GALILEO GALILEI

The father of modern astronomy provided the basis for our understanding of the Solar System

Italian astronomer, mathematician and physicist Galileo Galilei was born on 15 February 1564 in Pisa, Italy. He is often referred to as the father of modern observational astronomy due to his pioneering telescopic work. Vilified for supporting heliocentrism, he is one of the most important figures in the history of astronomy.

The eldest of seven children, Galileo was encouraged by his father, a musician and wool trader, to study medicine. Eventually, despite flirtations with becoming a monk – to which his father objected – he enrolled at the University of Pisa at the age of 17 to study medicine. At the age of 20, however, Galileo’s interest was piqued by physics. He observed the swinging of a lamp and noticed that each swing took the same amount of time. Galileo became the first person to realise this law of the pendulum, and he began to devote more time to mathematics.

At this time, Aristotle’s assertion that heavier objects fell faster than lighter objects was being challenged. Legend has it that Galileo climbed to the top of the Tower of Pisa and dropped various balls of differing weight, showing that they all landed at the same time and thus proving Aristotle wrong. Famously, during the Apollo 15 mission in 1971, astronaut David Scott recreated the experiment on the lunar surface by dropping a hammer and feather and showing they fell at the same rate in the absence of air.

Following a string of inventions, including a compass and thermometer, Galileo became interested in a device that could make distant objects look much closer after hearing of it during a holiday to Venice in 1609. Galileo frantically went about designing his own such device, which we now know as the telescope, and eventually presented it to the senate in Venice.

His first major discovery was that the Moon was a heavily cratered and rough body rather than the smooth spheroid it had been thought to be before. In 1610 he built a more powerful telescope and discovered three of Jupiter’s four largest moons, which are now known as the Galilean moons in his honour. Galileo also discovered the rings of Saturn, sunspots and the rotation of Venus. The discovery of the Galilean moons was the most revolutionary because it meant that there were objects in the sky not moving around Earth, but rather around other objects. Galileo’s discovery added considerable weight to the Copernican idea that the Sun, rather than Earth, was at the centre of the Solar System.