There is no sadder sight in the world than to
see a beautiful theory killed by a brutal fact.
Thomas Henry Huxley (1825-95)
In this essay, I would like to share with you some of the achievements of one of greatest scientists who ever lived; Galileo Galilei, whom I believe without question was the first 'modern' physicist. The journey we are about to embark upon is pretty much a personal view of Galileo - gained from various sources - since his life, particularly his later life, was full of controversy. In fact, even today philosophers argue about his 'motives'. For example, some claim that he was a 'Copernican' zealot who was out to discredit the Church, but there are others who believe he was simply trying to prepare the Church for the changes in beliefs and dogma that he knew science was to bring about. Yet another view has been proposed in which he was condemned by the hostility of contemporary philosophers who exploited the position of the Church. Whichever position you take there is no doubt Galileo had a profound effect on the development of science. He was very much at the forefront of introducing mathematical methods into science rather than relying on philosophy as so many of his predecessors, dating back to Aristotle, had done. His was a search for laws not causes.
It should surprise no-one that the evolution of modern physics began in Renaissance Italy; it had been, after all, the birthplace of the poetry of Dante and Petrach, the writings of Machiavelli, the art of da Vinci, Boticelli, Cellini and Michelangelo, the music of Desprez and da Palestrina - and even the fine culinary craft and the cookbooks of da Como, di Messibugo and Scappi! The Renaissance brought about a brilliant revival in learning, culture and appreciation, and so it was entirely appropriate there should be a 'rebirth' of scientific enquiry and understanding. In a previous article I described how after centuries of investigations by Greek philospher-scientists like Archimedes and Aristotle, the study and development of the physical sciences changed but slowly for some 1400 years after the death of Ptolemy. As we have seen, Aristotelian philosophy suited the beliefs of the Church fathers and so in Europe in particular, Aristotle's work was taken to be authoritative in all matters by the Church and State and any questioning or opposition to the accepted scientific principles ran the risk of severe penalty - even death as the sometimes fiery and outspoken Giordano Bruno found out . It is against this sort of background that I find the accomplishments of the scientists of the late Renaissance, like Galileo, so remarkable.
Galileo Galilei was born in Pisa, in Tuscany, on the east coast of Italy, on February 15, 1564 - the very day that the artist Michelangelo died. His father, Vincenzo Galilei (ca. 1525-1591), was well educated and a talented musician who published a book in the field of musical theory in 1581. He had probably been a musician in the Court at Florence, but for financial reasons he was forced to move to nearby Pisa, some years before the birth of his eldest son Galileo, where he became a trader. Very little is known about his mother Giulia Ammannati. Eventually, Galileo was to have two younger brothers and four sisters. One of his brothers, Michelangelo, was shiftless and irresponsible and caused him considerable anxiety in later life.
The family stayed in Pisa until Galileo was ten and then moved back to Florence. After some schooling there he was sent to an ancient Jesuit school at the Camaldolese monastery of Vallombrosa, near Florence, where he was so attracted by the quiet, studious life that he entered the order as a novice. However, his father wished him to study medicine and took him back to Florence, where he continued his studies with the monks though no longer as a prospective member of the order. Obviously, he did well because in 1581, at age 17, he enrolled at the University of Pisa. To please his father he studied medicine but he became more and more interested in mathematics and mechanics, although there was no serious department of mathematics at the University at that time. During a vacation period at home in 1583 he went secretly to the home of a family friend for lessons in mathematics. When his father Vincenzo discovered what was going on, he wisely changed his mind and allowed Galileo to study science.
It is believed that it was inside the Cathedral of Pisa during prayers Galileo watched a monk in the upper gallery draw the large chandelier towards himself, light the candles and release it. Apparently, he noticed that when it first started to swing, it moved swiftly through the darkness covering a large arc of swing. As the length of the arc decreased the speed of the lamp also seemed less. Instinctively, he used his pulse to measure the time of swing - he later claimed he could discriminate 1/10th of a pulse beat. As far as he could determine the time it took to swing did not depend on the length of the arc of swing.
