Hello, and welcome to Western SIV, episode two hundred and seventy one, Galileo, Part three. Quote. When Galileo caused balls, the weights of which he had himself previously determined to roll down an inclined plane, a light broke upon all the students of nature. They learn that reason has insight into only that which it produces after a plan of its own, and that it must not allow itself to be kept, as it were, in nature's leading
strings, but must itself show the way. End quote Emmanuel Kant, Critique of Pure Reason, seventeen eighty one. The question, of course, is was Galileo an experimental scientist? To a large extent, I suppose that's been the question I've continuously posed throughout this series. Few subjects in the history of science are more contested. Even today. There are a number of possible sources of confusion here. First, of course, what is an experiment? In
modern usage? The idea of an experiment involves the reproduction of some naturally occurring phenomenon in a carefully controlled and therefore artificial setting what Kant called reason proceeding quote after a plan of its own end quote. We might distinguish between an experiment which is designed to play a part within an argument, perhaps even to test
a hypothesis, and an experience. An experience is different. I personally have experienced thunder a lot, but I don't have any idea how to create an experiment that would establish the cause of thunder. Now, the other part of this is observation, because observation tends to be the phrase that gets used the most, especially amongst early modern astronomers. Observation can be placed somewhere between experience
and experiment. Having observed, for example, that I see lightning before I hear thunder, and having hypothesized that they both have the same cause, I would actually be a good step of the way toward devising an experiment that would make it possible to compare the speed of sound with the speed of light. Now, of course, in order to avoid unnecessary complications, this is a very loose determination of the word experiment, or at least the concept of experiment.
Galileo had experiments, and I've called them experiments, and frankly, it would probably be more accurate oftentimes to speak of these as observations. For example, Galileo's trajectile experiment, you know, is really more of a observation. He probably just recognized that it formed a parabola based off what he was watching. He didn't attempt a series of controlled observations. He didn't study what would happen if he changed the speed dramatically of the projectile. In other words,
he didn't really tinker with any of the variables. Now, the distinction between an observation and an experiment might be something that means refinement even in our modern world. But everyone knows, i think, collectively, what an observation is and generally how you do it. But such was not the case in Galileo's world. Cicero's Latin had no word for either experience or experiment. Experimentum enters Latin around the year sixteen hundred, but even Galileo rarely uses the term when
writing. He in fact, only uses the Latin for experiment twice, and only once does he use the term in Italian. Galileo indeed assume that there were only two types of knowledge, knowledge based on proof like mechanics, and knowledge based on experience. He did, however, have a term for testing a hypothesis In Latin. This is called periculum fosserae, which means literally to put to the test. This is not necessarily the same thing as our modern
term hypothesis. It wasn't an open ended test. Instead, the idea was more like having a range of possibilities you considered in advance, and then the experiment ticked off the boxes yes or no. So really it's very much a binary operation. It's either a zero or a one depending on what happens. Thus, it's not clear yet if it should be too soon to say that
Galileo was an experimental scientist. It may be frankly anachronistic at best. Certainly he used experiments or things that look like experiments, but he was never an experimental scientist in our modern sense of the world. Not that that diminishes his value to the development of experimental science in any way. A classical example of our tendency to overestimate the value of our own knowledge is in a passage of the Two Ciances by Galileo. Here he tells us to fill a glass container
with wine and seal it with a stopper containing a very small hole. The hole needs to be so small that there will be no flow of wine out of the container if we hold it upside down. Now, place this container upside down in a basin of water. Slowly, very slowly, the wine will drift out of the bottom of the container and fall to the bottom of the basin, while the water will seat it up into the container. Essentially, the water and the wine will switch spots. The great historian Andrea Corey
read this passage and thought it was ridiculous. Everyone knows that you can dilute wine with water, so he reasoned that in this case you would both end up with a basin and a container full of diluted wine. Thus, he concluded that what he was reading and Galileo was actually a thought experiment. Galileo could never have tried it out in practice. Corey's conclusion is remarkable, as he could hardly have imagined that Galileo did not know that you could dilute wine
