Pioneers Of Astronomy: Galileo

PIONEERS OF ASTRONOMY: GALILEO

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If the 16th Century saw the emergence of the mystically inclined scientist, the 17th was when the first real scientists came on the scene. It was not the case, though, that mysticism was abandoned as sharply as one century becomes the next. Indeed, mystically inclined scientists like Kepler were alive and working even as the scientists that we shall soon meet were establishing the importance of testing a hypothesis with experimentation.

EARLY YEARS

Galileo’s story begins long before he was born, with the adoption of a new family name. A 15th Century ancestor of his called Galileo Bonaiuti was a magistrate and physician. He gained such respect in his community that the family changed its name to Galilei in his honour. Galileo’s father was called Vincenzio. Born in Florence in 1520, he became a professional musician with an interest in mathematics. He married Guila in 1562 and they had seven children, three of whom died in infancy. Galileo was the eldest.

The family were well respected and held quite a high place in society, but their finances were not really sufficient to maintain a high standard of living. Money worries would play a role in Galileo’s drive toward inventiveness. Until he reached the age of eleven, Galileo was educated at home, mostly by his father with occasional input from a tutor. By 1575, it was time for him to begin proper schooling and Galileo was sent to a monastery. There was no religious motivation behind this decision; it was just good for his education. However, when Galileo went to a monastery in Vallombrosa, he fell in love with the monastic way of life. When he was fifteen, he joined the order as a novice. It seems his father was quite distressed at this turn of events. When Galileo developed an eye infection, his father took the opportunity to take his son out of the monastery to see a doctor in Florence. The topic of returning to the monastic way of life was never discussed again.

EDUCATION

But, even if Galileo would not become a monk, he would certainly have to take up some kind of profession. His father was a working musician and he had taught his son to be an accomplished player of the lute. However, Vincenzio was well aware that it was a struggle to live as a musician and he was keen to see Galileo follow a different career. The choice seemed obvious. His son should follow in the illustrious footsteps of Galileo Bonaiuti and become a physician. Accordingly, in 1582 Galileo joined the university of Pisa as a student of medicine. Actually, it seems that two Galileos joined up at this time: One was the real Galileo and the other was a more legendary character whose achievements owe more to exaggerated stories than anything else. The real Galileo was not particularly interested in medicine and he earned the nickname ’Wrangler’ because he would argue with his masters over Aristotelian teachings. For instance, he quickly realised that hailstones refuted the argument that heavy objects fall the fastest. How so? Well, despite being all different sizes, hailstones hit the ground at the same time. If Aristotle were right, this must have meant that the heavy stones were manufactured higher up in the clouds than the lighter ones. Just at the right height, in fact, to ensure they fell on the ground together. Galileo saw that there was a simpler explanation, that they all fall at the same speed regardless of weight.

In 1583, circumstances occurred that compelled Galileo to change his career. It was customary at the university for the court of the Grand Duke of Tuscany to take up residence from Christmas to Easter. Thanks to family contacts, Galileo got to know Ostilio Ricci, who was the court mathematician. Attending a lecture given by Ricci, Galileo learned for the first time that there was a world of mathematics beyond arithmetic. He decided to quit medicine and begin training as a mathematician. His father was not happy with this turn of events. He was well aware that the money to be made as a doctor of medicine was way more than could be made teaching maths, and anyway it was extremely hard to find employment as a mathematician. So when Galileo requested a transfer, his father said no. Not that this deterred him, since Galileo simply stopped studying medicine and concentrated on his favoured topic. The result was that he left the university in 1585 with no degree.

THE CHANDELIER AND THE PENDULUM

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Before he left, Galileo gained a crucial insight thanks to a chandelier. Sometime between 1584 and 85, he found himself in a particularly dull sermon. As it is wont to do in such circumstances, Galileo’s mind began to wander until he noticed a chandelier swinging to and fro. To amuse himself, Galileo used his pulse to time the swing of the pendulum as the arc that the chandelier moved over slowly decreased. He found that, regardless of how short or long the arc was, a pendulum always took the same amount of time to complete a swing. Legend has it that Galileo rushed home and knocked up a grandfather clock then and there. Not surprisingly, this is an exaggeration. In actual fact, a seed was planted in Galileo’s mind that would not bear fruit until 1602 when he would perform various experiments to show that the swing of a pendulum is dependent only on its length and not its weight or the length of the arc it is swinging through.

