[wolfekeeper]

According to Relativity, it is not possible to unambiguously compare two clocks which are moving in different inertial frames of reference, and distant from each other (or in non-inertial frames of reference).

Depending on what you mean by that, it's probably not true. You can place a second clock or measuring device (or camera) at any particular point in space, arbitrarily close to where a moving clock is going to be and record the time on the moving clock as it goes past.

Relativity doesn't work by smoke and mirrors; if a clock appears to be running slow (after you've allowed for light speed and other optical issues if you're viewing it from a distance) then it IS actually running slow.

[Geezer]

if a clock appears to be running slow (after you've allowed for light speed and other optical issues if you're viewing it from a distance) then it IS actually running slow.

You keep using the phrase "running slow". It may be more a point of semantics, but unless the clock is defective, it is not running slow. All you can say is that it was subjected to different time from another clock.

"Slow" suggests one clock was correct while the other was not, but, in fact, both clocks are correct.

[imatfaal]

Hmm - not sure I agree there, the fact that the equation arise together does not mean that they are interchangeable, or that one encompasses the other.  Time dilation is a real effect - and is not caused, nor mediated by length contraction; they both exist.  Whilst there is no method I can envisage that could separate them that does not mean that one is subsumed by the other.

For the second time, I never said they were the same thing. I said that the equations of electromagnetism give rise to time dilation, lorentz contraction and lack of simultaneity in material held together by charged particles (things like clocks).

These are 3 separate effects that, together, give relativity.

  Relativity flows from the constancy of physical laws in all inertial frames - the speed of light being the most important of those; this of course agrees with the prediction of the maxwell equations of the speed of electromagnetic radiation.  but this is not a purely electromagnetic effect.

And weak and em are unified by the electroweak - but at 10^14K; if they were unified for atmospheric particles we would have noticed earlier :-)   

Aren't muons considered point particles anyway - how can you length contract a point particle?

Muons are time dilated - and I cannot see how that can dilation could be shown to be merely a function of a length contraction, and especially not merely as an electromagnetic effect.

You do sound very, very confused. I never said that either. You would have to look at the equations of the electroweak force  no doubt they have the same relativistic invariants that standard electromagnetism shows.
[/quote]

lets not have jibes about confusion.  Exactly which electroweak equations deal with muons in the atmosphere?  ie what did you mean by this     "Sure, but weak and electromagnetism are intimately related; they're part of the electroweak theory, which has recently been bolstered by the Higgs boson work." in relation to the decay of muons.  The electroweak theory governs at very high energies; the electromagnetic and the weak are separate forces at the energies we are talking about.  So help me in my confusion - what does the electroweak have to do with it?

Muon decay, which is governed by the weak, shows time dilation - how do maxwell's equations work in this area?

[imatfaal]

OK - All the Einstein was wrong - the aether exists - etc has been moved (again) to New Theories.  Please keep it there.  Thanks

[Geezer]

The trick is using a convenient frame as if it is a preferred frame so that time can be treated as if it's running slow in other frames

I don't think anyone is saying that time is "running slow" in other frames (if they are, I don't think they should be). If you prefer, every atom has its own "frame" and therefore, its own time. No atom is fast, and no atom is slow.

We can clump a bunch of atoms that experience similar accelerations together into a "frame", but that's a bit artificial, although it may be convenient.