Back in his room he made and tested various pendulums and he discovered two things:
One story that Vincenzio Viviani (1622-1703) - who edited the first edition of Galileo's collected works in 1655-1656, over a decade after his death - tells is that Galileo, being nearly penniless, tried to use his discovery to earn money. He still had some interest in medicine so he developed a string pendulum of variable length - he said a doctor could adjust the string so that the oscillation coincided with a patients heart-beat, therefore the patients pulse rate was given by the 'length of the pendulum'. On subsequent visits or during treatment the doctor could get an accurate measure of any changes in the heart rate by comparing the 'new' length with the previous one. Apparently, the pulsilogium became very popular but it was so simple it probably didn't earn any money! However, this story is not correct; it seems more likely that the pulsilogium was invented around 1602 by Santorio Santorii (1561-1636) - later appointed professor of medical theory at Padua. He was a friend of Galileo's and so it is likely they discussed it. But it did lead to a totally new concept in time-pieces and Galileo himself sometime later built a pendulum clock with an escapement that allowed a toothed wheel to advance one tooth at a time; the fore-runner of the modern pendulum clock. The first proper pendulum clock was actually constructed some years after Galileo's death by Christian Huygens.
At University, Aristotle's texts were the approved books and Galileo studied them diligently - he also read the texts opposed to Aristotle, which were certainly not approved of by his professors! Galileo was outspoken and often expressed doubts about the validity of Aristotle's theories. His behavior was unprecedented for the period and earned him the nickname 'The Wrangler' from both professors and students. Galileo's father had worked hard to keep his son at University but after three years he had reached the limit of his resources. So Galileo tried for a scholarship but since he often disputed Aristotle's ideas, his scholastic record was 'poor' - as his answers were very rarely 'correct' - and none of his teachers were inclined to support him. Therefore, he left University in 1585 without a degree and returned to the family home in Florence. For four years he continued to learn mathematics and mechanics by himself. He discovered the work of Archimedes and became a devoted fan; Archimedes had been a practical experimenter as well as a theorist.
It was probably at about this time that Galileo began to develop what we now call the scientific method; that is the combination of hypothesis (or theory), prediction and experiment. This approach, involving careful measurement, began to replace the ancient search for causes with the modern search for physical laws.
He also earned some money tutoring in Florence and Siena but he was continually looking for something more permanent (much like the students of today!). His mathematical abilities were becoming recognized even among in Florentine literary circles. In 1588 he was invited to address the Florentine Academy on the location, size and arrangement of hell as described in Dante's Inferno. The influential head of the literary academy subsequently helped Galileo in gaining his next two jobs. He applied for the vacant Chair of Mathematics at Bologna in 1588 but was rejected. Rather surprisingly, considering his previous history, he was given the Chair of Mathematics at Pisa in 1589, a very poorly paid position since mathematics was regarded of minor importance in Pisa. He gave his first lecture on November 12, 1589, aged 25 years. You can imagine the satisfaction he must have felt - he had become a University Professor entirely on the strength of his own efforts, ability and dedication. Naturally, he had to teach astronomy and this meant teaching the Ptolemaic, earth-centered, theory. Obviously, had he not done so, his career would have come to an abrupt end. Whether he actually believed in the earth-centered system is a moot point; in some of his writings at the time he certainly referred to 'errors' in the Aristotelian view.
He stayed at Pisa for three remarkably productive years - it was there that he laid the foundations for his studies of motion - using his scientific method. Let me describe some of his discoveries.
Galileo realized that time was an important ingredient in studying motion. Aristotle had said it was where something was and so distance or position were important. (Aristotle had adopted Empedocles ideas about the four fundamental 'elements' - fire, water, earth and air - and four qualities in paired opposites - heat and cold, wet and dry. So every object has its proper place so, for example, since a stone contains a lot of earth, it falls to the earth, since smoke contains air, it rises into the air, etc.) He also added a fifth, defining the heavens as being made of an unalterable substance called quintessence.