In the years after leaving university, Galileo gained a good reputation as a natural philosopher and he began to write scientific papers. But at the same time he was barely scraping together a living and scientific work had to be financed, then as now. Really, Galileo’s only option was to find a patron, and that person turned out to be the Marquis Guidobaldo del Monte, who had written a book about mechanics and was keenly interested in science. Thanks in part to this man’s influence, Galileo returned to the university of Pisa as a professor of mathematics. His salary was sixty crowns per year- rather less than the two thousand crowns per year that the professor of medicine earned, as his father no doubt made clear. Galileo needed to supplement his earnings, and so he began private tuitions for those who could afford it. This actually proved useful, since ’those who could afford it’ were exactly the sorts of families that could get your name heard in all the right places. That aside, Galileo was not very happy at the university. He was required to teach Aristotle even though he disagreed with a lot of it, and he hated the way his fellow masters cared more for the trappings of office than the advancement of knowledge.

It may have occurred to you that the whole debate over falling objects could have been resolved if only somebody had dropped weights and noted the results. Legend has it that Galileo himself dropped weights from the Leaning Tower of Pisa around the time of his professorship, but this is yet another legend. Somebody really did perform the experiment in 1612 and noted that the heavier weight hit the ground slightly before the lighter one. This certainly does not prove Aristotle was right all along, since the difference was tiny and can be explained by taking wind resistance into account. The experimenter, though, claimed victory and this prompted Galileo to pen a withering response. The point is that Galileo was not adverse to arguing his case and the Leaning Tower experiment clearly vindicated him. And yet there is no record of him performing the experiment himself so it is beyond doubt that he never did it.

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Galileo’s finances were pretty poor and they were about to get a lot worse. In 1591, Vincenzio died. As the men of the household, Galileo and Michelangelo (his brother) became responsible for providing their sister with a dowry. In theory, both brothers shared this responsibility but in reality Michelangelo never paid his share and would even borrow money off of Galileo that he would not pay back. This was a bugbear for Galileo, who enjoyed the fine things in life whenever he could afford it. It was partly the financial squeeze that tempted Galileo to apply for the chair of mathematics at Padua, which paid better than his current job. But another reason was that Padua was part of the Venetian Republic, a place rich and powerful enough to stand up to Rome, and where new ideas were encouraged. Galileo took up his new post in 1592. Here, he wrote a treatise on military fortifications and also produced a book based on his lectures on mechanics. All this helped Galileo to cement his reputation but he was still very much plagued by money worries. If only he could invent something really useful, much of his problems would be solved.

GALILEO THE INVENTOR

Galileo invented various things, some of which failed and some that met with relative success. Among the latter was a compass that he developed and sold in the 1590s. This was a calculating device and its original purpose was to help gunners work out the elevation needed to reach targets. Later, it developed into an all-purpose calculating machine and Galileo made a healthy profit by selling the compass cheaply, but charging people to learn how to use it. This proved a shrewd business move for a while, but once other people learned how to use it as well, there was little he could do to prevent them passing their knowledge on. Business dried up.

Before the money dried up, the boost in Galileo’s earnings came at just the right time. This was because in the same decade he entered into a stable relationship with Marina Gamba- a relationship that would produce two daughters in 1600 and 1601 and a son in 1606. In between these dates, Galileo was subjected to bouts of misfortune and also managed to improve his position as a man of science. A particular instance of bad luck occurred in 1603. Galileo and two of his friends were staying in a villa near Padua, and the room they stayed in had a rather novel ventilation system. It was provided with cool air from nearby caves through a system of ducts. Unfortunately, it seems the cave also contained a poisonous gas and when this filled the room, Galileo and a guest were taken seriously ill, while the third guest died. For the rest of his life, Galileo would suffer various ailments and he always attributed his poor health to that incident with the poison gas.

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In 1604, Galileo conducted experiments that disproved the Aristotelian view that heavier weights would fall faster. Rather than drop his weights from a height, Galileo’s experiments consisted of rolling balls down a slope. This lead him to various conclusions that contradicted Aristotelian thinking. For one thing, he discovered that acceleration due to gravity is independent of the weight of an object. But he also came to realise that there was something wrong with the Aristotelian view that an object would be at rest unless a force acted upon it. Take this book, for example. If you give it a good shove, it will move for a short while before coming to a halt. As all objects behave the same way, Aristotle reasoned that the natural tendency of objects was to be at rest and anything moving (like planets) were only doing so because a force acted upon them. But Galileo’s experiments lead him to a different conclusion: That an object is at rest because a force is acting on it- the force of friction. Rolling balls down an incline and allowing them to roll up another plane, Galileo saw that if friction was absent, the ball would always roll up to the same height that it started from. Furthermore, he discovered that the shallower the incline was, the longer the ball had to travel to get up to the height it started from. If an object were travelling along a horizontal plane and there was a complete absence in friction, Galileo saw that it would be forever in motion.

