Re: Relativity IQ Test. Synching Clocks Absolutely.
From: sal (pragmatist_at_nospam.org)
Date: 08/26/04
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Date: Wed, 25 Aug 2004 22:29:11 -0400
On Wed, 25 Aug 2004 21:45:39 +0000, h wrote:
> On Tue, 24 Aug 2004 08:29:45 -0400, sal <pragmatist@nospam.org> wrote:
>
>>On Tue, 24 Aug 2004 10:19:49 +0000, h wrote:
>>
>>> On Mon, 23 Aug 2004 22:53:55 -0400, sal <pragmatist@nospam.org> wrote:
>>>
>>[ snip chop hack cut elide ]
>>>>
>>>>The result of syncing by averaging differences they way you have
>>>>proposed will be, according to SR, identical to simply E-syncing them
>>>>to start with.
>>>
>>> Now here we differ.
>>> E-synching and 'absolute-synching' are very different animals.
>>
>>You would need to demonstrate that with an experiment. As I said, SR
>>predicts the results will be identical.
>>
>>So does Ritz/Fox emission theory, for that matter.
>
> Let's make it clear what we are talking about here.
>
> 1) B and C are moved L units apart and their rates synchronized.
Whoa -- you started by having B and C synced while together, _then_ moved
apart. Let's stick with that, OK?
So after they're moved apart, EITHER they're still in sync, OR your
postulated universe is even stranger than SR's.
And let's add one more thing: The operators at B and C have wristwatches
(called B' and C'), and after B and C are moved, they set their watches to
match B and C. SO, we now will have a record at location B and location C
of what the original, _synchronized_ readings of B and C would have been,
if you never fooled with them after moving them.
OK so far?
> 2) A moves at v from left to right and B and C are adjusted to A's time
> when A is adjacent.
> 3) without changing any settings, A is moved at the same relative speed
> from right to left. B and C read A's clock when it is adjacent.
> *****************************
> Let's assume that SR is correct.
>
> Let A's and B's readings be set to zero when A is adjacent to B.
>
> A will run slower than B and C by 1/gamma.
>
> In L/v secs, B reads L/v and A reads (L/v)/gamma So C's reading will lag
> B's by (L/v)*(1-(1/gamma)) *****************************
>
> With the same reasoning, when the experiment is repeated with A's
> direction reversed, A's reading when passing C will be
> (L/v)*(1-(1/gamma)) ahead of its reading when it passes B.
>
> Let the difference between A's and C's reading be X. Since C's clock has
> been set to lag B's by the interval (L/v)*(1-(1/gamma)) and since A
> again takes L/v secs to reach B, the difference between B's and A's
> clock readings when A is adjacent to B, will be X +
> 2*(L/v)*(1-(1/gamma)) ***************************** How do B and C use
> this knowledge?
>
> Subtract X from this latter equation and half it. Advance C's reading by
> that amount.
>
> B and C are now absolutely synched.
OK, now, to start with, they were not e-synced at all. They were just
moved apart, after being put in sync while right next to each other.
That's what you said in the original post, and I like that better than the
E-syncing version -- it's more clear-cut.
The wristwatches of the operators STILL are set to that original,
colocation-synchronized time.
How do you, Henri, think the final times on B and C after your "absolute
syncing" will differ from the times shown on the B' and C' wristwatches?
I think they won't differ at all -- or, more precisely, (C - C') will be
exactly equal to (B - B').
If you think they won't be equal, then please tell me in which direction
they'll differ -- will B' be behind B, while C' is not behind C? Or will
be C' be behind C, while B' will match B? Or what?
If they're still synced the way they were to start with, as it appears to
me they will be, then the extra "average-syncing" step hasn't done
anything that I can see.
> They are definitely not E-synched as you claim.
Again, tell me what you expect the actual difference to be, in qualitative
terms, between the readings on B and C and the readings on B' and C'.
As far as I can see there won't be a difference.
[ snip ]
> The trouble with you SRians is that you seem to think TIME travels at
> the speed of light.
Yes, that summarizes it pretty well -- C is fixed, so if I see light
"moving slowly" over where you're standing, I'd say time itself was
running slower for you. That's what happens in a gravity well, for
example.
> It doesn't.
> It doesn't travel at all.
That's a good statement, too -- in the 4-dimensional geometric view of SR,
_nothing_ _moves_. Everything is laid out on the 4 dimensional manifold
and it just sits there, and we can measure distances and switch coordinate
systems however we like. There's no actual motion of anything to worry
about -- everything stays where you put it, and it's always in the same
place, no matter how you look at it.
If SR is a religion, then this should be its mantra:
NOTHING MOVES
(Actually, that's just for the geometric version -- in the 3+1
view stuff still moves.)
> Each specific 'instant' is simultaneous
> throughout the whole universe. It does not depend on the velocities of
> any observers.
Ah, but now you are expressing an opinion about reality. In the SR model,
that statement isn't true.
> Clocks B and C have been absolutely synched in all frames.
Again, that's an opinion about reality -- you haven't _proved_ that in any
way that I could see.
>>> You don't understand the significance of E-synching.
>>
>>You exchange time signals with the assumption that the speed of light is
>>isotropic, and use that to set the clocks. If SoL isn't really
>>isotropic it might be possible to find some way of syncing the clocks
>>that produced a different result.
>
> Precisely. It is called absolute synching. This also provides a way to
> measure OWLS.
I still don't see the difference, in effect, between what you did and
simple slow-transport out from a central point, at which location the
clocks were synchronized while they were adjacent.
No exchange of light signals is necessary, and SR says the result is the
same either way.
[snip]
>
> Not so. Any careful transportation will retain absolute synch between
> two clocks that were absolutely synched whilst together.
AH HAH -- Now _that_ should be testable.
Einstein says it is identical to E-syncing. It shouldn't be hard to sync
them up, transport them far apart in opposite directions, and then use GPS
or some other E-syncing proxy to see if their time still agrees.
In fact, it may already have been done.
> The interesting conclusion is that clocks B and C can be synched in
> exactly the same absolute manner by this experiment, WHETHER OR NOT SR
> IS CORRECT.
Yes, for sure -- the only problem with it is that if SR is correct, then
you've only synced them in one frame, just like slow-transport and
E-syncing do.
-- I can be contacted through http://www.physicsinsights.org
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