To study objects as they fell Galileo needed to 'slow them down' and so he developed the 'inclined plane'. He also developed a sensitive water clock to measure time, although he still tended to use his pulse - I don't know about you but I think if I was on the verge of a discovery, or I was feeling feverish, or recovering from a party the previous night, my pulse rate would be very unreliable! Nevertheless, over the next 10-15 years he made some important discoveries. He also argued that Aristotle was wrong as far as falling object were concerned. According to popular legend he demonstrated this phenomenon from the leaning tower of Pisa, but Galileo never mentioned it although his biographer Viviani claims he did it many times.
Galileo argued that in the absence of air resistance a feather and a hammer would fall at the same rate. This was demonstrated very effectively by Astronaut David Scott in 1971 when he dropped a hammer and a feather at the same time on the moon. All of his ideas about motion were new and revolutionary but Galileo didn't formally publish his results until about 40 years later, as we shall see.
His questioning of Aristotelian ideas caused enormous resentment among the faculty at Pisa, as did his lampooning of their costumes (which, at that time, were like togas). He also upset Ferdinand I, the Grand Duke of Tuscany, by some tactless remarks about a scheme to improve the harbor at Livorno. And he had some financial problems; since his father had died in 1591 Galileo, the eldest son, had assumed responsibility for the family. He had to provide marriage dowries for his sisters Virginia and Livia and he was always bailing his young brother Michelangelo and his family out of trouble. So he decided he should leave Pisa and seek his fortune elsewhere.
Accordingly, in 1592 Galileo took the Chair in Mathematics at the University of Padua - receiving something like three times his previous salary - where he stayed for 18 years. Padua, near Venice and the Adriatic was one of the centers of Renaissance learning. The university was therefore much more tolerant of 'new' ideas although Cesare Cremonini, the Head of Philosophy, was a strong advocate of Aristotle's every word. There was a very active intellectual community in Padua itself and Galileo was very happy there. It was there he met Father Paolo Sarpi and Robert Cardinal Bellarmine who were to play important roles in his career as a scientist. The fact that he was greatly respected by both men, even though they were in sharp opposition to his views, says much about his abilities and personality, particularly if you bear in mind that Bellarmine was to become one of the Cardinals of the Inquisition who sentenced Giordano Bruno to death in 1600. Galileo never married but lived for 10 years with Marina di Andrea Gamba (from about 1600 to 1610) and they had two daughters Virginia and Livia, born in 1600 and 1601, respectively, and a son, Vincenzio, born in 1606. On none of the baptismal records is Galileo named as the father; in the case of Virginia she was described as "daughter by fornication of Marina of Venice" with no mention of the father, on Livia's record the name of the father was left blank and on Vincenzio's record it states 'father uncertain'.
Galileo mixed with society and became well-known and well-liked and was consulted on all sorts of matters. For instance, it is reported that a shipyard owner asked him whether it would be better to position the rowlocks on the side of the boat or on a projecting strut. Galileo replied that since the oar acted as a lever, with the fulcrum or pivot point at the blade, it did not in the least matter ... it's not clear what the boat-builder did! He completed most of his work on motion and mechanics while he was at Padua. His association with Marina came to an end when he eventually left Padua in 1610 to return to Pisa, but the two of them remained on excellent terms apparently, and Galileo even carried on a cordial correspondence with the man, Giovanni Bartoluzzi, whom Marina eventually married in 1613. His two daughters left with him but his son, who was then only 4 years old, remained with his mother for several years but eventually joined his father a few years later .
