[Rockhounds] OT: Death Rays and melting stones

[DonH]

J Bryan Kramer wrote:

> And how would you hold a heavy block of stone precisely in the focal point
> of a 3 meter disk. The FP would be 1.5 meters in and what ever distance up.
> And then move it fractionally so it made an exact cut?


Good point.  And again, I would point out (as I did previously) that a 
parabola only focuses the rays at the focus when it is pointed directly 
at the source.  That is why, when I look out my back window on to the 
lawn between the buildings, all the TV dishes are pointed in the same 
direction.  Otherwise they wouldn't work.  Therefore a block of stone 
would be in the way of the very light source needed to provide the energy.

http://www.analyzemath.com/parabola/parabola_focus.html

A parabola does not take energy from one direction and focus it in 
another direction.  Period.  Case closed.

Don