WEBVTT 1 00:00:19.199 --> 00:00:23.679 Hello, and welcome to Western SIV, episode two hundred and seventy one, 2 00:00:24.199 --> 00:00:30.559 Galileo, Part three. Quote. When Galileo caused balls, the weights of 3 00:00:30.600 --> 00:00:35.719 which he had himself previously determined to roll down an inclined plane, a light 4 00:00:35.799 --> 00:00:41.119 broke upon all the students of nature. They learn that reason has insight into 5 00:00:41.320 --> 00:00:44.679 only that which it produces after a plan of its own, and that it 6 00:00:44.759 --> 00:00:48.679 must not allow itself to be kept, as it were, in nature's leading 7 00:00:48.719 --> 00:00:56.240 strings, but must itself show the way. End quote Emmanuel Kant, Critique 8 00:00:56.240 --> 00:01:02.399 of Pure Reason, seventeen eighty one. The question, of course, is 9 00:01:03.159 --> 00:01:07.159 was Galileo an experimental scientist? To a large extent, I suppose that's been 10 00:01:07.159 --> 00:01:14.400 the question I've continuously posed throughout this series. Few subjects in the history of 11 00:01:14.439 --> 00:01:19.040 science are more contested. Even today. There are a number of possible sources 12 00:01:19.040 --> 00:01:25.799 of confusion here. First, of course, what is an experiment? In 13 00:01:25.840 --> 00:01:30.680 modern usage? The idea of an experiment involves the reproduction of some naturally occurring 14 00:01:30.719 --> 00:01:40.239 phenomenon in a carefully controlled and therefore artificial setting what Kant called reason proceeding quote 15 00:01:40.519 --> 00:01:47.000 after a plan of its own end quote. We might distinguish between an experiment 16 00:01:47.519 --> 00:01:51.799 which is designed to play a part within an argument, perhaps even to test 17 00:01:51.799 --> 00:01:57.319 a hypothesis, and an experience. An experience is different. I personally have 18 00:01:57.599 --> 00:02:01.879 experienced thunder a lot, but I don't have any idea how to create an 19 00:02:01.920 --> 00:02:08.240 experiment that would establish the cause of thunder. Now, the other part of 20 00:02:08.240 --> 00:02:15.879 this is observation, because observation tends to be the phrase that gets used the 21 00:02:15.000 --> 00:02:23.719 most, especially amongst early modern astronomers. Observation can be placed somewhere between experience 22 00:02:23.919 --> 00:02:30.319 and experiment. Having observed, for example, that I see lightning before I 23 00:02:30.360 --> 00:02:35.639 hear thunder, and having hypothesized that they both have the same cause, I 24 00:02:35.639 --> 00:02:38.560 would actually be a good step of the way toward devising an experiment that would 25 00:02:38.560 --> 00:02:42.280 make it possible to compare the speed of sound with the speed of light. 26 00:02:43.919 --> 00:02:47.199 Now, of course, in order to avoid unnecessary complications, this is a 27 00:02:47.360 --> 00:02:53.840 very loose determination of the word experiment, or at least the concept of experiment. 28 00:02:54.120 --> 00:03:00.879 Galileo had experiments, and I've called them experiments, and frankly, it 29 00:03:00.879 --> 00:03:06.879 would probably be more accurate oftentimes to speak of these as observations. For example, 30 00:03:07.599 --> 00:03:14.759 Galileo's trajectile experiment, you know, is really more of a observation. 31 00:03:15.360 --> 00:03:22.520 He probably just recognized that it formed a parabola based off what he was watching. 32 00:03:23.960 --> 00:03:29.599 He didn't attempt a series of controlled observations. He didn't study what would 33 00:03:29.639 --> 00:03:34.840 happen if he changed the speed dramatically of the projectile. In other words, 34 00:03:35.080 --> 00:03:40.319 he didn't really tinker with any of the variables. Now, the distinction between 35 00:03:40.319 --> 00:03:46.400 an observation and an experiment might be something that means refinement even in our modern 36 00:03:46.400 --> 00:03:53.400 world. But everyone knows, i think, collectively, what an observation is 37 00:03:54.039 --> 00:04:00.680 and generally how you do it. But such was not the case in Galileo's 38 00:04:00.759 --> 00:04:11.280 world. Cicero's Latin had no word for either experience or experiment. Experimentum enters 39 00:04:11.360 --> 00:04:17.120 Latin around the year sixteen hundred, but even Galileo rarely uses the term when 40 00:04:17.160 --> 00:04:25.920 writing. He in fact, only uses the Latin for experiment twice, and 41 00:04:26.040 --> 00:04:31.879 only once does he use the term in Italian. Galileo indeed assume that there 42 00:04:31.879 --> 00:04:39.720 were only two types of knowledge, knowledge based on proof like mechanics, and 43 00:04:39.800 --> 00:04:45.560 knowledge based on experience. He did, however, have a term for testing 44 00:04:45.600 --> 00:04:54.759 a hypothesis In Latin. This is called periculum fosserae, which means literally to 45 00:04:54.839 --> 00:05:00.839 put to the test. This is not necessarily the same thing as our modern 46 00:05:00.920 --> 00:05:08.800 term hypothesis. It wasn't an open ended test. Instead, the idea was 47 00:05:08.839 --> 00:05:14.639 more like having a range of possibilities you considered in advance, and then the 48 00:05:14.759 --> 00:05:20.040 experiment ticked off the boxes yes or no. So really it's very much a 49 00:05:20.319 --> 00:05:26.480 binary operation. It's either a zero or a one depending on what happens. 50 00:05:27.560 --> 00:05:30.759 Thus, it's not clear yet if it should be too soon to say that 51 00:05:31.079 --> 00:05:38.439 Galileo was an experimental scientist. It may be frankly anachronistic at best. Certainly 52 00:05:38.800 --> 00:05:43.959 he used experiments or things that look like experiments, but he was never an 53 00:05:43.959 --> 00:05:48.000 experimental scientist in our modern sense of the world. Not that that diminishes his 54 00:05:48.120 --> 00:05:54.839 value to the development of experimental science in any way. A classical example of 55 00:05:54.879 --> 00:05:59.519 our tendency to overestimate the value of our own knowledge is in a passage of 56 00:05:59.560 --> 00:06:04.000 the Two Ciances by Galileo. Here he tells us to fill a glass container 57 00:06:04.040 --> 00:06:09.920 with wine and seal it with a stopper containing a very small hole. The 58 00:06:09.959 --> 00:06:13.079 hole needs to be so small that there will be no flow of wine out 59 00:06:13.120 --> 00:06:16.279 of the container if we hold it upside down. Now, place this container 60 00:06:16.360 --> 00:06:21.480 upside down in a basin of water. Slowly, very slowly, the wine 61 00:06:21.519 --> 00:06:26.639 will drift out of the bottom of the container and fall to the bottom of 62 00:06:26.680 --> 00:06:30.680 the basin, while the water will seat it up into the container. Essentially, 63 00:06:31.079 --> 00:06:36.800 the water and the wine will switch spots. The great