THE FOUNDATIONS OF SCIENCE

These experiments are milestones for two reasons. Firstly, Galileo was the first scientist to appreciate that experiments are never perfect representations of the real world. Rather, scientists will often take complex models and break them down into simple components with idealised rules. In this case, the idealised rule is the removal of friction which, of course, is always evident in the real world. A more modern example of an idealised model would concern the orbit of the planets. In the real world, it would be necessary to calculate the gravitational interplay between all the planets, satellites and the Sun. However, doing so would involve calculations so intensive that even a supercomputer would balk at the challenge. So scientists will instead pretend that only the Sun exerts an influence, figuring that its immense gravitational field overwhelms everything, anyway.

The other reason why Galileo’s experiments are so important is because they laid down the foundations upon which Newton would build his own work. Galileo’s work on acceleration helped Newton formulate his own theory of gravity and Galileo’s work on friction would form the corner-stone of Newton’s laws of motion. For this reason, although Galileo was not the first true scientist, he can with some justification be called the father of modern physics.

As if being the father of modern physics was not enough, Galileo is also the father of modern astronomy. He first developed a taste for studying the heavens in 1604 when he witnessed the same supernova that Kepler had seen. Like others before him, Galileo realised that the new star was a nail in the coffin of the idea that the celestial sphere was unchanging. Galileo wrote down his ideas in the form of a poem, explaining that no parallax could be observed because of the sky’s enormous girth. These views are clearly pro-Copernican, but if there is one thing everybody knows about Galileo, it is that he was persecuted for these very beliefs. So, what happened to ensure that this toasted member of a free-thinking Republic would one day face the threat of torture, simply because of his views?

THE THREAT OF WAR

The situation began to change in 1605 when Paul V was elected Pope. Although he was officially the head of the Catholic faith, the real power behind the throne of St Peter at that time was Cardinal Roberto Bellarmine. Indeed, the new Pope was well aware that the Cardinal would have been Pope if he had put his name forward for consideration. Paul V intended to tighten his grip on Catholic states and extend the authority of the Church. But, he did not have an army to help him achieve his aim and had to rely on others, or on the Inquisition. The Venetian Republic was a particular thorn in his side. A man named Paolo Sarpi was the theological adviser to the Doge and he was arguing against the notion that kings and the Pope had the divine right to wield power. Rather, he believed that the way to heaven could be found in spiritual works. This way of thinking put Sarpi in conflict with Cardinal Bellarmine, who was very much in favour of the Pope’s divine right to rule. In 1606, Paul V retaliated by excommunicating the Doge of Venice, along with all his officials, Sarpi included. The response was to carry on with business as usual and the Pope’s next move was to expel all Jesuits from the Venetian Republic.

Things were rapidly deteriorating to the point where it seemed a war was almost certain, with Spain on the side of the Pope and Protestant France fighting with Venice. As it happens, a war never took place and Sarpi was invited to Rome in order to argue his case with Cardinal Bellarmine. This was an offer that Sarpi declined, knowing full well that torture would be used to make him see the error of his ways. But, Sarpi did not escape retribution forever, because on 7th October 1607 he was viciously attacked in the street by five men. They stabbed him fifteen times and left him with the blade embedded in his skull. Incredibly, Sarpi lived to tell the tale but his fate carried a strong message to radical thinkers like Galileo. Even if the Venetian Republic continued to stand up to Rome, nowhere in Italy was safe for those who failed to toe the line. And yet, within two years Galileo would design the world’s most powerful telescope and make discoveries that would bring him face to face with the notorious Spanish Inquisition.

GALILEO AND THE TELESCOPE

The first time that Galileo heard about the device was in July 1609 during a trip to Venice. The rumours that reached him did not concern Digges’s invention, since reports of his achievement did not reach Italy. Rather, they concerned a Dutch spectacle maker named Hans Lippershey who had ’invented’ a telescope without knowing that Digges had beaten him to it. Lippershey evidently did not think his invention had much use beyond mere novelty value, since he was selling them as toys in Paris. Having picked up on the rumours, Galileo turned to his friend, Sarpi, for further information. Sarpi then revealed that he had known about the device for months and had even talked about it with a former pupil of Galileo’s called Jacques Badovere. He had not discussed it with Galileo because he was busy as adviser to the Senate and still felt weak from the attack. Anyway, Sarpi placed no particular significance on this toy.

