SR and one-way light speed tests

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Larry]: But what about the situation where the pipe and all clocks are stationary wrt each other?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

If only one frame is involved, all clocks can be synchronzied in that frame. SR is irrelevant because there are no "relativity of motion" issues when there is no relative motion. That is how GPS manages to work without need of relativity -- all bodies are considered to be instantaneously motionless in a single frame.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I suppose this is where the time slippage factor raises its ugly head?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

"Time slippage", "desynchronization", and "lack of remote simultaneity" are manifestations of the same phenomenon. -|Tom|-

(Here is here I find out if I really understand this SR crud as well as I think I do.)
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[tvf]
If only one frame is involved, all clocks can be synchronized in that frame. SR is irrelevant because there are no "relativity of motion" issues when there is no relative motion.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Check. And that synchronization is accomplished by swapping pulses of electromagnetic energy between the clocks. This requires that one make an assumption (theory dependent) about the speed of those pulses, and that is why “ … a one-way speed-of-light measurement independent of theory is impossible in principle <b>without using FTL signals</b>.” (emphasis added).

But a rotating pipe can “simulate” (as described earlier) that FTL signal, and allow clocks that are not in contact to be synchronized without using EM energy. Within one FOR all theories of relativity reduce to the same set of equations (x’ = x, y’ = y, z’ = z and t’ = t) because all velocity dependent factors reduce to one or zero and the primed coordinates ARE the original coordinates.

Thus we have a theory-independent (or perhaps an all-theory-compatible) alternative method of instantaneously synchronizing remote clocks in a single FOR. And that allows us to measure the speed of light in one direction.

(Hmmm. Seeing it in your minds eye is a lot easier than putting it in words. But I think this is adequate.)

Regards,
LB

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Larry]: But a rotating pipe can “simulate” (as described earlier) that FTL signal, and allow clocks that are not in contact to be synchronized without using EM energy.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Assume the rotating pipe with a stripe along its length has one end at the observer and the other stretching into the distance. As you merely look at the pipe along its entire length, you will see the stripe twisted because you will see parts of the pipe as they were one light-time ago, and not as they are now. The farther away the pipe part, the farther into the past you see it.

So it is natural for the stripe to look twisted. In SR, it looks twisted for yet another reason -- because real, physical time is different at different distances for all frames other than your own.

It is therefore impossible to use the pipe rotation in a frame-independent way to synchronize clocks, because real, physical time will be different at different places along the pipe length (according to SR). Because real, physical time is different, so are all physical phenomena different, which is why a test is impossible even in principle. Separating what you *see* from what is physically real requires fore-knowledge of the light propagation speed. In particular, it requires knowing whether light propagates at speed c or speed c+-v -- which is what you had hoped to determine with an experiment. -|Tom|-

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[tvf]
... As you merely look at the pipe along its entire length, you will see the stripe twisted because you will see parts of the pipe as they were one light-time ago, and not as they are now. The farther away the pipe part, the farther into the past you see it.

So it is natural for the stripe to look twisted. ...<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Yes. On each revolution I “see” the clock at the far end of the pipe detecting the stripe at some time after the clock next to me detects the stripe. This is an illusion caused by light time delay that I don't care about. This illusion would occur even if motion were not relative and/or if we had real live super FTL signals at our disposal.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote> ... In SR, it looks twisted for yet another reason -- because real, physical time is different at different distances for all frames other than your own.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Yes again – IF there is relative motion – IF there is a frame other than my own. But there isn’t. The far end of the pipe and its clock are not moving relative to me or to the clock at the close end. That causes gamma to be one (1) and the time “slip” factor to be zero (0) in the Lorentz transform.

Because relative speed is zero (i.e. we are doing everything in one frame) time (real time, not the light-time-delayed image of time) at the far end of the pipe (and everywhere in between) is the same as time at the close end.

Regards,
LB

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[Larry]: Because relative speed is zero (i.e. we are doing everything in one frame) time (real time, not the light-time-delayed image of time) at the far end of the pipe (and everywhere in between) is the same as time at the close end.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

You lost me. Synchronization of clocks in a single frame has never been a problem. A simple exchange of light signals will do that. Relativity only comes into play when there exists some relevant relative motion.

Your proposed one-way SOL test will merely verify that the speed of light is c in any one frame by definition. But it cannot test what happens when an observer has a relative motion because time for that observer is everywhere changed from that in the original frame. So the measured speeds change too. -|Tom|-

(ArGGGH. I can see it, but I can't say it.)

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[tvf]
Your proposed one-way SOL test will merely verify that the speed of light is c in any one frame <b>by definition</b>. (emphasis added).<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Yes, and that definition (and therefore theory dependency) comes from ...
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
... (a) simple exchange of light signals ...<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

In order to rid ourselves of theory dependency we need a way to sync clocks that doen't use a "simple exchange of light signals". Your c-gravitons would do nicely, but we don't know how to use them yet.

However, clocks that were synched using a truly instantaneous signal would be even better. The stripe on my pipe might LOOK like it spirals, but in reality (and in the frame of the pipe and the two clocks) it does not. After dissipating any non-rotational energy it behaves just like an ideal pipe. The clocks can be synched just as if we had a literally instantaneous signal.

====

(Plan

Suppose we figure out how to detect and use c-gravitons for signaling. And suppose their average speed turns out to be 100 trillion c.

We could use them to sync some clocks and measure the one way speed of light.

What would be a simple, "block diagram" description of that measurement experiment (keeping in mind the context of our discussion)?


LB