Italian astronomer and mathematician Galileo Galilei built his first telescope in 1609. Using it he saw craters and mountains on the Moon.
Galileo is best known for gathering evidence that supported the Copernican theory that the Earth revolved around the Sun. At the time, Galileo's discoveries were controversial because they challenged the Catholic Church's beliefs and resulted in him being put on trial and imprisoned.
Photo: Illustration showing Galileo in 1638 (Mary Evans Picture Library)
The Italian astronomer challenges orthodox views.
The 17th century scientist sees blemishes on the Sun.
The Italian physicist and mathematician Galileo Galilei was the first person to observe the Sun through a telescope. He saw sunspots moving across the Sun's surface and realised that it was rotating.
Dr Allan Chapman explains the instrument's development.
Sir Patrick Moore's guest Dr Allan Chapman explains the telescope's development and importance.
The Italian astronomer's findings challenge orthodox views.
Galileo observes the surface of the Moon for the first time and describes an uneven, imperfect heavenly body.
Patrick Moore talks about early Moon observer Galileo.
Sir Patrick Moore and his guest Dr Allan Chapman from Oxford University marvel at how accurate Galileo's maps of the Moon were given that he was using only the most basic of telescopes.
Galileo Galilei (Italian pronunciation: [ɡaliˈlɛːo ɡaliˈlɛi]; 15 February 1564 – 8 January 1642), often known mononymously as Galileo, was an Italian physicist, mathematician, engineer, astronomer, and philosopher who played a major role in the scientific revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism. Galileo has been called the "father of modern observational astronomy", the "father of modern physics", the "father of science", and "the Father of Modern Science".
His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter (named the Galilean moons in his honour), and the observation and analysis of sunspots. Galileo also worked in applied science and technology, inventing an improved military compass and other instruments.
Galileo's championing of heliocentrism was controversial within his lifetime, when most subscribed to either geocentrism or the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism due to the absence of an observed stellar parallax. The matter was investigated by the Roman Inquisition in 1615, which concluded that heliocentrism was false and contrary to scripture, placing works advocating the Copernican system on the index of banned books and forbidding Galileo from advocating heliocentrism. Galileo later defended his views in Dialogue Concerning the Two Chief World Systems, which appeared to attack Pope Urban VIII, thus alienating not only the Pope but also the Jesuits, who had both supported Galileo up until this point. He was tried by the Holy Office, then found "vehemently suspect of heresy", was forced to recant, and spent the rest of his life under house arrest. It was while Galileo was under house arrest that he wrote one of his finest works, Two New Sciences, in which he summarised the work he had done some forty years earlier, on the two sciences now called kinematics and strength of materials.