Who first
noticed sunspots? It's hard to say, as the records
left by many ancient peoples have been lost (or not
kept in the first place). But as early as 28 B.C.,
astronomers in ancient China recorded systematic
observations of the cycles of what looked like
small, changing dark patches on the surface of the
sun. And there are some early references to
sunspots in the writings of Greek philosophers from
the fourth century B.C. However, none of the early
observers could explain what they were seeing. What
could sunspots be?
Sometimes,
strongly held beliefs interfered with the process
of understanding. The ancient Greeks, and other
Europeans after them, were highly influenced by the
teachings of Aristotle, a Greek philosopher who
held that the sun and the heavens were ideal, an
embodiment of unblemished perfection. So, many
early European astronomers who saw sunspots were
puzzled. How could there be spots on the sun? As
Dearborn puts it, 'That's why, when Galileo turned
his telescope on the sun, and said "hmm! there are
definitely blemishes on the sun,' it was such a
striking discovery."
By observing the
sun closely over a period of several weeks, Galileo
noticed the shape of the sunspots became
foreshortened as they approached the edge of the
visible sun. He realized that this would only
happen if the spots were objects on the surface of
the sun, and not if they were spherical planets or
moons passing before the sun. So he concluded that
the spots must be on the surface. Though he
admitted that he was unsure what the spots were, he
suggested that they could be clouds.
|