WEBVTT 00:00:00.000 --> 00:00:03.960 We are diving deep today into a single seismic 00:00:03.960 --> 00:00:06.620 figure whose life marks the exact moment the 00:00:06.620 --> 00:00:13.810 European mind shifted gears. Galileo. It's truly 00:00:13.810 --> 00:00:17.010 difficult to summarize his impact. Galileo, born 00:00:17.010 --> 00:00:20.129 in 1554, isn't just a historical figure. He is 00:00:20.129 --> 00:00:22.890 the origin point for so much of what we now call 00:00:22.890 --> 00:00:25.489 modernity. Right. He's widely credited as the 00:00:25.489 --> 00:00:27.649 father of modern science, the father of, well, 00:00:27.690 --> 00:00:30.670 modern era classical physics, of observational 00:00:30.670 --> 00:00:32.750 astronomy, and critically, the scientific method 00:00:32.750 --> 00:00:35.149 itself. You're really looking at the foundational 00:00:35.149 --> 00:00:37.609 architect of how we approach verifiable knowledge. 00:00:38.200 --> 00:00:40.240 And when you examine the source material we've 00:00:40.240 --> 00:00:42.340 gathered, this incredibly rich, comprehensive 00:00:42.340 --> 00:00:45.320 summary of his life and work, what becomes immediately 00:00:45.320 --> 00:00:47.280 clear is his sheer range. I mean, he was a true 00:00:47.280 --> 00:00:49.679 polymath. Absolutely. We're exploring the intersection 00:00:49.679 --> 00:00:52.579 of astronomy, physics, engineering, natural philosophy 00:00:52.579 --> 00:00:55.380 and mathematics, all funneled through one man's 00:00:55.380 --> 00:00:57.960 relentless curiosity. So our mission in this 00:00:57.960 --> 00:01:00.460 deep dive is to really unpack the entire spectrum 00:01:00.460 --> 00:01:02.600 of his career. We'll follow him from his origins 00:01:02.600 --> 00:01:06.120 in Pisa, where necessity shaped his early inventive 00:01:06.120 --> 00:01:08.239 genius. And that necessity part is key. It's 00:01:08.239 --> 00:01:10.760 crucial. Then we'll move through his revolutionary 00:01:10.760 --> 00:01:13.159 work in kinematics, the science of motion, and 00:01:13.159 --> 00:01:16.519 his, well, explosive astronomical discoveries, 00:01:16.900 --> 00:01:20.079 culminating, of course, in his historic and devastating 00:01:20.079 --> 00:01:22.799 conflict with the church over heliocentrism. 00:01:22.819 --> 00:01:25.980 To understand the drive behind his work, you 00:01:25.980 --> 00:01:28.359 absolutely need that personal context. Yeah. 00:01:28.560 --> 00:01:30.700 Galileo's career was propelled by this powerful 00:01:30.700 --> 00:01:34.299 and often contradictory force. The pure intellectual 00:01:34.299 --> 00:01:37.540 thrill of discovery mixed with raw, grinding 00:01:37.540 --> 00:01:40.900 financial necessity. He needed reliable income, 00:01:41.019 --> 00:01:43.480 which pushed him heavily toward practical engineering 00:01:43.480 --> 00:01:46.319 and commercially viable inventions very early 00:01:46.319 --> 00:01:48.900 in his life. That financial pressure is the perfect 00:01:48.900 --> 00:01:50.959 lens through which to view his early career because 00:01:50.959 --> 00:01:53.239 it fundamentally dictated his academic trajectory 00:01:53.239 --> 00:01:55.980 and his inventive output. Okay, let's start there 00:01:55.980 --> 00:01:58.620 then, with his roots in Pisa. part of the Duchy 00:01:58.620 --> 00:02:00.859 of Florence. He came from a culturally sophisticated 00:02:00.859 --> 00:02:04.000 but not wealthy background. Right. His father, 00:02:04.180 --> 00:02:06.959 Vincenzo Galilei, was a major figure in the music 00:02:06.959 --> 00:02:09.960 world, a leading lutenist, a composer, and a 00:02:09.960 --> 00:02:13.280 music theorist. And Galileo himself was an accomplished 00:02:13.280 --> 00:02:15.800 musician. He played the lute and had a lifelong 00:02:15.800 --> 00:02:18.639 interest in harmony and acoustics. But musical 00:02:18.639 --> 00:02:21.139 distinction doesn't exactly equate to financial 00:02:21.139 --> 00:02:23.939 security, especially not in 16th century Florence. 00:02:24.180 --> 00:02:26.439 Not at all. And this is where that notorious 00:02:26.439 --> 00:02:29.340 financial burden kicks in, and it's a story of 00:02:29.340 --> 00:02:33.740 familial duty and, well... Tell us more about 00:02:33.740 --> 00:02:35.120 that. It sounds like more than just standard 00:02:35.120 --> 00:02:37.500 debt. Oh, it was much more than personal debt. 00:02:37.580 --> 00:02:39.580 It was structural, a familial responsibility. 