Galileo, on the other hand, was quick to realise that the telescope could be very useful for both military and trade purposes. Wars could be won and fortunes could be made by those who first spotted a ship on the horizon. Clearly, the telescope could be tremendously useful and Galileo believed it could be his ticket to fame and fortune. The first thing he needed to do was to get his hands on a telescope. While he was still in Venice, he learned that there was a Dutchman selling them in Padua. Unfortunately, by the time he reached Padua he learned that the man had travelled to Venice with the intent to sell his telescope to the Doge. It seemed all too likely that Galileo would miss out on a golden opportunity, so it was imperative that he quickly built his own telescope. Within twenty four hours he had constructed a superior example, despite knowing nothing more than that the device consisted of a tube with two lenses. The reason why Galileo’s telescope was an improvement was because it employed a convex and concave lens to provide an upright image. On the other hand, his rival’s telescope had two concave lenses and its image was upside down. Having finally constructed his telescope, Galileo sent a coded message to Sarpi. As adviser to the Senate, Sarpi saw to it that any decision concerning the Dutch visitor was delayed. Galileo used this breathing space to further improve his telescope, making one ten times more powerful and set in a tooled leather case. Having sensationally demonstrated his telescope in Venice, Galileo presented it to the Doge as a gift. In return, the Doge offered Galileo Tenure for life at the University of Pisa, with his salary doubled to 10,000 crowns per year. The only fly in the ointment was that the deal would include more troublesome teaching duties, but he nonetheless accepted the offer.

By December, yet more improvements had yielded a telescope with twenty times magnification and he produced nine such instruments by 1610. These were sent to various people, although the only fellow astronomer so honoured was Kepler. As for Galileo, he turned his telescope to the heavens and made some sensational discoveries. For the sake of convenience, I have decided to lump all of Galileo's discoveries, but you shouldn’t take that to mean that he discovered everything on one momentous night. Rather, the following examples were the product of many months at the telescope.

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What Galileo saw totally contradicted the Earth-centric (or Ptolemaic) worldview, while at the same time lending support to the Copernican idea of a solar system. Remember, that the Ancients believed that the planets were flawless spheres, but when Galileo turned his telescope to the Sun, the moon and the planet Saturn, he found that this was simply not the case. The moon’s surface was a battlefield of craters and mountains. Galileo used the shadows to estimate the height of these mountains at several kilometres high. The Sun revealed flaws in the shape of blemishes that are now called sunspots, and these helped Galileo to show that the Sun rotates on its axis- a discovery that lent plausibility to the idea that the Earth could also turn on its axis. As for Saturn, Galileo’s telescope revealed what looked like two ears on either side of the globe. Because his telescope was so weak by future standards, Galileo never learned the true nature of those ears, a mystery that remained until 1659 when Christian Huygens used a superior telescope to view the planet’s famous rings.

This, by the way, just goes to show what good bedfellows science and technology are. A new technology might provide tantalising glimpses of a deeper truth and this calls for improvements which is where science comes in. Furthermore, the improved technology may shine new light on the science that provided them. In the case of the telescope, the need to see further into the heavens has pushed the science of optics to produce better and better lenses. Today, the pinnacle of telescope design is surely the space-based Hubble telescope that has revealed wonders beyond the imagination of the early astronomers.

THE MOONS OF JUPITER

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Galileo had clearly shown that the notion of flawless spheres was false and that contrary to popular opinion there was lots about the heavens that the likes of Aristotle had not known about. But there is little doubt that the most important observations concerned Jupiter and Venus. In the case of Jupiter, Galileo turned his telescope to it on the night of 7th January 1610 and became the second person to discover some tiny stars alongside it. The first person to make the discovery was a German astronomer called Simon Marius. If that name is not as familiar as Galileo, it’s because Marius failed to attribute any significance to those tiny specks of light and did not continue to observe them. But Galileo did carry on observing them over many nights and came to realise that they were really moons in orbit around Jupiter. He named these four moons the Medicea Sidera or Medician Stars, but today we honour Galileo by re-naming them the Galilean Moons. As for Marius, he did gain some recognition when his suggestion that the moons be named after the amorous conquests of the Jupiter of Roman legend was accepted and the satellites are indeed called Io, Europa, Ganymede and Callisto.

