1609    Galileo Galilei demonstrates his first telescope to Venetian lawmakers.

1610    Galileo Galilei observes three of the four largest moons of Jupiter for the first time. He named them, and in turn the four are called the Galilean moons. Ganymede not discovered by him until January 13.

1610    Galileo Galilei discovers Ganymede, 4th moon of Jupiter.

1612    Galileo Galilei becomes the first astronomer to observe the planet Neptune, although he mistakenly catalogued it as a fixed star.

1632    Galileo's ''Dialogue Concerning the Two Chief World Systems'' is published.

1633    Galileo Galilei arrives in Rome for his trial before the Inquisition.

1633    The formal inquest of Galileo Galilei by the Inquisition begins.

1633    The Holy Office in Rome forces Galileo Galilei to recant his view that the Sun, not the Earth, is the center of the Universe.

1633    Galileo Galilei is tried before the Congregation for the Doctrine of the Faith for teaching that the Earth orbits the Sun.