didn't invent the telescope, but he was the first astronomer
who used it in a systematic way. His own telescope was a model
he'd made himself. The things that he saw through it, and
wrote about, caused a revolution in science, and a tremendous
political and religious controversy.
Every day at the same time, Galileo charted the movements
of the sunspots he saw through his telescope. They moved in
such a precise direction that Galileo became sure the Sun
was rotating on an axis. Up until this time, sunspots had
been attributed to atmospheric phenomena: events that took
place around the Sun, not on it.
Galileo published some letters in 1613 with his findings.
They included his drawings of the sunspots. But the idea that
the Sun had "blemishes" on it disturbed a lot of
people, especially the leaders of the very powerful Roman
Catholic Church. To them, everything in the heavens was made
of an unchanging perfect substance. And anyone who didn't
agree was treading on dangerous ground.
They warned Galileo not to discuss his radical ideas. But
he continued to study the heavens, and became more and more
convinced that Copernicus's theory of a Sun-centered universeanother
belief that the Church was trying to represswas correct.
Eventually, in 1630, the Vatican officially denounced Galileo
for "publishing certain letters on the sunspots"
and for believing and teaching that the Earth revolved around
Galileo had cause for concern, because in 1600, Giordano Bruno,
a philosopher who supported Copernicus's theories, was burned
at the stake. The Vatican gave Galileo an opportunity to renounce
his ideas, and he did. Nonetheless, he was forced to spend
the rest of his life under house arrest at his home in Florence.
He died in 1642.
Learn more about Galileo
on the Rice University Web site.
Learn more about Sunspots
on the Exploratorium's Sunspot Web site.