Now the past, by a virtue of being passed, remains forever inaccessible to us. It is no more we cannot reach it. It is only from its traces and remains from its debris, which are still present works of art, monuments, documents which have escaped the ravages of time and mankind, that we attempt to construct it. But objective history, the history men make and
suffer, is not concerned or hardly with the history of historians. It allows the survival of things of no value to the historian mercilessly destroys the most important of documents, the most beautiful of works, the most impressive monuments. What it leaves or has left behind are mere fragments of what we should need. Accordingly, historical reconstructions are inevitably fragmentary, uncertain, and even doubly uncertain.
En Alexandre Corre, nineteen sixty one. Our knowledge of Galileo's life is derived essentially from three sources. One is Vincenzo Ivanni, who was his last student. He wrote Galileo's first biography, not published until seventeen seventeen, about fourteen years after Viviani had died, When he passed his personal papers became the property of his nephew, and then to the nephews of his nephew. How they ended up becoming discovered for what they were is a bit of a tail in
and of itself, you see. One day in the spring of seventeen fifty, Giovanni Battista Neely, a man of Florence of letters, made a detour to buy some cold meat from a butcher he normally did not frequent when out in the countryside with his friends. He unwrapped the meat, he noticed that the waste paper it was wrapped in appeared to be something written by Galileo.
Returning with all possible haste to the butcher, but taking the precaution of concealing his discovery from his friends, he eventually traced the butcher's waste paper to its source, a large bin overflowing with documents in Viviani's old house. His grand nephews were selling off the paper in small parcels as wrapping paper, but we're happy to sell the whole bin to Nelli. Nelly used his treasure trove to write a life of Galileo, and the papers he acquired eventually ended up in
the Florentine archives. There they were used by the greatest of all Galileo's scholars, Antonio Favarro, who produced what is known as the National edition of Galileo's work around the year nineteen hundred, printed in twenty volumes. By the way, Favarro was meticulous, and almost everything about Galileo that we know today Favarro knew over one hundred years ago. But Favarro was not an impartial scholar, I mean no one is. He labored to defend Galileo's reputation as a scientist,
as a man, and as a pious Catholic. Inconvenient details he buried, he brushed them aside, or just shows to change them to the best possible light. They were never two. Favado's credit suppressed completely when Galileo died in sixteen forty two. He had been living in Florence for more than thirty
years, accumulating letters and papers. But when he moved from Padua to Florence in sixteen ten at the age of forty six, he must have packed his clothes, books, papers, telescopes and lens grinding machinery to be loaded under the backs of donkeys or mules, and presumably me threw a lot of things away, as we all do when we move right. In Fravado's edition of the o Peire, the letters to, from, and about Galileo occupy nine of the twenty volumes. One of these, volume ten, contains all the
letters for the first forty six years of his life. Another volume, fifteen, contains letters for just a single year, sixteen thirty three, the year, as we'll see of Galileo's inquisition trial. The imbalance is frustrating, of course, in that Galileo made no major scientific discoveries after the age of fifty, and yet the bulk of the evidence that survives come from the last decades of his life. In addition, when Galileo went blind in sixteen thirty seven,
he lost control over his own papers. Things he would have once thrown away were now faithfully kept. Now, thanks to those three men, Vivanne, Nelly and Favarro, we know a great deal about Galileo, and it's frankly easy to be overwhelmed by the bulk of this knowledge. Remember, one volume of a twenty volume set is just letters from one year. It's also easy to forget that most of our important source consists of an old bin full
of papers. We have no way of knowing how many documents had already been extracted from the bin and used to wrap various lunch meets. Unfortunately, it's not our only problem. All the documents in the bin had first been sifted through by Viviani. From Galileo's death until his own death in seventeen oh three, Viviani was engaged in a campaign to restore his master's reputation, blated,
of course, by the Inquisition's condemnation of him in sixteen thirty three. He wanted to see Galileo given a proper burial under a tomb worthy of his status as a great scientist. He wanted to see his works, including his scientific correspondence published. Because he could achieve neither of those objectives, he turned the facade of his own house into a monument to Galileo, recording at length and in stone all his scientific achievements, but making no mention of either Copernicanism or
of the Inquisition trial and the condemnation. An essential element in Viviani's campaign to recuperate Galileo's reputation was his insistence that Galileo was a good Catholic. Galileo was portrayed by Viviani as dismayed by the publication of his works abroad after sixteen thirty three, in direct defiance, as we'll see of the inquisition, the evidence
to the contrary, which was and remains incontrovertible, Viviani quietly suppressed. It has been suggested that Viviani genuinely believed that Galileo's Copernicanism represented a tragic intellectual error. Yet the evidence rather suggests that, as Galileo's faithful disciple, he skillfully combined outward conformity to the requirements of the Church with private dissent. Now, how far did Viviani's single minded preoccupation with Galileo's reputation lead him to falsify historic
record? That he falsified to some degree, I think every single historian I have read suggests is one hundred percent true. He planned to publish an exchange of letters between Galileo and Genevan by the name of ele do Yo Tati, a Genevan who was nominally a Protestant but had some close relations the number of unbelievers on the subject of measuring longitude, telling the Atati that he would alter or omit some sentences that might provoke hostility to Galileo and make it difficult to
obtain a license to publish. But what did he plan to leave out? And this is just an example of what we don't know. Viviani separated out thirteen letters on longitude so that they survived to be published in seventeen eighteen, at which point they were destroyed. We cannot tell how extensively they would have been revised Viviani had been able to publish them, although there is another case in which we can a little bit see Viviani's hand rewriting a letter in order
