Today, we blow bubbles. 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.
If you go to Amazon.com and type in
the title Soap Bubbles, you'll be
surprised. I just did, and I got eighteen
hits. That's because soap bubbles are being used to
teach all kinds of things about the science of
applied mechanics.
One of these books has been in print for a century.
It is Soap Bubbles and the Forces which Mould
Them, published in 1902 by the Society for
Promoting Christian Knowledge. It's based on three
lectures given by Victorian science-writer Charles
Vernon Boys.
And this book comes out of something much older. C.
V. Boys' lectures were part of a series given for
children at the London Institution. They were
carrying on a London tradition begun by gentle
Michael Faraday, the father of modern electrical
science, in 1826. Faraday immersed himself deeply
in public science-lectures for children.
Once you turn the pages in Boys' book, you see that
it's about more than just soap bubbles. He treats
everything connected with surface tension and
surface forces in liquids. His examples are a
marvel. He explains the distillation process behind
wine tears -- that pattern you see when fortified
spirits climb up the side of a glass and fall back
down, making it appear that the cup is weeping.
Boys pulls up an exhortation against strong drink
from the Book of Proverbs, which, he
believes, describes wine tears. "Look not thou upon
the wine when ... it moveth itself aright."
He shows how to make what I used to call a water
bomb when I was a kid -- flimsy paper folded into a
small origami box that you can fill with water and
throw at one another on a hot summer's day. He
shows how capillary action either raises or lowers
the liquid level in a capillary tube, depending on
the contact angle. He shows how to shape soap
bubbles into every form imaginable.
I like the one where he floats a sieve in a tub of
water. With the right surface characteristics of
the sieve wire and the mesh size, surface tension
can keep water from entering the holes. Then he
quotes from one of Edward Lear's Nonsense
Songs:
They went to sea in a sieve, they did,
In a sieve they went to sea:
In spite of all their friends could say,
On a winter's morn, on a stormy day,
In a sieve they went to sea.
See, Boys says--they really could've done it!
There seems no end. Boys speaks of singing water
jets, beaded water jets, and beaded spider webs. He
calls all of nature into a microcosmic display of
surprise and beauty. He makes water leap and dance.
Boys himself did everything -- he worked in a coal
mine, he served as president of the Physical
Society of London.
We fret about education today -- how to use TV and
the Internet. Then we read this nineteenth- century
teacher, buoyed by the joy of the magic in it all,
reminding us that, whatever we do for students, it
must well up out of our own fervor, intelligence,
and imagination.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
C. V. Boys, Soap Bubbles and the Forces which
Mould Them, Garden City, NY: Doubleday Anchor
Books, 1959.
For more on surface tension and the surface layer,
see: J. H. Lienhard IV and J. H. Lienhard V,
A Heat
Transfer Textbook, Cambridge, MA:
Phlogiston Press, 2000-2002, Chapter 9. You may
obtain a digital copy of this source free of charge
by clicking on the title.
The aerodynamic breakup of a 0.2 inch diameter jet
moving at 123 feet per second illustrates the
potential complexity of surface-tension-governed
phenomena.
(photo by John
Lienhard)
The Engines of Our Ingenuity is
Copyright © 1988-2002 by John H.
Lienhard.
