HOWEVER...

And it will do very little to tanks or other metal objects for a reason that is almost as old as warfare¾and here we refer to the great historical hoax that Archimedes set fire to Roman ships with mirrors concentrating sunlight on them. This fairy tale entered Western folklore in the 12^th century, more than 1400 years after Archimedes' untimely death at the hands of some cultural antecedents of the Soviet army. But once a myth takes hold, it is hard to eradicate¾like the "near-catastrophe" of Three Mile Island.

One of several reasons why this story is recognizable as a hoax is that even with a laser, Archimedes could not have kept the point of incidence stationary on a ship rolling on the waves¾and it takes several seconds to set fire even to a stationary piece of paper with a lens focusing the sun on it.

Quite similarly, a laser beam can melt a hole through metal, provided it stays in the same spot for long enough to deliver the necessary energy, and delivers it faster than it can be carried away by heat conduction. The "long enough" is the difficulty that one might call the Archimedean headache; but there is now an aspirin for it¾the computer.