Re: Is Lorentz contraction objectively real?

From: Dale Trynor (dalet_at_nbnet.nb.ca)
Date: 09/14/04 

Date: Tue, 14 Sep 2004 05:24:58 GMT

Tom Roberts wrote:

> Eugene Shubert wrote:
>
>> The question is, Is Lorentz contraction objectively real?
>
>
> That, of course, depends strongly on what you mean by "objectively real"
> -- there is no objective meaning to that phrase (:-)).
>
> When I carry a 2-meter long rod through a doorway that is 1 meter wide,
> I must rotate it so its 2-meter length is not parallel to that 1-meter
> aperture. Is that "objectively real" -- if so, then so is "Lorentz
> contraction"; if not, then not. Note I did NOT shorten the rod in any
> way, I merely rotated it to fit.

[snip]

>>
>> Right. And the question is, How could there ever be objectively real
>> experimental evidence demonstrating that Lorentz contraction is real

Dale Trynor wrote:
I wanted to post in this thread quite some time ago but was afraid it
could become a long one.
One of the best gedankens to work with on this subject is by asking
about if a relativistic ring made up of meter sticks end on end, would
such a ring contract or stay unchanged and examining the how or why of
it all.

Have you seen my post of about a year or so ago on the tank tread paradox.
It worked with a gedanken that examined the idea of how a tank tread
would measure from diferent observers prospectives if one side of it was
motionless wrt the observers of the ring, as it traveled around a giant
ring thats also around a strobe in the middle of the ring. Using a
strobe pulse alows us an instant of time where we can more easily model
what would be photographed by a camera of the tank's treads.

Some things to get you started is by asking yourself how observers would
view a pulse of light from the strobe as it reflects from all the
different areas of the ring. Make the ring 1 light day wide and note how
the observers at the edges of the ring will first see the strobe pulse
and will need to wait 1 day to see the last reflection of the pulse from
its farthest point. Note how simultaneity arguments become interesting
because of the way all our observers will still know that the strobe was
at the center when it pulsed and could easily be made to believe that it
must have simultaneously arrived at all the other areas on the ring even
if they must wait 1 day for the last reflected light to see its proof.

Now the tricky part here is to try and estimate how the tank tread could
appear shorter if they were motionless while on the rings edge. You got
two choices, ever you will see fewer links of the same rest 1 meter
length each or the non moving links must appear in the same number but
now appear shorter than 1 meter each. In case you havent noticed thats
not easy to do if they are non moving they cant be measured shorter. On
the other hand if the tread must become angled so the strobe pulse
arrives at different times on each link giving us a way to explain why
fewer would be exposed and or why they would apear shorter, but then the
problem on how would it still be fixed on the rings edge. What would the
observers on the tank itself observe.

I will add some more tomorrow if you are interested and for now have
some fun trying to solve it.
Dale

>> without equally compelling experimental evidence that nature favors
>> E-synchronization above ~S-symmetry?

[snip]

> Somehow, imagining sliding rulers does not agree with "the most
> obvious"....
>
>
> Tom Roberts tjroberts@lucent.com