Galileo's Sidereus nuncius [Starry Messenger]
© William C. Kimler
is the publication as it first appeared
in 1610. The book caused a sensation across Europe, making Galileo and
his observations famous. For one thing, he provided drawings protraying
the physical nature of the moon, with its mountains and valleys and shadows.
he radically altered the perception of the planets with his telescopic
observations on Jupiter. He noted and mapped the positions of Jupiter's
associated stars, which changed position each night:
Each large circle in the figure to the left represents Jupiter; the
asterisks are the points of light near Jupiter. Each line is one of the
figures from Sidereus nuncius, in which he presented his drawings
of Jupiter and its associated "planets" one at a time. In the text Galileo
described his observations and reasoning about the movement of the small
points of light. I've taken all the drawings of Jupiter from the successive
nights in the original text, and combined them into this figure. The diagrammatic
presentation gives you the clue to what's going on -- the points can be
connected to form cycles about Jupiter, or in other words, "satellite"
moons in orbit.
The only way to see this was with a telescope, and his contemporaries
realized that Galileo had provided a new kind of evidence and new questions
for astronomy. The new argument was a definitive disproof of Ptolemy (and thus Aristotle)
-- obviously more than one center of motion is not an impossibility after
Moons image construction by W. C. Kimler