WHAT THE MOONS PROVED

The discovery of moons in orbit around Jupiter was extremely important for several reasons. Firstly, it was final and definitive proof that the mystics did not know everything about the universe. After all, they never mentioned that Jupiter was like a solar system in miniature. And the fact that it was a solar system in miniature provided Galileo with the perfect counter to one of the most popular arguments against the Copernican model. Many of its detractors pointed out that the Moon was in orbit around the Earth, so the Earth itself could not move or else its satellite would be left behind. But, Jupiter was acknowledged to be in orbit by everybody and its moons were clearly in orbit as well. And if that piece of evidence was not proof enough, there was further evidence to be found by observing Venus. In fact, what Galileo saw had been predicted in a letter written by a former pupil of his called Benedetto Castelli. He explained that if Venus could be shown to have phases like the Moon, this would be consistent with Copernicus but not Ptolemy. The reason lies in where the Sun is placed. In the mystics’ version, the Sun lies outside the orbit of the planet and from Earth Venus is always in crescent phase. But, in the Copernican model the planet is lit from the centre of its orbit and so it waxes and wanes just like the Moon. Galileo had been observing Venus before he read the letter and he was able to confirm that the Copernican model was correct. This is an important outcome, not only because it further validated the notion of a solar system, but because it is also an early example of the most powerful scientific method. That is: a prediction was made about how the real world might work and was tested against reality and found to be consistent with the model.

GALILEO’S BOOK

Galileo wrote about his findings in a book called The Starry Messenger which came out in March 1610. The book made him famous throughout the world. Furthermore, in May Galileo was offered the post of Chief Mathematician at the university of Pisa, Philosopher and Mathematician to the Grand Duke of Tuscany for life. To further sweeten the deal, there were to be no teaching duties whatsoever and Galileo was released from any obligations to pay his brother’s share of the outstanding dowries (he had already paid more than his own share). Taking up the new post would require tearing up the contract with the Venetian Republic. But Galileo pointed out that the promised pay increase had never materialised so he considered the contract to be null and void. When Galileo journeyed to Florence in October to begin his new duties, it marked the end of his relationship with Marina Gamba. They split amicably and Galileo’s daughters stayed with their mother, while his son only stayed until old enough to join him. But any personal problems would take a backseat compared to the hornet’s nest that Galileo’s discoveries would stir up.

THE ESTABLISHMENT RESPONDS

Remember that the Ptolemaic system was more than a model of the universe. It also supported an entire theological-philosophical worldview that had been built up around it. Bringing the authority of the Ptolemaic system into question undermined the power of the Church, because if they couldn’t be trusted to get the correct model of the universe, what else might they have gotten wrong? Galileo was careful never to publicly announce that his evidence supported Copernicus, instead preferring to simply present it and let the facts speak for themselves. But the real die-hards simply refused to acknowledge the facts and instead attributed what they saw to a fault in Galileo’s instrument.

This, by the way, is par for the course in science. Don’t be fooled into thinking that today a theory is quickly abandoned once it is found to be wrong because it is still very hard to overthrow established ideas. Scientific theories are different to religious dogma in the way that they are never absolute truths. Rather, they are models that may or may not fit whatever available data we have. The data available to the Ancient Greeks suggested an Earth-centric universe and it was only later that further data showed the flaws in this model. Today, there is evidence to show the idea of oil being a fossil fuel might be wrong, but don’t expect the old guard to be particularly open to these radical theories. Of course, today an opponent of the established view faces ridicule, whereas in Galileo’s day you faced being burned as a heretic. In all fairness to the Aristotelians, while we may scoff at their attempts to explain away Galileo’s discoveries, it is not unknown for instrument error to be behind supposedly remarkable discoveries. Perhaps the most famous example is Percival Howell who in November 1894 announced he had seen canals on Mars. This was sensational news: Evidence that a sophisticated culture existed on the Red Planet. Alas, the truth is that these canals were really the product of a faulty lens.

GALILEO REPLIES

As for Galileo, he countered his critics by testing their hypothesis. He observed hundreds of objects close up with the naked eye, and then at a distance through his telescope. He could see nothing through his instrument that was not there in reality and this convinced him that his evidence was also real. In March 1611, Galileo was given the opportunity to present his evidence to the highest authority in the Catholic church- Pope Paul V. He was even allowed to address His Holiness standing, as opposed to on his knees. During his stay in Rome, Cardinal Bellarmine looked through the telescope and set up a scientific subcommittee to examine the evidence. The Jesuit members of the subcommittee confirmed much of the evidence and it became official that Venus exhibited phases, Jupiter had moons and so on. However, no further implications arising from these facts were discussed.

