Galileo Galilei
There was a time when priests decreed the laws of science. That was what was happening in Italy and much of the rest of the Western world when Galileo Galilei was born in Pisa in 1564.
Although
the Renaissance was at its height, it had not led to a liberation in scientific
thought. In fact, the Catholic Church – in its Counter-Reformation
against the rise of Protestantism – was doing everything it could
to keep a grip on its power. The Inquisition, the threat of excommunication
and the very real risk of execution – the Church would burn the
philosopher Giordano Bruno in Rome in 1600 – they all helped keep
potential heretics in their place.
No matter how good your ideas, it was simply not possible to disagree with the Church's view of nature, which was based on the theories of Aristotle (384–322 BC) and Ptolemy (2nd century AD). In the astronomy of the latter, the Earth sat at the centre of a perfect universe, with the heavenly bodies, including the Sun, circling round it, perfect spheres in the celestial dome. And Aristotle's physical laws were also holy writ.
So, when a young, outspoken Italian named Galileo Galilei began contradicting the Church's teachings via his experiments and observations, it was sure to cause a stir.
Chandeliers and pendulums
Galileo did not have an easy start in life. His father Vincenzio Galilei claimed to be of noble birth, but he was simply a musician, one who constantly argued with his patrons about the mathematics behind musical harmony and the rhythms of nature. Such arguments, while perhaps stimulating the young Galileo's mind, tended to reduce patronage, and the family was always short of money.
Galileo was first educated by monks. Then, Vincenzio, hoping that his son might make a better life for himself, decided that Galileo should study medicine. In 1581, at the age of 17, he entered Pisa University, his family having previously moved to Florence.
Legend has it that, during his first year at the university, Galileo noticed a chandelier, suspended from the ceiling in the cathedral, swinging in the wind. By counting the timing of each swing using the beats of his pulse, he observed something that no one had realised before: the time it takes for a pendulum to swing to and fro is the same regardless of the length, or amplitude, of the swing – a property we now call 'isochronism'. This discovery, although probably apocryphal in the detail, would lead to the development of accurate timekeeping regulated with a pendulum.
Birth of the 'wrangler'
Galileo quickly grew bored with the quackery that was 16th-century medicine. The more he observed the world and listened to what he was being taught, the more he realised that something was sorely amiss with 'science'. Just as his father saw that rigid theory was muffling new musical forms, so his eldest son came to see the Aristotelian view as restraining scientific inquiry. But tact was not Galileo's forte. His fiery arguments, quick-witted retorts and quarrels with colleagues and professors led them to nickname him the 'wrangler'.
When Galileo ran out of money in 1585, he dropped out of university to follow his interest in mathematics and science. He returned to Florence, got a position as a lecturer at the Florentine Academy and began inventing in his spare time. His hydrostatic balance brought him early fame, while his 1589 theory of the centres of gravity won him the honourable, albeit poorly paid, post of mathematics lecturer at Pisa University. He remained there for three years and then, in 1592, moved on to a mathematics professorship at the University of Padua, where he flourished for 17 years.
It was during this period that he made a concerted attack on Aristotle's theories on motion that then prevailed in physics. This resulted in his law of falling bodies.
From the Earth to the stars
Galileo began to regard Aristotelian philosophy and Ptolemaic astronomy with increasing unease. In 1609, when he heard about a new device that could make distant objects appear closer, he reasoned it might help him study the heavens and so settle his mind. He improved on the original Dutch design of the telescope and began looking skywards.
He saw that the surface of the Moon was not smooth and perfect but full of craters, and realised that the Milky Way was made up of countless stars, none of which was orbiting the Earth. He saw spots marring the surface of the Sun, and crucially observed moons orbiting Jupiter. This last discovery had a profound effect on him. If the Earth truly was at the centre of the universe with all the heavenly bodies circling it, as Ptolemy claimed, how could some of them be spinning around Jupiter?