00:02:40.219 --> 00:02:43.180 The big problem was his younger brother, Michelangelo, 00:02:43.259 --> 00:02:46.340 also a musician, perhaps a bit less stable than 00:02:46.340 --> 00:02:49.620 Galileo. He repeatedly failed to contribute his 00:02:49.620 --> 00:02:52.020 promised share of the dowries owed to their brothers 00:02:52.020 --> 00:02:54.400 -in -law. And that's a critical detail. In that 00:02:54.400 --> 00:02:57.060 era, dowries were often installment payments 00:02:57.060 --> 00:02:59.560 or contractual obligations that could lead to 00:02:59.560 --> 00:03:01.560 serious legal disputes if they weren't fulfilled. 00:03:01.800 --> 00:03:04.780 Exactly. The Snorrises detail legal attempts 00:03:04.780 --> 00:03:07.439 by their in -laws to secure these long overdue 00:03:07.439 --> 00:03:10.909 payments, which created immense stress. On top 00:03:10.909 --> 00:03:13.469 of that, Michelangelo in his musical wanderings 00:03:13.469 --> 00:03:15.969 often borrowed funds from Galileo that he needed 00:03:15.969 --> 00:03:18.229 for his own survival. So it was a constant drain. 00:03:18.389 --> 00:03:21.069 A constant financial drain. It just amplified 00:03:21.069 --> 00:03:23.770 Galileo's desire to create inventions that would 00:03:23.770 --> 00:03:26.650 bring him immediate, reliable, and maybe even 00:03:26.650 --> 00:03:30.610 patented income. So his father, Vincenzo, he 00:03:30.610 --> 00:03:33.090 had a clear vision for Galileo's future, right? 00:03:33.169 --> 00:03:35.409 He was hoping to bypass the unpredictability 00:03:35.409 --> 00:03:38.560 of an academic or artistic life. He did. When 00:03:38.560 --> 00:03:40.500 Galileo initially enrolled at the University 00:03:40.500 --> 00:03:43.800 of Pisa in 1580, it was not for science. His 00:03:43.800 --> 00:03:45.879 father insisted he pursues a medical degree. 00:03:46.159 --> 00:03:48.560 Why medicine? He believed firmly that a physician 00:03:48.560 --> 00:03:50.740 commanded a far higher and more stable income 00:03:50.740 --> 00:03:53.319 than a mathematician or a philosopher. It was 00:03:53.319 --> 00:03:55.939 a pragmatic choice. Which leads us directly to 00:03:55.939 --> 00:03:58.800 that crucial pivot that really changed the course 00:03:58.800 --> 00:04:00.759 of science. He was supposed to be studying Galen 00:04:00.759 --> 00:04:02.840 and Hippocrates, but through a stroke of chance, 00:04:03.020 --> 00:04:05.560 he found his true calling. The story goes that 00:04:05.560 --> 00:04:08.000 he accidentally attended a lecture on Euclidean 00:04:08.000 --> 00:04:10.419 geometry, just stumbled into it, and that one 00:04:10.419 --> 00:04:12.800 chance encounter was enough to spark his passion. 00:04:12.979 --> 00:04:15.539 And his father was not pleased. Not at first. 00:04:15.879 --> 00:04:18.379 He spent the next few months trying to persuade 00:04:18.379 --> 00:04:21.060 his highly pragmatic and reluctant father to 00:04:21.060 --> 00:04:23.000 let him switch his studies to mathematics and 00:04:23.000 --> 00:04:25.860 natural philosophy. Vincenzo eventually agreed, 00:04:26.160 --> 00:04:28.779 but only after a lot of debate, likely still 00:04:28.779 --> 00:04:31.670 worried about his son's future income. and his 00:04:31.670 --> 00:04:33.870 early work is just defined by these beautiful 00:04:33.870 --> 00:04:38.379 fundamental observations almost accidental insights 00:04:38.379 --> 00:04:41.240 that he turned into scientific principles. The 00:04:41.240 --> 00:04:44.019 swinging chandelier is the iconic start. That 00:04:44.019 --> 00:04:46.980 observation happened in 1581, reportedly in the 00:04:46.980 --> 00:04:50.339 Cathedral of Pisa. He noticed a large lamp suspended 00:04:50.339 --> 00:04:52.800 by a long chain swinging widely because of air 00:04:52.800 --> 00:04:55.000 currents, and he started comparing the time it 00:04:55.000 --> 00:04:57.240 took for the chandelier to complete one full 00:04:57.240 --> 00:05:00.540 oscillation to his own pulse. He's using his 00:05:00.540 --> 00:05:03.319 own heartbeat as a clock. Exactly. And he noticed 00:05:03.319 --> 00:05:05.740 that even as the arc decreased, as the swings 00:05:05.740 --> 00:05:08.319 got shorter and shorter, the time period remained 00:05:08.319 --> 00:05:11.139 constant. That's the principle of isochronism. 