Engines of Our Ingenuity

No. 2242:
THE FLYING CIRCUS OF PHYSICS

by John H. Lienhard

Today, a book of questions. 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.

I've been reading a 1975 edition of Jearl Walker's The Flying Circus of Physics. You may know Walker for his Amateur Scientist column in Scientific American. He would tell us how we could use the stuff in our households to make anything from a camera to a radio -- how we could do experiments in fluid mechanics or in biology. The column had begun in 1928. Walker took over as its third author in 1978, and he did it for twelve years. He was chosen because of his fine work in this old Flying Circus book.

In any case, the book is unlike anything you'll find today. He poses over 600 questions and leaves them all unanswered. Instead, he references over sixteen hundred sources for extended discussions of the questions.

Poisson spot
A typical question: Why the strange concentric rings

Example: Why is boiling noisy when the water's still cool, and quiet when it reaches a rolling boil? Since I've done a lot of research on boiling, I know that the answer might be sketched in a sentence, or elaborated into a full paper. Even now, we have much more to learn about how bubbles collapse in the cool water above a heater, and how the liquid then hammers upon the heater surface.

That's how science works at its best. A question answered is a question killed, unless the answer leads to the kind of understanding from which new questions spring. I saw a fog bow on the Oregon coast last year -- an eerie rainbow-like affair, but much thicker and almost solid white. And I failed to question it further. Here Walker asks what causes fog bows and why are they so unlike rainbows. Chagrined, I go looking for the answer; and doors open.

Droplets in a fog bow (sometimes called a sea dog) are much smaller than those in a rainbow. The normal optics of a Newtonian prism still operate in rainbow-sized droplets, but when droplet sizes are down near the wavelength of visible light, they no longer refract colors cleanly. Colors all merge into white. Now that I know that much, I need to learn (or figure out) the fog bow has to be placed, and why its droplets are so small. I know just enough to have a clearer picture of all that I don't yet know.

Standing waves And I've cheated you here: I've quoted two questions, then told you the answers -- robbed you of the fun of finding them yourself. So more questions: Should I use a heavy bat or a light one if I'm going to bunt? Why is summer hot when we're furthest from the sun? How does rifling enhance shooting? Why can't we make snowballs in very cold weather? Should we walk or run in the rain?

By the way, The Flying Circus of Physics is still in print, although Scientific American has long since dropped The Amateur Scientist. And Walker's new expanded editions include answers. What Walker did in the first edition simply could not long be tolerated in our answer-oriented world. But then, you and I can always read the new edition with a postcard in one hand, covering up the answers and engaging the sheer joy of searching them out ourselves.

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

(Theme music)


J. Walker, The Flying Circus of Physics, (New York: John Wiley & Sons, Inc. 1975). For information on the 2nd edition, which came out in 2006, see: http://www.flyingcircusofphysics.com/ Here you will find vastly increased numbers of questions and sources. I am grateful to Prof. Walker for permission to use the two images above.

For more on the noisy boiling question, see A Heat Transfer Textbook, Chapter 9, Experiment 9.1. For more on the standing wave question above, CLICK HERE.. And for more on fog bows, see: http://www.atoptics.co.uk/droplets/fogbow.htm

A fog bow A fog bow over the south Oregon coast (Photo by JHL)


The Engines of Our Ingenuity is Copyright © 1988-2006 by John H. Lienhard.