to protect Galileo's reputation. Viviani had in his possession. So far as we can tell, around one hundred letters between Galileo and Diatatdi, but yet none of these survive. Forty are completely lost. The rest are preserved only in partial copies made by Viviani, or, in the addition of seventeen eighteen, or in two cases, copies made by a third party. Of course, it's theoretically possible that every one of the letters that did not survive until seven
eighteen went to wrap lunch meets. But I think what's much more likely, and what most historians seem to agree is that these letters were probably destroyed by Viviani himself, mostly because they contained proof that Galileo had continued to advocate for Copernicanism after sixteen thirty three. Of course, the charge is a serious one. I Viviani was prepared to falsify the record, then we must assume that
he destroyed any evidence which cast out on Galileo's Catholic piety. On the twenty fourth of July sixteen seventy three, he wrote to a scientist and diplomat in Flanders saying that he had heard an edition of Paolo Sarpi's letters which were soon to be published in Amsterdam, and that there might be some letters between Galileo
and sarp in this anthology. Now, of course, sarp who had been a close friend of Galileo's, was actually notorious throughout Europe as the author of the quote History of the Council of Trent, widely regarded as the most effective piece of anti Catholic propaganda to have been published since the days of Lutheran Calvin. The publication of such a correspondence, even if it only concerned scientific matters,
would Vianni felt be fatal to Galileo's reputation. Viviani went to great lengths after this to try to prevent the publications of these letters, even though ultimately he was not successful. I think this story is important because it represents a cautionary tale about reconstructing history before the modern age. We simply do not have all of the documents that passed into Viviani's hands. We have some of them, but doubtless many were lost and many others deliberately destroyed in order to try
to portray Galileo as a Catholic piety. Hence, we need to be comfortable with some gaps in our understanding and knowledge. I will, when possible, try to fill in some holes with some basic inferences, but I will of course concede that those are inferences and not hard facts, and I will delineate those when they occur. So getting to Galileo, the story, of course, begins with his birth. Galileo's father, Vincenzo, was a musician from
the Italian city of Florence. In fifteen sixty two. We get our first mention of Vincenzo in any surviving public record when he shows up in the city of Pisa and founds a music school. He married in the July of fifteen sixty two. Galileo, his oldest child, was born on February the fifteenth, fifteen sixty four. We know that Vincenzo received a portion of his wife's dowry and silk, leading historians to conclude that he married into a family of
cloth merchants. Galileo himself was originally intended for the wool business. That plan would of course, never come to pass. Later in life, Galileo would complain that he never received anything of value from his father, quite the scathing criticism. And we do not know, of course, much about the lives of young people in general during the pre modern period, and Galileo is not an exception to that rule. But we do know from old stories that he
developed an appreciation early on for working with his hands. He would spend hours building models and other trinkets. This scale would serve him well later in life. In fact, for twenty years, Galileo had the best telescopes in Europe because he built them himself. Other astronomers had to buy lenses and try to just kind of jimmy rig them in the contraption. Now, the young Galileo would have got the finest education available during that time for someone of his class,
consisting of course of Latin, Greek and Aristaeleian logic. He began school in Pisa, but moved to Florence when he was ten. For a brief moment, we know that Galileo considered entering the seminary. This was when he was around fourteen years old, but his father had more mundane plans for his son and would not allow it. History and science will thank him for that. At the age of sixteen, Vincenzo was now determined to send his son
to university. The plan was for him to become a doctor. Despite the fact that Galileo claimed his father never gave him anything, he did at least implicitly get something from him. Vincenzo was an early proponent of what we would call music theory today. He wrote an important book on the subject, titled Dialogue on Ancient and Modern Music in fifteen eighty one, and crucially, he wrote in Italian, not Latin, which would inspire Galileo to do the same
later. Critically, if we're kind of looking for some parallels between Vincenzo and his son, Galileo, Vincenzo also conducted a series of experiments on strings and their influence on the sound that was produced. How much of these experiments Galleo witnessed we can't be sure. With given Galileo's later emphasis on experimental analysis, I think it's safe to say he picked up some of what his father was
putting it down. Galleo would forever remain a musician's son. Later, when describing reform, he would compare any sort of change to tuning an organ. Perhaps the elder Vincenzo did symbolize failure to his son, he certainly presented him with a model of forwarded ambition. Vincenzo always saw himself as a great man, for who all his modest success at court had never been given his due. Galileo's refus usual to submit to censorship, to sync back into anonymity may
be interpreted as a refusal to relive his father's failed life. But Vincenzo's most significant example to his son definitely lay elsewhere, and I already mentioned it. The culture of late sixteenth century Italy was one obsessed with the imitation of ancients and classics, in philosophy, in medicine, in law, and sculpture, the ancient models were still the ones to follow. Of course, in music the situation was always more complicated. Vincenzo accepted the current view that ancient music
was monadic while modern music was polyphonic. Ancient music, he thought, spoke directly to the soul and was far superior to anything produced by the moderns. But while he experimented with a different number of ancient compositions, none survive, but they're thought to have been sort of precursors to opera. For the most part, Vincenzo always wrote in what we would call modern music, it might be thought that the idea of progress is sort of anachronistic, as we might
apply it to the world of Galileo's youth. Certainly, as we've discussed on this podcast several times over the past couple weeks, the notion of progress is something that was just totally foreign to early modern Europe, certainly outside the fields of painting and mathematics. The idea of progress, of growth, of change all being positive things, I mean, that was tenuous at best in the
sixteenth century. Yet, despite placing himself firmly on the side of progress, which he's going to do Galileo's ultimate fate would be sadly to repeat what his father had done. Vincenzo Galileo rejected the Pythagorean notion of a harmony that ran through the cosmos and implied that there could be no music of the spheres.