During 1603 Galileo began to study acceleration. Since the 14th century the assumption had been made that during acceleration successive spurts of speed took place, each speed being uniform while it lasted and greater than the one before. Galileo started out with that idea but soon had to abandon it in favor of smoothly increasing speed. Although technically his major contributions were in mechanics and the study of motion, he is probably most well-known for his astronomical observations. At that time there were two opposing theories for the solar system. The Ptolemaic system, introduced by Claudius Ptolemy of Alexandria (90-168 AD), put the earth at the center and was based on circles and spheres, which were considered 'pure' and was consistent with Aristotelian philosophy. It explained phenomena such as 'retrograde' motion and was without question the 'approved' theory. Measurement played no part in Aristotelian cosmology. However, Nicholas Copernicus put forward a contrary view in his 20-page hand written book known simply as Commentariolus in about 1507 and in his great book De Revolutionibus published in 1543 - with the sun at the center - and the battle was joined!
"Surely, if the earth moved there would always be a howling gale",
"and we'd be blown away."
Also, clerics said that the scriptures were plain enough, for example:
Joshua had, at one time, ordered the sun to stop - therefore the sun
must be moving!
In reality, the authorities who, being guided by philosophers, believed emphatically in the Ptolemaic system, at first took little notice of the Copernican theory because they regarded it as a passing fad, rather as we may regard some of the fashions and music of teenagers today. It didn't disappear of course and towards the end of the 16th century it was very risky to be a supporter of the Copernican theory, as Giordano Bruno discovered.
Tycho Brähe (1546-1601) had modified Ptolemy's model by keeping the earth at the center but having the planets orbit the sun. However, very few scientists took this seriously (and certainly not Galileo). It was obvious that by 1597 Galileo had developed a preference for the 'Copernican' system - he said so in a letter to Johannes Kepler (1571-1630), who at that time wasn't so sure about circular orbits either! It appears that Galileo accepted this new astronomy because it was consistent with his theory of tides not because of any astronomical observations. However, he was being paid to teach Ptolemaic theory at Padua and so he did not publicly admit his beliefs until 1604.
In October 1604 when Galileo was corresponding with Father Sarpi about his law of falling bodies a supernova appeared in the evening sky. (A similar new star has appeared in 1572 and had been proved by Tycho Brähe to be in the fixed stars. According to Aristotle's principles no change could take place in the heavens because everything was made of a perfect substance called quintessence; change could only occur in the elemental materials of earth, water, air and fire.) Galileo wrote to astronomers in other cities and quickly formed the view that the new star was located in the heavens. The new star had created a great deal of interest in the general population and in a series of three public lectures Galileo stated that Aristotle had simply been mistaken. The ranking Professor of Philosophy, Cremonini, immediately sprang to Aristotle's defense. Although he and Galileo were good personal friends, their discussion soon became a feud. Cremonini simply could not accept that a mere physicist or mathematician could deliver a fundamental blow to all natural philosophy! In a book published early in 1605 his answer was that the ordinary rules of measurement did not apply to vast distances and one had to distinguish between celestial and elemental material. Galileo framed his reply - under an assumed name - in a book involving a dialogue between two Paduan peasants in a rustic dialect. His peasant spokesman asked what philosophers knew about measuring anything. It was the mathematicians, he said, who could be trusted because they didn't care whether they were dealing with quintessence or polenta (which, if you don't know, is a form of Italian porridge made of maize or barley!) because that could not change distance .
He spent the summer of 1605 in Florence as tutor in mathematics to the young prince Cosimo de' Medici. Although well established with the ruling family he needed their assistance in securing his reappointment at Padua, which he knew was in danger because of his conflict with the philosophers. The Tuscan ambassador at Venice did take part in the negotiations for his reappointment and an increase of salary.
