According to legend, Archimedes helped defend the city of Syracuse (no, not in New York) by building a mirror that would focus the sun's rays onto a ship and set it aflame. Supposedly, the mirror was not parabolic. It approximated a parabola with seven flat pieces (the center a hexagon, each flange a rectangle). The six flanges were each connected to the center by a hinge, and they could move together to adjust focus.

Unfortunately, this is probably a myth. Why? First, assuming that the mirror could focus enough sunlight to work, you'd have to keep it focused on the same spot on a moving ship long enough to get the fire going. Also, early histories only say that Archimedes found out how to 'hurl fire' at the enemy ships. Nothing about mirrors is mentioned; it was probably the product of a hyperactive imagination (maybe ol' Arch did something involving catapults instead).

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