Sounds are the imperfect products of particular physical objects. His son was to end up destroying the natural correspondences that were supposed to exist between the microcosm, that is, the little world of humankind and the macrocosm, the divinely ordained universe, and he was to remap the cosmos so that heaven and Hell could no longer be located in a physical space. He was to leave many of his readers longing for a past that was no longer attainable, just like those who
read Vincenzo likely felt. Galileo was born in Pisa, spent much of his childhood there, went to university there, and got his first real job there. But Viviani always thought it was important to stress that Galileo was a Florentine gentleman who just happened to spend a few years in Pisa and mary there. Throughout his life. Galileo did the same always referring to himself as a man
of Florence. Italians frequently identified people from the towns that they came from, for example, Leonardo da Vinci from Vinci Pierto, Perugio and the piece Ins and some others too still naturally call Galileo Galileo il Pisano, but this would not have made Galileo happy. Pisa at this point in the seventeenth century was a sleepy backwater. Sure, it had once been a free and independent city, a bustling port on the River Arno, but now the population had declined
to the point where there were hardly ten thousand people left. The streets were half empty, and the university only had a local reputation. Florence, on the other hand, was the capital of Tuscany. It had a population of eighty thousand. That's where power was concentrated and fashion were set. Galileo inherited his father's conviction that Florence was and would always be his true home. He went back to Pisa as a student, to the world of his mother's family,
with no sense that he was going home. In the university register, he entered his name as Florentinas, which means from Florence, not Pisa, on us from Pisa. In later years, it was commonly assumed that he had been born and raised in Florence, but there was some gossip to the contrary. An enemy denouncing him to the Inquisition said that he represented himself as a Florentine, but that he was in fact a piece in Galileo remained an
inhabitant of a very small part of northern Italy throughout his entire life. Honestly, really small. If you just take out a map right now in a compass and draw a circle with Florence at the center and with a radius of about two hundred and seventy five kilometers or one hundred and seventy miles, Galleo
never once in his life stepped outside that circle. Genoa population sixty thousand to the north and west, Venice one hundred and fifty thousand people to the east, and Rome one hundred and ten thousand to the south marked the limits of his travels. In a telling phrase, he once described someone who had been to Genoa, Rome and Milan as having seen the world. His brother would go much farther. He went to Poland in search of work as a musician,
Galleo stayed close to home. It's true that he talked of traveling further to Naples, even Spain, and when he did he always looked south, not north. The books he wrote made the long journey across the Alps, but Galleo the man never did. In Padua, he taught students from across Europe, but as far as we know, he never went to visit any
of them. Europe in general had changed a lot during Galleo's life. We're going to get into this much more in the next few weeks, but overall, power and wealth was in the process of shifting permanently in Europe, from south to north, from Catholic to Protestant. The world of Europe, dominated by Mediterranean cultures was going away, and it was permanently fading. Not that anybody knew that at the time. For example, when he was four years
old, the Dutch revolt against Spain began. Six years after he died, the Dutch got their independence. Now. Interestingly, though at least based on what survives, it seems that Galileo had very little interest in European politics. He was, though more modern than many of his contemporaries. He only wrote one book in Latin, The Starry Messenger. Everything else he wrote in the
vernacular today we anagronistically call that language Italian. Galleo wrote in the name tongue of Florence, though though his books traveled widely, even as far away as Russia. Sadly, we know far too little about Galileo's intellectual development between fifteen eighty one, when he was a university student and sixteen ten, when he became famous. Frankly, most of what gets written in secondary histories and biographies that try to recount this period of his life is purely or at least mostly
conjectural. There's really a double process that's going on during this time period. First, there is definitely the invention of a new physics, a physics which will ultimately be codified by Newton. Galileo develops an idea of inertia, discovers the law of acceleration of falling bodies, the parabolic path of a projectile, and the principle of a pendulum, the principle that every pendulum keeps time and that any two pendulums at the same length keep the same time, and he
formulates for the first time the idea that motion is a relative complex. These five innovations, taken together, constitute the most important development in science between Aristotle and Newton, or, in the words of a contemporary of Galileos, the most important advance in philosophy for two thousand years. Now. Second, there's also a crucial advance in this time period in the experimental method. Galleo did
not invent the experimental method, and his commitment to it was limited. Nevertheless, he definitely put it to more effective use than anyone had ever done previously, and it was his students who became the most effective proponents for an experimental science. Now, the problem with kind of looking at this process from a macro level is that it's very easy for us today to underestimate the obstacles that stood in the way of these two key developments. It's perfectly possible to carry
out experiments without having any grasp of the power of the experimental method. It's equally possible to discover one or another element of the new physics, the parabolic path of a projectile, for example, without having any grasp of the full range of interlocking arguments that became apparent to Galileo by sixteen ten. Thus, if we are to do justice to Galileo and Galileo's achievement, we have to see that he advanced step by step, really without knowing where he was going.
Only at the very end could he look back and recognize that what he had done was construct a new side. Ants now we know this. In fifteen eighty one, Galileo went to university to study medicine. This meant learning math and even a little astronomy. Okay, well, really astrology. Reading a patient's horoscope was one hundred percent part of one's medical practice in the sixteenth
and seventeenth centuries, so knowing what the stars were saying very important. Again, according to Viviani, Galileo made an important discovery even before he really started to study mathematics. One day, when he was attending a service in the cathedral, he noticed a lamp dangling from a long chain. It had recently been lit, and as a result, it was swinging slowly back and forth.
Counting the length of each swing against his pulse or against the beat of the liturgical music, he realized that even though the arc of each swing was shorter than the one before, re swing took the same amount of time. Viviani says that He went on to confirm this by experiment. Galileo thus had now discovered an accurate way of counting time before the invention of the pendulum clock. As an aside, clocks were driven by weights and were far from accurate.
Now. Initially as a medical student, he even used a pendulum, really, I think, for the first time that we know of, to measure the pulse rate of patients, thus immediately taking a theoretic concept and giving it a practical application. Sadly, though Viviani's story about the pendulum has long been dismissed as a myth, there is no evidence at all for Galileo's interest in pendulums until about twenty years later. Frankly, we'll probably never know if
the young Galileo sought to measure the duration of a pendulum swing. Being said, I'm not going to say it didn't happen. It's certainly possible given his later interest in motion. But again, it's one of the problems that we deal with here in the early modern period when we're going off of secondary histories such as Viviani's. After three and a half years of studying medicine in Pisa,
Galileo returned to Florence in fifteen eighty five to study mathematics. At this point, he was clearly no longer parroting what his father wanted to hear. Galleo had, for better or worse, decided to be his own person. It's interestingly also during this time period that Galileo's love of an interest in Archimedes, the Greek mathematician and scientists of the third century BCE, became apparent,
and it would be so for the rest of Galleo's life. In fact, Galleo's later love of Archimedes would prove to be a bit of an impediment for the man first and often cited as the real Western scientist. For all his genius, Archimedes was never a scientist in the modern sense of the word, because he didn't conduct experiments Galileo will. That's what sets Galleo apart, and that tension is evident at this point Galileo's life until the moment he dies.
Galileo's relationship to Archimedes is immediately apparent. In a work Vivianni tells us he wrote back in fifteen eighty six, and it survives in several manuscript copies, titled The Little balance. Archimedes is and was famous for crying eureka as he leapt from the bath and ran naked through the streets of Syracuse. It's solved a problem that seemed insolvable. Hero the King of Syracuse, had given a
goldsmith some gold from which a crown had been made. The crown weighed the same as the gold out of which which it was supposed to have been made, but the king came to suspect that the goldsmith had adulterated the gold with silver and had stolen some. He was, however, reluctant to melt the crown down in order to find out whether or not his suspicion was justified. One day, Archimedes noticed that as he got out of the bath, the level of the water rose. By putting the crown in a tank, one
could measure the amount of water it displaced. Silver weighs less than gold, so a crown of silver would be larger than a crown made of the same weight of gold. By measuring the volume of the crown, one could tell approximately the portion of silver and gold in it. This has always been seen as an example of Archimedes' brilliance as a scientist. Not in Galleo's view though, because the proposed solution was too crude, the measurements would be merely rough.