00:05:11.300 --> 00:05:14.060 So he went home to test it. Correct. When he 00:05:14.060 --> 00:05:16.740 returned home, he tested this with pendulums 00:05:16.740 --> 00:05:19.199 of equal length, setting one to swing widely 00:05:19.199 --> 00:05:21.759 and one with a tiny arc, confirming they kept 00:05:21.759 --> 00:05:24.439 time together. Now, we do have to add a little 00:05:24.439 --> 00:05:27.899 caveat for you here. This property, isochronism, 00:05:28.060 --> 00:05:30.769 is only approximately true. Right. The period 00:05:30.769 --> 00:05:33.089 does change a little. It does. The period of 00:05:33.089 --> 00:05:35.089 a pendulum varies slightly with the amplitude 00:05:35.089 --> 00:05:37.730 of the swing. It took almost a century until 00:05:37.730 --> 00:05:39.990 Christian Huygens mathematically refined the 00:05:39.990 --> 00:05:42.449 properties of the cycloid to understand true 00:05:42.449 --> 00:05:45.529 isochronism, which then allowed him to create 00:05:45.529 --> 00:05:48.930 the first highly accurate pendulum timepiece. 00:05:49.170 --> 00:05:51.569 But Galileo's observation was the foundational 00:05:51.569 --> 00:05:54.129 breakthrough. Beyond the pendulum. What were 00:05:54.129 --> 00:05:56.230 the early inventions that secured his reputation 00:05:56.230 --> 00:05:58.490 in the scholarly world, the ones that bridged 00:05:58.490 --> 00:06:00.709 his practical skills and his mathematical mind? 00:06:00.930 --> 00:06:03.910 He was a fantastic practical engineer. In 1586, 00:06:04.089 --> 00:06:06.250 he published a small book detailing the design 00:06:06.250 --> 00:06:08.709 of a hydrostatic balance he had invented, known 00:06:08.709 --> 00:06:11.269 as la bilancetta. And what did that do? This 00:06:11.269 --> 00:06:13.730 balance was designed to accurately measure the 00:06:13.730 --> 00:06:16.009 relative densities of objects by weighing them 00:06:16.009 --> 00:06:19.750 in air and then in water. This publication, though 00:06:19.750 --> 00:06:22.589 short, was his first major intellectual success. 00:06:22.730 --> 00:06:25.209 It brought him widespread scholarly notice across 00:06:25.209 --> 00:06:28.230 Italy. I noticed the source material also mentions 00:06:28.230 --> 00:06:30.889 his study of disegno. Can you define that for 00:06:30.889 --> 00:06:33.310 us and explain how it connected to his engineering 00:06:33.310 --> 00:06:35.730 work? Right. Disegno in the Renaissance context 00:06:35.730 --> 00:06:38.610 means so much more than simple drawing. It encompasses 00:06:38.610 --> 00:06:42.290 the entire concept of design, drawing, and crucially, 00:06:42.350 --> 00:06:45.050 the underlying mathematical principles needed 00:06:45.050 --> 00:06:47.850 for projection and perspective. Ah, so it's a 00:06:47.850 --> 00:06:50.889 technical skill. A highly technical skill. Galileo's 00:06:50.889 --> 00:06:53.110 early applied career involved teaching perspective 00:06:53.110 --> 00:06:55.970 and chiaroscuro, the dramatic use of light and 00:06:55.970 --> 00:06:59.110 shadow, at the Accademia delle Arti del Disegno 00:06:59.110 --> 00:07:02.490 in Florence starting in 1588. This training was 00:07:02.490 --> 00:07:04.870 essential. It equipped him not only to draw his 00:07:04.870 --> 00:07:07.490 scientific observations with precision, but also 00:07:07.490 --> 00:07:09.949 to think spatially and mathematically about design 00:07:09.949 --> 00:07:12.370 and engineering problems. So he wasn't just a 00:07:12.370 --> 00:07:15.089 math guy, he was a design guy too. Precisely. 00:07:15.089 --> 00:07:17.509 And his other early engineering included creating 00:07:17.509 --> 00:07:20.350 a thermoscope. a forerunner of the modern thermometer, 00:07:20.589 --> 00:07:23.310 though it lacked a standardized scale, and various 00:07:23.310 --> 00:07:25.970 military compasses, which he later refined into 00:07:25.970 --> 00:07:28.290 highly marketable instruments. This combination 00:07:28.290 --> 00:07:30.949 of mathematical theory and practical design quickly 00:07:30.949 --> 00:07:34.279 secured his academic path then. It did. He secured 00:07:34.279 --> 00:07:36.759 the prestigious chair of mathematics in Pisa 00:07:36.759 --> 00:07:40.500 in 1589. But the intellectual environment, well, 00:07:40.639 --> 00:07:42.480 it truly blossomed when he moved to the much 00:07:42.480 --> 00:07:45.759 larger University of Padua in 1592. He taught 00:07:45.759 --> 00:07:48.199 geometry, mechanics, and astronomy there for 00:07:48.199 --> 00:07:50.899 18 years. This was his period of stability. And 00:07:50.899 --> 00:07:53.839 practical innovation, yes. He even secured a 00:07:53.839 --> 00:07:56.519 patent during this time, linking right back to 00:07:56.519 --> 00:07:59.730 that necessity for income. In 1594, he obtained 00:07:59.730 --> 00:08:01.850 a patent from the Venetian Republic for a horse 00:08:01.850 --> 00:08:03.649 -powered water pump designed for irrigation. 