Today, we ask why more of the ancients didn't study astronomy. 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 science historian Jacob Bronowski raises an odd question and offers an even odder answer. The question is, "Why did astronomy develop in the old world, but not in the new one?" In the Southern hemisphere no civilization at all developed astronomy. In the Americas, only the Aztecs did serious astronomy before Columbus. The Aztecs were fine mathematicians, but their astronomy dealt only with time-keeping -- with calendars. They didn't invent planetary models, and they didn't use the stars to navigate. The Mediterranean civilizations knew the world was round centuries before the birth of Christ. But that idea never occurred to people in the New World or in the Southern Hemisphere.

Bronowski suggests that two elements drove the development of astronomy. One was the Northern Star -- that great celestial flagpole that was a point of reference to people in the North. Without it, the starry host was relatively random and uninteresting in the Southern hemisphere.

The Aztecs had the polestar to guide them, and they took an interest in the heavens. So it seems odd that, even knowing mathematics, they didn't develop theories and models for the movements of the stars.

But the second missing element outside of Europe, Asia, and North Africa was the wheel -- that strange device, so simple to those who know it and so unimaginable to those who don't. The wheel led us to see the rotary motion of planets and of a round earth. The steady rotary repetition of planetary and astral positions gave ancient sailors courage to step away from shore, and modern astronauts courage to step away from air and gravity.

Bronowski finally takes us to Easter Island -- to that primitive, landlocked, land-imprisoned people who came there some 1200 years ago. Those people gazing at a featureless sky were reduced to making huge statues of identical faces -- 40-ton monoliths called Ahu, with their backs to the sea, gazing inward on a world complete in itself -- a world which, unlike ours, cannot open up to infinity.

Easter Island, with its sad stone faces, becomes Bronowski's metaphor for a world without the wheel and without the polestar. Without these two triggers to the imagination, more than just astronomy is missing. The whole dream-driven technology that shapes our world is absent. Without the polestar and the wheel, Easter Island life becomes featureless -- without hope or fear or adventure or change.

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

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See Bronowski, J., The Ascent of Man, Boston: Little, Brown and Company. 1973, Chapter 3, The Starry Messenger. This is also available on videotape and film.

This old episode presents a pretty simplistic account of Easter Island. For a better telling of the Easter Island story, see Episode 1053.