historian Andrea Corey 64 00:06:38.240 --> 00:06:42.519 read this passage and thought it was ridiculous. Everyone knows that you can dilute 65 00:06:42.560 --> 00:06:46.839 wine with water, so he reasoned that in this case you would both end 66 00:06:46.920 --> 00:06:50.160 up with a basin and a container full of diluted wine. Thus, he 67 00:06:50.279 --> 00:06:56.839 concluded that what he was reading and Galileo was actually a thought experiment. Galileo 68 00:06:56.879 --> 00:07:01.839 could never have tried it out in practice. Corey's conclusion is remarkable, as 69 00:07:01.839 --> 00:07:06.240 he could hardly have imagined that Galileo did not know that you could dilute wine 70 00:07:06.240 --> 00:07:13.639 with water. But no one actually repeated this experiment until nineteen seventy three, 71 00:07:13.759 --> 00:07:18.639 and when they did, it turned out that Galleo was right and Corey was 72 00:07:18.680 --> 00:07:25.360 wrong. So there's an important general conclusion here that we can draw from this, 73 00:07:26.199 --> 00:07:31.560 and that is there's no way of testing whether Galileo was an experimental scientist 74 00:07:32.399 --> 00:07:38.800 other than by trying to replicate the experiments he describes. It used to be 75 00:07:38.879 --> 00:07:42.639 thought that he had laid claim to a significant number of experiments that he had 76 00:07:42.639 --> 00:07:48.199 never actually conducted. Yet there really appears to be in all of his writings 77 00:07:48.720 --> 00:07:55.399 only one example of his representing a guestimate as if it were an actual experiment. 78 00:07:57.160 --> 00:08:01.399 Hence, in the end, even if Galileo did not follow all the 79 00:08:01.439 --> 00:08:07.639 tenets of experimental science as we call it today, there is no doubt, 80 00:08:07.680 --> 00:08:16.160 at least in my mind, that Galileo effectively invented the modern idea of experimental 81 00:08:16.199 --> 00:08:24.839 science, and the importance of that invention simply cannot be overstated. One of 82 00:08:24.920 --> 00:08:31.879 the most important pieces of evidence we have relating Galileo and experimental science is a 83 00:08:31.959 --> 00:08:39.480 letter from sixteen oh one in which he details a classic experiment designed to prove 84 00:08:39.559 --> 00:08:45.840 the isochronicity of the pendulum. In order to understand this experiment is necessary for 85 00:08:45.960 --> 00:08:50.000 us to take a quick step backward. In on Motion, Galileo describes experiments 86 00:08:50.080 --> 00:08:56.840 involving bodies rolling down in kline slopes, Yet also in his textbooks on mechanics, 87 00:08:56.519 --> 00:09:01.320 compared the force required to pull an object up an inclined slope a perfectly 88 00:09:01.360 --> 00:09:07.200 smooth object, in this case over a perfectly smooth slope, with the force 89 00:09:07.240 --> 00:09:13.039 required to just lift it vertically straight up. It was easy to see that 90 00:09:13.080 --> 00:09:16.360 an incine slope was simply a way of slowing down the acceleration of a falling 91 00:09:16.399 --> 00:09:22.039 object. It could be hypothesized at the speed at the bottom of the incline 92 00:09:22.080 --> 00:09:24.639 slope, assuming no friction, would be the same as the speed that the 93 00:09:24.679 --> 00:09:28.320 object would reach if it had fallen from the same height, and that the 94 00:09:28.399 --> 00:09:31.960 time it would take to descend the slope would be in the same ratio to 95 00:09:33.000 --> 00:09:35.600 the time of the fall as the length of the slope to the height of 96 00:09:35.639 --> 00:09:39.120 the fall. If one could devise an exact enough way of measuring time, 97 00:09:39.679 --> 00:09:46.559 one could confirm this hypothesis by rolling balls down polished surfaces. Galileo, of 98 00:09:46.600 --> 00:09:50.279 course, didn't know that rolling balls behave slightly differently to sliding objects because they're 99 00:09:50.440 --> 00:09:58.879 rotating at some point. Galileo carried out experiments to confirm this result, but 100 00:09:58.080 --> 00:10:03.039 he will have been con fit of it long before he tested it. He 101 00:10:03.120 --> 00:10:05.639 knew the results could never be perfect, of course, the ball would never 102 00:10:05.679 --> 00:10:13.000 be perfectly round, the slope never be perfectly polished, but all in all, 103 00:10:13.639 --> 00:10:20.559 the results were entirely satisfactory. Galleo then asked himself a follow up question. 104 00:10:20.480 --> 00:10:24.720 Suppose an object takes one unit of time to fall an arm's length, 105 00:10:26.720 --> 00:10:31.679 is there a formula for calculating the length and steepness of all the possible slopes 106 00:10:31.120 --> 00:10:35.440 that an object would slide down in the same unit of time. Clearly, 107 00:10:37.000 --> 00:10:41.039 the longer the slope, the steeper it had to be, until a slope 108 00:10:41.039 --> 00:10:46.080 of eighty nine degrees is going to be nearly an arm's length. The shorter 109 00:10:46.159 --> 00:10:50.279 the slope, the nearer it must approach the horizontal, until a slope of 110 00:10:50.360 --> 00:10:56.639 one degree will have almost no length at all. Galileo probably doodled around with 111 00:10:56.759 --> 00:11:01.000 lengths and slopes until you realized that if all the slopes ended at the same 112 00:11:01.080 --> 00:11:07.080 point, then all the starting points would form a curve. What sort of 113 00:11:07.080 --> 00:11:11.919 a curve? The simplest curve is a circle, And Galileo was soon able 114 00:11:11.960 --> 00:11:16.440 to demonstrate, on the basis of his earlier hypothesis that if a circle were 115 00:11:16.440 --> 00:11:20.200 placed either vertically, then an object sliding down any part of it to the 116 00:11:20.240 --> 00:11:26.480 lowest point would take the same time as an object sliding on the other side. 117 00:11:26.279 --> 00:11:30.399 There was no need to test this. It was simply had to be 118 00:11:30.440 --> 00:11:33.519 true if the initial assumption was true, and any test of the initial assumption 119 00:11:33.559 --> 00:11:39.399 would confirm this. Essentially, what Galileo is doing here is constructing a science 120 00:11:39.399 --> 00:11:46.039 of falling bodies, which functions like mechanics. It was idealized, abstract, 121 00:11:46.120 --> 00:11:52.120 and of course concluded only imaginary bodies. But it was of course deductively true 122 00:11:52.720 --> 00:12:00.720 given an initial hypothesis and definition. But what about the pendulum. Surely all 123 00:12:00.799 --> 00:12:05.559 pendulums of the same length would take the same time to swing through different arcs, 124 00:12:05.559 --> 00:12:09.120 whether wide or narrow. Galileo could see that this should be true, 125 00:12:09.919 --> 00:12:13.960 But try as he might, he could not find a geometrical method of proving 126 00:12:15.000 --> 00:12:20.600 it. He had no mathematical procedure for handling a constantly changing angle of dissent. 