It wasn't worthy of Archimedes. What he must have done is take a very precise balance and use it to weigh the crown in both air and in water. For it's much easier to measure weights exactly than it is to measure volumes exactly. By doing the same with both gold and silver, you could work out exactly how much heavier than water gold silver the crowns were. What Galileo was introducing was a concept called specific gravity, and he goes on to
provide a table of specific gravities of different materials. Once you knew the specific gravity of gold, silver, and the crown, you could tell exactly, not just approximately, what the crown was made of. The concept of specific gravity is important, and Galileo was putting it too sophisticated use. But Archimedes
had the concept too, and here's the key. The difference between Galileo and Archimedes is that Galileo wanted to measure more exactly, and having measure one substance, he wanted to go on and measure others, and thus in order to do this, he had to devise a new method of measurement. Hence, one of the key things that changes during Galileo's life in terms of science is the desire to be not just close, but exact. If nothing else.
The little balance shows that from the very beginning Galileo was preoccupied with precise measurements. Yet this would be crucial to his development as an astronomer and eventually a scientist. Shortly after writing his work on pendulums, in the last months of fifteen eighty seven, Galleos sent to the leading mathematicians of northern Italy his solutions to a problem that derived from Archimedes' work. He had been working on this
problem for a couple of years. It was presented to him by his first patron, whose work was to have a significant influence on Galileo up until the time of his death. The issue was how do you calculate the center of gravity of various solids, and Galileo remained sufficiently fond of his solutions to publish
them at the end of his life. The first problem addressed by Galileo was that of determining the center of the gravity of a yard arm, which has spread along its equal distances a series of five weights, each weight weighing from one to five units. His solution to the problem puzzled leading professors of mathematics at the Jesuit College in Rome. Surely he had defined the problem in such a way that the solution was already included in the definitions. Galleo's response to
these inquiries was not to restate his proof indifferent terms. It was not to argue that the proof was valid and did not include the logical flaw that they were attributing to it. It was to send both of his correspondents a new drawing of the problem, in which the five weights were bunched up together instead of being spread out. If they looked at the drawing, he said, they would understand his solution. One man found Galileo's response satisfactory, but another
repeated that this was not a proof. Strictly speaking, Galileo's reply was no reply at all. His response to a question about logic was to offer a different way of visualizing the problem. His claim was that you could see that his answer was correct. Galileo's argument may not be logical, but we are likely today to find it convincing because we live in a culture. We're seeing is believing. We have X rays, we have CT scans, we have
a brand new telescope that can gaze billions of miles into the distance. Ours is of visual culture, and Galileo is one of the people who constructed that culture. One of the great puzzles of history is why it took three hundred years to invent the telescope. Eyeglasses were invented in twelve eighty four. The telescope, which was basically just a combination of two lenses from glasses, did
not come around until sixteen oh eight. One answer is that the telescope and the microscope are profoundly problematic because they require you to rely on one sense, and one sense alone, the sense of sight. Sight had always been regarded as the sense which was most easily deceived. What is perspective painting, of course, but a deception of the eye. The apostle Thomas didn't believe that Jesus had risen from the dead when he saw him. Belief came only after
he touched him. And after all, what most lenses do is they magnify and they distort it. They are deceptive. The fundamental realization that our own capacity to see depends on a lens within the eye came only with Kepler's production of optics in sixteen oh four, just before the invention of the telescope, and so sight, particularly when dependent on a lens, was to be trusted
only when it could be confirmed by touch, sound, or smell. To take the idea of a telescope seriously, you must entrust yourself to your eyes, turning into the heavens. You had to trust it to provide information on a world you would never be able to touch, or gear or smell. Galileo was willing to do that. He was willing to entrust himself to his eyes, hence his conviction that the telescope could tell him all he needed to
know. But the scale of the cultural resistance to purely visual information is easy to illustrate because astronomers had always relied on such information. According to the astronomers, the planets moved along complicated paths through the skies at the cycles on circles, effectively spirals. According to the philosophers, these were merely hypotheses to quote save the appearances end quote workarounds to produce results that matched the data In reality.
They insisted the planets were attached to crystalline orbs that performed perfect circles in the heavens. The result was mutually incomprehensible. This was clearly the case when in sixteen sixteen, a Catholic cardinal argued Copernicanism was a hypothesis, just like epicycles. No one thought they were real, so what's the point in worrying about whether or not Copernicism was true. Galleo's response was simple. Every astronomer
thought epicycles were real, and every Copernican thought that Copernicism was true. But the astronomers could not see their epicycles. They deduced their existence from compiling tables in which they recorded locations of planets in the sky. What they could see and what they could believe were two different things, even if the astronomer's knowledge
was grounded in visual information. The astronomers by sixteen sixteen not only had new evidence of the telescope, they were working in a culture which was increasingly receptive to visual information. It's a nice coincidence that the first recorded instance of the phrase seeing in believing in English dates to sixteen oh nine, the year of Galileo's first telescopic observation. Galileo was well aware that the revolution he was seeking
to bring about required a new attitude to the senses and to vision. In particular, We who take that attitude for granted have great difficulty in imagining the obstacles Galileo and his friends first had to overcome. In the dialogue, he or rather the person speaking for him, tells the following story. This is
a lengthy quotation. One day I was at the home of a very famous doctor in Venice, where many pearsons came on account of their studies, and others occasionally came out of curiosity to see some anatomical dissection performed by a man who was truly no less learned than he was, a careful and expert anatomist.
