 m is measured in the other frame as a moving 
distance that appears to be *contracted* to only 6 m.

Of course, you could say that in SRT one has an "expanded" view of the 
moving distance that is at any time next to one's ruler due to the apparent 
contraction of the moving system. That is however only good for confusing 
matters. Clearly, you managed to confuse yourself with it.

[skip more talk about expansion]

> 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

The brackets make your above statements ambiguous, and in principle 
selfcontradictory.

Instead, you were discussing the original interpretation of SRT according to 
which one unknown inertial frame corresponds to the ether, so that one has 
as metaphysics:

- contraction of moving objects wrt the ether
- apparent contraction of ether distances wrt a moving inertial frame (that 
is assumed to be at rest, by convention)

> 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.

That is incompatible with SRT. I must conclude that your version of SRT is 
erroneous.

> 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.

I can make no sense of that last sentence, but your reference below 
clarifies it.

> (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.

I see that also Tom Roberts tried in the past but could not get through to 
you - thus I won't try more after this.
Now I copy your stuff here, and will comment only this time:

On Feb 2 2000, 9:00 am, "z@z" <z...@z.lol.li> wrote:
> :  = Tom Roberts
> ::  = Wolfgang G.
>
> :: But I cannot believe that the basic asymmetry in the ether has no
> :: effect at all. Isn't there a problem with the intensity of light?

If there were, then this would "kill" SRT - the math is identical.

> :: Intensity is inversely proportional to the distance square. If the
> :: ether is the medium of light, then light intensity decreases with
> :: ether distance, doesn't it?
> :
> : Yes, when measured in the ether frame. But intensity is also
> : proportional to the solid angle subtended by the detector, and
> : _that_ is not invariant. Do the computation and you will find
> : that competing effects cancel out exactly.
>
>       | - - - - - - - o - - - - - - - |
>    detector       source of       detector
>                     sound
>
> The sound intensity registered by the two detectors, unlike the
> measured frequency, is not independent of the speed of the medium
> (the air) wrt the system.
>
> A spherical light wave is Lorentz invariant:
>
>   x^2 + y^2 + z^2 = (ct)^2   -->  x'^2 + y^2 + z^2 = (ct')^2
>
> But I don't think that all segments corresponding to given solid
> angles are Lorentz invariant in the same way. We can for instance
> divide the original spherical wave into two parts separated by
> the circularly propagating wave
>
>   x = 0, y^2 + z^2 = (ct)^2
>
> Thinking about stellar aberration is enough to recognize that
> this circular wave cannot be Lorentz-transformed to
>
>   x' = 0, y^2 + z^2 = (ct')^2
>
> This means that if the number of photons per solid angle is
> uniform in the system at rest then it cannot be uniform in the
> moving system and vice versa.
>
> In SR it is reasonable to assume that it is always the frame
> of the source where the number of photons per solid angle is
> uniform. I doubt however that this is a reasonable assumption
> in an ether theory.

Why? it's a matter of momentum conservation. Even more, Ives *derived* SRT 
based on the ether postulate plus conservation of energy and momentum.

>       | - - - - - - - o - - - - - - - |           -->
>    detector       spherical       detector         v
>                  light source
>
> Let us assume that this system moves at v = sqrt(0.99)c wrt the
> ether and that the distance between the source and each dectector
> is compressed from 10 m (restlength) to 1 m in the ether.

I can't make sense of that sentence...

> Whereas light to the right detector has to travel over 199.5 m in
> the ether, the light path to the opposite detector is only 0.5 m.

>   1 m / (1 - sqrt(0.99) = 199.5 m
>   1 m / (1 + sqrt(0.99) =   0.5 m
>
> The sound analogy would result in an intensity difference
> factor of (199.5 m / 0.5 m)^2. So the intensity registered by
> the left dectector would be (at least) 159 thousand times
> stronger than by the right detector.

Maybe you think that as measured in the rest frame (or ether frame), the 
light will be emitted uniformly. Tom Roberts already told you that that is 
not so. Experiments with moving gamma sources confirm that the radiation is 
concentrated forward, as theory predicts: what is sent out under a straight 
angle in the moving frame, is sent out nearly straight forward in the lab 
frame.

> Wolfgang Gottfried G. (0:032.6)

> Cheers, Wolfgang

Good luck,
Harald

> ________________________________________________________________________
>
> 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.
>
>