00:08:03.970 --> 00:08:07.449 His time at Padua, until 1610, was his stable 00:08:07.449 --> 00:08:09.370 base where he developed his most fundamental 00:08:09.370 --> 00:08:11.769 physical theories. Though the world wouldn't 00:08:11.769 --> 00:08:14.470 truly know his name until he aimed a lens at 00:08:14.470 --> 00:08:16.189 the sky. And that's when everything changes. 00:08:16.470 --> 00:08:19.269 The narrative takes a really sharp turn in 1609. 00:08:20.029 --> 00:08:23.069 The telescope had just been invented, or at least 00:08:23.069 --> 00:08:26.449 described, in the Netherlands. Galileo didn't 00:08:26.449 --> 00:08:28.970 invent the concept, but he revolutionized the 00:08:28.970 --> 00:08:31.689 instrument and, critically, his application of 00:08:31.689 --> 00:08:33.950 it. That is the perfect distinction. He developed 00:08:33.950 --> 00:08:36.129 his own refracting telescope, or canocchiale, 00:08:36.330 --> 00:08:39.269 after hearing descriptions of Hans Lippershey's 00:08:39.269 --> 00:08:42.190 1608 patent attempt. But where others produced 00:08:42.190 --> 00:08:44.710 these crude instruments, Galileo quickly mastered 00:08:44.710 --> 00:08:47.509 the optics. He ground his own lenses to achieve 00:08:47.509 --> 00:08:50.350 far greater clarity and magnification up to about 00:08:50.350 --> 00:08:52.649 30 times. And his instrument was immediately 00:08:52.649 --> 00:08:55.049 practical. which of course helped fund his research. 00:08:55.289 --> 00:08:57.850 It was highly practical. Unlike the Kruder models, 00:08:58.149 --> 00:09:00.870 his instruments produced magnified, upright images 00:09:00.870 --> 00:09:03.870 on Earth, making them ideal terrestrial spyglasses. 00:09:04.250 --> 00:09:06.710 He quickly saw the commercial application, demonstrating 00:09:06.710 --> 00:09:09.690 them to Venetian lawmakers in August 1609, who 00:09:09.690 --> 00:09:11.590 used them for military and merchant observation. 00:09:12.049 --> 00:09:14.370 He was making money off them. He was. Selling 00:09:14.370 --> 00:09:16.049 these instruments to merchants who found them 00:09:16.049 --> 00:09:17.970 indispensable at sea and for coastal defense 00:09:17.970 --> 00:09:21.029 became a profitable sideline. It finally generated 00:09:21.029 --> 00:09:22.990 that reliable income he had sought for years. 00:09:23.519 --> 00:09:25.860 But the real revolution began when he pointed 00:09:25.860 --> 00:09:28.580 that profitable instrument up. He published his 00:09:28.580 --> 00:09:32.259 initial findings in March 1610 in the brief treatise, 00:09:32.279 --> 00:09:35.879 Sedarius Nuncius, or Starry Messenger. The book 00:09:35.879 --> 00:09:37.960 was essentially a declaration of war against 00:09:37.960 --> 00:09:41.519 the entrenched Aristotelian cosmology. And the 00:09:41.519 --> 00:09:44.460 first casualty of that war was the moon. Now, 00:09:44.519 --> 00:09:46.419 Thomas Harriot may have viewed the moon first, 00:09:46.620 --> 00:09:49.399 but Galileo was the first to scientifically interpret 00:09:49.399 --> 00:09:51.980 what he saw. When he aimed his telescope at the 00:09:51.980 --> 00:09:54.840 moon in November 1609, he didn't see a perfect 00:09:54.840 --> 00:09:57.440 translucent sphere. He saw a landscape. Yes, 00:09:57.559 --> 00:10:00.779 a world. By observing the uneven line where the 00:10:00.779 --> 00:10:03.580 light ended, the Terminator, he correctly deduced 00:10:03.580 --> 00:10:05.779 that the irregular waning of light was caused 00:10:05.779 --> 00:10:08.639 by lunar mountains and craters. He even estimated 00:10:08.639 --> 00:10:10.519 their height based on the length of the shadows. 