[ExI] QT and SR
John K Clark
jonkc at bellsouth.net
Sat Aug 23 17:00:22 UTC 2008
"Jeff Davis" <jrd1415 at gmail.com>
> I cannot compete with Mr. Bell's rep on this matter, nor can I agree
> with him. So I'm screwed.
You're not screwed. I think you would agree that if relativity is
consistent and the string breaks in one point of view it must break in
So let's forget about the string for the moment and just imagine
observing 2 distant spaceships at rest relative to you in the night sky
90 degrees apart. Suddenly at the same instant (from your point of
view) both start accelerating to the same very high speed in the
same direction. The apparent distance between spaceships does not
change, but imagine if it did; 90 degrees of the night sky would start
to contract to a point even though neither you nor any of the trillions
of stars in that part of the sky changed their motion one bit.
Obviously it's crazy that now we can only see 270 degrees of the
universe because of what two distant spaceships did. In the real
world particles really do accelerate up to very high velocities but the
night sky does not behave in this chaotic fashion. If you trained a
very powerful telescope on each individual spaceship you would find
they have contracted in the direction of motion, but not the distance
Now forget the spaceships and just observe a string moving very
fast, it will contract in the direction of motion just like spaceships;
put these two things together and you can only have a broken string.
I admit it's a little more difficult to see that the string must break
from the point of view of the spaceships, especially the trailing ship.
I think much of the confusion comes from using terms and reasoning
appropriate for Special Relativity but don't work at all for General
Relativity, and in this thought experiment things are accelerating
so it's General Relativity's gig.
Although it can be a useful approximation if things don't become too
extreme there really is no such thing as an "accelerating frame of
reference". For example, an observer on the lead ship will know
with certainty that he is accelerating and know the direction it is
occurring, he will note that the following spaceship is keeping up
with him so it must be accelerating too. According to the equivalence
principle this is the same as neither spaceship having an engine and
both are just sitting on the surface of the Earth, one at sea level and
the other on top of a small hill. The lead spaceship must be deeper
into that gravitational well (the one at sea level), so when he looks
at the clock in the following spaceship (the one on the hill) he will
find that clock running faster than his own.
> alas, the time lag thing upon which Johns argument is built is
> merely the plain vanilla time lag of information transmitted by
> speed of light EM, and can be disposed of with a mere wisp of
Einstein's made his breakthrough in Relativity not through
mathematical skill but because his intuition told him that this
"time lag" was not an artifact of the particular commutation
system used but a fundamental property of the universe.
It is all very well to say that "the instant I started moving the
fellow at the other end of the string told me he's not moving,
but "really" he is moving"; but this "reality" can never be
confirmed. Einstein's intuition said this "time delay" was saying
exactly what it seemed to be saying, everything came from that.
John K Clark
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