It happened on this day that, when he was investigating the source and origin of the nerves, about which there exists a notorious controversy between the gallonist and parapactic doctors, the anatomist showed that the great trunk of nerves, leaving the brain and passing through the nape of the neck, extended on down the spine, and then branched out through the whole body and that only a single
strand as fine as a thread rived at the heart. Turning to a gentleman whom he knew to be a parapactic philosopher, and on whose account he was exhibiting and demonstrating everything with unusual care, he asked this man whether he was at last satisfied and convinced that the nerves originated in the brain and not in
the heart. The philosopher, after considering for a while, answered, you have made me seen this so plainly that if Aristotle's text were not contrary to it, stating clearly that the nerves originate in the heart, I should be forced to admit it was true. End quote. Thus, for Aristotelians, seeing was never the same as believing, But for Galileo, seeing was believing, and this is one of the biggest changes Galileo brings to Western science.
Galileo put a lot of emphasis on diagrams and visual representations of the truth. Galleo believed that a mathematician without a diagram was only half a mathematician at best. There are various ways to interpret Galileo's method of thinking with diagrams. It was, of course, to an extent, a personal peculiarity. Galileo might have been an artist, the diagrams that he did are that good. But
Galileo's insistence on diagrams was also just part of a bigger cultural shift. The printing press and advances therein had made the reproduction of high quality images for the first time possible, so to an extent, Galileo also sensed a change and decided to ride the wave. As I mentioned before, we know very little about Galileo's early life even after sixteen ten. What we see of Galileo is mainly what he wanted us to see. Those thoughts and feelings he chose to
conceal have long seemed forever lost. There is, however, one source which enables us to kind of get a glimpse into the real thinkings in life of a younger Galileo. In early fifteen eighty nine, Galileo was trying to establish himself as a mathematician and doing some tutoring on the side. Seems like he had taught mathematics in Florence and in Siena, and in that spring of fifteen eighty nine he was living in Pisa, having taught in a local monastery.
He returned from Pisa to Florence, about sixty miles to celebrate Easter, and fell in with an old friend, a guy by the name of Giovambattista Ricae Soli, who was a wealthy young man. They studied philosophy, mathematics, and poetry together, as friends did on the Renaissance. They slept in the
same bed. One night, giom Vambista woke him. A year later, Galileo could still remember giovan Bista reaching for him, getting his arm around his neck, and assured him that he Giombandista, had been condemned to death. What would happen to him? Did Galileo think? Would he be executed by having his head chopped off, or would he be burnt alive? His crime was to have been given a funeral address for the Grand Duke when the Grand
Duke was still alive. He had, in fact given such an address to the local Academy, an organization of young intellectuals, and it was half serious, half playful. But the crime was actually that the Grand Duke was dead, having died on the October seventeenth, fifteen eighty seven. Night after night, for thirty days and nights, Galleo struggled to persuade his friend that no
one had condemned him to death, but without success. Geo Vambista was mad, he was insane and was going about in public wearing mourning clothes for his own funeral. Eventually, hoping to escape justice, he ran away to Stoia and was brought back a prisoner by his relatives. It was clear, though, that he was going to set out again, and it was agreed by his family that Galileo and a relative would travel with him to ensure his safety.
So Gio Bambisti, together with one of his relatives, and Galileo, set off across northern Italy, wandering from place to place, traveling sometimes by night, sometimes off the beaten path, as Giobombista fled his imaginary enemies. A couple of days before whit Sunday, which is seven weeks after Easter, they arrived in Genoa, where they finally were able to persuade their insane friend to seek medical advice. Twelve days later, Galileo returned to Florence to take
care of business. Some eight weeks had now passed since Giovambista had woken Galileo in the middle of the night to discuss his coming execution. They next met near the end of September, when Galileo set out with some relatives to try to persuade Giovambista. When the meantime had traveled to Milan and Rome to return to Florence, he found his friend still wearing the clothes in which he had set out on his travels in the spring and unable to sleep through the night.
By this time, Giobambista had donated all his worldly goods to his relatives. Throughout the weeks that Galileo was in gio Bambista's company, his friend was spending as though he thought he only had days to live. None of this money ended up in Galileo's hands. When Giobambista lost money to Galileo playing cards, Galleo tried to return the money to him, he paid towards his own
board and lodging in Genua. Now. Later on, Giovambisti's relatives accused Galileo of stealing money from him in genuine but no one seems to believe the relatives, and it's easy to imagine why. On one occasion, Giovambisti had caused someone to mistake Galleo for a bandit and take aim at him with an arquebus, but fortunately the powder was damp. Galileo had been greatly distressed by this incident, but still he did not abandon his friend. In fact, it's
evident that Galileo was genuinely fond of his companion. In trial documents, he always speaks him with respect and insists there is no disgrace in lunacy, for disgrace comes only from those things over which we have control. He was in a difficult position throughout, acting both as Gioe Bambisti's friend and as an agent of his family, who were trying to prevent him from coming to harm.
We may guess he was strongly opposed to those who wanted to solve the problem by tying up Giovambisti and holding him prisoner, But he seems to have kept the respect of everyone concerned. It is true that this little adventure wasn't without its benefits. It gave Galileo an opportunity to see what he referred to as the world, but only a patient and benevolent person could have stood Giovambisti's company
month after month. It's worth stressing this because Galileo was not a particularly good father and Frankly, later in life, he rarely showed any interest in the welfare of others. His work was soon to become more important to him than
his loved ones. If we are going to look at his character, though, and if you're going to make an argument that Galileo had a good character, a strong character, it must be given on the strength of these months in fifteen eighty nine that he spent day and night in gioe Bambisti's company trying to ensure that his friend came to no harm. But if we're going to continue to look at Galileo's character, that brings us to one of the trickiest
issues when it comes to modern day Galileo scholarship. Several scholars have devoted whole volumes to this said issue. In this case is Aristotle. Aristotle was the authority in modern Europe for centuries. Aristotelian logic was the only acceptable method for debate and logical reasoning in Western Europe, and such absolutely was the case in the early seventeenth century. Galileo eventually becomes known as the most aggressive anti Aristotelian
of his age. It's therefore difficult to discover that he described himself in sixteen forty, at the very end of his life as a good Aristotelian. What in the world are we to make of this? Amongst Galileo's surviving papers, there are three philosophical texts, two treatises on Aristotle's posterior Analytics and one on Aristotles on the Heavens. At first blush, these all look like pro Aristotle works, but the problem for relying on these is that they're not scholarly works.
