Re: The Spin Proviso to Relativity

From: Ben Bean (kavs_delethis__at_sysmatrix.net)
Date: 10/23/04 

Date: Sat, 23 Oct 2004 05:15:06 -0400

"Paul B. Andersen" <paul.b.andersen@hia.no> wrote in message
news:clb3rc$hde$1@dolly.uninett.no...
>
> "Ben Bean" <kavs_delethis_@sysmatrix.net> skrev i melding
news:RO-dnYVWccAX2OXcRVn-jA@sysmatrix.net...
> >
> > "Ben Bean" <kavs_delethis_@sysmatrix.net> wrote in message
> > news:3M2dncxUAuaje-rcRVn-jg@sysmatrix.net...
> > >
> > > "Paul B. Andersen" <paul.b.andersen@hia.no> wrote in message
> > > news:cl899p$25n$1@dolly.uninett.no...
> > > >
> > > > "Ben Bean" <kavs_delethis_@sysmatrix.net> skrev i melding
> > > news:ktKdnS2bLsm8GurcRVn-rg@sysmatrix.net...
> > > > >
> > > > > "Paul B. Andersen" <paul.b.andersen@hia.no> wrote in message
> > > > > news:cl6d07$8jb$1@dolly.uninett.no...
> > > > > >
> > > > > > "Ben Bean" <kavs_delethis_@sysmatrix.net> skrev i melding
> > > > > news:B8SdncZcW_z2v-ncRVn-oA@sysmatrix.net...
> > > > > > > I am eager to hear wisdoms in answer to the quandary below
stated.
> > > > > > >
> > > > > > > SCENARIO: You stand on a planet just like Earth, but there's
no
> > > > > atmosphere.
> > > > > > > You stand on the equator and hold your hands up to the air so
that
> > > they
> > > > > are
> > > > > > > a meter apart. [Relax, this is NOT a study in relative
> > simultaneity
> > > like
> > > > > the
> > > > > > > Barn/Pole thing.] As you stand there a huge spacecraft coasts
by
> > > just
> > > > > > > overhead, just beyond your reach. The ship seems motionless to
> > you,
> > > > > > > hovering, because it is going eastward at a speed to exactly
match
> > > the
> > > > > > > planet's tangential rotational speed. As you reach up, your
> > > outstretched
> > > > > > > fingertips are just about touching the 842-meter mark and the
> > > 843-meter
> > > > > mark
> > > > > > > on the rule graduated on the enormous ship's straight
exterior.
> > > > > > >
> > > > > > > Here's the quandary: the spaceship occupants can EMPHATICALLY
> > assert
> > > > > that an
> > > > > > > all-way light beacon pulse emitted midway between their ship's
842
> > &
> > > > > > > 843-meter marks will hit the two nearby meter marks
> > simultaneously,
> > > > > > > according to their native frame's clocks and such. Yet the guy
on
> > > the
> > > > > planet
> > > > > > > cannot make the same claim?? When does an arbitrary local span
> > > become
> > > > > > > tantamount to an SR scenario. In spite of Sagnac, there must
> > surely
> > > be
> > > > > some
> > > > > > > carry-over; I mean you're just about TOUCHING that other
frame,
> > > > > comoving.
> > > > > > >
> > > > > > > -Ben
> > > > > >
> > > > > > Of course the guy on the planet will agree that the light will
hit
> > the
> > > two
> > > > > metre
> > > > > > marks simultaneously. That is, if he had one clock at each side
of
> > > > > himself,
> > > > > > and he E-synched those clocks, they would show the same when hit
> > > > > > by the light.
> > > > > > However, if the two clocks were showing UTC, they would NOT
> > > > > > show the same when hit by the light.
> > > > > > Clocks on the surface of the Earth showing UTC are NOT
synchronous
> > > > > > in the Earth fixed frame. They are synchronous in the non
rotating
> > > > > ECI-frame.
> > > > > >
> > > > > > Paul
> > > > > >
> > > > > >
> > > > > Great answer! Uh, but, whereas I know what ECI stands for, I am at
a
> > > loss as
> > > > > to what UTC stands for.
> > > >
> > > > UTC means "Coordinated Universal Time", and to say it simple,
> > > > it is the same as local mean time.
> > > > See also my response to "sal".
> > > >
> > > > > But I think it matters not. You say that Earth's
> > > > > surface clocks can all be synched to the non-rotating ECI, which
> > > suffices.
> > > >
> > > > Yes, and I say that this IS how we synchronize clocks on the Earth.
> > > >
> > > > > I
> > > > > don't necessarily buy your dismissal of Sagnac (of course I am
> > > > > misinterpreting perhaps), but your answer suggests that a light
signal
> > > takes
> > > > > the same time to go from NY to LA as the reverse, as long as you
use
> > the
> > > > > non-rotating ECI clocks as your basis.
> > > >
> > > > UTC clocks on the Earth ARE "rotating" along with the Earth.
> > > > I said they are synchronised (simultaneously showing the same)
> > > > in the ECI-frame, NOT that they are stationary in the ECI-frame.
> > > > And if you measure the time light takes to go from NY to LA with
> > > > these UTC clocks, you will find that it is different from the time
> > > > it takes to go in the reverse direction.
> > > > This IS the "Sagnac effect".
> > > >
> > > > > I guess that makes sense alright, but
> > > > > it's insufficient. The guy reaching up and touching the inertially
> > > moving
> > > > > space ship -- he has a wrist watch on each arm and he claims they
are
> > > > > synchronized. His clocks belong to a frame that IS rotating. I'm
just
> > > not
> > > > > sure. Again, what is UTC, Universal Time something?
> > > >
> > > > If this guy claims his writs watches to be synchronized, he will