In 1609, while he was still hard at work on his studies and writings about motion, he heard about a new invention in Holland, the telescope. In fact, a patent had been sought by Hans Lippershey on October 2, 1608 and Father Sarpi heard about it before the year was out. It seems that Galileo did not believe the rumors at first but after consulting with Sarpi in Venice in July 1609, he became convinced. Galileo had again been seeking a salary increase and had been told there was little hope. Realizing the importance of a telescope to Venice as a maritime power he hurried back to Padua and built one of his own. In August 1609 he exhibited it to their Highnesses and members of the senate in Venice, and in a letter to his brother-in-law he said they were astonished when he took them onto the top of the highest Bell Tower and they could see clearly ships approaching the harbor that were hardly visible to the naked eye! Although he was apparently offered life-tenure at Padua at nearly double his salary the contract was very confused and following many misunderstandings he suddenly felt homesick for Florence.
Galileo did not invent the telescope, the person usually favored is Hans Lippershey, a lens-grinder who lived at Middleburg on the Dutch Island of Walscheren although the history is confused . However, the idea of using lenses as 'optical aids' can be traced back to the end of the 13th century when Alexandro della Spina (d. 1313) and Salvino degl'Armati (d. 1317) reported the invention spectacles. Although Lippershey was denied a patent he was asked by the Dutch government in 1608 to produce a 'two-eyed' version of the telescope - we now call them binoculars - and in 1609 spy-glasses were actually on-sale in Paris! They gave upright images and were intended for terrestrial use although there is a note in a brochure, dated November 22, 1608, that says that a telescope could also be used for 'seeing stars which are not ordinarily in view because of their smallness'. So Galileo was not the first to look at the stars but there is little doubt his telescopes were certainly optically superior. It is believed that altogether Galileo constructed many telescopes during his lifetime, of which a few survive today.
Using his telescopes  (the best was 32x) Galileo studied a variety of objects in the solar system around 1609-1610:
Early in March 1610 Galileo published these discoveries in his Siderius Nuncius (Starry Messenger) dedicated to Grand Duke Cosimo de' Medici of Tuscany. During his Easter vacation he visited the Tuscan court and his appointment as chief mathematician and physicist with a non-teaching appointment at the University of Pisa was a mere formality. He finally moved to Florence in September 1610 having sent his daughters (then aged eight and ten years) there earlier to be with his mother and leaving his son (aged four years) with Marina Gamba until old enough to leave her care.
His discoveries, published in the Starry Messenger, produced violent reactions:
Almost everything he looked at seemed to contradict the earth-centered theory of Ptolemy and the 'perfect' models of Aristotle. His discoveries had put him in serious danger and he was beginning to get himself into very deep water with the Catholic Church. In fact, he and his colleagues used to send coded messages and anagrams to each other to announce their findings and to ensure that they would be properly credited later with their discoveries! (Anagrams were similarly used by both Newton and Huygens.)
His long period of service at Padua brought honor - the Department of Physics is named after him - as well as some controversy to the University. Grand Duke Cosimo thought that Tuscany probably offered Galileo a better 'political climate' for his studies. However, the republic of Venice was a true republic. The Venetian Senate was sharply opposed to any foreign intervention, even if cloaked in the sacred authority of the Church of Rome. On the other hand the grand dukes of Tuscany remained subservient to the Church of Rome. Galileo, aged 46, who was about to write his first real scientific treatise, didn't realize he was leaving the relative security of Venice and beginning to put himself in jeopardy in Tuscany; he truly believed the most difficult times had passed. In 1611 he was elected to the Accademia dei Lincei - the so-called 'academy of the lynx-eyed' ... the lynx was intended to symbolize the sharp eyes of science. The academy was really the first organization that could be considered a scientific academy and had been founded in Rome in 1603.
Shortly afterwards Galileo became involved in a dispute with philosophers, led by Ludovico delle Colombe, a Florentine philosopher, about condensation and rarefaction and more generally about the veracity of mathematics and physics. These disputes became very serious and together with Galileo's three Letters on Sunspots published in 1613 placed him in increasing jeopardy. The highly personal attacks by philosophers meant that he became increasingly vulnerable to various theologians for his 'anti-clerical' and 'heretical views'. In December 1614, for example, Thomas Caccini devoted a sermon in the principal Church in Florence that denounced mathematicians in general and the Galileists in particular, his text being the miracle of Joshua, which I've already referred to. In fact, it was not clear that the Church of Rome was entirely anti-Galileo because the early Church Fathers had recommended against any linkage of Christian faith with matters that were irrelevant to salvation, and particularly if time spent on studying them would interfere with time better spent in devout meditation. Indeed, that had more or less been the separation urged by St. Augustine.
