[ExI] QT and SR

John K Clark jonkc at bellsouth.net
Mon Aug 25 21:36:34 UTC 2008

"Lee Corbin" <lcorbin at rawbw.com>

> First you say that they're 90 degrees apart in my field of vision,
> then they take off in the same direction (presumably away
> from me).

If the spaceships are going directly away from you that would lead to
a rather dull thought experiment. I thought it was obvious they were
moving parallel to you. Apparently not. My point was that if the
spaceships were 90 degrees apart when they were stationary they
would remain 90 degrees apart when they were moving fast,
although each individual spaceship would contract in the direction
of motion. The string would contract too, so something's got to give.

> The apparent distance between them *does* decrease

Probably not spaceships but things in space very often do accelerate
up to very high speeds. If the above were true the night sky would
look chaotic. I do not observe the night shy to be chaotic, it's not
engineered but it's not chaotic.

> Well, no, that's not correct. According to his *measurements*
>(beyond mere observations) the trailing spaceship is not keeping
> up with him.

I should have said almost keeping up with him, certainly he will
know the other ship must be accelerating and will note that the
guy's clock is running fast. I'm not sure I know what you mean by
measurements beyond mere observations.

> Yes, but that does not address the heart of the mystery.
> I need to go dig  out that excellent paragraph you wrote which
> I vividly remember as a  complete explanation (much better
> than my own earlier and longer one).

Is this what you're talking about?

"If tacked a string inside the cockpit of my accelerating spaceship
from the front to back the string would NOT break because the 
atoms and electromagnetic fields inside the string would shrink at 
the same rate as the atoms in the cockpit walls. However if I tied a
string from the front of my spaceship to the back of another 10 feet
ahead of mine and accelerating at the same rate the string would 
break because the atoms in the sting would shrink just as they did
before but there is nothing else between the two spaceships to
counterbalance that effect, there is only empty space."

"Also, when you hear the term "same frame of reference" it usually
refers to an inertial frame of reference, but this one is accelerating
so you have to be careful;  then you can have all sorts of pseudo 
forces operating WITHIN the frame, like tides. For example, General 
Relativity tells us that rockets firing their engines is equivalent to 
them falling in a gravitational field. If they were falling toward a 
Neutron Star the lower one would be a little closer to the star and 
so puller a little faster than the one above and so the string would
break even though some might say they are in the same frame
of reference."

  John K Clark

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