Galileo rushed into print in 1610 with his book The Starry Messenger. The papal court was at first impressed, despite the fact that Galileo had contradicted Ptolemy and implied that the theory of the Earth orbiting the Sun – propounded by the Polish astronomer Copernicus in 1513 – was true.
Raising suspicions
Galileo's
popular lectures and fast-selling books soon created a groundswell of
positive public opinion. He was offered a lifetime appointment to Padua
University – much to the chagrin of the Aristotelian professors.
They felt threatened by his observations, which could lead to the crumbling
of their philosophy and, thus, their livelihoods. Fortunately for them,
Galileo refused the offer, instead taking up the patronage of Cosimo de'
Medici II, the grand duke of Tuscany, and moving back to Florence.
But the Aristotelians were still worried. For them, the only course of action was to raise suspicions about Galileo's motives in the eyes of the Church. After all, who was this upstart who was telling the world that he could interpret God's universe better than the theologians?
The Jesuit cardinal Robert Bellarmine first tried to warn Galileo that his ideas would lead to trouble, and then, on 5 March 1616, issued a decree that declared Copernicus, and therefore Galileo, wrong. Galileo lay low for a while but continued his studies, developing new ideas and working on experiments to prove them.
Two systems on a collision course
In 1623, he dedicated his latest book – on the nature of reality – to the new pope Urban VIII who, as Maffeo Barberini, had been a good friend and protector. Urban was rather pleased and Galileo went to Rome hoping to have the earlier decree revoked. Instead, the papal court granted him permission to write about his ideas as long as he presented a balanced case for both the Copernican heliocentric (Sun-centred) and the Ptolemaic geocentric (Earth-centred) systems.
The resulting book, published in 1632, was Dialogue Concerning the Two Chief World Systems – Ptolemaic and Copernican, in which the bias towards the Copernican theory was strongly evident. The Church acted. With his book banned and illness and old age having taken its toll, Galileo was charged with heresy and, in April 1633, was taken to Rome for trial.
Null and void
In a moment of unheard-of leniency, the Church offered Galileo a deal: if he recanted his belief that the Earth moves around the Sun, he would avoid life imprisonment and instead be placed under house arrest on his estate at Arcetri, near Florence. Galileo agreed, and publicly declared his theories null and void and put the Earth back in the static centre of the universe. However, legend has it that, as he left the court, Galileo stubbornly muttered: 'Eppur si muove' – 'And yet it does move.'
Ensconced at Arcetri (and despite the fact that he was now blind), Galileo continued to theorise and experiment on the nature of the universe, publishing Discourses and Mathematical Discoveries Concerning Two New Sciences in 1639. But when he died on 8 January 1642, he was still muzzled by the Church.
The legacy
If his lack of diplomacy landed Galileo in trouble, it was his remarkable ability to reduce problems to very simple terms on the basis of everyday experience and common sense that established his mind as one of the greatest in science. His fundamental concepts on motion – such as his idea about inertia, in which an object will indefinitely remain stationary or follow its path in a straight line unless and until an external force acts on it – were later fleshed out by Isaac Newton in his laws of motion.
But even more importantly, Galileo's use of experiment and observation to prove mathematical descriptions of natural phenomena laid the foundations for the whole of modern science. New ideas challenge received wisdom. Galileo realised that mathematics could describe the universe, and with this tool, he destroyed the theories of Ptolemy and Aristotle – that the celestial bodies above the Moon were somehow separate from the Earth below.
A hammer and a feather
In 1971, the Apollo 15 astronauts dropped a hammer and a feather in the near-vacuum of the Moon. The two objects plummeted to the lunar surface, untroubled by air resistance, and landed at precisely the same moment, proving Galileo correct 328 years after his death.
The Catholic Church took a little longer. In 1979, Pope John Paul II set up a committee to study the Galileo case, and five years later, its findings were made public. But it wasn't until 1992 that the Vatican finally admitted that Galileo had been right.
