The major events in Astronomy

Precession

134 BCE

1° 134 BC Hipparchus discovers precession, prepares stellar catalog. Hipparchus compared his own observations with earlier ones to discover precession, the slow change in the direction of the Earth's polar axis.

Earth has dipole magnetic field

Sep 13, 1600

1600 William Gilbert proposes Earth has dipole magnetic field. Gilbert proposed that the Earth acts like a big magnet whose field aligns the small magnet used as a compass needle.

Telescope for astronomical observations

Sep 13, 1609

1609 Galileo uses telescope for astronomical observations. Galileo didn't invent the telescope but he was among the first to use a telescope to examine the heavens.

That a central force leads to orbital motion

Sep 13, 1646

1646 Robert Hooke shows that a central force leads to orbital motion. Hooke used a pendulum to demonstrate to the members of the Royal Society that in order to stay in orbit, the planets must be continually pulled toward the Sun.