At the end of 1615 Galileo felt he had to go to Rome to argue his case against Aristotle before various groups. In early 1616 he wrote a report about his theory of tides to Cardinal Orsini who approached the pope. Cardinal Bellarmine advised that Galileo's views about the sun-centered solar system be put to the so-called theological qualifiers. Their recommendations of censure were read at a weekly meeting of the cardinals of the Inquisition on February 24, 1616, and the pope, Pope Paul V, asked Bellarmine to notify Galileo in writing that he could not hold nor defend Copernican theory. If Galileo resisted, then he was to be warned not to 'hold, defend or teach' the propositions, lest the Inquisition proceed against him. It should be pointed out, however, because of future ramifications, that it was greatly disputed whether the word 'teach' was specifically included. At the next meeting of the Cardinals, Bellarmine reported that Galileo had been advised of the Pope's decisions and had accepted it. Also, a decree was issued that placed on the Index of Prohibited Books all works in which motion of the sun and stability of the sun were treated as real or unreconcilable with the Bible. In addition, so-called 'corrections' were called for in Copernicus's De Revolutionibus.
Unabashed, Galileo returned to Florence and continued to study the eclipses of Jupiter's moons. In 1623 he published The Assayer in which he outlined his scientific reasoning and contrasted it with what he called ... the tiresome logical quibbles that seemed to satisfy philosophers. Just before it was published, Pope Urban VIII succeeded Pope Paul V and the Accademia dei Lincei decided to dedicate the book to him. Galileo visited Urban and after six audiences it appears he was given permission to publish his tide theory provided the earth's motion was taken as hypothetical; thus the earlier edict of the qualifiers and the Inquisition would be satisfied.
Intermittently from 1624 Galileo wrote his Dialogue concerning two chief systems of the World, the Ptolemaic and Copernican, which he finished at the end of 1629 but because of numerous delays due to difficulties of getting a license, first in Rome and then in Florence, the book wasn't published until February 1632. He had wanted to call it Dialogue of the Tides but the censors made him change it.
Galileo didn't want to simply 'state' his results as we do in publications today; he used conversations between three persons:
in indirect style, spread over a period of four days.
They had met at Sagredo's palace in Venice to discuss the universe, with special reference to the problem of whether the Earth travels around the Sun or whether it is a rest at the center of the universe. The dialogue form was used for two reasons. Firstly, it was a particularly popular approach used to educate the public, and secondly, the author, Galileo, could detach himself from commitment to views that might be objectionable. The dialogue contained both the pro's and con's of the two theories and was written in Italian - the 'popular' language of the people - rather than Latin, the usual choice of scholars.
Naturally, poor Simplicio was hopelessly 'out-gunned' and 'outmaneuvered' by the logic and the arguments of Salviati and Sagredo, and so on numerous occasions he had to agree with them about the Copernican system. Because Galileo had good 'connections' he managed to get the book through the censors, including the Pope, and when it finally appeared it received a tremendous amount of publicity.
However, the full wrath of the Church descended on him almost immediately and in August 1632 the Inquisition ordered all sales to stop, even though the book was licensed. He was accused of ridiculing Pope Urban VIII - who had suddenly changed his attitude because he realized that Galileo had placed the defense of the Aristotelian view in the mouth of a simpleton and also because he had been shown an unsigned memorandum from 1616 that forbade Galileo to teach Copernican idea's.