with water. But no one actually repeated this experiment until nineteen seventy three, and when they did, it turned out that Galleo was right and Corey was wrong. So there's an important general conclusion here that we can draw from this, and that is there's no way of testing whether Galileo was an experimental scientist other than by trying to replicate the experiments he describes. It used to be thought that he had laid claim to a significant number of experiments that he had
never actually conducted. Yet there really appears to be in all of his writings only one example of his representing a guestimate as if it were an actual experiment. Hence, in the end, even if Galileo did not follow all the tenets of experimental science as we call it today, there is no doubt, at least in my mind, that Galileo effectively invented the modern idea of experimental
science, and the importance of that invention simply cannot be overstated. One of the most important pieces of evidence we have relating Galileo and experimental science is a letter from sixteen oh one in which he details a classic experiment designed to prove the isochronicity of the pendulum. In order to understand this experiment is necessary for
us to take a quick step backward. In on Motion, Galileo describes experiments involving bodies rolling down in kline slopes, Yet also in his textbooks on mechanics, compared the force required to pull an object up an inclined slope a perfectly smooth object, in this case over a perfectly smooth slope, with the force required to just lift it vertically straight up. It was easy to see that an incine slope was simply a way of slowing down the acceleration of a falling
object. It could be hypothesized at the speed at the bottom of the incline slope, assuming no friction, would be the same as the speed that the object would reach if it had fallen from the same height, and that the time it would take to descend the slope would be in the same ratio to the time of the fall as the length of the slope to the height of the fall. If one could devise an exact enough way of measuring time,
one could confirm this hypothesis by rolling balls down polished surfaces. Galileo, of course, didn't know that rolling balls behave slightly differently to sliding objects because they're rotating at some point. Galileo carried out experiments to confirm this result, but he will have been con fit of it long before he tested it. He knew the results could never be perfect, of course, the ball would never be perfectly round, the slope never be perfectly polished, but all in all,
the results were entirely satisfactory. Galleo then asked himself a follow up question. Suppose an object takes one unit of time to fall an arm's length, is there a formula for calculating the length and steepness of all the possible slopes that an object would slide down in the same unit of time. Clearly, the longer the slope, the steeper it had to be, until a slope
of eighty nine degrees is going to be nearly an arm's length. The shorter the slope, the nearer it must approach the horizontal, until a slope of one degree will have almost no length at all. Galileo probably doodled around with lengths and slopes until you realized that if all the slopes ended at the same point, then all the starting points would form a curve. What sort of
a curve? The simplest curve is a circle, And Galileo was soon able to demonstrate, on the basis of his earlier hypothesis that if a circle were placed either vertically, then an object sliding down any part of it to the lowest point would take the same time as an object sliding on the other side. There was no need to test this. It was simply had to be true if the initial assumption was true, and any test of the initial assumption
would confirm this. Essentially, what Galileo is doing here is constructing a science of falling bodies, which functions like mechanics. It was idealized, abstract, and of course concluded only imaginary bodies. But it was of course deductively true given an initial hypothesis and definition. But what about the pendulum. Surely all pendulums of the same length would take the same time to swing through different arcs,
whether wide or narrow. Galileo could see that this should be true, But try as he might, he could not find a geometrical method of proving it. He had no mathematical procedure for handling a constantly changing angle of dissent. Indeed, he was bluntly stuck. But this is when he stumbled upon a new author named Gilbert, and Gilbert was all about experiments. In fact,
he had shown that you could prove theories through experiments. Could Galileo show through an experiment that all pendulums of the same length will swing through differing arcs at the same time? Could he prove this new law in fact, if he couldn't in theory. It is precisely this experiment that Galleo describes in the first of his letters. After he read Gilbert, he wrote to a friend in Fact, describing pendulum experiments with which he claims he was able to demonstrate
this law. Now, these experiments for historians have always been difficult, because we know that Galileo's hypothesis is false. The length of the pendulum has to be made to alter very slightly as it swings if every swing, whether wide or narrow, is to take the same time. Galileo says that a pendulum swinging through a large arc and a pendulum swinging through a small arc will swing together, never getting the swing out of step with the length of the pendulum.
