Re: Einstein's Train Gedanken Re-visited

On Jun 24, 1:20 am, "Whoever" <no...@xxxxxxxxxxx> wrote:
"Bruce Richmond" <bsr3...@xxxxxxxxxxx> wrote in message

news:dcf2a5b6-21b5-4d0f-bd5b-0ff69cf82776@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

On Jun 23, 10:54 pm, "Whoever" <no...@xxxxxxxxxxx> wrote:
"Bruce Richmond" <bsr3...@xxxxxxxxxxx> wrote in message
news:2939b7dd-20fb-43d8-9210-3f346f67e78f@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
For starters what you proposed and what you described were not the
same thing.

Yes .. they are

Your discription still had the clock(s) moving on the
earth's surface.

No .. it clearly didn't.  Only one of them.

Ok, I'll grant you that.  I misinterperted what you were saying.

That's ok .. glad we cleared that up





==>> >> So .. what would happen if we moved the clocks apart at the same
speed
according to the (almost) inertial frame of the center of the
earth.
So
(for example) the one moving with the earth would stay 'still'
(relative
to
the earth) and the other one move away at twice the speed of
earth's
rotation in the opposite direction.

==

See there "the one moving with the earth would stay 'still' (relative to
the
earth) "

So they are still moving along curved paths in the
ECI system.

Yes they are

Combine that with the fact that even the ECI system is
not truly inertial and it becomes very unlikely that the effects will
cancel out.

http://en.wikipedia.org/wiki/Earth_Centered_Inertial

"It should be noted that ECI frames are not truly inertial since the
Earth itself is accelerating as it travels in its orbit about the
Sun."

Grr ... Picky .. so the only affect is due to the movement of the earth
around the sun and the sun around galactic core, and whatever
non-inertial
movement the galaxy may have.

So .. ignoring those effects .. treating the ECI as inertial for the sake
of
this thought experiment .. (which seemed to be obvious from context, but
I
see we need to make it explicit) what do you claim about the clocks as
described?- Hide quoted text -

- Show quoted text -

I thought the whole purpose of this exercise was to get clocks in sync
without using light signals so that a real world experiment could be
done to measure one way light speed isotropy.

Yeup .. this would be one way to do it .. moving one way westward with the
appropriate speed would keep it in sync.

Or ... put both clocks on a train heading west at the appropriate speed ,
and do mutual clock transport there and they'd be in sync and the train
frame would then be (close to) inertial.  Again, we're ignoring here the
orbit of the earth, perturbations from other bodies, movement of sun around
galaxy etc.  its pretty much impossible to get a perfectly inertial frame ..
and that a suitable train and track (or plane) would be very impractical :)

The plane sounds like the best idea so far. It could be done. And
according to SR the clocks should stay in sync as they are moved
apart, and when moved slowly still be in sync when brought back
together.

But once again we are using an assumption of SR to come to that
conclusion. LET says that the clocks go out of sync when apart but
return to being in sync when brought back together. What's more, if
you check them using light signals when they are apart you will
measure them to be in sync, if you assume that light travels at c
relative to your central master clock. But since it is highly
unlikely that the master clock is at rest in the ether frame that is
not a valid assumption.

So besides the slight non-inertial effects you mentioned above you
will also have the problem that the clock will get out of sync due to
the acceleration to get it up to speed and deceleration stop it.

You could avoid that by transferring time setting to another 'stationary'
clock at the appropriate point when the moving clock goes past.  A bit like
the twins paradox version that uses three clocks to avoid acceleration
issues.

You also have the problem that after stopping the transported clock,
even if it is in sync, the clocks are not at rest in the ECI system.

But they are accelerating (rotating) the same, so would stay in sync with
each other.

If you manage to throw a ball to someone on the other side of a merry-
go-round while it is spinning its time of flight will be different
than if it weren't spinning.

Yeup .. and if you throw it "at" then, it will miss :):)  Always a fun game
to try when you're on a merry-go-round

Yes, it's my turn to be picky ;)~

:):)- Hide quoted text -

- Show quoted text -

.

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