Unveiling the Universe

Galileo Galilei, the great Italian astronomer and mathematician, was born on February 15, 1564. Although his ideas were condemned as heresy by the Roman Catholic Church, Galileo revolutionized man’s concept of Earth’s place in the heavens. He did so by providing strong observational evidence supporting the views of Copernicus, who said that the Sun, not Earth, is the center of the solar system.

Galileo was the first person to use an extraordinary new invention – the telescope – to examine the heavens. With his telescope Galileo discovered four bright points of light circling Jupiter. The objects were Jupiter’s four largest moons: Io, Europa, Ganymede, and Callisto.

This finding was a key piece of evidence in support of the Copernican view of the heavens. Others had argued that if Earth really orbited the Sun our Moon could not keep up. By demonstrating that other moons could orbit another planet that everyone agreed was in motion itself, Galileo disproved this notion.

Galileo also turned his instruments on Venus, our nearest planetary neighbor. Again his telescope revealed crucial evidence in defense of the Copernican view of the solar system: Venus, like Earth’s Moon, exhibits phases. If the Sun and planets orbited Earth, Venus would always appear as a crescent. But Galileo found that Venus displays both crescent and gibbous phases, meaning that it must be in orbit around the Sun.

Galileo’s work is honored and respected today, but in the seventeenth century it created major problems for the astronomer. After an appearance before the Roman Inquisition he was forced to deny his own findings and was placed under house arrest for the last decade of his life.


Flowers are part of our universe. Photo: GrandQuebec.com