Galleo describes the differences of arc that he has in mind. Modern theory suggests that these two pendulums would be an entire swing out of step after only thirty or more swings. The conclusion, therefore is either Galileo never actually conducted the experiment that he describes in these letters, or he simply made up the
results, or maybe there's a third option. The third option is that if you do perform this experiment incorrectly, you do get the result that Galileo describes, because what happens is that Galileo was trying to allow for air resistance, and therefore he changed the calculations in order to make it look like the pandulums
had swung at the same time. In other words, what he's doing is his account trying to account at least for variable air resistance without being able to do so, and to an extent, I suppose falsified the results, although it was a falsification based on assumption that he certainly believed. So what all of these experiments lead Galileo two is a final conclusion that gives an explanation of a path followed by a projectile. In other words, he's finally able to
explain what he observed in fifteen ninety two. And really what this is is the culmination of hundreds of different experiments and observations that finally allow him to prove that a cannon would shoot furthest if it's set at an elevation of forty five degrees, and he could use his pendulum now to measure time more accurately than ever before. What he wanted to do, of course, was get these results into print. They would establish a new science. They would encourage others
to adopt the experimental method. They would prove finally Galileo was a worthy successor to Archimedes, and they would show Copernicanism was one hundred percent compatible with the laws of physics. In sixteen oh four, Galileo was forty years old. It had served a long apprenticeship. It was beginning, at long last to make some headway against his financial burdens. He was about to become famous. He began writing in Latin, of course, the book that he knew would
have an impact far greater than anything else. The evidence suggests indeed, by sixteen oh eight he had come really close to finishing this book that we can find its text produced in Latin, within its Italian dialogue on the two sciences. But one thing that's really interesting about all of this is that if Galileo was an experimental scientist, that is not how he wanted to present himself to the world. He wanted Europe to look on him as another Archimedes, the
ultimate deductive scientist. The true role of experiment, in Galilee's mind was not to explain the true role of experiment was to establish facts that deductive reasoning could then explain. Galileo's experiments were preparatory procedures undertaken in his quest for proofs. In fact, part of the reason Galileo fastidiously avoided using the term experiment was his desire to avoid being labeled an experimental scientist. It did not work.
To one contemporary Galileo was quote the founder of the experimental method in all its exactness end quote. After his death, Galileo's students founded the Academia del Cimento, dedicated to the pursuit of scientific knowledge through experiment and experimentation. Frankly, a Galileo published his book on Projectiles and Falling Bodies and done nothing else. He would have been a significant figure in the history of science, the founder
of modern physics, the greatest physicist before Newton. In later years, Galleo's friends urged him repeatedly to publish, but he didn't do so until sixteen thirty eight. This is a thirty year delay that cries out for an explanation. I mean Galleo had endless opportunities to publish. He could have published at any time after sixteen sixteen. Banned from defending Copernicanism. This would have been the sensible thing to do. He even had a clean copy of a draft prepared
in sixteen eighteen so that he could resume work. And for this delay, there's really only one explanation that works, and that is in Galileo's mind, this project was inseparable from the much larger and in his mind more important one, the campaign to vindicate Copernicus. Prestige and fame weren't enough for Galleo. Proving ours thought all wrong wasn't enough for Galleo. Revolutionizing physics is not enough for Galileo. There was something else that mattered. But what exactly was that
something? And this is I think, really the question, because it defines what Galileo was all about. And in Galileo's view, the answer to this question is obvious. He wrote as follows. Quote. The constitution of the universe, I that is, Galileo believe, may be set in first place among all natural things that can be known, for coming before all others in grandeur by reason of its universal context. It must stand above them all in
nobility, as their rule and standard. End quote. No other thing stood above the universe in Galileo's mind, everything depended upon it, and in his mind Copernicus had it right. But how to prove it well? The answer, it turns out, as we'll turn to now, is you have to change how you see. In autumn of six oh four, a new star appeared in the sky. News of it spread rapidly amongst those interested in astronomy. Thirty years earlier, in fifteen seventy two, ticobrahe had turned a new
star into quite the celebration throughout Europe. Now, of course, the problem is is, according to Aristotelian philosopher, the heavens were unchanging, eternal, perfect. There could be no change in the heavens, and any change that did take place had to occur in the vicinity of Earth. In their view. Consequently, the choice was simple. Either that new star wasn't new at all, it had always been there, or it wasn't a star at all,
but some peculiar phenomenon in the atmosphere. Since Tico's new star soon disappeared, the argument was left unfinished, to be immediately reawakened by the appearance of this nova in sixteen oh four. As a Copernicus Galileo, of course, knew where he stood. If Copernicus was right, the distinction between a sublunary and superluinary world was misconceived. There was no distinction between Earth and the heavens.
