Today, let's be pedants. 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.
Take a word -- say, elastic: As a pedantic engineer
I'll tell you that an elastic material deforms in direct proportion to the
load we put on it. Release the load and it exactly reverses that deformation.
So, even though glass is half as stiff as steel, it is elastic, while soft
rubber turns out to be inelastic. Rubber deforms one way as we load it, and
another way as we unload it.
Yet, by a second definition of the word, rubber is elastic. That definition
merely says that an elastic material comes back to its original state when we
unload it. Rubber does do that much.
In still another use of the word, to be elastic, something need only recover --
like, say, hurt feelings. So many related meanings, and those meanings can
Not all multiple meanings are that tricky. Mischief arises when meanings lie
close to each other. Context keeps us from confusing a golf club with
the club house. We become muddled when, say, we throw about the
many-hued word love -- or the technical word, efficiency. Engineers
will quote many different automobile efficiencies -- each important, no two the same.
Or take the word pedant: Is a pedant someone who's, ipso facto,
boring? Or is it someone who wants to get things right? Our language has another
word, not much used, that carries less baggage. That word is precisionist
-- someone who simply works at being precise -- like an orchestra violinist or a brain
surgeon. That's pedantry that we should all keep in the back of our minds as we write
Definitions are often the enemy of precision because they're all circular. We define
every word with other words that have to be defined by more words still. Caught in
that great looping circular trap, we gain a precise understanding only when we
visualize the truth of a thing beyond the words we use to describe it.
Example: to bring out the inner pedant in a scientist, just ask the difference between
centrifugal and centripetal forces. When we swing a rock on the
end of a rope it takes a force to keep bending the rock's path to a circle. Cut the
rope and the rock flies off on a tangent. One of those words (don't ask me which)
describes the force on the hand holding the rope; the other, the force acting on the
rock. That's silly! All forces act in both directions. Should I give one name to
the force of my feet the floor and another to the force of the floor on my feet? I
don't see the sense of that.
Centrifuge developed for NASA by J. Lienhard for observing boiling at various gravity levels. The
centripital/centrifugal forces in the test capsule created elevated gravity within it.
Click on the image to see it at high resolution.
Leonardo da Vinci once said:
If you wish to demonstrate in words ... do not meddle with things
appertaining to the eyes by making them enter through the ears, for
you will be far surpassed by the painter.
So we erect the word pedant as armor against that occasional person who needs to explain
all reality in that single limited language of words. All of us, now and then, stumble
into a verbal morass. That happens when we mistakenly tread on the turf of matters that
should be left to an equation, a sonata, or a cartoon.
I'm John Lienhard, at the University of Houston, where we are interested in the way inventive minds work.
My thanks to linguist Richard Armstrong and theoretical mechanic Lewis Wheeler for their counsel.
For the Leonardo quotation, see: E. Belt, Leonardo the Anatomist. (New York: Greenwood
Press, Pubs., 1969). (Original printing, Univ. of Kansas Press, 1955.) See
Episode 2017 for more on the very peculiar "elastic" characteristics of rubber.
I allude to stress/strain hysteresis in rubber at the beginning of this episode. For more on
that topic, see the section on elastic hysteresis in the
Wikipedia article on Hysteresis.
For more on the centrifuge experiment pictured above see this NASA CR-1551 Report.
I've probably awakened the inner pedant in many listeners with my dismissal of centripetal
and centrifugal. Googling these words, we find talk of a reactive centrifugal force --
the force "paired" with a centripetal force. The plot thickens when one speaks of a force
associated with a Coriolis acceleration -- debate goes on whether that can be called a real
force. Perhaps such distinctions have merit, but my point is that if merit exists, it will
not be captured in words alone. (Many such issues torment physicists. I am reminded of Steven
Hawkings famous statement, "When I hear about Schroedinger's cat, I reach for my gun.")
The Engines of Our Ingenuity is
Copyright © 1988-2011 by John H. Lienhard.