This Day in History: 1610-01-07

In 1610 Galileo Galilei first used his new instrument, the telescope (which he constructed based on a child’s toy being sold in the marketplace in Italy) to look at the planet Jupiter.

The telescope was invented in the Netherlands in 1608, credited to Hans Lippershey, a Dutch optician. Hearing of this new device, Galileo built his own version, enhancing its magnification from 3x to about 20x by grinding and polishing lenses with precision.

Galileo began using his telescope to observe the night sky in the Autumn of 1609. His discoveries, published in “Sidereus Nuncius” (The Starry Messenger) in 1610, challenged long-standing views of the universe based on Aristotelian and Ptolemaic systems.

On the 7th of January 1610, he began to observe the planet Jupiter. He discovered four moons orbiting Jupiter (now known as the Galilean moons: Io, Europa, Ganymede, and Callisto), demonstrating that not all celestial bodies revolved around the Earth. His findings supported the Copernican heliocentric model and laid the groundwork for modern astronomy.

His discoveries, particularly his support for heliocentrism, brought him into conflict with the Catholic Church, which upheld the geocentric view. This eventually led to his trial and condemnation by the Inquisition in 1633.