00:10:10.799 --> 00:10:12.840 This was catastrophic for the old worldview, 00:10:13.019 --> 00:10:16.509 wasn't it? It was. Aristotelian cosmology held 00:10:16.509 --> 00:10:18.809 that the celestial realm was made of a perfect, 00:10:19.009 --> 00:10:22.230 immutable, crystalline substance, completely 00:10:22.230 --> 00:10:24.610 distinct from the corrupted Earth. By showing 00:10:24.610 --> 00:10:27.129 the moon was imperfect, mountainous, and geologically 00:10:27.129 --> 00:10:30.490 similar to Earth, Galileo began to dismantle 00:10:30.490 --> 00:10:32.629 the physical basis for the separation between 00:10:32.629 --> 00:10:34.850 the heavenly and terrestrial realms. This was 00:10:34.850 --> 00:10:38.210 the first literal crack in the celestial spheres. 00:10:38.389 --> 00:10:40.929 A perfect way to put it. Then came Jupiter, which 00:10:40.929 --> 00:10:43.590 provided the first irrefutable observational 00:10:43.590 --> 00:10:46.309 evidence for a system of motion that did not 00:10:46.309 --> 00:10:48.450 center on Earth. Walk us through that discovery. 00:10:48.769 --> 00:10:52.110 On January 7, 1610, Galileo observed what he 00:10:52.110 --> 00:10:55.330 first thought were three small fixed stars close 00:10:55.330 --> 00:10:57.850 to Jupiter. But over the subsequent nights, their 00:10:57.850 --> 00:10:59.830 positions shifted. Sometimes three were visible, 00:11:00.009 --> 00:11:02.289 sometimes only one. And they seemed to be changing 00:11:02.289 --> 00:11:04.309 their arrangement around Jupiter, not the Earth. 00:11:04.509 --> 00:11:07.230 By January 15, he realized they weren't stars 00:11:07.230 --> 00:11:09.769 at all. He knew they were bodies orbiting Jupiter. 00:11:10.129 --> 00:11:13.190 He initially identified three and soon after 00:11:13.190 --> 00:11:16.350 the fourth. He named them the Medician stars 00:11:16.350 --> 00:11:19.649 to honor his potential patron, Cosimo II de' 00:11:19.669 --> 00:11:22.350 Medici, who would soon employ him as chief mathematician 00:11:22.350 --> 00:11:24.889 and philosopher to the Grand Duke of Tuscany. 00:11:25.389 --> 00:11:27.470 And we know them as the Galilean satellites, 00:11:27.830 --> 00:11:32.029 Io, Europa, Ganymede, and Callisto. Exactly. 00:11:32.090 --> 00:11:35.450 And the implication was profound. Here was a 00:11:35.450 --> 00:11:38.409 clear case of smaller bodies orbiting a larger 00:11:38.409 --> 00:11:41.509 central body that was not Earth. This shattered 00:11:41.509 --> 00:11:43.870 the fundamental Aristotelian and Ptolemaic principle 00:11:43.870 --> 00:11:46.250 that all heavenly bodies must revolve around 00:11:46.250 --> 00:11:49.200 the Earth. What was the immediate official reaction 00:11:49.200 --> 00:11:51.659 to this discovery? I can't imagine it was universally 00:11:51.659 --> 00:11:54.360 accepted. Oh, not at all. It was met with intense 00:11:54.360 --> 00:11:57.220 skepticism and sometimes outright denial. Many 00:11:57.220 --> 00:11:59.360 traditionalists refused even to look through 00:11:59.360 --> 00:12:02.059 the telescope, arguing the instrument was deceptive. 00:12:02.159 --> 00:12:04.440 We have the famous example of Martin Horky, a 00:12:04.440 --> 00:12:06.419 student of the traditional astronomer Megini. 00:12:06.600 --> 00:12:08.759 What did he say? He claimed that since the telescope 00:12:08.759 --> 00:12:11.779 made certain fixed stars appear double, the instrument 00:12:11.779 --> 00:12:13.879 itself must be producing illusions, and therefore 00:12:13.879 --> 00:12:16.950 it was just inventing the moons. Ah. The classic 00:12:16.950 --> 00:12:20.590 argument against a disruptive technology. Attack 00:12:20.590 --> 00:12:23.529 the tool, not the theory. But the evidence was 00:12:23.529 --> 00:12:26.139 eventually overwhelming. The Jesuit astronomers, 00:12:26.320 --> 00:12:28.799 led by Christopher Clavius at the Collegio Romano, 00:12:29.000 --> 00:12:31.899 confirmed the observations. While they initially 00:12:31.899 --> 00:12:35.519 adopted a geoheliocentric model, like Tycho Brahe's, 00:12:35.639 --> 00:12:38.299 to fit the new data, their confirmation lent 00:12:38.299 --> 00:12:41.179 massive credibility to Galileo. He received a 00:12:41.179 --> 00:12:43.779 hero's welcome in Rome the following year. Beyond 00:12:43.779 --> 00:12:46.500 the cosmological implications, the discovery 00:12:46.500 --> 00:12:49.779 of Jupiter's moons had a powerful practical application, 00:12:50.159 --> 00:12:52.639 linking back to the great problem of navigation. 