Today, we lay numbers out on a dial. The University
of Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
I was reading a murder
mystery in bed the other evening — about a police
chief looking for a murder weapon. It was a
forty-millimeter handgun. I almost gagged.
That gun would've had a barrel over an
inch-and-a-half in diameter.
Then, halfway through the book, that was corrected
to forty caliber (or two-fifths of an
inch.) So it seems that neither author nor editor
associated a mental picture with the size of the
weapon. Forty-millimeter and forty-caliber were
Think for a minute about numbers. They can be used
to enumerate — like counting the number of people
in a room or the number of years you've lived. We
can also use them to express measurements — like
temperature, length, or time. Then they represent
arbitrary tic-marks on some sort of scale — a
thermometer or a clock face.
Those marks can be close together, like
millimeters, or farther apart, like inches. And
here rises a really basic issue of scientific
literacy. If we don't form mental pictures of those
various scales, they'll never be more than noise in
Do you remember when, in 1999, people managing a
Mars orbiter confused English and metric units? A
125-million-dollar mission ended up splattered over
Mars' surface. And such errors become even more
likely when units are compounded, as in miles per
hour, degrees per inch, or square feet.
A tour guide in a
large plant recently told us how big the plant was.
"It's five miles," she said. But the place was
neither that long nor that wide. So I asked, "Do
you mean five square miles?" "Well," she replied,
"I don't think all of them are square."
She knew the plant by appearance. But five
miles were simply words that she'd been told
to use. You hear this kind of misuse all the time.
An advertisement proclaims that a heating unit puts
out 14,000 Btu's. Well, that's nice, but how often
— every month or every second?
We've carefully formed a language to express the
technical complexities around us. Bowdlerizing that
language is a dangerous form of malapropism. Surely
any of you would react if I said a person had a
"photogenic memory" or that I like "parakeet
flooring." Such meaningless phrases as, "The
turbine puts out one megawatt per hour," or "That
wire supplies 2000 volts of power," represent a
much worse form of illiteracy.
It's worse because we all traffic in electric
power; we all use heating and cooling systems; and
we all meter our living space in square feet,
square meters, or square miles. You and I need to
understand just what a megaton of explosive can
do, or what a 25-mile-per-gallon fleet
average means in everyday traffic.
We need to view physical units as the rich and
expressive language that it is. And
that is why I tremble when I imagine
looking down the barrel of that forty-millimeter
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
For listeners who wonder about the two examples of
technical malapropism above: A megawatt is
already a rate of producing power. It means
"one million Joules per second." A volt is a measure
of electric potential, not power. Electric power is
the product of the current flowing the wire and the
voltage driving it.
The Engines of Our Ingenuity is
Copyright © 1988-2003 by John H.