Today, fog in the forest. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
Legend has it that a London
headline once cried, Thick fog over the
Channel: Continent Isolated. So: did you
ever wonder why fog doesn't just fall to the
ground? Fog is made of small water droplets, far
more dense than air. What holds it up? The diameter
of those drops is under a thousandth of a
millimeter, and a dense fog can hold as many as
10,000 droplets per cubic centimeter.
Since fog droplets are so small, the force of air
molecules bumping into them swamps out the force of
gravity. If you look through a microscope at tiny
particles in a fluid, they dance about the way
molecules do -- up, down, left, right -- under the
impact of other molecules.
Last week, two New York Times articles
talked about fog. One was the obituary of Meredith
Gourdine, president of Energy Innovations here in
Houston. Gourdine was already on his way to
becoming one of America's great black engineers
when he won a silver medal in the 1952 Olympics
long jump. After that, he earned a Ph.D. in
engineering at Cal Tech. During his long and
productive life, Gourdine received seventy patents.
Most of them had to do with fog.
Gourdine invented means for dispersing fog and
smoke. By applying strong electrical forces to
those tiny droplets he created means for making
them go where he wanted them to.
Nature has her own means for laying hold of fog,
and that's what the second article was about. The
great Redwood trees need a lot of water. Think
about the pump that'd be needed if water had to go
from the ground up to branches over 300 feet in the
air. Redwoods need no such pump, because they drink
fog. They're designed to take in water from the top
down. Redwoods have dense upper branches and
needles. Fog condenses on the needles and drips
downward. What the tree doesn't soak up, it rains
down upon the ground below. The redwood's fairly
shallow root system extends far outward from the
trunk to receive all the water caught by the tree.
The tree also waters the ecosystem in its shadow.
Cut down a redwood forest and you rob every other
plant of its water supply. That eliminates the
plant sustenance needed to replenish the trees
themselves. By now we've cut down 96 percent of all
virgin redwood stands. Unlike smaller trees, they
don't grow back in twenty to fifty years. And,
since a single redwood tree can be worth a hundred
thousand dollars to a logger, the economic
motivation for cutting it down is immense.
An ecological rule of thumb says that the
environmental impact of killing off any species
increases with its size.
That's because large living things powerfully shape
their surroundings, and redwoods are the largest
living things on earth. So when fog wreathes the
trees, far more process goes on than we see. It is
no wonder that T.S. Eliot could write,
... scent of pine and the woodthrush
Singing through the fog
What images return
O my daughter.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Litsky, F., Meredith Gourdine, 69, Athlete and
Physicist. New York Times Obituaries,
Tuesday, November 2, 1998, p. A29.
Yoon, C. K., Clues To Redwoods' Mighty Growth
Emerge in Fog. New York Times, Tuesday,
November 24, 1998. (This article is largely based
upon work by plant ecologist Todd Dawson, UC,
One should be aware that the name Energy
Innovations also belongs to a cluster of three
Houston companies that do oil-related consulting
and service. These companies have no connection
with Meredith Gourdine's company. They are:
Energy Innovations Inc.,
Energy Innovations Technical Services, and
Energy Innovations Group
After this episode aired, listener Dennis Dria
wrote to question my "largest living thing" remark
about the great redwood tree. he pointed out that
an extremely large fungus in Michigan covers an
area exceeding 30 acres. His estimate is that it is
larger by volume than the redwood by a factor of
Early morning fog along Houston's Braes Bayou
The Engines of Our Ingenuity is
Copyright © 1988-1998 by John H.
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