00:12:53.320 --> 00:12:55.600 That's the universal clock concept, a brilliant 00:12:55.600 --> 00:12:58.960 idea. Galileo realized that the eclipses of these 00:12:58.960 --> 00:13:01.080 four moons were frequent, highly predictable 00:13:01.080 --> 00:13:04.240 events. If you could precisely time these eclipses 00:13:04.240 --> 00:13:06.480 from any location on Earth, you could use them 00:13:06.480 --> 00:13:08.879 as a universal clock to compare your local time 00:13:08.879 --> 00:13:11.120 with a known reference time. And that would solve 00:13:11.120 --> 00:13:13.220 the longitude problem. That's the holy grail 00:13:13.220 --> 00:13:15.799 of 17th century navigation. So this was a critical 00:13:15.799 --> 00:13:18.240 issue for maritime powers. Why didn't he win 00:13:18.240 --> 00:13:20.419 the great navigation prizes offered by Spain 00:13:20.419 --> 00:13:22.899 and Holland? The difficulty was purely practical. 00:13:23.399 --> 00:13:26.080 You simply cannot accurately observe the tiny, 00:13:26.139 --> 00:13:29.659 fleeting eclipses of these moons from the pitching, 00:13:29.779 --> 00:13:32.600 rolling deck of a ship at sea. The method was 00:13:32.600 --> 00:13:35.139 far too complex and the instrument too unstable. 00:13:35.519 --> 00:13:37.879 But it worked on land. It was extremely effective 00:13:37.879 --> 00:13:41.039 on land. It was successfully utilized by surveyors 00:13:41.039 --> 00:13:43.820 for large land -based projects, including the 00:13:43.820 --> 00:13:46.799 remapping of France starting in 1681. Okay, so 00:13:46.799 --> 00:13:49.200 the moon is imperfect. Jupiter has its own moons. 00:13:49.440 --> 00:13:53.120 But the final, most... devastating piece of observational 00:13:53.120 --> 00:13:55.940 evidence for the Copernican model came from Venus. 00:13:56.580 --> 00:14:00.259 Starting in September 1610, yes, Galileo observed 00:14:00.259 --> 00:14:03.240 that Venus exhibits a full set of phases crescent, 00:14:03.320 --> 00:14:06.879 half gibbous and full, just like our moon. This 00:14:06.879 --> 00:14:08.860 was, as you said, the critical observational 00:14:08.860 --> 00:14:11.659 blow against the polymaic geocentric model. Why 00:14:11.659 --> 00:14:13.620 could the old model not account for a full set 00:14:13.620 --> 00:14:16.220 of phases? Lay out the geometry for us. It's 00:14:16.220 --> 00:14:18.919 all about where Venus is relative to the sun 00:14:18.919 --> 00:14:21.450 and earth. In the traditional strictly Ptolemaic 00:14:21.450 --> 00:14:24.250 geocentric model, Venus's orbit had to be arranged 00:14:24.250 --> 00:14:26.389 either entirely on the near side of the Sun, 00:14:26.490 --> 00:14:28.370 between the Earth and the Sun, or entirely on 00:14:28.370 --> 00:14:31.009 the far side. If Venus was always between Earth 00:14:31.009 --> 00:14:33.610 and the Sun, it could only ever show crescent 00:14:33.610 --> 00:14:36.450 or new phases. If it was always beyond the Sun, 00:14:36.629 --> 00:14:39.289 it could only show gibbous or full phases. You 00:14:39.289 --> 00:14:42.330 couldn't get both. But seeing a full phase means 00:14:42.330 --> 00:14:45.970 we must be viewing Venus when the Sun is illuminating 00:14:45.970 --> 00:14:48.809 its entire face. Which requires Earth and Venus 00:14:48.809 --> 00:14:51.230 to be on opposite sides of the Sun. So Venus 00:14:51.230 --> 00:14:54.009 has to be orbiting the Sun. Exactly. The observation 00:14:54.009 --> 00:14:56.909 of the full set proved unequivocally that Venus 00:14:56.909 --> 00:15:00.049 orbits the Sun. This was powerful proof for the 00:15:00.049 --> 00:15:02.629 Copernican model, although many astronomers at 00:15:02.629 --> 00:15:06.549 the time compromised. They adopted hybrid geoheliocentric 00:15:06.549 --> 00:15:09.629 models like the Ticonic system. What was that? 00:15:09.909 --> 00:15:11.970 That's where the planets orbit the sun, but the 00:15:11.970 --> 00:15:14.870 sun still orbits a stationary Earth. It satisfied 00:15:14.870 --> 00:15:17.610 both the Venus observation and the belief in 00:15:17.610 --> 00:15:20.070 a fixed Earth. It was a very clever, mathematically 00:15:20.070 --> 00:15:22.769 sound compromise for the time. He also turned 00:15:22.769 --> 00:15:24.629 his instrument towards Saturn and spots on the 00:15:24.629 --> 00:15:27.409 sun. His observations of Saturn in 1610 were 00:15:27.409 --> 00:15:30.690 initially confusing. He saw what he thought were 00:15:30.690 --> 00:15:33.309 two smaller companion bodies, thinking it was 00:15:33.309 --> 00:15:36.429 a triple system. When he observed it again a 00:15:36.429 --> 00:15:38.889 few years later and the rings were oriented edge 00:15:38.889 --> 00:15:42.090 -on to Earth, they seemingly vanished. It caused 00:15:42.090 --> 00:15:44.129 him great confusion until they reappeared in 00:15:44.129 --> 00:15:47.549 1616. He didn't correctly identify the rings, 00:15:47.669 --> 00:15:49.769 but he was the first to document the strange 00:15:49.769 --> 00:15:52.669 phenomenon. And his work on sunspots also caused 00:15:52.669 --> 00:15:55.309 controversy. Absolutely. His studies, published 00:15:55.309 --> 00:15:57.789 in Letters on Sunspots, showed blemishes on the 00:15:57.789 --> 00:16:00.490 face of the supposedly pristine, immutable sun. 00:16:01.000 --> 00:16:03.539 This was yet another piece of evidence directly 00:16:03.539 --> 00:16:06.639 contradicting the Aristotelian concept of unchanging 00:16:06.639 --> 00:16:08.360 perfection in the heavens. He was just piling 00:16:08.360 --> 00:16:11.480 on the evidence. One observation at a time. He 00:16:11.480 --> 00:16:13.279 also looked beyond the solar system, observing 00:16:13.279 --> 00:16:15.840 the Milky Way and realizing it was not a continuous 00:16:15.840 --> 00:16:19.019 luminous fog, but a dense multitude of individually 00:16:19.019 --> 00:16:22.179 resolvable stars packed together. He was literally 00:16:22.179 --> 00:16:25.299 charting a new, far vaster universe. And we can't 00:16:25.299 --> 00:16:27.840 forget his near discovery of Neptune. Fascinating 00:16:27.840 --> 00:16:31.120 footnote. It really is. He observed Neptune in 00:16:31.120 --> 00:16:34.720 1612 while tracking Jupiter and its moons. He 00:16:34.720 --> 00:16:37.320 recorded it in his notebooks, noting its small 00:16:37.320 --> 00:16:39.899 size and dim appearance, and he even noticed 00:16:39.899 --> 00:16:42.320 its motion relative to the background stars over 00:16:42.320 --> 00:16:44.419 a few nights. But he didn't realize what it was? 00:16:44.600 --> 00:16:47.840 No. He recorded it simply as an unremarkable 00:16:47.840 --> 00:16:50.720 dim star, not realizing he had glimpsed an entirely 00:16:50.720 --> 00:16:53.000 new planet which wouldn't be officially discovered 00:16:53.000 --> 00:16:56.100 for another two centuries. An incredible what 00:16:56.100 --> 00:16:59.210 -if moment in science history. Galileo's fame 00:16:59.210 --> 00:17:01.629 rests so heavily on the telescope, but his most 00:17:01.629 --> 00:17:04.589 enduring fundamental legacy is really the scientific 00:17:04.589 --> 00:17:07.190 methodology he brought to physics. He didn't 00:17:07.190 --> 00:17:09.369 just point a telescope at the sky, he pointed 00:17:09.369 --> 00:17:12.009 mathematics at the physical world. That is the 00:17:12.009 --> 00:17:14.710 pivotal shift. He is credited with making original 00:17:14.710 --> 00:17:17.049 and foundational contributions to the science 00:17:17.049 --> 00:17:19.609 of motion kinematics through an innovative approach, 00:17:19.910 --> 00:17:22.549 combining rigorous, measurable experiments with 00:17:22.549 --> 00:17:25.130 precise mathematical theory. This was a radical 00:17:25.130 --> 00:17:27.309 departure from the purely qualitative science 00:17:27.309 --> 00:17:29.829 of Aristotle, which relied primarily on deduction 00:17:29.829 --> 00:17:32.710 and reasoning from first principles. That mathematical 00:17:32.710 --> 00:17:36.430 worldview is perfectly crystallized in his famous 00:17:36.430 --> 00:17:39.819 quote from the Essayer. It's his scientific credo, 00:17:39.839 --> 00:17:55.359 he wrote. He's basically saying the universe 00:17:55.359 --> 00:17:58.480 has a code and the code is math. He is, and this 00:17:58.480 --> 00:18:00.380 statement establishes the modern requirement 00:18:00.380 --> 00:18:03.019 that physics must be both described and tested 00:18:03.019 --> 00:18:06.000 using mathematics. To make that testing rigorous, 00:18:06.279 --> 00:18:08.680 he needed consistency reproducible standards 00:18:08.680 --> 00:18:11.079 for measurement, especially for time. Which was 00:18:11.079 --> 00:18:13.539 a huge problem. A huge problem. He established 00:18:13.539 --> 00:18:15.500 the need for reproducible standards of length 00:18:15.500 --> 00:18:18.700 and, crucially, time for his experiments, forming 00:18:18.700 --> 00:18:21.119 a reliable inductive foundation for confirming 00:18:21.119 --> 00:18:23.920 mathematical laws. Given the technology of the 00:18:23.920 --> 00:18:26.240 time, measuring very short intervals of time 00:18:26.240 --> 00:18:28.750 for accelerated motion was extremely difficult. 