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 ultimately one of the most important figures in the history of astronomy.

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 take medicine.

While a student, however, Galileo’s interest was piqued by physics. He observed the swinging of a chandelier and noticed that each swing took the same amount of time, no matter the distance. Galileo became the first person to realise this law of the pendulum, and he began to devote more time to mathematics.

He left university without a degree after becoming disinterested with medicine, and started tutoring students in mathematics to make money. He eventually ended up back at the University of Pisa as a teacher rather than a student.

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 therefore proving Aristotle’s theory 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 with his telescope 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. With his telescope Galileo also discovered the rings of Saturn, sunspots and the rotation of Venus.

The discovery of the Galilean moons was the most revolutionary, though, namely because it meant that there were objects in the sky not moving around the Earth, but rather around other objects. Galileo’s discovery added considerable weight to the Copernican idea that the Sun, rather than the Earth, was at the centre of the Solar System.

Galileo’s assertions were denounced by the Church, and he was tried for heresy. Initially found innocent, he was ultimately found guilty after further provocations and sentenced to house arrest at the age of 68 when he was old and sick. He eventually passed away on 8 January 1642, but his legacy continues to live on to this day. As a testament to his work the spacecraft that NASA sent to Jupiter in 1989, which revealed much of what we know of the Jovian system to date, was named in his honour.

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