Today, what happened after Galileo? The University
of Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
Galileo was a hard act to
follow. He died the year Isaac Newton was born, but
Newton's day wouldn't dawn 'til half a century
later. Much of the dust kicked up by Galileo in the
early seventeenth century would settle by then. So
let's look at Galileo's immediate wake.
The person to meet is French
philosopher Pierre Gassendi -- born in 1592, 28
years after Galileo and four years
before his fellow philosopher Descartes.
Gassendi became a priest and, at 25, began a
five-year stint teaching about Aristotle.
By this time, the noose of the Inquisition had not
yet tightened around Galileo's neck; but it
soon would. Galileo's
earlier writings, critical of Aristotle's science
were well known, and Gassendi had read them. He was
already skeptical of Aristotle, and now he picked
up his own attack.
Well, not just on Aristotle, but on the whole
philosophy of scholasticism. When you read about
Gassendi, you usually get learned philosophical
treatises that miss much of the technical content
of his work. Here's an example:
Gassendi believed in empiricism. Galileo, had
reasoned that, if you drop an object within some
moving framework, it will share in the motion of
that frame. While Gassendi accepted that, he knew
it needed experimental verification. So he arranged
to have a weight dropped from the mast of a rapidly
moving ship. The weight landed at the foot of the
mast and not behind it.
In 1640, that experiment gave enormous validity to
Copernican dynamics, and it might've saved Galileo
from some of his troubles. It's also the key to
demonstrating why a satellite orbits, rather than
falling straight down to Earth.
Gassendi's greatest contribution was breathing life
back into the atomic theory. The scholastics had
taken the old Greek idea
that all matter is formed of four essences, Earth,
Air, Fire, and Water. Galileo had opposed that.
Gassendi went further. He correctly said that all
material phenomena arise from the indestructible
motion of atoms -- that the makeup of anything is
based on incessant atomic motion. He used that fact
to explain air pressure.
He attacked another scholastic view when he argued
that time and space exist, whether or not anything
is happening within them. That's the basis of
Newtonian mechanics, although it's taken some-thing
of a beating from relativity theory.
As an engineer, I like to look at anything as
rarified as Gassendi's philosophy and say, "Yes,
but where does the cement come out?" In Gassendi's
case, the cement came out of the mixer in the form
of the robust experimental science established
during the mid-1600s.
That's why Gassendi was able to give us a number
for the speed of sound on a normal day at Earth's
surface. It was within seven percent of the correct
value. He also influenced the writer Cyrano de Bergerac to begin
writing science fiction. And all that, four hundred
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
B. Rochot, Gassendi (Gassend), Pierre. Dictionary
of Scientific Biography (C.C. Gilespie, ed.) New
York: Charles Scribner's Sons, 1970-1980.
You will find much about both Galileo on the Rice
University Galileo web pages. See:
The Engines of Our Ingenuity is
Copyright © 1988-2003 by John H.