Portrait of Galileo Galilei Courtesy of Ottavio Leoni, Reunion des Musees Nationaux

Galileo Galilei was an Italian astronomer and physicist who lived between 1564-1642. He challenged Aristotle's ancient proposition that heavenly bodies were divine and therefore perfect and blemish-free.

In 1609, Galileo became first person to use a telescope to look at the heavens. He discovered sunspots, and craters and peaks in Earth's moon.

The telescope also allowed Galileo to confirm the work of Copernicus in that the planets circle the Sun (as opposed to all heavenly bodies circling the Earth). Galileo's work offended the Roman Catholic Church and he was convicted of heresy in 1616 by the Inquisition. It wasn't until 1992 that Pope John Paul II announced that the Catholic Church erred in condemning Galileo's beliefs. Sentenced to house arrest for the later years of his life, Galileo is remembered as a martyr for scientific truth.