Today, we learn to look for the door into summer.
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 asking friends
what they hear when I say the word
tunnel. None have given me the common
Freudian stuff, and only a few mentioned
claustrophobia. A different theme entirely emerged
-- far stronger and far more positive.
One said, "Tunnels are connections." One recalled
that Greek oracles always spoke from within caves.
One way or another, tunnels remind us of the subtle
ways we get to the other side of trouble. For some,
going through a tunnel is death and rebirth.
When I put the question to a theoretical chemist,
she hesitated -- then said, "Oh, you mean
underground tunnels!" Her first thoughts had not
been of subways and caves, but of quantum physics.
But even there the word is a metaphor for breaking
Here's how it works: Electrons are bound to atoms
by electric forces. They seem to be trapped.
Classical physics says that it is "impossible" for
them to escape.
But when we study quantum physics, we find that a
tiny electron is far less definite than objects in
our much-larger world. It doesn't have a precise
location. The electron is most likely here -- but
it might also be over there at the very same
If that sounds like nonsense, it's because we're
too large. We can't experience that vagueness
directly. When we talk about matter in so small a
form as an electron, our whole solid vocabulary for
material existence breaks down.
Sixty-five years ago, classical physicists imagined
that electrons were held to atoms by an
insurmountable energy barrier -- a wall they
couldn't get through. Now quantum physics says that
a few electrons can walk right through the wall --
as though it weren't even there.
Scientists who traffic in those mysteries call such
an escape "tunneling." The electrons seem to tunnel
through the energy barrier and escape their
inescapable prison just as surely as occasional
captives tunnel their way to freedom. Jean Paul
Sartre described what that electron does. He said,
Let us not look for the door, and the way out,
anywhere but in the wall against which we are
That image of escape where we thought escape was
impossible recurs. Remember the story about the
house cat who went from door to door, on a cold
winter's day, looking for the one door that led
into summer. Well, the metaphor of the tunnel --
and of the quantum mechanical tunnel -- reminds us
that we can pass through the wall. We can find the
door into summer. There are ways to tunnel through
our impossible troubles -- after all.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
I am grateful to Theresa Kavenaugh Lienhard, Brown
University Chemistry Department, and Don Kouri, UH
Chemistry Department, for their cogent discussions of
quantum tunneling. Sartre credits Ralph Waldo Emerson
with the "wall" idea that I quote.
For more on the matter of tunneling, see the
proceedings of the Smithsonian Institution's
symposium on its tunneling exhibition, Down
Under: Tunnels Past, Present, and Future,
National Museum of American History, Saturday,
October 23, 1993.
I say more about tunnelling as a metaphor in
Episodes 51, 664, and 849. For a more technical look at
tunnelling, try the search function, using the word
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
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