From: Georgi Guninski <guninski@guninski.com>
   >Disclaimer: I am lamer in physics.
   >I think the analogy shows that FTL (superluminal) speed exist and is
   >experimentally observed, this doesn't contradict relativity.
   >What contradicts relativity is _communication_ or clock
   synchronization
   >faster than light.
   >IIRC if you point powerful projector at the Moon and move it slightly,
   >this light on Moon will move FTL at least from your point of view.
   >Jim's horse was something like this.
   Yes, this is what I was alluding to when I used the term, "phase
   velocity".
   [1]https://en.wikipedia.org/wiki/Phase_velocity    Although, it isn't
   really clear from this article
   that the phase can travel far faster than 'c', nevertheless the
   information the wave transmits
   is limited to its "group velocity", which cannot travel faster than
   'c'.
    [2]https://en.wikipedia.org/wiki/Group_velocity

   The moon's diameter is about 2169 miles.  If you aimed a laser beam to
   one edge
   of the moon, and then quickly (0.01 second) moved the beam to the other
   edge,
   the spot would look like it's travelling at 216,900 miles per second,
   well beyond 'c'.
   (ignoring the fact that the moon is a spheroid, not a flat surface, of
   course.)
   There is no actual communication from those two points on opposite
   sides of the moon,
   nor are massive particles moving from one point to the other.
   I learned my physics from course 8.03 at MIT, with the coursebook by
   Bekefi and
   Barrett, titled "Electromagnetic Waves and Vibrations".
   [3]https://mitpress.mit.edu/books/electromagnetic-vibrations-waves-and-
   radiation
   Unfortunately, that was the last advanced physics course I took, having
   to focus on my
    major, chemistry.     The next Physics course, that I didn't take, was
   8.04, "Quantum
   Physics".
   [4]http://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-201
   3/
   Not that I didn't learn quantum at all, but I learned it from the
   direction of chemistry.
   That class was 5.61, and 5.62,  Physical Chemistry.
    [5]http://search.mit.edu/search?site=ocw&client=mit&getfields=*&output
   =xml_no_dtd&proxystylesheet=http%3A%2F%2Focw.mit.edu%2Fsearch%2Fgoogle-
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   +Home&as_dt=i&oe=utf-8&departmentName=web&filter=0&courseName=&q=5.61&b
   tnG.x=0&btnG.y=0

References

   1. https://en.wikipedia.org/wiki/Phase_velocity
   2. https://en.wikipedia.org/wiki/Group_velocity
   3. https://mitpress.mit.edu/books/electromagnetic-vibrations-waves-and-radiation
   4. http://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2013/
   5. http://search.mit.edu/search?site=ocw&client=mit&getfields=*&output=xml_no_dtd&proxystylesheet=http://ocw.mit.edu/search/google-ocw.xsl&requiredfields=WT%2Ecg_s:Course+Home|WT%2Ecg_s:Resource+Home&sectionlimit=WT%2Ecg_s:Course+Home|WT%2Ecg_s:Resource+Home&as_dt=i&oe=utf-8&departmentName=web&filter=0&courseName=&q=5.61&btnG.x=0&btnG.y=0