The Earth was in the heavens and inseparable from them. If there was some change on Earth, then equally there could be change in the heavens. As someone who taught the military sciences, Galileo also knew how to measure distances. He knew it was not necessary to approach an object to work out how far away it was, so long as there was some other point of reference whose distance was known. By looking at an object from different positions, you
could see how its relationship to other objects altered. Simple geometry could turn a measurement of a parallax into a calculation of distance. If the new star, when looked at from different places on the Earth's surface, had an unchanging relationship to the star around it, then it was very far away, clearly much further away than the moon. Galileo had soon collected the information to prove that the new star was indeed a star, that it was certainly not closer to
the Earth than the moon. He gave a series of public lectures on the new Star, attracting large audiences and provoking vigorous debate. Galileo must have considered publishing a version of his lectures on the nova. Certainly, given the mood in Europe at the time, they would have sold well and would have constituted his first proper scientific publication. In the autumn of sixteen oh four, Galileo could show that the new star's location appeared to be the same when viewed from
different European cities. The star then disappeared below the horizon of the night sky, to reappear in the spring of sixteen oh five. It was clearly Galileo's hope that when it reappeared, its relative position would have changed. If Copernicus was correct, he would now be looking at it from a point distance from
his previous point of operation by the diameter of the Earth's orbit. Galileo must have waited with anxious anticipation for the star's re appearance, but there was no change in its location, and while this was a disappointment, it wouldn't have been much of a surprise given Galileo's understandings. Be that as it may. Galileo's letter made it clear this was a star. This was something in the heavens, and it was new. And it turned out Galileo had some i'll
put it in air quotes support. You see. In addition to Galileo's letter slash pamphlet, a second pamphlet appeared defending Galleo's interpretation of the New Star. It was printed in Florence in sixteen oh six, and it was written by ali Berto Mari. But it was a ruse. Mari was Galileo. He had written under a pseudonym. Now, interestingly, in this pamphlet, MARII, that is, Galileo never explicitly discusses Copernicism, indicating maybe he knew he
wasn't supposed to. But he does refer to Copernakiss a few times, always with approval. So after just some heated arguments and good natured mockery of the Ristotelian establishment, Galileo's first involvement in astronomy came to an end, and he turned his attention back to physics. Early in sixteen oh eight, however, a Dutch spectacle maker discovered that if a convex lens was held behind a concave lens, you could enlarge the image. He mounted the lenses in a tube
with a sliding mechanism, thereby making the first telescope. Soon a number of different people were claiming to be the inventor, and word of the discovery spread rapidly. In May of sixteen oh nine, Galileo claimed to have quote unquote reinvented the telescope. Would that really means in this instance is that he made a telescope without ever really seeing one, and without having been given an account of how one was constructed. He would later claim that reinventing was just as
difficult as inventing. Archimedes, after all, had invented weapons of war that no one had been able to reinvent. Galileo would also claim that his knowledge of optics was crucial for being able to reinvent and improve the telescope. Galileo certainly had some knowledge of optics, but it is not clear that this played a significant role in either the reinvention or the improvement of the telescope. All that was involved was intelligent trial and error, in other words, experimentation.