Before he returned to Florence, Galileo joined one of the first ever scientific societies that had been established in 1603. It was here, during a banquet held to honour Galileo, that the name ’telescope’ was first coined. Hitherto, it had been called a spyglass or an optic instrument. When Galileo returned home, it was to a hero’s welcome. Not only did he bring glory to the name of Tuscany but he had also received some sort of official approval for his work. Or so he thought. Actually, the meeting with Galileo prompted Cardinal Bellarmine to advise Pope Paul V to set up a papal commission to determine whether or not the Copernican view should be made officially heretical. It was decided that the idea of the Earth moving, or that the Sun lay at the centre of the universe, were both heresy. Meanwhile, Galileo had relaxed slightly in his decision not to talk publicly about the Copernican universe. This was not the first time he had let his feelings be known, because he had written a book about sunspots that featured an appendix in which he clearly stated his approval of the system. The upshot of this and his other, unpublished comments (not to mention the extraordinary success of his visit to Italy’s capital) began to attract bad feeling against Galileo. He felt he should journey to Rome and resolve the matter.

THE HERETIC

Knowing he was on his way, the Pope had to make a decision as to what to do with Galileo. On 26th February 1616, Paul V passed on his instructions to Cardinal Bellarmine, who would act as his personal representative. The astronomer was to be warned that it was heretical to believe that the Earth moved or that the Sun was the centre of the universe. Provided Galileo fully complied with the first directive, he would be allowed to teach the Copernican system, provided that it was made abundantly clear that these were heretical views that he did not believe in. But if (and only if) he showed the slightest signs of reluctance to do as he was told, then a second warning would be issued: One that would also deny him the right to teach the Copernican system.

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Two days later, on 24th February 1616, Galileo arrived and was received by Bellarmine. The Cardinal told the astronomer that he should do as instructed and then lead him into a room in which sat several people. Galileo knew full well that these people were members of the Inquisition and he carefully listened to what they had to say and made it clear that he had no objections. But then the Inquisition issued the second warning- the one that also forbade Galileo to teach Copernican theory. A furious Bellarmine ushered Galileo out of the room, and in the meantime an unsigned, un-notarized and un-witnessed set of minutes were deposited in the official records by the Inquisition. The meeting greatly concerned Galileo, who had consultations with the Pope on March 11th 1616. In the friendly conversation that followed, the astronomer was assured that he would be in no danger while Paul V lived and had done nothing wrong in the eyes of the Church (as certain rumours suggested). Also, Cardinal Bellarmine issued a sworn statement that Galileo had merely been told what the official position of the church was. Relieved, Galileo returned to Tuscany.

THE THIRTY YEARS WAR
By the time the 1620s came around, though, the Thirty Years War was well underway and the political situation in Italy changed. This was brought about by the death of three key people. In 1621, Pope Paul V died. Although Galileo had been assured of protection under his rule, there was no guarantee that his successor would be so inclined. Secondly, Cardinal Bellarmine also passed away, and that meant Galileo had no witnesses to the goings on at the meeting of 1616. The third person to die was Cosimo II. His eleven year old son, Ferdinando, ascended the throne with his mother and grandmother acting as Regents. Although Galileo was still in favour, the fact that a minor was on the throne greatly weakened Tuscany’s ability to influence Italian politics and there was no longer any protection from Tuscan states if you fell out of favour with Rome. And Galileo had been stirring up trouble for himself. A few years previously, in 1618, three comets had appeared, prompting the Jesuits to write outlandishly about their significance. This prompted Galileo to write a famous response in which he claimed the universe could only be understood using the language of mathematics. He also derided the Jesuits for dealing in mere fairy stories, a comment that was sure to cause resentment.

Still, at first things went quite well for Galileo. The new Pope was called Gregory XV and he granted the astronomer permission to write a book called The Assayer. He also received a doctorate from the University of Pisa in June 1623. Originally, The Assayer was dedicated to Gregory XV but he was an elderly man who died before the book reached the printing stage. Succeeding him was Cardinal Maffeo Barberini, who took the name of Urban VIII. The Lynceans changed the book so that it was dedicated to the new Pope and the cover was adorned with three bees- the Barbarini arms. When the Pope received a copy of The Assayer, he was greatly amused at the digs at the Jesuits.