127 00:12:22.799 --> 00:12:28.919 Indeed, he was bluntly stuck. But this is when he stumbled upon 128 00:12:28.960 --> 00:12:35.320 a new author named Gilbert, and Gilbert was all about experiments. In fact, 129 00:12:35.360 --> 00:12:41.519 he had shown that you could prove theories through experiments. Could Galileo show 130 00:12:41.559 --> 00:12:48.360 through an experiment that all pendulums of the same length will swing through differing arcs 131 00:12:48.399 --> 00:12:54.759 at the same time? Could he prove this new law in fact, if 132 00:12:54.799 --> 00:13:01.519 he couldn't in theory. It is precisely this experiment that Galleo describes in the 133 00:13:01.519 --> 00:13:05.039 first of his letters. After he read Gilbert, he wrote to a friend 134 00:13:05.080 --> 00:13:11.240 in Fact, describing pendulum experiments with which he claims he was able to demonstrate 135 00:13:11.279 --> 00:13:16.639 this law. Now, these experiments for historians have always been difficult, because 136 00:13:16.919 --> 00:13:22.879 we know that Galileo's hypothesis is false. The length of the pendulum has to 137 00:13:22.879 --> 00:13:28.879 be made to alter very slightly as it swings if every swing, whether wide 138 00:13:28.960 --> 00:13:33.200 or narrow, is to take the same time. Galileo says that a pendulum 139 00:13:33.240 --> 00:13:39.320 swinging through a large arc and a pendulum swinging through a small arc will swing 140 00:13:39.360 --> 00:13:43.240 together, never getting the swing out of step with the length of the pendulum. 141 00:13:43.320 --> 00:13:48.080 Galleo describes the differences of arc that he has in mind. Modern theory 142 00:13:48.200 --> 00:13:54.480 suggests that these two pendulums would be an entire swing out of step after only 143 00:13:54.559 --> 00:14:03.519 thirty or more swings. The conclusion, therefore is either Galileo never actually conducted 144 00:14:03.519 --> 00:14:11.759 the experiment that he describes in these letters, or he simply made up the 145 00:14:11.840 --> 00:14:18.360 results, or maybe there's a third option. The third option is that if 146 00:14:18.399 --> 00:14:24.559 you do perform this experiment incorrectly, you do get the result that Galileo describes, 147 00:14:26.960 --> 00:14:31.080 because what happens is that Galileo was trying to allow for air resistance, 148 00:14:33.200 --> 00:14:39.080 and therefore he changed the calculations in order to make it look like the pandulums 149 00:14:39.120 --> 00:14:43.639 had swung at the same time. In other words, what he's doing is 150 00:14:43.679 --> 00:14:48.039 his account trying to account at least for variable air resistance without being able to 151 00:14:48.120 --> 00:14:54.679 do so, and to an extent, I suppose falsified the results, although 152 00:14:54.720 --> 00:15:00.519 it was a falsification based on assumption that he certainly believed. So what all 153 00:15:00.600 --> 00:15:07.679 of these experiments lead Galileo two is a final conclusion that gives an explanation of 154 00:15:07.720 --> 00:15:13.000 a path followed by a projectile. In other words, he's finally able to 155 00:15:13.159 --> 00:15:18.919 explain what he observed in fifteen ninety two. And really what this is is 156 00:15:20.360 --> 00:15:28.799 the culmination of hundreds of different experiments and observations that finally allow him to prove 157 00:15:30.519 --> 00:15:35.240 that a cannon would shoot furthest if it's set at an elevation of forty five 158 00:15:35.279 --> 00:15:41.000 degrees, and he could use his pendulum now to measure time more accurately than 159 00:15:41.039 --> 00:15:45.360 ever before. What he wanted to do, of course, was get these 160 00:15:45.399 --> 00:15:50.600 results into print. They would establish a new science. They would encourage others 161 00:15:50.600 --> 00:15:56.600 to adopt the experimental method. They would prove finally Galileo was a worthy successor 162 00:15:58.039 --> 00:16:04.559 to Archimedes, and they would show Copernicanism was one hundred percent compatible with the 163 00:16:04.679 --> 00:16:11.240 laws of physics. In sixteen oh four, Galileo was forty years old. 164 00:16:11.080 --> 00:16:17.200 It had served a long apprenticeship. It was beginning, at long last to 165 00:16:17.240 --> 00:16:21.559 make some headway against his financial burdens. He was about to become famous. 166 00:16:22.320 --> 00:16:26.159 He began writing in Latin, of course, the book that he knew would 167 00:16:26.159 --> 00:16:30.159 have an impact far greater than anything else. The evidence suggests indeed, by 168 00:16:30.159 --> 00:16:36.200 sixteen oh eight he had come really close to finishing this book that we can 169 00:16:36.240 --> 00:16:41.000 find its text produced in Latin, within its Italian dialogue on the two sciences. 170 00:16:41.519 --> 00:16:45.519 But one thing that's really interesting about all of this is that if Galileo 171 00:16:45.679 --> 00:16:49.440 was an experimental scientist, that is not how he wanted to present himself to 172 00:16:49.480 --> 00:16:55.080 the world. He wanted Europe to look on him as another Archimedes, the 173 00:16:55.200 --> 00:17:00.879 ultimate deductive scientist. The true role of experiment, in Galilee's mind was not 174 00:17:00.919 --> 00:17:07.000 to explain the true role of experiment was to establish facts that deductive reasoning could 175 00:17:07.079 --> 00:17:15.839 then explain. Galileo's experiments were preparatory procedures undertaken in his quest for proofs. 176 00:17:17.160 --> 00:17:22.079 In fact, part of the reason Galileo fastidiously avoided using the term experiment was 177 00:17:22.119 --> 00:17:30.240 his desire to avoid being labeled an experimental scientist. It did not work. 178 00:17:32.759 --> 00:17:38.880 To one contemporary Galileo was quote the founder of the experimental method in all its 179 00:17:38.920 --> 00:17:47.319 exactness end quote. After his death, Galileo's students founded the Academia del Cimento, 180 00:17:48.160 --> 00:17:55.519 dedicated to the pursuit of scientific knowledge through experiment and experimentation. Frankly, 181 00:17:55.880 --> 00:18:00.359 a Galileo published his book on Projectiles and Falling Bodies and done nothing else. 182 00:18:00.880 --> 00:18:04.839 He would have been a significant figure in the history of science, the founder 183 00:18:06.000 --> 00:18:11.000 of modern physics, the greatest physicist before Newton. In later years, Galleo's 184 00:18:11.000 --> 00:18:17.599 friends urged him repeatedly to publish, but he didn't do so until sixteen thirty 185 00:18:17.599 --> 00:18:22.880 eight. This is a thirty year delay that cries out for an explanation. 