Today, our notion of cause and effect changes
forever. 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.
Author James Gleick tells
about MIT meteorologist Edward Lorenz. In 1960
Lorenz tried to model the weather. He wrote
simplified equations and solved them on a primitive
computer. Sure enough, his output did behave a lot
like real weather. His colleagues watched over his
shoulder. They were fascinated.
One day, Lorenz tried to continue a run he'd done
the day before. He restarted it halfway through. He
put in a number from the first run. The output
started out just the way it had the day before.
Then it began to diverge, crazily.
The equations were the same. The starting point was
the same. But the results diverged. Lorenz checked
his computer. He checked his arithmetic. Nothing
had changed. Same equations, but on subsequent days
the results diverged.
There was one difference, but how could it matter?
Lorenz rounded off the fourth decimal place of the
starting number on the second day. So he stopped to
consider. All weather predictions do what his
program just did. You can predict the weather for
the day after tomorrow. Stretch that to a week, and
your prediction always departs from reality.
The implication was staggering. We've always
presumed that if you barely change a cause, you'll
barely change the effect. Suddenly, Lorenz saw that
the weather would change utterly if you started
things out just a little differently.
No wonder real weather is so unpredictable! Weather
obeys physical laws. But if you change one breath
of air, those laws will spin out in a wholly
different story.
Meteorologists began talking about something they
called the Butterfly Effect. The idea was
that if a butterfly chances to flap his wings in
Beijing in March, then, by August, hurricane
patterns in the Atlantic will be completely
different.
Not long after that day in 1960, the scientific
world began changing. Perhaps all kinds of nasty
problems we can't solve are nasty just because we
can never state them accurately enough.
Lorenz had taken the first step on the road to
showing that our world is far more chaotic than we
dreamed. For generations engineers and scientists
have been predicting things. But we've only
predicted those things that are predictable -- the
breaking load on beams -- the thrust of a rocket.
And weather, of course, is just one face of the
larger thing we all want to know, but which we
never shall predict. Somewhere in the world, a
butterfly will always flap its wings and thwart our
age-old craving to predict -- our own future.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