UPSETTING THE ESTABLISHMENT

In 1624, Galileo again journeyed to Rome and received several honours. But, as far as the astronomer was concerned, the greatest honour of all was when he was given permission to write a book about the two world systems. The catch (of course) was that Galileo had to make it clear that the Copernican theory was a heresy that he did not believe in. Galileo had secretly been organising his notes and theories into a book for some time and with official approval he settled down and completed it in November 1629. The book itself was called A Dialogue on the Two Chief World Systems and it took the form of a dialogue between two people (one who stands for the Ptolemic model, the other on the side of Copernicus), with a third acting as an impartial witness who interrogated the other two with pertinent questions. Although Galileo was not supposed to take sides, his supposedly impartial commentator increasingly came down in support of the Copernican theory. The names of his characters also betrayed his true feelings. The character in support of Copernicus was called Salviati- and Galileo had a friend called Filipino Salviati who died in 1614. By giving his character the same name as an old friend, Galileo was steering dangerously close to supporting heretical views. As for the supporter of the Ptolemic system, his name was Simplicio. On one hand, the inspiration for the name could have come from an Ancient Greek called Simplicius who had written a commentary on Aristotle. But equally, the name also implied that anyone who believed Ptolemy was right must be a bit simple.

Once written, the book had to pass a censor in Rome and gain the official seal of approval before it could go into production. The man who checked the manuscript was Niccolo Riccardi, a Dominican Father who had passed The Assayer without changes. Galileo delivered the manuscript in may 1630 but had to leave in June when plague spreading south across Italy threatened to reach Florence and disrupt communications. Having checked the book, Father Riccardi was largely happy with the bulk of it, only requesting alterations to its preface and conclusion.

Various factors delayed printing of the book. It would have been produced by the Lycians in Rome, but the Chief Lynx (Prince Federico Cesi) died in August 1630 and all affairs were thrown into confusion following his demise. The plague also had a negative impact. The book finally went on sale in March 1632, with the first few copies dispatched to Rome. The first person to receive a copy was a nephew of the Pope’s called Cardinal Francesco Barberini and he wrote a letter to its author, telling him how much he enjoyed it. But his uncle, Pope Urban VIII, was not so enamoured. Part of the problem lay with the extra material that the censors had included. Having written out the changes, they were sent to Galileo accompanied by a covering letter that stated, the author may alter or embellish wording, so long as the substance is preserved. Unfortunately for him, Galileo did indeed make alterations, but in a way that would land him in deep trouble. The preface explained that the Copernican view represented therein was only hypothetical. Galileo had these words set in a different typeface to the rest of the book and this implied that the opinion of the preface was not that of the author. Also, the closing words of the book (in which the reader is again reminded that the Copernican worldview is only a theory) is spoken by Simplicio. Because he is the only character in the book that ends up supporting Ptolemy, Simplicio is the only character who could have spoken those words. But they were exactly the words that the Pope had uttered. When he read the character of Simplicio repeating them, he felt the implication was that he himself was a bit simple. Greatly angered at this perceived slight, Urban VIII ordered a Papal commission to search for a way to prosecute Galileo. Searching through the records, the commission discovered the unsigned minutes from the meeting of 1616. Here was damning evidence: Proof that Galileo had been ordered not to teach Copernican theory. Accordingly, Pope Urban VIII summoned Galileo to Rome, where he was to stand trial for heresy. He also did his best to stop Dialogue from being circulated but it was already available, so he was too late.

A TRIAL AND HOUSE ARREST

When Galileo received his summons, he did his best to avoid or delay the trip to Rome. He claimed that he was too old and frail to make the journey. This was no lie: The sixty nine year old suffered many debilitating complaints. He also asked the state of Tuscany for help. Unfortunately, Federico II’s youth and inexperience at the time (he was 19) meant Galileo could not count on the kind of support that Venice had once afforded Sarpi. Unable to put it off, Galileo travelled to Rome and arrived on 13th February 1633. He was treated well by his accusers- allowed to stay in rooms at the Tuscan embassy in Rome before the trial started. Even during the trial, Galileo’s accommodation was a hotel room, and not a damp dungeon. Even so, he was kept awake every night by his chronic arthritis.