186 00:18:23.200 --> 00:18:29.200 I mean Galleo had endless opportunities to publish. He could have published at any 187 00:18:29.240 --> 00:18:33.359 time after sixteen sixteen. Banned from defending Copernicanism. This would have been the 188 00:18:33.400 --> 00:18:38.160 sensible thing to do. He even had a clean copy of a draft prepared 189 00:18:38.160 --> 00:18:42.640 in sixteen eighteen so that he could resume work. And for this delay, 190 00:18:42.640 --> 00:18:48.319 there's really only one explanation that works, and that is in Galileo's mind, 191 00:18:48.960 --> 00:18:55.519 this project was inseparable from the much larger and in his mind more important one, 192 00:18:56.359 --> 00:19:02.680 the campaign to vindicate Copernicus. Prestige and fame weren't enough for Galleo. 193 00:19:03.359 --> 00:19:08.440 Proving ours thought all wrong wasn't enough for Galleo. Revolutionizing physics is not enough 194 00:19:08.960 --> 00:19:18.000 for Galileo. There was something else that mattered. But what exactly was that 195 00:19:18.160 --> 00:19:26.319 something? And this is I think, really the question, because it defines 196 00:19:26.799 --> 00:19:32.000 what Galileo was all about. And in Galileo's view, the answer to this 197 00:19:32.079 --> 00:19:37.759 question is obvious. He wrote as follows. Quote. The constitution of the 198 00:19:37.839 --> 00:19:41.960 universe, I that is, Galileo believe, may be set in first place 199 00:19:42.400 --> 00:19:48.880 among all natural things that can be known, for coming before all others in 200 00:19:48.000 --> 00:19:55.799 grandeur by reason of its universal context. It must stand above them all in 201 00:19:55.920 --> 00:20:04.880 nobility, as their rule and standard. End quote. No other thing stood 202 00:20:04.880 --> 00:20:11.759 above the universe in Galileo's mind, everything depended upon it, and in his 203 00:20:11.960 --> 00:20:21.200 mind Copernicus had it right. But how to prove it well? The answer, 204 00:20:21.240 --> 00:20:23.720 it turns out, as we'll turn to now, is you have to 205 00:20:23.839 --> 00:20:40.039 change how you see. In autumn of six oh four, a new star 206 00:20:40.279 --> 00:20:45.680 appeared in the sky. News of it spread rapidly amongst those interested in astronomy. 207 00:20:45.599 --> 00:20:51.720 Thirty years earlier, in fifteen seventy two, ticobrahe had turned a new 208 00:20:51.799 --> 00:20:56.079 star into quite the celebration throughout Europe. Now, of course, the problem 209 00:20:56.200 --> 00:21:03.160 is is, according to Aristotelian philosopher, the heavens were unchanging, eternal, 210 00:21:03.759 --> 00:21:07.440 perfect. There could be no change in the heavens, and any change that 211 00:21:07.519 --> 00:21:12.880 did take place had to occur in the vicinity of Earth. In their view. 212 00:21:12.960 --> 00:21:17.880 Consequently, the choice was simple. Either that new star wasn't new at 213 00:21:17.880 --> 00:21:21.440 all, it had always been there, or it wasn't a star at all, 214 00:21:21.960 --> 00:21:27.960 but some peculiar phenomenon in the atmosphere. Since Tico's new star soon disappeared, 215 00:21:29.000 --> 00:21:33.839 the argument was left unfinished, to be immediately reawakened by the appearance of 216 00:21:33.920 --> 00:21:41.319 this nova in sixteen oh four. As a Copernicus Galileo, of course, 217 00:21:41.400 --> 00:21:45.880 knew where he stood. If Copernicus was right, the distinction between a sublunary 218 00:21:47.160 --> 00:21:53.480 and superluinary world was misconceived. There was no distinction between Earth and the heavens. 219 00:21:53.920 --> 00:21:59.359 The Earth was in the heavens and inseparable from them. If there was 220 00:21:59.400 --> 00:22:03.400 some change on Earth, then equally there could be change in the heavens. 221 00:22:04.640 --> 00:22:10.799 As someone who taught the military sciences, Galileo also knew how to measure distances. 222 00:22:11.759 --> 00:22:15.319 He knew it was not necessary to approach an object to work out how 223 00:22:15.319 --> 00:22:18.960 far away it was, so long as there was some other point of reference 224 00:22:18.160 --> 00:22:25.240 whose distance was known. By looking at an object from different positions, you 225 00:22:25.279 --> 00:22:30.799 could see how its relationship to other objects altered. Simple geometry could turn a 226 00:22:30.839 --> 00:22:36.559 measurement of a parallax into a calculation of distance. If the new star, 227 00:22:36.640 --> 00:22:40.839 when looked at from different places on the Earth's surface, had an unchanging relationship 228 00:22:40.880 --> 00:22:45.799 to the star around it, then it was very far away, clearly much 229 00:22:45.119 --> 00:22:52.440 further away than the moon. Galileo had soon collected the information to prove that 230 00:22:52.519 --> 00:22:56.960 the new star was indeed a star, that it was certainly not closer to 231 00:22:56.000 --> 00:23:00.240 the Earth than the moon. He gave a series of public lectures on the 232 00:23:00.279 --> 00:23:07.640 new Star, attracting large audiences and provoking vigorous debate. Galileo must have considered 233 00:23:07.640 --> 00:23:12.759 publishing a version of his lectures on the nova. Certainly, given the mood 234 00:23:12.799 --> 00:23:17.799 in Europe at the time, they would have sold well and would have constituted 235 00:23:18.039 --> 00:23:23.759 his first proper scientific publication. In the autumn of sixteen oh four, Galileo 236 00:23:23.880 --> 00:23:29.440 could show that the new star's location appeared to be the same when viewed from 237 00:23:29.440 --> 00:23:34.119 different European cities. The star then disappeared below the horizon of the night sky, 238 00:23:34.759 --> 00:23:41.079 to reappear in the spring of sixteen oh five. It was clearly Galileo's 239 00:23:41.079 --> 00:23:45.640 hope that when it reappeared, its relative position would have changed. If Copernicus 240 00:23:45.680 --> 00:23:49.799 was correct, he would now be looking at it from a point distance from 241 00:23:49.799 --> 00:23:56.519 his previous point of operation by the diameter of the Earth's orbit. Galileo must 242 00:23:56.519 --> 00:24:03.440 have waited with anxious anticipation for the star's re appearance, but there was no 243 00:24:03.599 --> 00:24:07.480 change in its location, and while this was a disappointment, it wouldn't have 244 00:24:07.480 --> 00:24:14.519 been much of a surprise given Galileo's understandings. Be that as it may. 245 00:24:14.839 --> 00:24:19.240 Galileo's letter made it clear this was a star. This was something in the 246 00:24:19.279 --> 00:24:25.920 heavens, and it was new. And it turned out Galileo had some i'll 247 00:24:25.920 --> 00:24:32.079 put it in air quotes support. You see. In addition to Galileo's letter 248 00:24:32.160 --> 00:24:37.759 slash pamphlet, a second pamphlet appeared defending Galleo's interpretation of the New Star. 249 00:24:38.359 --> 00:24:44.480 It was printed in Florence in sixteen oh six, and it was written