Despite being nearly 70 and in poor health Galileo was told to travel to Rome or be forcibly brought in chains. Due to bad weather and numerous delays along the road for quarantine because of the plague, he didn't arrive until February 1633. He was reexamined by the Inquisition starting on April 12, 1633. Galileo produced the signed affidavit from Bellarmine, based on the Cardinal's ruling, that only included the words '... not hold, nor defend ...' Copernican ideas. Since the memorandum in the Pope's possession with the word '... teach ...' in it was unsigned, Galileo could not be acquitted without damaging the reputation and authority of the Roman Inquisition. So it was privately arranged that he should admit to some wrong-doing with the understanding he would be treated leniently. Galileo acknowledged in writing that he had reread his Dialogue and agreed that in some places he had perhaps gone a little too far with some of his arguments but he denied any sinister intent. Subsequently, on June 22, 1633 he was forced to recant his views under a charge of 'vehement suspicion of heresy':
"I, Galileo ... do swear that I have always believed, do now believe and,
help shall believe hereafter, all that which is held, preached and taught
Holy Catholic and Apostolic Church. ... I must altogether abandon the
that the Sun is the center of the world and immovable, and that the Earth
is not the center
of the world and moves and that I must not hold, defend or teach in any
verbally or in writing, the said false doctrine ..."
(Legend has it - although probably incorrect - that immediately after sentence he murmured under his breath, 'Eppur si muove' ... 'and yet it [the earth] does move'.) The book was placed on the Index of Prohibited books, where it remained for almost 200 years, although that could have hardly worried Galileo since there were so many copies in circulation that no Papal edict could make any difference. Still, expecting a light sentence, he was crushed by his condemnation to indefinite imprisonment. The Tuscan ambassador in Rome successfully contrived to have the sentence commuted to custody of Archbishop Piccolomini of Siena, whose humanity and understanding literally saved Galileo's sanity and life.
During his imprisonment several books were published attacking the Dialogue but, of course, he was not allowed to reply. He still worked with students and devoted himself to his final great work, Discourses concerning New Sciences that dealt with his theories of fracture and of motion, the book that many regard as his finest. It was completely anti-Aristotelian and he used the same three characters and style as before. The manuscript was completed in 1636 but because the Inquisition had banned all of his writings, the book was taken to Holland where it was published by Louis Elzevir in 1638.
"I am satisfied and accept them as true and valid."
He was, of course, accepting that Aristotelian theory was wrong.
Galileo's health was rapidly failing, he suffered bouts of asthma and he went blind in 1638 a devastating blow for some-one who had such a special talent for observation. Nearly helpless, he could only be visited by people who had been 'approved' by the Holy Office although he was allowed to visit his son during part of 1638 so he could consult with doctors. At the end of 1638 the restrictions were relaxed a little and a young scholar, Vincenzio Viviani, who later wrote the first biography of Galileo , moved into his villa. In 1641 he was joined by Evangelista Torricelli (1608-1647), who became eminent in his own right and is best remembered as the inventor of the barometer.
In closing, it is worth considering why Galileo was subjected to persecution in a way which his famous colleagues and contemporaries were not. Part of the reason was that he was an Italian and the Italy of those times was no place for anyone with unorthodox views about religion or philosophy. Galileo was a good Catholic, but he had the vision to see that the moment had come to separate religion from pure science, and that made him immediately vulnerable to philosophers who had the two subjects so intimately interwoven. Galileo's physics was based on measurements, which led to laws, and his question in 1605 ... "What has philosophy got to do with measuring anything?" ... surely didn't sit well with philosophers! Nicholas Copernicus had come to the same conclusion but was prudent enough to withhold publication of his great book De Revolutionibus until he was out of reach of his enemies; Tycho Brähe was in much less danger because his system of the universe retained the central Earth and so did not conflict with orthodox teaching; Johannes Kepler was a Copernican, but he lived beyond the immediate jurisdiction of Rome, and in any case, his books were mainly addressed to other scientists rather than the general public ... as I mentioned earlier, his Dialogues, the main cause of his falling foul of the Inquisition, was written in Italian rather than Latin and was therefore intelligible to the non-specialist. Furthermore, it was taken to be a personal insult to the Pope.
