Galileo Galilei

Galileo Galilei (1564-1642) – Astronomer and Scientist. Galileo developed a superior telescope and made many significant discoveries in astronomy. He was sentenced to life imprisonment by the inquisition for his support for the Copernican theory that the sun was at the centre of the solar system.

Galileo was born in Florence, Italy in 1564 to a poor but noble family. His parents recognised their child’s innate intelligence and talents and so made sacrifices to have him educated. At his father’s insistence, Galileo studied the profitable career of medicine. But, at the University of Pisa, Galileo became fascinated in a wide range of subjects. He was also critical of many of Aristotle’s teaching which had dominated education for the past 2,000 years.

Galileo was appointed to be a mathematics professor at the University of Pisa, but his strident criticisms of Aristotle left him isolated amongst his contemporaries. After three years of persecution, he resigned and went to the Yniversity of Padua, where he taught maths. His entertaining lectures attracted a large following and he was able to spend the next 18 years pursuing his interests in astronomy and mechanics.

During this time, Galileo made important discoveries about gravity, inertia and also developed the forerunner of the thermometer. Galileo also worked tirelessly on the science of gnomonics (telling time by shadows) and the laws of motion. It was in astronomy that Galileo became most famous. In particular his support for heliocentrism, he garnered the opposition of the Holy Roman Catholic Church.

Galileo came to the same conclusions of Copernicus – that the sun was the centre of the universe and not the earth. Galileo was also a great admirer of Johannes Kepler for his work on planetary motions; Galileo often wrote to Kepler.

” I esteem myself happy to have as great an ally as you in my search for truth. I will read your work … all the more willingly because I have for many years been a partisan of the Copernican view because it reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypothesis.” Letter to Johannes Kepler (1596)

By inventing the world’s first telescope, Galileo was able to make many ground-breaking explorations of the universe. He found that:

• Saturn had a beautiful ring of clouds.
• The moon was not flat but had mountains and craters.
• Jupiter had many moons which revolved around Jupiter rather than directly the sun.

Thus, Galileo not only had the mathematical proofs of Copernicus, but, also new proof from the science of astronomy. However, Galileo knew that publishing these studies would bring the disapproval of the church authorities. Yet, he also felt a willingness to risk the church’s displeasure.

“I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.”

— Galileo Galilei, Letter to the Grand Duchess Christina

The Church had already started to forbid Galileo’s teachings, especially anything that supported Copernicus. However, in 1623, a new pope, Pope Urban VIII seemed to be more liberally minded and he allowed Galileo to publish his great works on astronomy – supporting the ideas of Copernicus.

However, after publication, conservative elements within the Church sought to attack Galileo’s beliefs and writings. As a consequence, Galileo was arrested and imprisoned for several months. He was convicted of heresy and was forced to recant his beliefs. He spent the remaining years of his life under house arrest at Arceti.

Galileo had three children. He was especially close to one of his daughters, Polissena; she took the name of Sister Maria Celeste and entered a convent near Arceti.

“Philosophy [nature] is written in that great book which ever is before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.”

— – Galileo Galilei

Despite being censured by the church, Galileo continued to make discoveries until death overtook him in 1642. Under house arrest, he was able to write Two New Sciences, this summarised his earlier work on the new sciences now called kinematics and strength of materials He was blind by the time he passed away.

10 Galileo Facts

• He was born in Pisa, and studied at the University of Pisa
• His book Dialogue Concerning the Two Chief World System, defended the heliocentric view of the universe – with the earth not the sun at the centre.
• Using his own telescope, he discovered four moons of Jupiter – Io, Ganymede, Callisto, and Europa.
• His telescopes increased magnification from around just 2x to around 30x magnification.
• He also worked on the pendulum clock
• Inventions of Galileo included his own models of compass and thermometer. He wasn’t the first person to invent these, but he improved on their models.
• Galileo said on the force of nature. ‘ Nature is relentless and unchangeable, and it is indifferent as to whether its hidden reasons and actions are understandable to man or not.’
• Galileo was a pious Roman Catholic (he seriously considered priesthood as young man), though in science he didn’t accept the doctrinal view. The Bible shows the way to go to heaven, not the way the heavens go.”
• His daughter Maria Celeste was very devoted to Galileo, and she undertook to say his penitent psalms once a week on his behalf.
• Galileo’s Principle of Inertia -“A body moving on a level surface will continue in the same direction at constant speed unless disturbed.” was incorporated into Newton’s laws of motion.