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Heaven & Earth / Galileo

Galileo: a man

of many parts

Galileo Galilei (1564–1642) was
born into a respected but impecunious
Florentine family. Quick-witted, sharp-
tongued, good with his hands,
fond of wine and women, he eventually
settled upon a career in mathematics.
He became professor of mathematics
first at the university of Pisa and then,
from 1592, at the more prestigious
Venetian university of Padua. For the
next 18 years, “the happiest years of my
life”, he devoted himself to the study of
motion, magnets and many other topics,
but he published very little.
His telescopic discoveries, however,
earned him international celebrity and
enabled him to return to Florence as
“philosopher and chief mathematician”
to the Medici grand duke of Tuscany.
Cultured – he played the lute and wrote
on Dante and Tasso – and clubbable,
Galileo nevertheless made enemies
as easily as friends. Academic and
ecclesiastical opponents secured the
banning of his cherished Copernican
theory in 1616 and finally, after the
publication of his great pro-Copernican
Dialogue Concerning the Two Chief
World Systems, engineered Galileo’s
conviction by the Roman Inquisition in
1633 for “vehement suspicion of
heresy”. Condemned to house arrest in
Florence for the remainder of his life,
Galileo finally turned to the completion
and publication of perhaps his greatest
work, The Discourses on Two New
Sciences (1638), accurately describing Galileo was not the first
the motions of falling bodies, projectiles to study the heavens with a
and pendulums. Some of Galileo’s 1609 watercolour telescope. The brilliant English math-
sketches of the moon. His observa- ematician Thomas Harriot (c1560–1621), for
tions led him to doubt that the Moon’s example, viewed the Moon through a
surface was “precisely spherical”
telescope in the summer of 1609. Galileo
observed the Moon systematically through
Nuncius), which contained an account of his at least one complete lunar cycle (from
telescopic observations of the Moon and of crescent new Moon, through full Moon, to
the stars over the previous three or four waning crescent) in the autumn of that same
months. Page for page, at least, this slim year. Yet, in January 1610, his study of the
volume of some 40 quarto sides had a more Earth’s satellite was interrupted by his
immediate, widespread and profound sighting of four moons of Jupiter. Galileo’s
influence upon our understanding of the main objective now was to publish and
cosmos and of man’s place in it than any claim priority for this utterly unprecedented
other work in the history of modern science. discovery in The Sidereal Messenger.
Galileo’s discovery of four moons (Wotton’s However, he also decided to include his
“four new planets”) orbiting the planet drawings, descriptions and speculations
Jupiter was certainly the most unexpected about the Moon in the booklet.
revelation – and the reason he had to rush Galileo was not interested in just mapping
into print in order to establish his priority the Moon. He had a deeper scientific agenda:
– but it was probably his conclusions about he wanted to prove that the Moon was
the Earth-like nature of the Moon that had basically like the Earth, and thus that there ALAMY/GETTY
the greatest impact, at least upon the was no fundamental difference between the
Ottavio Mario Leoni’s portrait of Galileo
popular imagination. substance of the heavens and of the Earth.
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