> > > > probably mean that they simultaneously show the same in
> > > > his instantly inertial rest frame. (The inertial frame in which he
> > > > instantly is at rest.)
> > > > And his clocks will stay in synch.
> > > > If he measure the speed of light with these clocks, he will find
> > > > that it will use the same time in both directions.
> > > >
> > > > But if he compare them to two adjacent UTC clocks, he will
> > > > see that they are different, because his watches are NOT
> > > > synchronous in the ECI-frame.
> > > >
> > > > > The central question is, "How does light behave in the frame of
the
> > man
> > > > > standing with his arms outstretched (over his head), and ONLY
> > according
> > > to
> > > > > that man's native clocks & measures"? Can the man say that a light
> > > signal
> > > > > emitted midway between his hands arrives at each hand at precisely
the
> > > same
> > > > > time? Probably not.
> > > >
> > > > Yes, he can.
> > > > He will use his local frame.
> > > >
> > > > > But light would clearly not move relative to a
> > > > > theoretical aether fixed at the planet's center either. So there
must
> > be
> > > > > some give. Light must take less time to go westward than eastward
(on
> > > the
> > > > > spinning planet), which would be in line with the Sagnac findings,
but
> > > not
> > > > > so much less time as would be predicted by imagining the light
> > > travelling
> > > > > through some fixed aether frame anchored at the planet's center.
> > > > >
> > > > > It's confusing alright.
> > > >
> > > > Yes, it IS confusing. :-)
> > > > But remember this:
> > > > According to SR, the speed of light is c _in an inertial frame_.
> > > > As long as you remember this, it is quite obvious that if you
> > > > emit light in both directions from some point on the equator,
> > > > and guide the light (mirrors) around the Earth, the two light beams
> > > > will meat each other at the same point _in the ECI frame_
> > > > as they were emitted from. But then the point on the Earth
> > > > has moved, so one of the light beams has already passed
> > > > this point, while the other one has not yet reached it.
> > > > So _because_ the speed of light is c in the ECI-frame,
> > > > the two beams will NOT simultaneously reach the point
> > > > on the Earth from where they were emitted.
> > > > A clock at that point will thus measure the light to use
> > > > different times around the Earth in opposite directions.
> > > >
> > > > Paul
> > > >
> > > >
> > > >
> > >
> > > **********************************
> > > I REALLY REALLY GOT TO HAND IT TO YOU, PAUL B. ANDERSON...
> > > That's some mighty fine STRAIGHT SHOOTING and you sure as dang heck
got me
> > > to understand PERFECTLY!
> > >
> > > The guy can invent an inertial frame in which his two wristwatches are
> > > synched (but NOT E-synched, which is WRT the non-rotating ECI frame),
so
> > > long as the times and distances are minute enough. I garner this from
your
> > >
> > > > > ..Can the man say that a light signal emitted midway between
> > > > > his hands arrives at each hand at precisely the same
> > > > > time? Probably not.
> > > > Yes, he can.
> > > > He will use his local frame.
> > > >
> > >
> > > It must get messy if you try to concoct an inertial frame (too large)
to
> > > encompass eg. the span NY to LA for the duration it takes light to
> > transit.
> > >
> > > Yeah but nevermind -- I get it -- MANY MANY THANKS!
> > >
> > > -BB
> > >
> > >
> >
> > PBA:
> > I'm here to fix an apparent misunderstanding I had of your terminology.
What
> > E-synched (capital E) implies I'm not 100% certain, but it is NOT
> > specifically associated with UTC. The standing man can synchronize the
> > watches on his left and right hands WRT a concocted inertial frame that
> > closely approximates the actual arc he is moving on, and thus conclude
that
> > any light/radio pulse emitted halfway between his hands arrives at those
> > hands simultaneously. This works for the suitably small scale, but not
the
> > large?? ie. NY to LA.
>
> More or less, yes.
> Your shouting tells me that elaboration would be futile.

You're one sick & slimey limey, boy.

>
> > HONEST! I understood every word of your explanation (Many thanks) about
how
> > Sagnac truth messes up any hope of surface-resident synchronized clocks,
> > except by resorting to UTC (which is ECI-based); but under that UTC
scheme
> > you cannot make the claim which the standing man so yearns to make, ie.
that
> > light will expand outward uniformly east/west from a source point, per
his
> > vantage.
>
> Let me say it like this:
> I can claim that the light will expand uniformy from
> the point it is emitted _in the inertial frame in which he
> is instantly at rest when the light is emitted_.
> He is not stationary in said frame, but during the 2 ns the light
> takes to reach his hand, he will have moved 10^-33 meters
> from the point of emission.
> But 12 hours later, the light he emitted westwards will
> be 12 light hours east of him.
>
> Paul
>
>

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