by 250 00:24:44.880 --> 00:24:52.319 ali Berto Mari. But it was a ruse. Mari was Galileo. He 251 00:24:52.359 --> 00:24:57.319 had written under a pseudonym. Now, interestingly, in this pamphlet, MARII, 252 00:24:57.400 --> 00:25:04.440 that is, Galileo never explicitly discusses Copernicism, indicating maybe he knew he 253 00:25:04.519 --> 00:25:11.480 wasn't supposed to. But he does refer to Copernakiss a few times, always 254 00:25:11.799 --> 00:25:17.640 with approval. So after just some heated arguments and good natured mockery of the 255 00:25:17.720 --> 00:25:22.160 Ristotelian establishment, Galileo's first involvement in astronomy came to an end, and he 256 00:25:22.200 --> 00:25:26.599 turned his attention back to physics. Early in sixteen oh eight, however, 257 00:25:27.079 --> 00:25:33.559 a Dutch spectacle maker discovered that if a convex lens was held behind a concave 258 00:25:33.680 --> 00:25:38.119 lens, you could enlarge the image. He mounted the lenses in a tube 259 00:25:38.119 --> 00:25:44.680 with a sliding mechanism, thereby making the first telescope. Soon a number of 260 00:25:44.720 --> 00:25:48.880 different people were claiming to be the inventor, and word of the discovery spread 261 00:25:48.279 --> 00:25:56.440 rapidly. In May of sixteen oh nine, Galileo claimed to have quote unquote 262 00:25:56.640 --> 00:26:02.039 reinvented the telescope. Would that really means in this instance is that he made 263 00:26:02.079 --> 00:26:06.960 a telescope without ever really seeing one, and without having been given an account 264 00:26:07.079 --> 00:26:11.519 of how one was constructed. He would later claim that reinventing was just as 265 00:26:11.519 --> 00:26:18.359 difficult as inventing. Archimedes, after all, had invented weapons of war that 266 00:26:18.400 --> 00:26:22.319 no one had been able to reinvent. Galileo would also claim that his knowledge 267 00:26:22.359 --> 00:26:29.160 of optics was crucial for being able to reinvent and improve the telescope. Galileo 268 00:26:29.240 --> 00:26:33.519 certainly had some knowledge of optics, but it is not clear that this played 269 00:26:33.519 --> 00:26:38.039 a significant role in either the reinvention or the improvement of the telescope. All 270 00:26:38.079 --> 00:26:44.440 that was involved was intelligent trial and error, in other words, experimentation. 271 00:26:45.960 --> 00:26:49.440 Galileo saw at once that the number of possible lens combinations was limited, and 272 00:26:49.480 --> 00:26:55.440 so all he had to do now was try them out. Galleo's first telescope, 273 00:26:55.720 --> 00:27:00.000 using lenses made for spectacles, magnified only three times. The best Dutch 274 00:27:00.000 --> 00:27:07.119 telescopes of the day magnified double that, about six times. The lens quality 275 00:27:07.359 --> 00:27:11.400 definitely was poor. There would have been a halo consisting of the colors of 276 00:27:11.400 --> 00:27:15.960 the rainbow around the edges of every object, and the image would have been 277 00:27:15.960 --> 00:27:22.079 blurred because the curvature of the lens was irregular, its value limited. Galileo's 278 00:27:22.160 --> 00:27:27.440 true genius, though, was that he grasped at once that the telescope could 279 00:27:27.440 --> 00:27:33.960 be improved. Now today, we live in a world where manufacturers are constantly 280 00:27:33.000 --> 00:27:38.279 offering us improved version of products. So if you or I had been shown 281 00:27:38.319 --> 00:27:42.839 a primitive telescope, we would have asked immediately how it could be improved. 282 00:27:44.519 --> 00:27:49.240 Galleo's world wasn't like this, though. Even new technologies guns, printing presses, 283 00:27:49.279 --> 00:27:56.559 compasses were improved slowly and over very long periods of time. By the 284 00:27:56.559 --> 00:28:00.880 summer of sixteen oh nine, there were thousands of people mathematician, scientists, 285 00:28:00.920 --> 00:28:07.079 engineers who had seen and used the new telescopes, but Galileo was the only 286 00:28:07.200 --> 00:28:12.400 person, the only one who immediately saw the challenge how could it be improved. 287 00:28:14.519 --> 00:28:18.200 Everything that he had done throughout his life had prepared Galileo for this moment. 288 00:28:21.039 --> 00:28:25.319 Galileos soon that a telescope that magnified eight times. He took this to 289 00:28:25.480 --> 00:28:27.920 Venice, where he displayed it to the city's rulers. It may have been 290 00:28:27.960 --> 00:28:33.599 the first telescope many of them had seen, though some will have known that 291 00:28:33.680 --> 00:28:37.920 others were offering to sell the secret of how to make one. Standing on 292 00:28:37.000 --> 00:28:41.519 the top of the bell tower in Saint Mark's Square, they looked out to 293 00:28:41.599 --> 00:28:48.599 the sea and saw ships through Galileo's telescope that were invisible to the naked eye. 294 00:28:48.720 --> 00:28:56.079 The technology had obvious military potential. Galleo assured them that additionally, equally 295 00:28:56.160 --> 00:29:03.480 good telescopes could be made, supported by powerful friends and associates. He pressed 296 00:29:03.519 --> 00:29:07.519 his claim for reward, and it was agreed that he should receive an appointment 297 00:29:07.559 --> 00:29:11.680 at the university for life and a salary of one thousand ducats a year. 298 00:29:11.519 --> 00:29:15.279 In return, he agreed to spend the rest of his life in the service 299 00:29:15.319 --> 00:29:23.160 of the Venetian state. Now impartial bystanders soon started muttering the Galileo had practiced 300 00:29:23.359 --> 00:29:30.000 nothing but deception. Telescope vendors were spreading out across Europe carrying packs full of 301 00:29:30.079 --> 00:29:36.079 Dutch made telescopes. Soon one good bye a telescope quite cheaply in Saint Mark 302 00:29:36.160 --> 00:29:41.960 Square, right where Galileo had demonstrated this new invention. Now, this, 303 00:29:41.039 --> 00:29:45.599 of course is the first ambiguity, and we don't know the answer to this. 304 00:29:45.720 --> 00:29:49.920 But had Galileo presented himself as the inventor of the telescope or merely as 305 00:29:49.960 --> 00:29:56.359 an improver of the telescope? And of course that leads to another question. 