Today, Galileo looks at the moon. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
When Galileo was 25 years
old, he applied for a job teaching mathematics at
the Florentine Academy of Design. He didn't get the
job but the very fact he went after a post in
Florence's major art academy is important. Galileo
was a serious artist and a master of perspective
technique. Twenty years later, he found an
important use for that ability.
It was his artist's eye that finally cut through
our inability to see the moon's surface for what it
was. For Aristotle the moon had been a perfect
sphere, and that was how people still saw it in
1609. A perfect sphere, of course, is perfectly
smooth. The pure moon was not of base earth. The
16th century Church had used it as a symbol for the
Immaculate Conception. In 1609, an innocent was not
called pure as the driven snow, but rather pure as
the moon. People thought the markings they saw on
its surface were merely mirror images of the
Then an Englishman, Thomas Harriot, got his hands
on one of the new Dutch telescopes and produced a
crude sketch of the moon's surface. He drew the
terminator, separating light and dark, as a jagged
line. But he didn't suggest that the moon's surface
itself was jagged. Instead, he was puzzled as to
why a jagged line would appear on a smooth sphere.
Five months later, Galileo turned his own home-made
telescope on the moon. He hadn't yet seen Harriot's
sketch and he had two advantages. For one thing, it
was he who'd already put in motion a revolution
that would overturn 2000 years of Aristotelian
thinking. He wasn't committed to a perfect moon.
Galileo's second advantage was that he was an
artist. He made a set of sepia drawings of the moon
in its changing phases. They were beautiful
drawings with a wondrous luminescent glow. Yet they
left no doubt about the pockmarked surface. When
other people saw his drawings they promptly saw
what they hadn't been able to see before. Their
moon changed from smooth to rough in a blink --
like the shift in an optical illusion.
Galileo went on to calculate the height of lunar
mountains, from the shadows they cast. In no time,
contemporary poets -- Milton, Donne, and Dryden --
were writing about the craggy lunar surface. By
1612, when the Virgin appeared in a painting on the
ceiling of a new Roman Basilica, she was now
standing on a cratered moon.
Galileo passed this brush with the Church safely.
His troubles with the Vatican lay ahead of him. His
attacks on Aristotelian thinking would eventually
lead him into serious trouble. But for now, he'd
won a part of the battle without any real
I'm John Lienhard at the University of Houston,
where we're interested in the way inventive minds
Edgerton, S.Y., Jr., Galileo, Florentine 'Disegno,'
and the 'Strange Spottednesse' of the Moon. Art
Journal, Vol. 44, No. 1, 1984, pp. 225-232.
Ashworth, W. B. Jr., The Face of the Moon:
Galileo to Apollo: an Exhibition of Rare Books and
Maps, October 13, 1989 -- Februrary 28, 1990,
Kansas City, MO: Linda hall Library, 1989.
The Galileo sketches of the moon may be seen at:
This is part of an excellent Galileo website which I
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
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