Re: Circular motion in SR

On Mar 20, 4:53 pm, rbwinn <rbwi...@xxxxxxxx> wrote:
On Mar 20, 1:13�pm, PD <TheDraperFam...@xxxxxxxxx> wrote:




Special relativity does not and can not describe a satellite's orbit,
regardless of your uneducated suggestion. You want to use GR, which
you also do not understand.

Sorry, Eric, go try to snow someone else. �All you are doing is trying
to tell me that because you went to school and took some classes, you
are better than me. �This is a legal argument used by Europeans. �Here
in the United States people have equal rights. �As far as mathematics
is concerned, there is no obligation for anyone to follow your
dictates. �If special relativity can be applied to motion in a
straight line, it can also be applied to motion in a curved line.
That is one of the applications of calculus. �I can remember that
much.

And there is the boundary between math and physics. For while a
straight line and a curved line can have some of the same applications
mathematically, physically they are quite distinct. An object in
straight line motion can be accelerationless and inertial. An object
in a curved line cannot possibly be inertial. Newton understood this
point enough to distinguish the first and second laws of motion.

Well, all right, but there is still experiment. �Scientists claim they
orbited a clock in a satellite and when they recovered it, it had run
slower than an identical clock on earth. �So there is some correlation
between Special Relativity and a curved orbit.

Some, but it's not as tight as you think. Oh, and there is that
General Relativity business, too.

�According to
scientists, a moving clock is slower than a stationary clock whether
it is orbiting or moving in a straight line.

Well, no, that's not quite what it says, though I'm sure it's put that
way in comic-book versions of SR.
What it does say is that a non-straight path through spacetime has the
shorter proper time than a straight path through spacetime. This is
precisely also why the traveling twin comes back younger. It doesn't
have anything to do with whether one is moving and the other is not.
That is precisely the misconception that the twin puzzle is aimed to
correct. The neophyte looks at the traveling twin and says, "But
motion is relative, and I can take the traveling twin to be still and
the earth twin to be moving, and then the rule that the moving twin's
clock runs slower doesn't work." And the moral of that little story
is: that's right, and that's because which one shows lower elapsed
time has NOTHING TO DO with which one is moving, so erase that from
your wee little mind.

Well, that is interesting, but I never did think much about the
twins.  My equations indicate that according to the rotation of the
sun, they would both be the same age.

But the rotation of the sun is not the standard. The standard is
defined in terms of reproducible physical processes that can be
replicated locally.

If the traveling twin comes back, his heart having beaten only half as
many times as his Earth twin's, his hair still brown where the Earth
twin's has turned gray, and with the traveling twin's box containing a
radioactive isotope with an activity rate twice that of the Earth
twin's equivalent box, and the traveling twin's crystal-growing tank
exhibiting half the crystal growth of the Earth twin's equivalent
tank, it makes no sense to say that the traveling twin and all those
processes are nevertheless 40 years older even though by any standard
measure they match what would be expected of those process after 20
years.

That's why we HAVE standards for time that are based on locally
reproducible physical processes, so we don't HAVE to use some
ridiculous and arbitrary standard like the number of rotations of one
star in one galaxy chosen for no particular reason.

 The traveling twin would just
have a clock that registered less time than the clock of the one on
earth.


[rest ignored because of expiring attention]

PD
.

Relevant Pages

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    (sci.physics.relativity)
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  • Re: Circular motion in SR
    ... slower than an identical clock on earth. ... it is orbiting or moving in a straight line. ... precisely also why the traveling twin comes back younger. ...
    (sci.physics.relativity)