306 00:29:56.319 --> 00:30:00.960 If Galileo's telescopes were better than the other telescopes that were now generally available, 307 00:30:02.960 --> 00:30:06.759 was there a secret to their construction? Or could anyone who put in a 308 00:30:06.759 --> 00:30:12.000 little time and trouble produced an improved telescope. The Venetian establishment seems to have 309 00:30:12.039 --> 00:30:15.960 had its doubts. They couldn't go back on their word unless they were prepared 310 00:30:17.000 --> 00:30:21.359 to charge Galleo with a crime. But by the time the Venetian Senate came 311 00:30:21.400 --> 00:30:23.839 to vote on his reward, it seems clear they felt like they had been 312 00:30:25.160 --> 00:30:30.640 misled. Galileo's new appointment and his new salary was now only set to begin 313 00:30:30.720 --> 00:30:36.519 when his existing appointment came to an end, and the Senate decreed that his 314 00:30:36.559 --> 00:30:41.319 new salary was never to be increased. We could guess that Galleo was offended 315 00:30:41.319 --> 00:30:47.200 by this restriction, seeing it as an invitation to seek patronage elsewhere. The 316 00:30:47.279 --> 00:30:51.079 new salary was, after all, no better than one of his friends, 317 00:30:51.440 --> 00:30:55.440 who went on to double his salary in the years that followed. Although he 318 00:30:55.440 --> 00:31:00.200 didn't receive an appointment for life in sixteen oh nine, both Galleo and the 319 00:31:00.240 --> 00:31:06.880 rulers of Venice were trying to make sense of this new technology. Galileo was 320 00:31:06.880 --> 00:31:11.640 certainly in a position to guess that others would soon be able to produce telescopes 321 00:31:11.680 --> 00:31:15.680 as good as his. But it's also the case that Galileo had kept a 322 00:31:15.799 --> 00:31:22.160 lead in the production for the moment of high power telescopes. By the autumn 323 00:31:22.200 --> 00:31:27.480 of sixteen oh nine, he had a telescope that magnified twenty times. Four 324 00:31:27.559 --> 00:31:33.720 years later, by the beginning of sixteen thirteen, one that magnified thirty times, 325 00:31:33.359 --> 00:31:38.359 and he was still well ahead of the competition. In fact, Galileo 326 00:31:38.920 --> 00:31:47.440 managed to stay ahead for twenty years. Galileo really did have something to offer 327 00:31:47.519 --> 00:31:52.160 Venice, but his telescope was not a new invention, nor was it made 328 00:31:52.200 --> 00:31:56.599 with any special techniques. I don't think that there was any deception here when 329 00:31:56.599 --> 00:32:01.720 dealing with the Venetian government. Rather, what the Venetian government failed to comprehend 330 00:32:01.920 --> 00:32:07.119 was that when they were buying this new technology, they were buying the man 331 00:32:07.319 --> 00:32:13.799 who was committed to improving it. But again, that just wasn't the mindset 332 00:32:14.079 --> 00:32:16.680 of people in early modern Europe, so it's hard to fault them for it. 333 00:32:19.480 --> 00:32:22.559 Now. Interestingly, this is just kind of an aside, But around 334 00:32:22.599 --> 00:32:25.960 the same time we get some correspondence between Galileo and his younger brother. It 335 00:32:27.039 --> 00:32:30.279 seems that Galileo sent him a few telescopes so that he could give them to 336 00:32:30.359 --> 00:32:37.079 influential people and spread word of Galleo's discoveries. His brother sold the telescopes instead 337 00:32:37.240 --> 00:32:40.799 and kept the money. He wrote to Galleo a bit later asking for more 338 00:32:40.839 --> 00:32:46.759 telescopes to sell. Galleo didn't send any. The whole affair is an interesting 339 00:32:46.759 --> 00:32:51.119 reminder of the reality that the great men and women in the past didn't live 340 00:32:51.160 --> 00:32:57.279 in a bubble. They had annoying familial relations too. In Venice, in 341 00:32:57.599 --> 00:33:01.640 June and July, there's about sixteen hours of daylight and only eight in December 342 00:33:01.680 --> 00:33:06.920 and January. In the autumn of sixteen oh nine, as the days shortened, 343 00:33:07.279 --> 00:33:10.880 Galleo turned his improved telescope toward the heavens. He mounted it on some 344 00:33:10.920 --> 00:33:15.680 sort of stand, But still he had to learn how to slow his breathing. 345 00:33:15.400 --> 00:33:20.640 Even his pulse seemed to shape the telescope, and as the evening temperature 346 00:33:20.720 --> 00:33:27.319 dropped, the glasses kept missing up. In early January sixteen ten, he 347 00:33:27.359 --> 00:33:31.039 discovered he could reduce the halo round objects by fitting a circle of masking material 348 00:33:31.119 --> 00:33:36.960 with an oval hole on the end of it over the lens. In photographic 349 00:33:37.039 --> 00:33:42.240 terms, he stopped the lens down. Still, the stars remained mere points 350 00:33:42.240 --> 00:33:45.559 in the heavens, except that there were many more of them. Now he 351 00:33:45.640 --> 00:33:49.480 discovered that the Milky Way was not a mysterious white band in the sky, 352 00:33:50.160 --> 00:33:54.119 but a vast number of small stars, individually invisible to the naked eye. 353 00:33:54.240 --> 00:33:59.880 Elsewhere there were new stars to be seen. It's easy for the significance of 354 00:33:59.880 --> 00:34:04.079 these new stars to escape a modern reader. It might be thought, it 355 00:34:04.119 --> 00:34:08.760 hardly matters how many stars there are. But Galileo's contemporaries believed that the universe 356 00:34:09.079 --> 00:34:15.239 embodied a rational purpose the Sun, the Moon, and the stars existed for 357 00:34:15.320 --> 00:34:17.639 one purpose, and one purpose only, to give light to the Earth. 358 00:34:19.960 --> 00:34:25.480 Invisible stars were a weird new concept. What purpose could a star serve if 359 00:34:25.559 --> 00:34:31.159 no one could see it? Only a few Copernicans had imagined a universe so 360 00:34:31.320 --> 00:34:37.039 large that there were distant stars invisible from Earth. As for the planets, 361 00:34:37.800 --> 00:34:43.679 through Galileo's telescope, they were not points, but tiny discs floating in space. 362 00:34:45.119 --> 00:34:49.119 Naturally. Galileo turned his telescope to the Moon, which was so greatly 363 00:34:49.159 --> 00:34:52.360 magnified that he could look at it less than half the time even with his 364 00:34:52.760 --> 00:35:00.320 twenty power telescope. Everyone knew that the Moon wasn't perfectly uniform in a pearance, 365 00:35:00.400 --> 00:35:05.840 but the philosophers still insisted that it had to be a perfect sphere, 366 00:35:06.840 --> 00:35:13.760 even if parts of its surface were more reflective than others. If the Moon 367 00:35:13.800 --> 00:35:19.159 were smooth, the line between the illuminated half and unilluminated half should be perfectly 368 00:35:19.199 --> 00:35:23.880 irregular. But Galileo, looking through his telescope, could see that the line 369 00:35:24.119 --> 00:35:31.280 wasn't regular. Moreover, near the margin between the illuminated and ulluminated half, 370 00:35:31.719 --> 00:35:37.639 he saw two anomalies on the unilluminated side of the margin, he could see 371 00:35:37.719 --> 00:35:43.800 little flecks of light. The sun was clearly reaching some areas before it reached 372 00:35:43.840 --> 00:35:50.280 others. These must be high points. On the illuminated side, he could 373 00:35:50.320 --> 00:35:55.119 see dark spots which the illumination took longer to reach. These must be shadows. 