What we have here are Galileo's notes on other people's lectures. In essence, these treatises parrot other people's ideas, not Galileos. Hence we need to discout in them as evidence that Galileo was an Aristotelian. And neither is the comment that Galileo made in sixteen forty dispositive as to whether or not he was a quote unquote good Aristotelian. We have to remember this was well after the
Inquisition trial. His comment was probably much more about saving face and ensuring that he was no longer a target for Rome than about anything he really believed. I really hope that by the end of this series you accept the argument that Galileo truly was something new. He was not an Aristotelian by any stretch of the imagination. He was a new breed of scientists. In fact, he might have been the first ever modern scientist. In the autumn of fifteen eighty
nine, Galleo became a professor of mathematics at the University of Pisa. He had taken the first step on a to a professional career and to financial security. But frankly, we should not harbor any illusions about this first posting. It was one hundred percent a first job, right. The salary was significantly lower than might be expected. In fact, he was paid sixty florins, and to sort of put that into context, that was a lot less than
a yearly income for a decent Stonemason. It was not possible to become a gentleman on such an income. There were professors of philosophy in prestigious universities and institutions who were earning fifteen times as much as Galileo. In fact, one of Galileo's closest friends was earning seven hundred florins a year at Pisa. And this wasn't just because Galileo was starting out. The fact of the matter is mathematics was not a prestigious subject as far as other professors were concerned. It
had two really sort of plebeian functions. One introduce philosophy students to basic geometry and thus the ideas of a proof, and to provide medical students with the skills required to look at different astrological charts. Mathematics was regarded as intellectually uninteresting. It was purely technical, and the salary of mathematicians reflected this. Now, Galileo had been a student at Pisa as late as fifteen eighty five,
and so when he got there he would have had old friends. So it's highly likely that he found himself picking up on intellectual discussions that had interested him as a student. The intellectual life in Pisa was dominated by two different philosophers, Girolamo Boro and Francisco Buonacamicki. In fifteen seventy five, Boro had published a book on the movement of heavenly and light bodies. Galileo actually owned a
copy. In fifteen eighty nine, bon Amiki had on his desk an enormous manuscript on the same subject, although the book didn't appear into print until fifteen ninety one. Galleo had probably attended boon Amiki's lectures as a student, so the main arguments in the book would have been familiar to him even before he
read it. Now, Boro and Bonamiki disagreed radically on movement, as with most other things, and their colleagues and students were certainly aware of their disputes, particularly as students were required to engage in disputations, debates in which they take one side or the other. This was sort of a standard lesson planned
in medieval academic circles. Disagreements thus lay at the very core of intellectual life, and students were taught to approach central issues from sharply contrasting points of view. At the same time, permissible range of disagreement was set by the tradition of commentary, in other words, by Aristotle. Now, in order to understand the real dispute between Boro and Bonamiki, we first need a sense of those assumptions that all Aristotelians held in common, assumptions that Galileo was soon to
question, at least in part. First, Aristotelians drew a sharp distinction between natural and forced movement. If a ball is thrown, then that's forced movement. If it's dropped, it moves to its natural place of rest, and that's natural movement. If it's thrown upwards, then the ball decelerates as it rises, and this is because force movements tend to just peter out. If it's dropped, it it accelerates, and this is because natural movements tend to
speed up. If a ball is thrown, then there's initial forced movement, and then the ball drops downward. Aristotelians believe that only one type of movement could take place at a time. Thus a ball traveled in a straight line and then draw vertically if you threw it. They also held the view that any objects subjected to a force movement must be being moved by another object, or, in the case of the hand, by the will of the sentient
creature. It appeared to follow from this argument that once the ball leaves the hand, it ought, in principle, to come to a stop. Aristotle sought to solve this problem by arguing that the ball was pushed on its way by the air, which had been disturbed by the movement of the hand.
Later theorists argued that the ball had acquired some sort of internal energy or impressed force, just as it might acquire heat from the hand and stay hot even after it had been let go. Galileo would have found an account of impressed force in a textbook by Jesuit philosopher Benedict Pereira, which he used while working on his first study of falling bodies on motion. Crucially, all Aristotelians held the view that the heavier a ball was, the faster it would fall.
Now, all of this, of course, seems really bizarre to us. Definitely does to me, especially when you consider the movement of an obvious projectile. Aristotelians believed, however, that the universe consisted not only of weight but of lightness. If balls naturally move downwards, flames naturally move upward. Boro and Bonamiki were thus debating the natural movement of bodies downward and upwards, both movements they held continued until the body was obstructed or reached its natural place of
rest. In the case of a heavy body, this would actually be at the center of the Earth. In the case of a light body, it'd be an invisible frontier between the Earth and the Moon. I guess somewhere in the stratosphere. Because beyond this frontier, the only natural movement was circular movement.
All the heavenly bodies moved in perfect circles, So once you got up there, the rules of the game changed again, at least according to the followers of Aristotle in the heavens, what looked like change if you looked long enough, was just repetition. So if the heavier body is the faster it falls. But what is meant by heavy here? And what did Aristotle mean
by fast? Aristotle was cleared that speed was proportional to weight, as a sort of gross example, the body that weighed twice as much would fall twice as fast. The much more difficult question was how do we understand weight. The standard view was that weight was to be understood in a normal sense. A two pound lead weight would fall twice as fast as a one pound lead
weight. An alternative view was defended by Bonomiki. Heaviness should be understood as density or specific gravity, so that lead weights of different sizes would fall at the same speed, but they would all fall faster than wooden balls. Now confusingly, of course, Boro held a different view. He thought that weight
was situationally specific and related to the composition of the material. Aristotelians held that all earthly objects are made from four elements earth, water, which are heavy, fire which is light, and air, which could be either heavy or light depending on its location. And they all agreed that a wooden ball contained more air than did a lead weight. Boro's view was that when you weighted a wooden ball, the air in it had no weight, but the moment
it was dropped in air, the air becomes heavy. Thus, if you look at a lead weight and a wooden ball, which weighted the same when suspended in a balance, the wooden ball was in fact heavier because when it's falling, the air inside of it somehow gets added to the weight. And again I'm not saying that any of this is accurate, because it's not. But these are some of the efforts that early modern scientists I'm using that word
in air quotes go to try to make what they see fit Aristotle. And that's the problem is that coming out of the medieval age, people at universities and philosophers are trying desperately to get that square peg to fit into that round hole, rather than recognizing that, oh no, this needs a square peg hole. Aristotle was wrong. That's what we can't do. And getting back to the story for a moment. Borow had actually put this air heavy theory
to the test. He had gathered a group of philosophers at his house tossed comparable wed weights and chunks of wood out of an upstairs window. The wood had consistently reached the ground ahead of the lead. Now Bonomiki wasn't persuaded. You would first need to weigh the objects, he said, and make sure that the weight was identical. And there was also an obvious problem. The shorter the drop, the harder it was to see what was going on.