Galileo saw at once that the number of possible lens combinations was limited, and so all he had to do now was try them out. Galleo's first telescope, using lenses made for spectacles, magnified only three times. The best Dutch telescopes of the day magnified double that, about six times. The lens quality definitely was poor. There would have been a halo consisting of the colors of the rainbow around the edges of every object, and the image would have been
blurred because the curvature of the lens was irregular, its value limited. Galileo's true genius, though, was that he grasped at once that the telescope could be improved. Now today, we live in a world where manufacturers are constantly offering us improved version of products. So if you or I had been shown a primitive telescope, we would have asked immediately how it could be improved. Galleo's world wasn't like this, though. Even new technologies guns, printing presses,
compasses were improved slowly and over very long periods of time. By the summer of sixteen oh nine, there were thousands of people mathematician, scientists, engineers who had seen and used the new telescopes, but Galileo was the only person, the only one who immediately saw the challenge how could it be improved. Everything that he had done throughout his life had prepared Galileo for this moment. Galileos soon that a telescope that magnified eight times. He took this to
Venice, where he displayed it to the city's rulers. It may have been the first telescope many of them had seen, though some will have known that others were offering to sell the secret of how to make one. Standing on the top of the bell tower in Saint Mark's Square, they looked out to the sea and saw ships through Galileo's telescope that were invisible to the naked eye. The technology had obvious military potential. Galleo assured them that additionally, equally
good telescopes could be made, supported by powerful friends and associates. He pressed his claim for reward, and it was agreed that he should receive an appointment at the university for life and a salary of one thousand ducats a year. In return, he agreed to spend the rest of his life in the service of the Venetian state. Now impartial bystanders soon started muttering the Galileo had practiced nothing but deception. Telescope vendors were spreading out across Europe carrying packs full of
Dutch made telescopes. Soon one good bye a telescope quite cheaply in Saint Mark Square, right where Galileo had demonstrated this new invention. Now, this, of course is the first ambiguity, and we don't know the answer to this. But had Galileo presented himself as the inventor of the telescope or merely as an improver of the telescope? And of course that leads to another question. If Galileo's telescopes were better than the other telescopes that were now generally available,
was there a secret to their construction? Or could anyone who put in a little time and trouble produced an improved telescope. The Venetian establishment seems to have had its doubts. They couldn't go back on their word unless they were prepared to charge Galleo with a crime. But by the time the Venetian Senate came to vote on his reward, it seems clear they felt like they had been
misled. Galileo's new appointment and his new salary was now only set to begin when his existing appointment came to an end, and the Senate decreed that his new salary was never to be increased. We could guess that Galleo was offended by this restriction, seeing it as an invitation to seek patronage elsewhere. The new salary was, after all, no better than one of his friends,
who went on to double his salary in the years that followed. Although he didn't receive an appointment for life in sixteen oh nine, both Galleo and the rulers of Venice were trying to make sense of this new technology. Galileo was certainly in a position to guess that others would soon be able to produce telescopes as good as his. But it's also the case that Galileo had kept a lead in the production for the moment of high power telescopes. By the autumn
of sixteen oh nine, he had a telescope that magnified twenty times. Four years later, by the beginning of sixteen thirteen, one that magnified thirty times, and he was still well ahead of the competition. In fact, Galileo managed to stay ahead for twenty years. Galileo really did have something to offer Venice, but his telescope was not a new invention, nor was it made with any special techniques. I don't think that there was any deception here when
dealing with the Venetian government. Rather, what the Venetian government failed to comprehend was that when they were buying this new technology, they were buying the man who was committed to improving it. But again, that just wasn't the mindset of people in early modern Europe, so it's hard to fault them for it. Now. Interestingly, this is just kind of an aside, But around
the same time we get some correspondence between Galileo and his younger brother. It seems that Galileo sent him a few telescopes so that he could give them to influential people and spread word of Galleo's discoveries. His brother sold the telescopes instead and kept the money. He wrote to Galleo a bit later asking for more telescopes to sell. Galleo didn't send any. The whole affair is an interesting reminder of the reality that the great men and women in the past didn't live
in a bubble. They had annoying familial relations too. In Venice, in June and July, there's about sixteen hours of daylight and only eight in December and January. In the autumn of sixteen oh nine, as the days shortened, Galleo turned his improved telescope toward the heavens. He mounted it on some sort of stand, But still he had to learn how to slow his breathing. Even his pulse seemed to shape the telescope, and as the evening temperature
