Today, Mother Earth puts on a human face. 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 planet Earth has oddly lifelike traits. Wound it and it heals itself. When its weather or its chemistry changes, it changes to compensate. We're part of this equation. We're like specialized microbes in Earth's body. We carry out processes that help shape Earth. We can also affect Earth like a disease.

Deforest a part of Earth and it reacts. It forms new eco-subsystems. It alters its weather. Sometimes Earth creates a new face of beauty. Sometimes it carries away a permanent scar.

Earth has undergone huge physical changes during the 3½ billion years that it's sustained life. Yet it's always responded with processes that've held its mean temperature within plus-or-minus 9 degrees. We do the same thing. As we go from birth to age, our body temperature only flickers away from 98.6.

James Lovelock has spent his life looking at these processes. Lovelock knows gas chromatography. He's invented very delicate instruments to measure trace gases.

He watched Earth changing the gas distribution in the ocean and air in ways that look almost conscious. Earth responds to every assault on its ecosystem by making tiny adjustments. Yet some of those responses change flora and fauna enormously.

Every shred of the evidence says Earth runs like a single organism made up of living parts -- the way we're made up of living cells and microbes. Here Lovelock knew he was on the edge of trouble. It was too easy to guess that Earth is sentient like we are -- that it's self-conscious -- that it thinks and feels.

Lovelock finally threw caution to the winds and named the Being. He called Earth Gaia -- after the Greek Earth Mother. He didn't suggest Gaia has the human qualities of a goddess. But he did let the idea hover over his text.

Of course fringe groups have been quick to form Gaia cults. Of course scientists jitter around the Gaia concept like spit on a hot stove. Yet the idea's gaining. We begin to see ourselves as ants in a colony. We have some intelligence of our own. But our real wisdom is an aggregate thing -- woven in with the rest of the planet and its life.

So: Is Earth a great sentient intelligent being? Is She a wise Goddess after all? Does She give us a glimpse of the face of God? I struggle to stay agnostic on that point. But I harbor no tendril of doubt that Earth is far more than we'd thought.

We can't go too far wrong by honoring Her the way we would a live being. For you and I really are parts of a great whole. You and I misuse ourselves if Earth's well-being doesn't guide us -- in every choice we make.

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

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Lovelock, J.E., Gaia: A New Look at Life on Earth. Oxford: Oxford University Press, 1987 (an updated reprinting of a 1979 book.)

Joseph, L.E., Gaia: The Growth of an Idea. New York: St. Martin's Press, 1990.

Lovelock's most important ally in the Gaia formulation has been a conservative American microbiologist, Lynn Margulis. See Episode No. 700 for more of the Gaia theme.