Re: Einstein's math and physical objects

dseppala_at_austin.rr.com
Date: 01/09/05 

Date: Sun, 09 Jan 2005 14:42:54 GMT

On Sun, 09 Jan 2005 04:27:38 GMT, Tom Roberts <tjroberts@lucent.com>
wrote:

>dseppala@austin.rr.com wrote:
>> if I were to go into a lab here on
>> earth where the disk has zero velocity along the x-axis (as in the
>> final reference frame of the problem I posted), it is physically
>> impossible for me to have the two disks more than 180 degrees out of
>> phase without the wires crossing (touching). There is no way to make
>> that happen.
>
>Sure. But that is _NOT_ what happens when the twist is induced by the
>difference in simultaneity between initial and final inertial frames.
>
>In your example above, consider a series of X=constant planes, for the
>constant varying between 0 and L (the locations of the wo disks). Only
>in the first and the last planes are the wires at opposite points of the
>circle formed by the disks; indeed at x=L/2 the two wires intersect. But
>in the original situation being discussed, in the final inertial frame
>every one of those planes has the wires at opposite sides of that
>circle, and they never touch.
In the final reference frame, you say the wires never touch. Please
explain what keeps each of these wires from taking the shortest path
between the connection points on the two end disks. What makes these
wires behave differently then wires in the final reference frame that
weren't accelerated and are attached to the same points as the wires
that were accelerated?
Thanks
David

>
>You are too mesmerized by "wires stretching", and are ignoring the real
>cause of this -- the difference in simultaneity between different
>inertial frames. Go back and read my analogy of the focal plane camera
>scanning along x while the disks and wires are spinning -- that is a
>much better analogy than your completely-different situation above.
>
>
>> Several people who posted a response think that the wires remain as if
>> they were on the surface of a cylinder before, during and after the
>> acceleration as viewed by observers in the final reference frame.
>> This cannot be because Einstein's theory actually requires a physical
>> stretching of the wires during the acceleration because the two disks
>> are accelerated in an identical fashion as measured in the original
>> reference frame.
>
>You are ignoring the nature of the stretching (I'm back to the original
>situation here). The stretching is caused by the fact that in the
>initial frame the disks are a distance L apart, and in the final frame
>they are L*gamma apart. But the twisting is due to the differece in
>sinultaneity, and involves no stretching at all. And it is the
>combination of the twisting and the difference in simultaneity that
>keeps the wires on the surface of the cylinder in the final frame.
>
>
>> contrary to your posts, the wires do
>> not remain on the surface of a cylinder. That perhaps is what your
>> math tells you, but that is not what experimentally happens.
>
>You have not done the orignal experiment (accelerating the spinning
>disks+wires to a large velocity and then observing them). Simply
>stringing up some wires and disks and then twisting them does not come
>anywhere close to the physical situation of the original problem.
>
>Go back and read my analogy of the focal plane camera scanning along x
>while the disks and wires are spinning -- that is a much better analogy.
>
>
>Tom Roberts tjroberts@lucent.com

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