Today, we realize that life is instability. 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.
You're an alien observer on Mars. You have the same instruments we have on Earth. You want to know if there's any form of life in the solar system. Scientist James Lovelock asks how you'd decide.
First, you'd turn your telescope from planet to planet. Most are drab. Just one has a lovely blue and white luminosity. That's Earth. It's very pretty, but is it life-bearing?
Next you'd use spectroscopic chemical analysis. And you'd find something very strange. Only one planet has any oxygen to speak of in its atmosphere. That's Earth, and it has 21 percent.
Is oxygen needed to support life? We need it, but other life forms might not. So you still don't know. But wait: That oxygen will burn anything in sight. Combustion has gone to completion on every other planet. That means they're all as stable as the ashes in last night's fireplace.
Only Earth stays volatile and unstable. Only Earth rides the knife edge of chemical balance. Oxygen-generating processes go on, all the time. Fires and animal metabolism use up oxygen, all the time. Violate that balance just a little -- let the oxygen in air rise to 25 percent -- and plant life would become so much kindling wood. Let it drop just a little, and we'd all suffocate.
And there, says Lovelock, is what defines life. Every living thing uses corrective feedback to sustain the equilibrium of its own unstable self.
Indeed, he says, Earth not only shows life-likeness in its component parts. Earth as a whole is a lifelike organism. Lovelock even gives that organism a name. He calls it Gaia.
So feedback control of instability is the hallmark of life. That's what would tip our hand to the observer on Mars. Life is self-control, and self-control is freedom. We find analogies everywhere. For example:
We've craved the freedom to fly as long as we've had to walk this Earth. First we tried to imitate the birds with flapping wings. We failed. Then we tried to create stable powered gliders. We failed again.
Finally the Wright Brothers saw what no one else had seen. They invented an unstable airplane that could be controlled and corrected at every instant. And that's just how birds fly.
It's what we also do every moment. We correct ourselves from each instant to the next. We chance error and fix it in mid-flight. Then we're alive. Earth constantly makes and corrects errors while She sustains the life that comprises Her. And that's what we have to do if we mean to be wholly alive.
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.
Beyond Lovelock's arguments, I'm grateful for several conversations with people who helped me shape this idea. They are Judy Myers, Janet Allen, Farrokh Mistree, Karen Hall, and Donald Hall. For more on Gaia, see Episode 699.
From The Art of Flying, 1911