374 00:35:57.760 --> 00:36:01.519 Galileo's interest in painting and his experience looking at paintings where the tricks of 375 00:36:01.639 --> 00:36:07.079 light were used to convey textures and shapes, probably helped him understand what he 376 00:36:07.119 --> 00:36:13.360 was seeing. But he also grasped at once that what he was seeing was 377 00:36:13.440 --> 00:36:19.519 comparable to a familiar phenomenon on Earth. At dusk and dawn, the sun 378 00:36:19.639 --> 00:36:25.360 stays on the mountaintops when the valleys below are deep in shadow. Galileo therefore 379 00:36:27.119 --> 00:36:31.800 had discovered that the Moon had a landscape, a landscape of mountains and valleys. 380 00:36:32.719 --> 00:36:37.519 In this respect, it was just like the Earth, and this was 381 00:36:37.639 --> 00:36:44.159 corroboration of his view that the Earth seen from the Moon would look just like 382 00:36:44.239 --> 00:36:49.639 an enormous moon. But there was so much more. On January seventh, 383 00:36:50.159 --> 00:36:53.679 Galileo turned his telescope to Jupiter and noticed three stars arranged in a line, 384 00:36:53.679 --> 00:36:58.280 with the planet toe to the east, one to the west. He had 385 00:36:58.320 --> 00:37:01.639 assumed that these were yet more fixed stars, But the next day, when 386 00:37:01.639 --> 00:37:06.360 he looked again, now all three stars were to the west of Jupiter. 387 00:37:07.079 --> 00:37:14.239 Although Jupiter itself was moving from east to west, somehow, to fixed stars 388 00:37:14.880 --> 00:37:21.880 had overtaken Jupiter. Galileo now began to observe Jupiter every night. By the 389 00:37:21.920 --> 00:37:27.440 eleventh of January, he had decided that he was observing three satellites orbiting Jupiter. 390 00:37:28.280 --> 00:37:32.159 On the thirteenth he discovered a fourth. Galileo now knew he had made 391 00:37:32.199 --> 00:37:39.400 a truly momentous discovery. By January the thirtieth, he was in Venice arranging 392 00:37:39.440 --> 00:37:44.719 for the publication of a book on his telescopic discoveries, the mountains on the 393 00:37:44.719 --> 00:37:49.079 Moon, the nature of the Milky Way, the moons of Jupiter, all 394 00:37:49.119 --> 00:37:53.400 the while continuing his observations. Galileo was in a hurry. He knew other 395 00:37:53.440 --> 00:37:58.119 people had telescopes, and even if theres weren't as good as his, it 396 00:37:58.159 --> 00:38:01.679 probably wouldn't be long until someone else had a telescope capable of looking at Jupiter's 397 00:38:01.679 --> 00:38:08.280 moons, and so Galileo, now aged forty six, was writing a book. 398 00:38:09.239 --> 00:38:14.480 As he worked, he consistently tinkered with the title suggesting he believed the 399 00:38:14.480 --> 00:38:19.360 book was designed to become a work of great importance. It was common when 400 00:38:19.400 --> 00:38:22.360 printing a book to print the body of the book first, and then to 401 00:38:22.400 --> 00:38:25.639 add the prefatory matter. It's clear that this happened in the case of Galileo's 402 00:38:25.679 --> 00:38:32.000 observations. The large title on the first page to be printed was Astronomous Nunicus, 403 00:38:32.519 --> 00:38:39.639 which translates to the astronomical message or astronomical Messenger. In his correspondence, 404 00:38:39.639 --> 00:38:46.159 Galileo referred to the book in Italian as avisio stronimko or astronomical news, or 405 00:38:46.199 --> 00:38:52.119 maybe even starry news. But the fine old title, which was finished only 406 00:38:52.119 --> 00:38:58.599 as the last pages went to press on March the twelfth, was Siderius nuncus, 407 00:38:59.119 --> 00:39:05.159 or as we know the title today, the Starry Messenger, a Messenger 408 00:39:05.679 --> 00:39:12.239 from the stars. The book proved to be a collection of observations, or 409 00:39:12.280 --> 00:39:19.159 more like a report than a narrative work. Galileo despised books about books. 410 00:39:19.840 --> 00:39:22.159 Prior to him, that was kind of all you really ever got out of 411 00:39:22.199 --> 00:39:28.559 scientists. Galileo went out of his way in writing his book to prove it 412 00:39:28.639 --> 00:39:32.840 was different. Indeed, after its publication, every other book on the stars 413 00:39:34.079 --> 00:39:40.159 became irrelevant, at least according to Galileo. Galleo doesn't offer facts in The 414 00:39:40.199 --> 00:39:49.920 Starry Messenger. He offers us observations. Some require no interpretation at all, 415 00:39:50.039 --> 00:39:54.639 others just a little deductive reasoning. Shadows on the Moon become craters with a 416 00:39:54.679 --> 00:39:59.760 little thought. For example, some of the illustrations of the moon within the 417 00:39:59.800 --> 00:40:06.480 book book are amazingly accurate. They did have one significant flaw, however, 418 00:40:06.519 --> 00:40:10.639 which is puzzled later scholars. A singular feature, a crater, which Galleo 419 00:40:10.679 --> 00:40:15.639 describes as being as large as Bohemia. It appears in large effects, so 420 00:40:15.880 --> 00:40:20.840 big that critics have complained that if the illustrations were accurate, it would be 421 00:40:20.920 --> 00:40:24.119 visible to the naked eye. Now, the simple answer as to why this 422 00:40:24.280 --> 00:40:30.960 appears is that Galleo was persuaded that this singular feature was far larger and more 423 00:40:30.000 --> 00:40:36.719 noticeable than any other because he had already seen it with his naked eye. 424 00:40:36.880 --> 00:40:42.039 In the end, what's happening here in The Starry Messenger is Galileo is embellishing 425 00:40:42.079 --> 00:40:45.800 something because he believes so firmly that he is seeing it or has seen it 426 00:40:45.840 --> 00:40:51.519 with the naked eye. Did he probably not, But it doesn't change the 427 00:40:51.559 --> 00:40:57.880 fact that as a crater it's large. Now. Interestingly, after the Starry 428 00:40:57.920 --> 00:41:01.760 Messenger, Galleo did not include any illustrations in his books, and the reason 429 00:41:01.800 --> 00:41:07.519 is quite obvious. He expected readers to have or to obtain telescopes of their 430 00:41:07.559 --> 00:41:12.559 own. It was as though he was saying to all of Europe, the 431 00:41:12.599 --> 00:41:16.880 answers are there, go and see for yourselves. But then, on the 432 00:41:16.920 --> 00:41:22.159 twelfth of February, Galleo received a letter from Belisario Vinta, the secretary to 433 00:41:22.199 --> 00:41:28.320 the Grand Duke of Florence. He reported that the Grand Duke was quote unquote 434 00:41:28.679 --> 00:41:35.400 stupefied by news of Galileo's discoveries. Galileo replied the very next day with the 435 00:41:35.400 --> 00:41:38.360 Grand Duke, who was called Cosimo, he has succeeded his father here before, 436 00:41:39.400 --> 00:41:45.079 like some of these new satellites to be named the