Einstein's Starting Point

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I referred to a "Gravitational force signal". In principle, any oscillation of a source mass would send such a signal. But binary pulsars also accomplish this, and would make a nice gravitational clock.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
And such a signal (being a wave) would travel at c, right?
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Gravitation and electrodynamics do have similar behavior. Their forces propagate at FTL speeds. And when something disturbs the associated potential fields, those waves travel at speed c in both cases.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Or such a wave (being a signal) would not travel at c?
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The result still depends on how you synchronize clocks unless you use a <b>near-infinite-speed synchronization device such as gravitational force signals.</b><hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by rodschmidt</i>
<br />Einstein's starting point was to ask: What if you could follow a light wave at its speed?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
The point actually is that you can not follow a light wave at its speed as the latter is invariant in all reference frames. In other words, the usual concept of 'speed' can not be applied to light. Einstein tried to do this nevertheless (i.e. he assumed that he can add the speed of light vectorially to the speed of the source or observer) and as a consequence he had to re-scale the time and space units (time dilation,length contraction) in order to make the speed of light formally invariant.
I have treated this topic in more detail on my page www.physicsmyths.org.uk/lightspeed.htm .

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www.physicsmyths.org.uk
www.plasmaphysics.org.uk

Yes, you are talking about special relativity (SR). According to SR, if anything travels faster than c, there is a frame in which the travel is backward in time--the arrival event precedes the departure event.

Tom van Flandern says that the gravitational force is mediated by particles that travel faster than c. This theory is incompatible with SR. He says that SR is not correct, and that instead the universe is more correctly described by Lorentzian Relativity (LR).

So my desire was to retrace Einstein's reasoning in light of the possibility that SR might be wrong and LR might be right. Einstein started by asking what would happen if you could follow a light wave at its speed (perfectly allowable under the Newtonian rules that he was assuming). Einstein said that the light wave would look like a dipole hanging in space. This is a violation of Maxwell's laws (I don't know the details, this is just what I have read.) Einstein realized that his Newtonian assumptions must have been wrong, and so he derived the SR rules which Thomas is assuming as axiomatic first principles.

So the question is: Under LORENTZIAN Relativity, can you follow a light wave at its speed, and if you do, do you see a dipole hanging in space, and is there a violation of Maxwell's laws?

Thomas kindly attempted to answer by referring me to Einstein's SR, which does not address the question at all.

This is another one of those puzzles with no answer-like what comes first&lt; Is there some important point in getting this resolved?

You, your meterstick and your clock are made of atoms---subject to the limitations of SR and Maxwell's laws. A reference frame, on the other hand, is a figment of the imagination which can move at any rate you please relative to physical objects. Within a reference frame moving with a light wave, the light would be a dipole floating in space, and Maxwell's laws would have to be transformed to allow such an occurrence within that reference frame. You would need to devise a way to relate your imaginary reference frame's imaginary clock to real clocks.

The salient question then becomes: If real-world clocks in some real inertial reference frame are synchronized to one another, how does their time depend on position within your imaginary reference frame, moving at light speed?

The thing is what is there to gain from knowing this fact? If clocks measure the passing of time and light is an event it seems like asking apples about whats on tv tonight. I kind of dumb so maybe you can tell me how it is useful.