Engines of Our Ingenuity
No. 140:
SENSE AND NONSENSE

by John H. Lienhard

Click here for audio of Episode 140.

Today, we worry about good and bad technical information. 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 gap between our technical literacy and the things we have to know in today's world is growing. We're heaped with technical information. Some of it's accurate; some of it's terribly wrong; some of it's just innocently off-base.

A mechanic tells us a part in our car failed because it crystallized. He thinks that because fatigue-failures run along the grain of metals. Failure reveals a crystal structure that was there all along. Now there's no real harm in talking about crystallization. But we're surely better off knowing that metal doesn't mysteriously go bad with age and change its structure.

I was more worried by an ophthalmologist who said I should have laser surgery. "A laser," he explained, "carries both light and heat." Actually lasers are used in retinal surgery because they carry no heat whatsoever. The energy of a laser beam is all coherent light. It passes right through the optic fluid. It's transformed to heat only when it hits the retina. But optic fluid absorbs heat radiation. If there were any heat in a laser, it would be absorbed in the eyeball instead of the retina. The consequences of that are too horrible to think about. To this day, I don't know whether he actually knew how his laser worked or not.

We run into the same thing with some aluminum-siding and storm-window salesmen. It's fascinating to imagine a thermodynamics book based on some of their theories of heat.

But who am I to complain? As a joke, we start one chapter in our Heat Transfer book with a tall tale. It goes like this:

When I was a lad, winter was really cold. It would get so cold that if you went outside with a cup of hot coffee, it would freeze. I mean it would freeze fast. That coffee would freeze so fast that it was still hot after it froze. Now that's cold!
When someone looks me straight in the eye and says, "Gosh, I didn't know it could get that cold," then I have to repent my own sins.

We live in a technology-dense world. The engines of our ingenuity are everywhere, and we're terrifyingly naked when we don't know elementary things about how they work -- a little about the flow of electricity or fluids -- something about chemical reactions -- or the insides of our automobiles.

A world unknown is a world we can't cope with. It's not a nice place to live. You've heard people tell you with authority that hot water freezes faster than cold water, or that storm windows let heat flow only one way. We're in trouble if we don't have the tools to test statements like these. None of us can know everything we'd like to know. But we have to be educated well enough to be proper skeptics. We need the confidence at least to question the things so many people are telling us.

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

(Theme music)


J. H. Lienhard IV and J. H. Lienhard V, A Heat Transfer Textbook. 3rd ed., Cambridge, MA: Phlogiston Press, 2004, Click here for a free copy., pg. 193.

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

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