Galileo Galilei 15 February 1564 - 8 January 1642

The Father of Science

Galileo Galilei was an Italian Physicist, mathmatician, astronomer and a philosopher. He became known as 'The Father of Science' as he was the first man to confirm the phases of Venus and he also discovered the four largest satellites (moons) of Jupiter. These were later named the 'Galilean Moons' in his honour. Galileo's work remained controversial for many years as the general belief throughout the world of astronomy was that the Earth was the centre of the Universe.

In 1610, Galileo began to publicly announce his theory of heliocentrism (the idea that the sun is the centre of the Universe) when he was met with great opposition from fellow astronomers and clerics who eventually denounced him to the Roman inquisition in early 1615. Although he was cleared of any offense at the time, the catholic church nevertheless condemned his work and he was ordered to stop.

Later, in 1632, he began to defend his work when he published his book 'Dialogue Concerning the Two Chief World Systems'. He was again tried by the inquisition and found guilty of heresy and spent the rest of his life under house arrest.

Contributions to Astronomy

In 1581, Galileo began studying at the University of Pisa, where his father hoped he would study medicine. While at the University of Pisa, Galileo began his study of the pendulum while, according to legend, he watched a suspended lamp swing back and forth in the cathedral of Pisa. However, it was not until 1602 that Galileo made his most notable discovery about the pendulum - the period (the time in which a pendulum swings back and forth) does not depend on the arc of the swing (the isochronism). Eventually, this discovery would lead to Galileo's further study of time intervals and the development of his idea for a pendulum clock.At the University of Pisa, Galileo learned the physics of the Ancient Greek scientist, Aristotle. However, Galileo questioned the Aristotelian approach to physics. Aristotelians believed that heavier objects fall faster through a medium than lighter ones. Galileo eventually disproved this idea by asserting that all objects, regardless of their density, fall at the same rate in a vacuum. To determine this, Galileo performed various experiments in which he dropped objects from a certain height. In one of his early experiments, he rolled balls down a gently sloping inclined plane and then determined their positions after equal time intervals. He wrote down his discoveries about motion in his book, 'De Motu', which means 'On Motion.

Galileo made his first telescope in 1609, modeled after telescopes produced in other parts of Europe that could magnify objects three times. He created a telescope later that same year that could magnify objects twenty times. Galileo made his most important discoveries in 1610. During this year he discovered Io, Callisto, Europa and Ganymede, the four largest moons of Jupiter. It was also in this year that he discovered the phases of Venus and he noticed that these phases were very similar to those of our moon.