Letts 1
Olivia
Letts
Mr.
Percival
Astronomy,
Per. 3
12
Oct. 2012
Francesco
Grimaldi – A Life
Francesco
Maria Grimaldi had the opportunity to become highly educated, being born into a
well-respected and well-to-do family in 1618 in Bologna, Italy. The seventeenth century, generally
considered to be the final century of the Italian Renaissance, was a time
marked by both great religiosity and fervent intellectuality. Grimaldi’s life reflected this – by
1632, he and his brother Vincenzo had joined the Society of Jesus (for
Jesuits). He studied philosophy in
Parma, Ferrara, and Bologna. One
of his teachers, Giovanni Riccioli, would later assist and be assisted by
Grimaldi during some important experiments. From 1638 to 1642 he taught rhetoric and humanities at the
College of Santa Lucia at Bologna,
where he also studied theology after 1642. By 1647, he was qualified to teach philosophy, but this was
a time-consuming course to teach and thus, suffering from tuberculosis, he had
to teach something that he found “less strenuous.” He began to teach
mathematics and physics, being skilled in all branches. Full vows for
priesthood were taken by Grimaldi in 1651.
From the 1640s
until his death in 1663, he focused heavily on his chief interests, astronomy
and optics. He was the first to
observe and record the optical diffraction phenomenon; he was also the one to
name it (diffractio). This was discovered after during a
specific experiment in which he introduced sunlight into a darkened room
through a tiny hole, projecting it only a white surface. Between 10 and 20 feet from the slit,
Grimaldi put a thin, opaque rod into the cone of light so as to cast a shadow
on this white surface. He was
surprised to note that the shadow of this cone was far wider than how it was
geometrically predicted, and
Letts 2
also, there were external
diffraction bands of different colors bordering the shadow. The brightness of these colors was more
intense near the shadow, in fact.
In 1665 he published these findings. Grimaldi had conducted other experiments for diffraction,
where he discovered internal paired tracks of light and “fringing.” His findings further proved the fluid
nature of light as opposed to rectilinear passage. Grimaldi’s Physico-mathesis
de lumine, published in 1666, the
geometrical foundations for the wave theory of light were laid. Later, Isaac Newton would create a set
of careful measurements that made it clear that the phenomenon was of a
periodic nature. Yet this great
figure himself did not accurately reflect upon Grimaldi’s experiment, as he
treated the concept of diffraction like a mode of refraction, and he could not
explain the fringes of color that occurred around the shadow. Grimaldi as well was never able to
properly explain why diffraction occurred – his death was sudden and
interrupted further experiments with light - this was not accomplished by
anyone until Joseph von Fraunhofer could in the 1800s.
With
former teacher Riccioli, Grimaldi carried out another important experiment, in
which the two Jesuits dropped weights from a tower and timed the occurrences
with a pendulum. They discovered the time of the fall squared was proportional
to the distance of free fall source to rest. Grimaldi was considered vital to Riccioli’s completion of
his Almagestum novum, a major work which
actually made Riccioli an incredibly important contributor to astronomy and
falling bodies. Riccioli noted
Grimaldi’s great skill in devising and building telescopes and other
observational instruments, through which the two frequently observed celestial
bodies. Grimaldi is well-known for
his lunar measurements, and his famous selenograph of the moon. There is a copy of this lunar map in
the entrance to the National Space Museum in Washington, D.C. He began a trend of describing lunar
regions by naming them after famous astronomers and physicists. Grimaldi often did not receive proper
credit for his findings, and during his lifetime, his works were not published
by his name.
