Today, we wait for a star to fall upon us. 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.

John Donne once wrote a cynical poem with the words, "Goe and catche a falling starre." Don't look for honesty or fidelity, he said. It would be easier to catch a falling star.

Falling stars, or meteorites, are bits of cosmic junk -- kin to comets and asteroids. They run into our planet all the time.

We give these objects star names -- falling star, shooting star. The word asteroid means shaped like a star, even if real asteroids are lumpy and amorphous. The asteroid belt lies outside Earth's orbit. But much of its flotsam reaches us.

When meteorites pass into our atmosphere they burn as brightly as stars. Few reach the ground. They are food for poets. Yet that filigreed imagery could turn into our worst nightmare. Some of that orbiting iron is big enough to do terrible damage.

The last big object hit Earth in 1908. We're lucky it fell over empty Siberia. We think it was 90 feet in diameter. Maybe it was a comet -- mineral particles bound together in ice.

It came in over the Tunguska River, 600 miles north of Irkutsk. It exploded with a 50-megaton blast, 30,000 feet in the air, and left no crater. It flattened trees in a 13-mile radius. It roasted whole herds of reindeer. The human death toll was small. Tunguska was a very remote place.

The Tsarist government in Petersburg shrugged off the news. It had to be the raving of crazy peasants. Yet the blast covered Earth with a silvery dust. The next few nights were lit with a ghostly glow all over the world.

This became the stuff, not of poetry, but of science fiction. In a book titled Cauldron of Hell, an author suggests it wasn't a comet or meteorite at all, but an alien space probe. Maybe it'd been a meeting of matter and anti-matter.

But the event holds a more dire and concrete threat than that. Far larger objects ride in the edge of the asteroid belt. As many as 2000 small asteroids intersect Earth's orbit. Some are a mile wide. And even the small Tunguska object would've upended human history if it'd come in over Moscow or New York.

Now high-level groups in NASA, and worldwide, are studying the problem. We might have 20 years' warning for a big object -- far less for a Tunguska-sized impact. Maybe we can vaporize a patch on a large body with a neutron bomb. The resulting gas jet could then nudge the orbit enough to save us from extinction.

So what becomes of Donne's cynicism now? Maybe we actually will goe and catche a falling starre, after all. Once more the world, and our grasp of it, has to outrun our dreams. And that is both the joy and the great terror of the creative process.

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

(Theme music)

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Wasson, J.T., Meteorites, Classification and Properties. New York: Springer-Verlag, 1974.

Matthews, R., A Rocky Watch for Earthbound Asteroids. Science, Vol. 255, March 6, 1992, pp. 1204-1205.

Stoneley, J., Cauldron of Hell: TUNGUSKA. New York: Simon and Schuster, 1977.

The full text of Donne's poem, here so neatly undercut, is

SONG

Goe, and catche a falling starre,
Get with child a mandrake roote,
Tell me, where all past yeares are,
Or who cleft the Divels foot,
Teach me to heare Mermaides singing
Or to keep off envies stinging,
And find
What winde
Serves to advance an honest minde.

If thou beest borne to strange sights,
Things invisible to see,
Ride ten thousand daies and nights,
Till age snow white haires on thee,
Thou, when thou retorn'st, wilt tell me,
All strange wonders that befell thee,
And sweare
No where
Loves a woman true, and faire.

If thou findst one, let mee know,
Such a Pilgrimage were sweet;
Yet doe not, I would not goe,
Though at next doore wee might meet,
Though shee were true, when you met her,
And last, till you write your letter,
Yet shee
Will bee
False, ere I come, to two, or three.

Of course Donne had no way of knowing just what strange sights -- what things invisible to see -- really lay ahead. I hope he underestimated human capacity.

For more on the Tunguska explosion, see the following website: http://www.psi.edu/projects/siberia/siberia.html

For more on meteorite impacts, see Episode 1102.

The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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