Cosmic stars after him? 437 00:41:45.800 --> 00:41:49.360 Or would he prefer them to be named the Medician stars, given that 438 00:41:49.400 --> 00:41:52.400 they were four of them and he had three brothers. Quickly the answer came 439 00:41:52.440 --> 00:41:55.880 back. It was written on the twenty of the February and would have reached 440 00:41:55.920 --> 00:42:00.800 Galileo a few days later. Cosmic, they wrote, was too ambiguous it 441 00:42:00.840 --> 00:42:07.159 would not automatically make people think of Cosimo Medician was better. Galileo made his 442 00:42:07.239 --> 00:42:13.280 arrangements for publication at the end of January. He had an effect booked time 443 00:42:13.280 --> 00:42:16.559 on the press and could not wait for a reply. When Vinta's letter relaying 444 00:42:16.559 --> 00:42:22.320 the Grand Duke's choice arrived, the word cosmica was replaced with Medica. It 445 00:42:22.320 --> 00:42:27.000 would have been shortly after this that Galileo chose the final title for the book 446 00:42:27.400 --> 00:42:31.199 and wrote a prefatory letter in praise of Cosimo de Medici. There's another more 447 00:42:31.280 --> 00:42:37.079 significant discovery to be made from examining the surviving manuscript. There are three passages 448 00:42:37.119 --> 00:42:45.320 in this book in which Galileo unequivocally declares his support for Copernicanism. Now it's 449 00:42:45.440 --> 00:42:49.840 clear that when Galileo received Vinta's letter on the twelfth of February, he had 450 00:42:49.920 --> 00:42:55.960 virtually completed a draft manuscript which contained not a single reference to Copernicanism. The 451 00:42:57.000 --> 00:43:00.920 first and third sections of the book open with references to Venus and Mars orbiting 452 00:43:00.920 --> 00:43:06.000 the sun, but a knowledgeable contemporary would have been more likely to interpret this 453 00:43:06.440 --> 00:43:12.199 as a reference to Tico Brahe, not Copernicus. In mid February. Therefore, 454 00:43:12.599 --> 00:43:17.760 Galileo made two bold and consequential decisions. He decided to put a reference 455 00:43:19.199 --> 00:43:23.719 to sideda Cosmiica in the title of his book and into its conclusion. And 456 00:43:23.800 --> 00:43:30.639 he decided to commit himself explicitly to a Copernican argument and to include within his 457 00:43:30.719 --> 00:43:38.719 book an implicit attack on Tico Brahe. Galileo explains then that the phenomenon of 458 00:43:38.760 --> 00:43:43.559 earth shine and shows that the Earth lights the Moon just as the Moon lights 459 00:43:43.559 --> 00:43:49.599 the Earth. As Galileo says, earth shine is powerful evidence in favor of 460 00:43:49.639 --> 00:43:54.119 the Copernican claim that there's no difference between the Earth and the other heavenly bodies. 461 00:43:55.760 --> 00:44:00.960 Of the discovery is reported in The Starry Messenger. This is one of 462 00:44:00.000 --> 00:44:06.559 two which tell against the cosmology of Ticobrahe. The implications of the other, 463 00:44:07.079 --> 00:44:10.440 the discovery that planets can have moons so that the Earth principle could be a 464 00:44:10.480 --> 00:44:16.360 planet, were only put in the final pages. It's easy to see what 465 00:44:16.679 --> 00:44:23.480 changed, or at least what Galileo hoped was about to change. When Galileo 466 00:44:23.719 --> 00:44:29.360 entered into the contract with his princer, he was just an insignificant professor, 467 00:44:30.480 --> 00:44:35.840 But after the twelfth of February, he became convinced that he was about to 468 00:44:35.840 --> 00:44:42.320 receive the support of the powerful Medici family, and therefore he was ready to 469 00:44:42.360 --> 00:44:47.239 come out in support of Copernicanism. It's worth pausing to see what Galileo was 470 00:44:47.320 --> 00:44:52.679 doing in mid February. He was on the threshold of publishing a book that 471 00:44:52.719 --> 00:45:00.920 would stupefy the scholarly world. Success was assured this was definitely going to sell, 472 00:45:00.960 --> 00:45:05.000 and so he decided to raise the stakes and make a success uncertain. 473 00:45:05.840 --> 00:45:09.599 He committed himself to dedicating the book to Cosimo Dimnici before he even had permission 474 00:45:09.639 --> 00:45:15.000 to do so. Even more boldly, he decided to maximize the opposition to 475 00:45:15.039 --> 00:45:22.880 his book and minimize support for it by not making it simply anti Ptolemaic but 476 00:45:22.039 --> 00:45:30.119 explicitly Copernican. Of course, since he believed in Copernicanism, this had the 477 00:45:30.159 --> 00:45:34.960 advantage of allowing him to speak his mind, but it was a rash move 478 00:45:35.480 --> 00:45:40.000 to the extreme. Interestingly enough, if you look at the book, the 479 00:45:40.079 --> 00:45:45.840 rhetorical high point occurs in almost the exact middle, and it's remarkable in about 480 00:45:45.880 --> 00:45:53.719 three respects. It's transparently Copernican. It announces Galileo's great project, the system 481 00:45:53.760 --> 00:45:59.960 of the world, and it's only one of two places where Galleo ever uses 482 00:46:00.119 --> 00:46:06.920 the word experiment in Latin. Some of these passages lay out Galleo's thoughts on 483 00:46:07.000 --> 00:46:12.639 these new discoveries, and with these words he both announces an imminent intellectual revolution 484 00:46:13.320 --> 00:46:16.159 and provides a sketch of his much larger work, Dialogue, which would not 485 00:46:16.199 --> 00:46:22.800 be published until sixteen thirty two. Here's the relevant passage quote, Let these 486 00:46:22.840 --> 00:46:25.800 few things said hear about this matter suffice we will say more in our system 487 00:46:25.840 --> 00:46:30.039 of the world, where with very many arguments and experiments, a very strong 488 00:46:30.079 --> 00:46:35.559 reflection of solar light from the Earth is demonstrated to those who claim that the 489 00:46:35.599 --> 00:46:38.519 Earth is to be excluded from the dance of the stars, especially because she 490 00:46:38.599 --> 00:46:44.519 is devoid of motion and light. For we will demonstrate that she is movable, 491 00:46:45.119 --> 00:46:50.360 and that she surpasses the moon in its brightness, and that she is 492 00:46:50.440 --> 00:46:53.360 not the dump heap of filth and dregs of the universe. And we will 493 00:46:53.400 --> 00:47:00.199 confirm this with innumerable arguments from nature. End quote. The story Messenger was 494 00:47:00.239 --> 00:47:05.760 published on the thirteenth of March. Within a week, five hundred and fifty 495 00:47:05.760 --> 00:47:09.159 copies were gone. Galileo, who was supposed to get thirty free copies of 496 00:47:09.199 --> 00:47:15.119 the book received on these six. Because it's sold so quickly, there is 497 00:47:15.199 --> 00:47:22.400 no doubt that fame for Galileo had arrived at last. But at what cost.