The only way that you could measure this was to drop things from a greater height. And we know that in sixteen twelve Giorgio Corricio had tried dropping different objects of different weights but the same material from the top of the Leaning tower of Pisa. The result, he claimed, at least, vindicated Aristotle that
the speed of the fall proved proportional to the weight. Now, according to Viviani, Galileo, when he was teaching at Pisa, so sometime between fifteen eighty nine and fifteen had already carried out a test of dropping different objects of different weights but the same material from the top of the leaning tower. Pisa, and he had shown that these reached the bottom simultaneously. Now, but
this is like Viviani's story of the pendulum. He wants to present Galileo as an experimental scientist and to claim that he was so precocious that he founded modern physics almost effortlessly. But in this case, there is a manuscript on natural motion which was written sometime between fifteen eighty nine and fifteen ninety two, in which Galileo confidently claims that he knows what will happen in such a test. First, he writes, the lighter object moves faster, but then it's overtaken
by the heavier object, which reaches the bottom ahead of it. He has, he tells, us, done this experiment many many times times. Thus, it would seem perfectly straightforward to say that Galilea was carrying out experiments with falling bodies while he was at Pisa, and so clearly he was already an experimental scientist. Historians, however, have made the simple complicated. In nineteen thirty five, historian Lane Cooper published a whole book arguing that Viviani's story was
a myth, just like his story about the pendulum. In fifteen thirty seven. The great historian Alexandra Corre, an enormously influential historian of science, also dismisses the story as pure myth. This wasn't a real experiment, he writes, but an imaginary thought experiment. Now, such skepticism, I think is well grounded, because, of course, if you drop two objects of the same material but different weights from a high tower, you just don't get the
results that Viviani and Galileo describe. The heavier object is going to hit the ground well before the lighter object, and this is because the resistance of the air has more effect on the lighter object than it does on the heavier one. Galileo simply couldn't have carried out this experiment and obtained the results that are described by Viviani. He couldn't have done it. It's not possible now.
Unfortunately, Viviani, Cooper, and Core and modern physicists who write about high tower experiments share a fundamental misunderstanding, one that has profound implications for our whole understanding of what science is. They think that experiments are straightforward and that repeating them is unproblematic. Unfortunately, given the constraints that Galileo would have been working
with in the early seventeenth century. That is simply not possible. There's no way to recreate the standard conditions of a modern laboratory in seventeenth century Pisa. That just isn't. Now. In sixteen thirty eight, Galleo publishes a book Two New Sciences, in which he does explain the tower experiment. And again, while some historians have dismissed that as just a thought experiment, we know in sixteen forty one that other people were physically trying to replicate it, suggesting
at least Galileo's contemporaries believe the experiment was real. These attempt at replications were repeated throughout the sixteen forties. Now, all of this does support the claim that Galileo was truly the world's first experimental scientist. Just as Viviani wrote that being said, Galileo's experiment was far from perfect. It wasn't done in a vacuum where you could have accounted for air resistance. And moreover, just think
about it for a second. If you're trying to drop two objects of the same material, let's say lead, but of different sizes physically, that's hard imagine trying to drop a musketball you could hold that very easily in your fingers, and a cannon ball at the same time. The cannon ball requires a lot more grip strength to hold it aloft and let go at the exact same
time you're letting go of the musketball. And that's one of the biggest problems here, is that the two objects must be released at the identical moment, or the whole experiment is not valid, and so it's extremely unlikely that one or even two people could manage to drop both a musketball and a cannonball at
the exact same time. It's just not likely. Ultimately, Galileo wound up arguing that his theoretical model was more reliable than his real world experiment, arguing that two objects do fall at the same rate, even though that was flatly contradicted by the evidence at hand, proving once again the staying power of deductive reasoning and Aristotle. Galleo also recounted a slope experiment around the same time. Again, he reasoned that two objects should roll down the slope at the same
speed, regardless as to their weight. But again Galileo was doing the experiment in an effort to prove his theory. When the results of the experiment didn't match the theory, he did not reconsider the latter, considering the difference between theory and practicality. From the standpoint of rates of fall, so gravity, going back to kind of what Galileo was trying to prove. According to Aristotle, rates of fall were determined by the ratio between the weight of an object
the density of whatever was falling through. Aristotle believed that a vacuum was impossible, but if there were to be such a thing, the rate at which an object fell through a vacuum would be infinite, corresponding to the weight of the objects divided by zero. The object would no sooner enter the vacuum than it would emerge from the other side. It would be essentially instantaneous. It'd
be at two places at once, it'd be that fast. Archimedes had proposed that weight could be established by subtraction, so the object's absolute weight minus the weight of the medium that it to places. Others had argued something similarly. In the case of the rate of fall in a vacuum, the rate would
be determined by an object's specific gravity. Any led object would fall in a acum at a constant speed ten times faster than any wooden object, and since air weighs very little, the difference would be nearly the same in air. A simple thought experiment showed the need to think in terms of specific gravity rather than in total weights. According to Aristotle, a two pound weight would drop
twice as fast as a one pound weight. But supposing you attach two to one pound weights together with a metal rod, Now, at what speed does it go? From one point of view, it's now a two pound weight, but at the same time it's obviously still two separate one pound weights. The only logical conclusion is that the object falls at exactly the same rate as before. Consequently, all objects of the same material, no matter how much they weigh, will fall the same speed. Now, so this is Galileo's
basic theory. In on Motion, he rejects the Aristotelian assumption that there are upward tending objects as well as down tending ones, but he accepts the Aristotelian assumption that amongst downward tending objects, heavy objects will fall faster than lighter ones. Speed of fall should be constant, determined by specific gravity. Galleo takes it as assumed that where one force is continuously at work, the result and
absence of other factors is always going to be a constant speed. But if you actually drop an object, it starts from being stationary and accelerates downward. Why is this, Galleo says, It's because it has an impressed force that only gradually wears a way, just as in iron, losing heat more rapidly than wood. And this explains the unsatisfactory results obtained in the high tower and rolling ball experiments. Galleo argued, these experiments do not measure absolute rates of
fall. They measure only rates of acceleration. There is no way of measuring absolute rates of fall. We can only deduce them from principles. So once again what we see here is when Galileo is faced with the reality of the result of the experiment, he tends to reject it and lean back on theory.
