On 28 Mar 2006 22:10:52 GMT, in uk.sci.astronomy ,
(Richard Tobin) wrote:

In article ,
Mark McIntyre wrote:
Same with a very narrow angle pair of scissors
the crossing point can be made to advance at c (at least in
principle).

Er, no it can't. The classic mistake is to apply non-relativistic
equations of motion.

Yes it can. The scissor blades don't even have to be moving very fast
if the angle is narrow enough. Relativity doesn't come into it.

This is one of the classic paradoxes of SR. You're applying newtonian
mechanics, which are inapplicable. I suggest you do a quck websearch
for it, and consider that the scissors /bend/.

You could shine a beam of light onto the moon, and if you moved it
across the disk in 1/100 second (which you could do by hand if you had
a powerful enough hand-held laser) the spot would move faster than
light.

Er, no. Again you're applying newtonian mechanics. The light beam
would in fact /bend/ in such a way that the end moved at, at most, c.

If this puzzles you, please do study some SR texts.
Mark McIntyre
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