So the question remains; was Galileo condemned by the intrigue of philosophers who resented his questioning of their established views? Or rather, because he was a Copernican zealot and was simply punished by the Church Fathers who objected to his anti-Biblical, heretical views? I must say, I rather doubt the latter because there can be no doubt he knew about the Copernican theory in his youth but he did not admit publicly to his belief in it until he was 40 years old, hardly the act of a zealot. Furthermore, three Cardinals of the Inquisition refused to sign the sentence against Galileo in 1633 and surely they would not have done that unless they were certain about his Catholic faith.
 Bruno was burned at the stake in Rome in 1600 having been found guilty of heresy by the Inquisition. A Dominican friar, he was very outspoken and his ideas about the universe, among other things, were just too outrageous for the times. For example, he commented that the preface to the De Revolutionibus was written by one ignorant ass for the benefit of other ignorant asses! It had, in fact, been written by Andreas Osiander, a Lutheran clergyman, who supervised the preparation and publication of the book. The book declared that the sun Sas at the center of the universe, but because of his complete commitment to conventional dogma, Osiander had declared in the preface, and without Copernicus's knowledge, that the book was pure theory and not the literal truth.
 Galileo put his two daughters in a convent, probably because he felt he would be unable to provide suitable dowries for them. It took several years to make the arrangements since his daughters were so young. They eventually entered the convent of San Matteo, near Arcetri. Virginia took the veil in 1616, choosing the name Sister Maria Celeste, and Livia a year later became Sister Arcangela. His son Vincenzio was legitimized by the Grand Duke of Tuscany for whom Galileo went to work; of course, he would not have to provide a dowry for his son.
 It is on a similar point that I like to needle my philosophy colleagues at FAU! I tell them ... "physics differs from the fine-arts, literature and philosophy because it is self-testing, self-correcting and objective. The final arbiter is evidence obtained through experimentation, observation and measurement, not authority nor opinion."
 The true origin of the telescope is not clear. Both Roberto Recorde (1551) and Leonard Digges (1571) refer to the use of 'perspective glasses' to view distant objects; Digges also discusses using mirrors. Also, William Bourne (1585) and Giambattista della Porta (1589) claimed to have discovered a way to use two lenses to view distant objects. It seems that some sort of tube-type telescope was made in Italy about 1590 (Giambattista della Porta?), which was copied by a Dutch spectacle-maker named Zacharias Janssen in 1604. These telescopes consisted of a convex and a concave lens.
 Galileo refers (in Latin) to his device as a 'perspicillum' often translated as 'spyglass'. The word telescope was not coined until the year 1611 at a banquet honoring Galileo as he was inducted into the Academia dei Lincei.
 We also know that the Englishman Thomas Harriot (1560-1621) studied the Moon with a 6x instrument early in August 1609, but it was Galileo who made the telescope famous, through his many other discoveries.
 Although containing a number of rather obvious errors it contains a number of interesting anecdotes.
 When, in the 1730's, the Church finally allowed Galileo to be reburied in a grave with an elaborate monument, the monument in the Basilica of Santa Croce in Florence was built with the help of money left by Viviani expressly for that purpose. Viviani's own remains were moved to Galileo's grave as well.
The Universe of Galileo and Newton (Cassell Caravel Books, London, 1964).
Stillman Drake Galileo Studies (University of Michigan Press, Michigan, 1970).
Stillman Drake Galileo (Oxford University Press, Oxford, 1980).
Stillman Drake Galileo at Work (first published by the University of Chicago Press, Chicago, 1978; republished by Dover Publications Inc., New York, 1995).
Patrick Moore Watchers of the Stars (Michael Joseph Ltd., 1971)
M. Shamos Great Experiments in Physics (Dover Publications Inc., New York, 1987).