Almanac > Astronomers

Galileo Galilei

Galileo Galilei (1564-1642) was an Italian  scientist and mathematician who made significant contributions to the fields of astronomy and physics. 

In 1609, Galileo invented a telescope with a magnification power nearly 10 times greater than that of the primitive telescopes that existed in 16th century Europe.  The meticulous observations he made with his telescope led to the discovery of several significant astronomical objects in our solar system.

In particular, Galileo observed four small bodies orbiting Jupiter which he correctly identified as moons.  He used this observation as evidence for a heliocentric, or Copernican theory of the motions of planets. 

The heliocentric theory placed Earth at the center of the solar system and suggested that it has many orbiting bodies such as the Moon, the Sun, and other planets.  Galileo reasoned that if Jupiter, like Earth, had orbiting moons, then Earth might be just another one of the many planets of the solar system - not the center of the universe.

This assertion (among others) in his influential book Dialogue Concerning the Two Chief World Systems, resulted in a charge of heresy by the Catholic Church.  He was found guilty in 1633 and spent the rest of his life under house arrest.

In 1992, Pope John Paul II issued a formal apology for the Galileo trial.