Re: does circumference contract with velocity?

Subject: Re: does circumference contract with velocity?

sal <pragmat...@xxxxxxxxxx> wrote:
Gerald L. O'Barr wrote:
. . .

<deletes by O'Barr>

O'Barr wrote: . . .
These changes in the moving clock (your pocket
watch) do not show that there are any lack of
syncs between the clocks attached to the ring.

sal <pragmat...@xxxxxxxxxx> wrote:
Um, OK ... well, "synchronization" is something we
define, rather than something we measure. So, if
you're willing to include the above behavior in your
definition of "synchronized" then the clocks can be
considered synchronized.

O'Barr's comments:
Synchronization can be both defined and measured.
And in LET, this kind of syncing of clocks on a
rotating ring is an acceptable definition for a form
of synchronization.


sal <pragmat...@xxxxxxxxxx> wrote:
I said to start with that this was the "wrong" way
to synchronize the clocks. But, again, that's a
value judgment, and what you described certainly is
a form of synchronization: all the clocks are synced
relative to the inertial frame in which the ring's
center is stationary.

O'Barr comments:
Rotation is a form of absolute motion, and the
sync described above is an absolute type of sync. It
is important to know these things!

sal <pragmat...@xxxxxxxxxx> wrote:
As the term "synchronized" is most often used,
however, the fact that measured transmission
velocities are anisotropic, and the fact that
slow-transport of clocks (along the ring) doesn't
yield a "compatible" synchronization, is taken as
evidence that they're not "synchronized".

O'Barr comments:
In LET they would be considered to be synced.
Let does not expect the measured speed of light
between moving points that have an absolute sync to
be a constant measured velocity.

sal <pragmat...@xxxxxxxxxx> wrote:
Note that the "transmission velocities" which are
anisotropic include not just C, but also the
velocity of EM waves in materials, and signals in
wires, and even the speed of sound in a medium
moving with the ring.

O'Barr comments:
Sounds reasonable to me.


sal <pragmat...@xxxxxxxxxx> wrote:
Note, also, that as the radius of the circle becomes
very large, the problem becomes more acute.

O'Barr comments:
I am sorry, there is no problem. Therefore, it is
hard for this problem to become anything, let alone
more acute!

sal <pragmat...@xxxxxxxxxx> wrote:
With a very large radius of curvature, the line of
observers on the ring is traveling "almost"
straight, but their clocks cannot be synchronized
with a line of clocks which are momentarily flying
alongside them, but not attached to the ring.

O'Barr comments:
Well, they most certainly can be if you want to do
it. The sync can only last for a few seconds, until
they begin to move out of position. But as long as
they remain slightly together, during this time, an
SR sync can be applied.

sal <pragmat...@xxxxxxxxxx> wrote:
. . . If
one clock in the line of "linear free-flying" clocks
moving beside the "high-radius almost-straight" ring
is in sync with its neighbor on the ring, then other
pairs of clocks in front and behind will be off by
v*gamma*x where x is the distance from the pair that
is in sync (as measured in the "stationary" frame).
And, in the limit as the radius of curvature goes to
infinity, it's hard to see how to justify this --
the clock sync is "special" and "different" on a
ring, but the limit of a large ring is straight-line
motion, and we have to deal with a hiccup at the
point where one becomes the other.

O'Barr comments:
In LET, you have no problem at all. Both
approaches can be considered.
Let me explain something to you: In SR, in an
inertial reference frame, with all clocks in perfect
sync, you measure the velocity of all light to be a
velocity of c. But in this frame, if you move a
second frame with a velocity of v (like a train) but
you keep every clock on the moving frame to have the
same sync as the nearest non-moving clocks, you will
then measure the velocity of light past the train to
be c+/-v. This is all you are doing above. It works
the same way. There is nothing at all that is
strange or unreasonable. Einstein himself used this
c +/- v often in his calculations as being the
relative velocity between his train and light. It
was correct for the way it was being done.
Let me say this again: A moving set of clocks can
be synced to produce c, or c+/-v, all depending on
whether you are going to sync to a non-moving frame,
or if you are going to sync to your own frame. The
choice is yours.


O'Barr wrote:
What do you do for a living?
sal <pragmat...@xxxxxxxxxx> wrote:
Program computers.
Have you read my at theory?
No, I barely have time to read conventional physics
books, and I waste all the rest of my spare time on
stuff like this post.
Usually people get upset when I make a mistake!
I have never seen anyone as cool as you.
Gerald, you've gotta get involved in some activities
outside of Usenet!! Out in the real world I'd be
called an arrogant SOB with an anger management
problem if I talked the way I write in this
newsgroup; it's only here that I seem "cool" by
comparison with everybody else. Go meet some normal
people, some of them are really nice.

O'Barr comments:
I appreciate your advice! But if you program computers,
then you could run my at program! It is simple basic.
Visual basic would probably also work.


O'Barr wrote:
. . . Do you need L*v/c^2 derived?
Just use a velocity u, with u<<v, and take the
limit as u approaches zero.

sal <pragmat...@xxxxxxxxxx> wrote:
No, that's OK -- it's just the v*x*gamma from the
Lorentz transform with the gamma canceled out by the
length contraction (assuming you measured the length
in the moving frame). In any case I'm familiar with
the derivation. See, for instance,

http://www.physicsinsights.org/sagnac_1.html

(but note that the comments at the end of the page
regarding ring lasers are kind of wrong -- I need to
fix that, but not tonight...)

Thanks for reading.
Gerald L. O'Barr <globarr...@xxxxxxxxx>
Remove ... for e-mail.

.

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