On Jun 25, 2004, at 7:07 AM, Russell McMahon wrote:

> 2.    Look at waves hitting a beach or ripples hitting the edge of a
> pool
> etc. If the wave front is slightly off square, watch what happens to
> the
> contact point as the wave hits the edge or shore. Whiel nothing on the
> wave
> moves faster than wave speed, the contact point is related to the
> arctan of
> the contact angle. For very small angles, the contact point can travel
> at
> speeds of 100's of kilometres per hour when the wave is travelling
> under 10
> kph. Nothing physical is actually moving this fast but the motion can
> be
> very clearly observed.


There's a similar phenomena for EM/etc; either the 'group velocity' or
'phase velocity' of the waveform corresponding to something like a
fundamental packet;  (IIRC, it goes something like this.  A particle is
like a wave, right?  but you apply forier analysis to get something
that looks like the discontinuous waveform of a particle, and the
individual frequencies involved have to have propagation velocities
faster than C.
Unfortunately, you can do anything useful with those parts...)

BillW

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