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No. 252:
Star Wars

Today, we look for technology that can blow our troubles away. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The great weekly event during 1942 was Saturday afternoon at the Uptown Theater. Forty cents bought a bag of popcorn, a box of Milk Duds, and a movie ticket. I sat in the dark and watched young Ronald Reagan flying his airplane against terrible odds. Each week, it seemed, he shot down the same Chinese actors clad in Japanese uniforms; and America stayed safe for democracy.

Death was bloodless in the Uptown Theater. The enemy was mowed down from afar. Bullets, like laser beams, eliminated peril while it was still distant. They didn't actually break the skin. The bad guys were killed. Only the good guys were merely wounded, and they healed before the next battle.

Weapons in the Uptown Theater were like fictional death rays. You pointed a gun, and the enemy fell down. You dropped a bomb, and a bridge disappeared. It wasn't until 1947 that we began to learn what those bombs had really been doing.

So we aren't too surprised when we hear an enduring myth of early technology. According to the story, Archimedes created a huge mirror. He focused the sun's rays on the Roman fleet as it invaded Syracuse. He set it on fire from the distance of a bow shot. That tale has gone in and out of favor with historians ever since. Now physicist D.L. Simms gives us his careful analysis.

Simms thinks the story hangs on the edge of plausibility. Archimedes might just barely have known enough optics to make such a mirror. It's conceivable that he could have made it with an adjustable focal length. He might even have been able to keep a beam fixed on one spot long enough to ignite wood. But beyond all those terrible if's was the fact that the burning mirror didn't appear in the earliest accounts of the battle. The first versions tell us only that Archimedes's ingenuity had something to do with winning the battle and that fire was involved.

Simms concludes that the burning mirror was a wishful interpolation. Archimedes probably did find a way to hurl fire. But this 2200-year-old death ray was almost certainly imagined by a Byzantine writer hundreds of years later and attributed to Archimedes.

Death rays relate to warfare the way perpetual motion relates to energy production. They're devices that make everything easy -- machines to lift us above our dirty problems. We've dreamt of technology like that ever since Archimedes. We probably always will. Those dreams are a beginning, but good engineering weds our dream to the world it creates. Good engineers are interested in dreams that can be taken out of the Uptown Theater and held up to the bright light of a Saturday afternoon.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

D. L. Simms, Archimedes and the Burning Mirrors. Technology and Culture, Vol. 18, No. 1, pp. 1-24.

I wrote this episode in 1989. Since then, Simms has continued his work on Archimedes. Two new sources on this subject are: D. L. Simms, Archimedes the Engineer. History of Technology (ed.G.Holiister-Short and F.A.J.L.James) Vol. 17, 1995 (London 1996) pp.45-113; and D. L. Simms, Buffon's Burning Mirrors. Atti della Fondazione Giorgio Ronchi, Anno LIX, no.5 settembre-ottobre, 2004, pp. 711-742.


An 18th century conception of a burning mirror
(From Le Entretiens Physiques d'Artiste et d'Eudoxe, ou Physique Nouvelle en Dialogues, Qui Renferme Précisément ce qui s'est Découvert de plus Curieux & de plus Utile dans la Nature, Vol. III. 1745)