It was reason, not experience that generated science, because science is the study of necessary or causal relationships, And Galileo says precisely this and on Motion, and consequently, Galileo could quite happily declare in On Motion that his high tower and rolling ball experiments do not correspond to his theory, but that doesn't change the reality that the theory is correct. But there's a further argument in
Galileo's On Motion that any follower of Aristotle would have found baffling. According to Aristotle, there are two types of movement, natural movement, which is directed towards an end and stops when an object arrives at its natural resting place, and forced movement, which continues only for so long as there is a mover acting on the moving object. I talked about this before. This is what would cause a cannon ball to shoot straightforward until it runs out of momentum,
and then it would go straight down, which of course it doesn't. In his book on Motion, as others had done before him, Galleo modifies the account of forced movement to include a new idea impressed force. But he also invents a quite new type of movement, which he calls intermediate movement. Imagine a perfectly round ball on a perfectly smooth sheet of ice. The slightest touch will start it moving, and it will continue to move indefinitely. If this
seems like too much abstraction, think of a river. It flows constantly, but the gradient is often extremely small. That is the amount that the surface goes down below it is minute. It seems that the flowing water has almost no resistance to movement. Otherwise one would be able to identify a slope that was not steep enough for a river to run down it, but no such
decline exists. Aristotle held that the natural condition of all non heavenly things is to be stationary, and that all movement naturally ends in the cessation of movement. Galileo is now suggesting that movement might not have a natural end. This is a huge break from Aristotle. Now, the interesting thing about On Motion is that it's not a finished text. It's a series of drafts and notes which were evidently abandoned unfinished at some point. Why did Galileo stop work on
this, especially when there's so many new groundbreaking principles. Well, unfortunately Galileo doesn't say so. We're stuck speculating. There are two current theories. The first is that the experiments described in On Motion represent the beginning of Galileo's commitment to a program of experimentation. According to this theory, On Motion is abandoned
because Galileo could not generate experimental results that confirmed his theories. Now, this is kind of hard to believe, because, as I've talked about many times in this first episode, there's no evidence in the early fifteen nineties that Galileo saw experimental evidence as crucial. When experimental results were at odds with theory, he just said it was due to act accidental factors and stuck with the theory.
Now, the second reason why he might have abandoned on motion is that the ideas that Galleo was developing were just inconsistent and contradictory with one another. Having introduced the idea of intermediate motion, Galleo needed to follow through the logic of this way of thinking and replace his idea of impressed motion by a different
theory. Had he done so, he might have reached the conclusion that a few theorists had already reached in the Middle Ages, namely that falling bodies have no absolute rate of fall, but continue accelerating indefinitely in the absence of air
resistance as gravitational force pulls them downward in a never ending spiral. This would have involved abandoning his cherished idea that heavier bodies necessarily fall faster than lighter bodies, rather as is of course, true, all bodies would be subject to the same law of acceleration. But the fact of the matter is between fifteen eighty nine and fifteen ninety two, when he stopped work on on motion, Galleo was not capable of taking this step. He stalled, he stopped,
and eventually he gave up. One problem with this theory is that it implies that Galileo lacked a sort of intellectual killer instinct, and frankly, that's not convincing either. Had Galileo seen a problem, he would have tried to resolve it. We just know this based off of his life. And there's a third possibility. In fifteen eighty five, Giovanni Battista Benedicti published a new theory of motion. Like Galileo's theory, this was archiemti in sort of in its
nature, and very much a critique of Aristotle's views on natural motion. Like Galileo's, Benedicti's theory of forced motion was an impressed force theory, although he confusingly uses a different term. For a long time, the standard view has been that Galileo's argument is so close to Benedictte's that he just plagiarized it.
But had he. In the course of On Motion, Galileo does give credit to two modern authors, boro his colleague at the University of Pisa and a Jesuit Pereria, whose book was just kind of like a standard textbook at the time. His whole attitude is that of someone who has profoundly original argument to sort of add on to those two gentlemen. Now, of course, in certain respects, Galleo and Benedicti are very close in the thought experiment regarding the
two joint bodies. For example, they basically write the same thing, and yet Galileo never adopts Benedicti's wording or his vocabulary. In certain respects, Galleo and Benedictti differ, Yet Galleo never engages with Benedictti on these points or argues why his views are preferable. Indeed, I think On Motion is written as if Galileo had never heard of Benedicti, nor need he have, for he has many of the same sources our Comedees Pereira to draw on. And it's
worth remembering that there was no university library in sixteenth century Pisa. Books were expensive and Galleo was poor. He certainly didn't own many. Benedicti was not a well known author, and he had published in Venice. Bon Amiki, for example, who could afford to buy books, makes no mention of him
whatsoever in his own vast work on Motion. The first mention of Benedicti by a piece and author comes in the work by Galileo's close friend, but that doesn't get published until fifteen ninety seven, and it hardly constitutes evidence that Benedicti was being widely read in Pisa in fifteen ninety two. This points to a
possible explanation for Galleo's decision to abandon his work on on Motion. In the summer of fifteen ninety two, Galileo spent time in the company of two men who had certainly been reading Benedicti. Their names were Giadablo del Monte and Paolo Sarpi. If he explained his argument of on Motion to these two gentlemen, they probably would have immediately told him that he needed to read Benedicti and that
his core arguments were not original. And I think honestly this is the correct explanation for why Galileo abandoned On Motion around the time he learned of Benedici's existence, the intellectual enterprise which had produced on Motion just lost all significance for him.
Galleo abandoned on Motion not because he was unable to make his experiments come out right, not because he realized his argument was incoherent, not or not only because he had finally heard of Benedicti, but for one simple reason. He was now committed to giving an account of falling bodies on a moving earth. He had, in other words, converted to Copernicism, and this meant he could no longer rely on Archimedes for his understanding of movement. Now,
from a career perspective, Galileo's first university appointment had been a failure. He was paid little five mind, often for missing lectures and failing the dress code, and when his father died in fifteen ninety one, all he left him were debts. But as we will see next week, Galileo's biggest achievements in life actually lie just around the corner.