Galileo - if he had followed his father’s wishes - would have become a medical student. But he doesn’t seem to have been excited by his father’s career plan and having read Euclid and Archimedes, dropped out of his medical course.
His mathematical studies were more successful and in 1589 he got the chair of mathematics at Pisa, followed by a more lucrative position in Padua in 1592. Here he spent a happy 20 years and made many of his great discoveries.
He may be regarded as the first scientist, seeking truth through experiments rather than through thought alone.
He explored the laws of motion using experiments with falling bodies - dropping them over the sides of buildings, rolling them down inclined slopes and attaching them to pendulums.
His observations led him to some fundamental results, results that showed Aristotle had been mistaken.
All objects whatever their density fall at the same rate in a vacuum. Using a pendulum he realised his famous result that the distance a body moves from rest under uniform acceleration is proportional to the square of the time taken.
From this he also, in theory, designed a pendulum clock. His work propelled scientists to write about the natural world not by relying on pure reasoning and qualitative results but rather according to mathematical ones relying on experimentation.
Reports of a Dutch ‘spyglass’ led him early in life to look at lenses and he developed a telescope which allowed him to magnify objects by 8-9 times. He discovered many important things using his telescope.
He saw mountains on the moon, sunspots, 4 small bodies orbiting Jupiter and he realised that the Milky Way was made up of stars. His work helped to prove the Copernican heliocentric view of the Universe - that the Earth revolved around the Sun (Helios) rather than the reverse.
This was at odds with the beliefs of the Catholic Church but the two ideas were allowed to co-exist providing the Copernicans accepted that their view was a mathematical theory rather than an actuality threatening Christian belief.
In 1632 he published Dialogue Concerning the Two Chief Systems of the World - Ptolemaic and Copernican. He was ordered to appear before the Church authorities and told he had breached the rules.
He was sentenced to a life imprisonment for his beliefs. He continued working - his great mathematical work on motion was smuggled to Holland for publication -but the rest of his life was lived under the stain of heresy.
In October 1992, 350 years after his death, Pope John Paul 2, on behalf of the Catholic Church, admitted errors had been made and declared the case closed.