dropped, the glasses kept missing up. In early January sixteen ten, he discovered he could reduce the halo round objects by fitting a circle of masking material with an oval hole on the end of it over the lens. In photographic terms, he stopped the lens down. Still, the stars remained mere points
in the heavens, except that there were many more of them. Now he discovered that the Milky Way was not a mysterious white band in the sky, but a vast number of small stars, individually invisible to the naked eye. Elsewhere there were new stars to be seen. It's easy for the significance of these new stars to escape a modern reader. It might be thought, it
hardly matters how many stars there are. But Galileo's contemporaries believed that the universe embodied a rational purpose the Sun, the Moon, and the stars existed for one purpose, and one purpose only, to give light to the Earth. Invisible stars were a weird new concept. What purpose could a star serve if no one could see it? Only a few Copernicans had imagined a universe so
large that there were distant stars invisible from Earth. As for the planets, through Galileo's telescope, they were not points, but tiny discs floating in space. Naturally. Galileo turned his telescope to the Moon, which was so greatly magnified that he could look at it less than half the time even with his twenty power telescope. Everyone knew that the Moon wasn't perfectly uniform in a pearance, but the philosophers still insisted that it had to be a perfect sphere,
even if parts of its surface were more reflective than others. If the Moon were smooth, the line between the illuminated half and unilluminated half should be perfectly irregular. But Galileo, looking through his telescope, could see that the line wasn't regular. Moreover, near the margin between the illuminated and ulluminated half, he saw two anomalies on the unilluminated side of the margin, he could see little flecks of light. The sun was clearly reaching some areas before it reached
others. These must be high points. On the illuminated side, he could see dark spots which the illumination took longer to reach. These must be shadows. Galileo's interest in painting and his experience looking at paintings where the tricks of light were used to convey textures and shapes, probably helped him understand what he was seeing. But he also grasped at once that what he was seeing was comparable to a familiar phenomenon on Earth. At dusk and dawn, the sun
stays on the mountaintops when the valleys below are deep in shadow. Galileo therefore had discovered that the Moon had a landscape, a landscape of mountains and valleys. In this respect, it was just like the Earth, and this was corroboration of his view that the Earth seen from the Moon would look just like an enormous moon. But there was so much more. On January seventh, Galileo turned his telescope to Jupiter and noticed three stars arranged in a line,
with the planet toe to the east, one to the west. He had assumed that these were yet more fixed stars, But the next day, when he looked again, now all three stars were to the west of Jupiter. Although Jupiter itself was moving from east to west, somehow, to fixed stars had overtaken Jupiter. Galileo now began to observe Jupiter every night. By the eleventh of January, he had decided that he was observing three satellites orbiting Jupiter.
On the thirteenth he discovered a fourth. Galileo now knew he had made a truly momentous discovery. By January the thirtieth, he was in Venice arranging for the publication of a book on his telescopic discoveries, the mountains on the Moon, the nature of the Milky Way, the moons of Jupiter, all
the while continuing his observations. Galileo was in a hurry. He knew other people had telescopes, and even if theres weren't as good as his, it probably wouldn't be long until someone else had a telescope capable of looking at Jupiter's moons, and so Galileo, now aged forty six, was writing a book. As he worked, he consistently tinkered with the title suggesting he believed the
book was designed to become a work of great importance. It was common when printing a book to print the body of the book first, and then to add the prefatory matter. It's clear that this happened in the case of Galileo's observations. The large title on the first page to be printed was Astronomous Nunicus, which translates to the astronomical message or astronomical Messenger. In his correspondence, Galileo referred to the book in Italian as avisio stronimko or astronomical news, or
maybe even starry news. But the fine old title, which was finished only as the last pages went to press on March the twelfth, was Siderius nuncus, or as we know the title today, the Starry Messenger, a Messenger from the stars. The book proved to be a collection of observations, or more like a report than a narrative work. Galileo despised books about books. Prior to him, that was kind of all you really ever got out of scientists. Galileo went out of his way in writing his book to prove it
was different. Indeed, after its publication, every other book on the stars became irrelevant, at least according to Galileo. Galleo doesn't offer facts in The Starry Messenger. He offers us observations. Some require no interpretation at all, others just a little deductive reasoning. Shadows on the Moon become craters with a little thought. For example, some of the illustrations of the moon within the book book are amazingly accurate. They did have one significant flaw, however,
which is puzzled later scholars. A singular feature, a crater, which Galleo describes as being as large as Bohemia. It appears in large effects, so big that critics have complained that if the illustrations were accurate, it would be visible to the naked eye. Now, the simple answer as to why this appears is that Galleo was persuaded that this singular feature was far larger and more noticeable than any other because he had already seen it with his naked eye.