During the trial, various accusations were levelled at Galileo, including the fact that he had written the book in Italian rather than Latin, thereby allowing ’ordinary folk’ to understand its contents. But the main issue was whether or not he had disobeyed a direct order not to teach Copernican theory. To counter these accusations, Galileo showed the Inquisition the document signed by Cardinal Bellarmine that clearly showed he had not been forbidden from teaching Copernicus. But, the Inquisition were determined to get their man, and Cardinal Barberini made Galileo understand that they had ways and means to extract a confession from him, whether he was guilty or innocent. The astronomer was in no state to undertake torture (not that anyone could have suffered the terrible devices of the Inquisition) and so he made a famous statement in which he claimed not to believe in the Copernican worldview, and said he had allowed his own pride in his teaching abilities to represent heretical views in a plausible way. The legendary Galileo is supposed to have then muttered “eppur si muove” (yet, it does move) although the certainty of going to the Rack had he been overheard means this is surely another exaggeration. Once found guilty, Galileo was sentenced to life imprisonment. Of the ten Cardinals sitting as council of the Inquisition, only seven of them signed the sentence, with Barberini among the three who refused. It was also Barberini who helped soften Galileo’s sentence from house arrest at the Tuscan Embassy in Rome to confinement at his own house near Arcetri in 1634.

HIS GREATEST ACHIEVEMENT

Galileo may have spent his last years under house arrest, but he was by no means finished in his contributions to science. Perhaps his greatest achievement after his sentence was to produce a book called Discourses and Mathematical Demonstrations Concerning Two New Sciences. Smuggled out of Italy and published by Louis Elzevir in 1638, the book would prove to be tremendously influential on the development of science across Europe. The one exception was Italy itself, as the country suffered a downturn in scientific progress as a direct result of the condemnation of Galileo’s work by the Church. The book itself is quite possibly the first scientific textbook. Drawing upon everything Galileo had learned about mechanics, inertia and pendulums, it showed how the universe was driven by forces whose effect could be understood via the language of mathematics-a universe whose secrets could yield to the inquisitive mind. It was a calling to other potential scientists to abandon the mystics’ approach of philosophising about the world and instead adopt the method of investigating the world through experimentation. And others did indeed heed the call. Two years before the great man died, a Frenchman called Pierre Gassendi devised a way to test an old argument of the Ancients. As you may remember, the likes of Aristotle had claimed that if the Earth were moving and a stone were dropped from a tower, it would not land at its base but some way away. The fact that stones always land at the base of a tower suggested the Earth must be motionless. By the year 1640, technology had created a means to test this hypothesis. What Gassendi did was to borrow a galley from the French navy, which was the fastest transport on Earth at that time. As it was rowed flat out across a calm Mediterranean sea, Gassendi dropped weights from atop the mast. All of them landed at its base. This did not prove that the Earth was moving- it merely demonstrated the fact that one could neither prove nor disprove it by dropping stuff from a height. The experiment is also notable because it enabled Gassendi to glimpse a truth that would be fully revealed to Einstein in the 20th century. Although he never realised it, the Frenchman had stumbled upon one of the basics of Special Relativity. Had the galley been able to ride across the oceans without inducing vibrations or rolling on the waves, and Gassendi had been placed inside a windowless room on the ship, there would be no way of knowing if the ship were moving or not. An object in constant motion is equivalent to an object at rest.

GALILEO’S DEATH AND LEGACY

Galileo died peacefully in his bed sometime during the night of the 8th or 9th January 1642. He was two weeks away from his seventy eighth birthday. Thanks to his work, his name lived far beyond his physical self. The Galilean satellites are still in orbit around Jupiter, tempting generations of astronomers to train their telescopes upon that jewel of the night sky. Centuries after his passing, scientists continued to run experiments to test his theories. Standing on the Moon, you see the Earth rise above the horizon, just as the Sun or Moon do here on our home planet. If creatures lived on the Moon and their knowledge was equivalent to that of Aristotle, they would no doubt argue that the Moon was motionless with the Earth in orbit around it. But, the only forms of life known to have visited the Moon came from Earth, and they tested a hypothesis of Galileo’s. After the Leaning Tower experiment showed a slight difference in the time two weights took to reach the bottom, Galileo explained that wind resistance was responsible. To test this, astronauts who went to the Moon dropped a feather and a lead weight to see how they would behave in the vacuum of space. Galileo had been right all along.

An essay such as this cannot be written without relying on the hard work of prior writers who have recorded important information like dates and names. My reference was an excellent book by John Gribbin called 'Science: A History'.