In the end, what's happening here in The Starry Messenger is Galileo is embellishing something because he believes so firmly that he is seeing it or has seen it with the naked eye. Did he probably not, But it doesn't change the fact that as a crater it's large. Now. Interestingly, after the Starry Messenger, Galleo did not include any illustrations in his books, and the reason is quite obvious. He expected readers to have or to obtain telescopes of their
own. It was as though he was saying to all of Europe, the answers are there, go and see for yourselves. But then, on the twelfth of February, Galleo received a letter from Belisario Vinta, the secretary to the Grand Duke of Florence. He reported that the Grand Duke was quote unquote
stupefied by news of Galileo's discoveries. Galileo replied the very next day with the Grand Duke, who was called Cosimo, he has succeeded his father here before, like some of these new satellites to be named the Cosmic stars after him? Or would he prefer them to be named the Medician stars, given that they were four of them and he had three brothers. Quickly the answer came back. It was written on the twenty of the February and would have reached
Galileo a few days later. Cosmic, they wrote, was too ambiguous it would not automatically make people think of Cosimo Medician was better. Galileo made his arrangements for publication at the end of January. He had an effect booked time on the press and could not wait for a reply. When Vinta's letter relaying the Grand Duke's choice arrived, the word cosmica was replaced with Medica. It would have been shortly after this that Galileo chose the final title for the book
and wrote a prefatory letter in praise of Cosimo de Medici. There's another more significant discovery to be made from examining the surviving manuscript. There are three passages in this book in which Galileo unequivocally declares his support for Copernicanism. Now it's clear that when Galileo received Vinta's letter on the twelfth of February, he had
virtually completed a draft manuscript which contained not a single reference to Copernicanism. The first and third sections of the book open with references to Venus and Mars orbiting the sun, but a knowledgeable contemporary would have been more likely to interpret this as a reference to Tico Brahe, not Copernicus. In mid February. Therefore, Galileo made two bold and consequential decisions. He decided to put a reference
to sideda Cosmiica in the title of his book and into its conclusion. And he decided to commit himself explicitly to a Copernican argument and to include within his book an implicit attack on Tico Brahe. Galileo explains then that the phenomenon of earth shine and shows that the Earth lights the Moon just as the Moon lights the Earth. As Galileo says, earth shine is powerful evidence in favor of the Copernican claim that there's no difference between the Earth and the other heavenly bodies.
Of the discovery is reported in The Starry Messenger. This is one of two which tell against the cosmology of Ticobrahe. The implications of the other, the discovery that planets can have moons so that the Earth principle could be a planet, were only put in the final pages. It's easy to see what
changed, or at least what Galileo hoped was about to change. When Galileo entered into the contract with his princer, he was just an insignificant professor, But after the twelfth of February, he became convinced that he was about to receive the support of the powerful Medici family, and therefore he was ready to come out in support of Copernicanism. It's worth pausing to see what Galileo was doing in mid February. He was on the threshold of publishing a book that
would stupefy the scholarly world. Success was assured this was definitely going to sell, and so he decided to raise the stakes and make a success uncertain. He committed himself to dedicating the book to Cosimo Dimnici before he even had permission to do so. Even more boldly, he decided to maximize the opposition to his book and minimize support for it by not making it simply anti Ptolemaic but
explicitly Copernican. Of course, since he believed in Copernicanism, this had the advantage of allowing him to speak his mind, but it was a rash move to the extreme. Interestingly enough, if you look at the book, the rhetorical high point occurs in almost the exact middle, and it's remarkable in about three respects. It's transparently Copernican. It announces Galileo's great project, the system of the world, and it's only one of two places where Galleo ever uses
the word experiment in Latin. Some of these passages lay out Galleo's thoughts on these new discoveries, and with these words he both announces an imminent intellectual revolution and provides a sketch of his much larger work, Dialogue, which would not
be published until sixteen thirty two. Here's the relevant passage quote, Let these few things said hear about this matter suffice we will say more in our system of the world, where with very many arguments and experiments, a very strong reflection of solar light from the Earth is demonstrated to those who claim that the Earth is to be excluded from the dance of the stars, especially because she
is devoid of motion and light. For we will demonstrate that she is movable, and that she surpasses the moon in its brightness, and that she is not the dump heap of filth and dregs of the universe. And we will confirm this with innumerable arguments from nature. End quote. The story Messenger was published on the thirteenth of March. Within a week, five hundred and fifty copies were gone. Galileo, who was supposed to get thirty free copies of
the book received on these six. Because it's sold so quickly, there is no doubt that fame for Galileo had arrived at last. But at what cost.