00:18:28.970 --> 00:18:31.630 So how did he solve that practical measurement 00:18:31.630 --> 00:18:33.910 problem, especially for his experiments on falling 00:18:33.910 --> 00:18:37.230 bodies? Since gravity accelerates objects too 00:18:37.230 --> 00:18:39.609 quickly to measure with the era's crude clocks, 00:18:39.829 --> 00:18:42.670 like a pendulum or your pulse, he used inclined 00:18:42.670 --> 00:18:45.890 planes. He rolled balls down them to slow the 00:18:45.890 --> 00:18:48.769 acceleration down. A simple, elegant solution. 00:18:49.089 --> 00:18:51.609 It was. And for timing, he devised ingenious 00:18:51.609 --> 00:18:54.450 methods. The sources describe him using a very 00:18:54.450 --> 00:18:57.210 large vessel of water placed in an elevated position 00:18:57.210 --> 00:18:59.890 from which a thin stream flowed out of a small 00:18:59.890 --> 00:19:02.339 tube at the bottom. The water collected during 00:19:02.339 --> 00:19:04.160 the time of the descent was then weighed on a 00:19:04.160 --> 00:19:06.539 precise balance. So the weight of the water collected 00:19:06.539 --> 00:19:09.400 was his measure of time elapsed. He built a water 00:19:09.400 --> 00:19:11.980 clock. Precisely. A high -precision water clock. 00:19:12.160 --> 00:19:14.420 By slowing the motion and using this clock, he 00:19:14.420 --> 00:19:16.900 was able to ensure reproducibility and reliability 00:19:16.900 --> 00:19:19.819 in his measurements. A level of rigor almost 00:19:19.819 --> 00:19:22.359 unheard of outside of astronomical observation 00:19:22.359 --> 00:19:25.000 at the time. Let's discuss the iconic, albeit 00:19:25.000 --> 00:19:27.519 probably apocryphal, Leaning Tower of Pieces 00:19:27.519 --> 00:19:30.019 story. The famous story, which was popularized 00:19:30.019 --> 00:19:32.779 by his pupil Vincenzo Viviani after Galileo's 00:19:32.779 --> 00:19:35.059 death, claims he dropped balls of different masses 00:19:35.059 --> 00:19:36.980 from the tower to prove they fell at the same 00:19:36.980 --> 00:19:40.519 speed, thereby directly refuting Aristotle. But 00:19:40.519 --> 00:19:42.599 it probably didn't happen that way. Most historians 00:19:42.599 --> 00:19:45.140 now agree this was, at most, a thought experiment 00:19:45.140 --> 00:19:48.319 or a demonstration of a concept. Why would a 00:19:48.319 --> 00:19:50.740 physical drop from the tower have been problematic? 00:19:51.480 --> 00:19:54.039 Well, for one, the practical issues of air resistance 00:19:54.039 --> 00:19:56.900 would have been significant. And the rapid speed 00:19:56.900 --> 00:19:59.099 of descent would have made precise measurement 00:19:59.099 --> 00:20:01.660 impossible in a public setting. It would have 00:20:01.660 --> 00:20:03.940 just muddied the result. His true experiments 00:20:03.940 --> 00:20:06.359 were done privately and carefully on the inclined 00:20:06.359 --> 00:20:08.900 plane. And what those inclined plane experiments 00:20:08.900 --> 00:20:11.400 revealed was the foundational law of kinematics. 00:20:11.799 --> 00:20:14.619 The distance traveled is proportional to the 00:20:14.619 --> 00:20:17.220 square of the time elapsed during uniform acceleration. 00:20:17.779 --> 00:20:20.470 How did he arrive at this mathematically? This 00:20:20.470 --> 00:20:23.009 is where his geometrical mastery comes in. He 00:20:23.009 --> 00:20:25.509 derived the law using an abstract geometrical 00:20:25.509 --> 00:20:28.569 argument, not just by fitting his data. If you 00:20:28.569 --> 00:20:31.529 imagine graphing velocity over time for an object 00:20:31.529 --> 00:20:34.809 accelerating uniformly from rest, the graph is 00:20:34.809 --> 00:20:37.769 a straight line starting from zero. The total 00:20:37.769 --> 00:20:40.029 distance traveled is represented by the area 00:20:40.029 --> 00:20:42.349 under that velocity -time graph, which forms 00:20:42.349 --> 00:20:45.259 a triangle. A triangle, yes. And the area of 00:20:45.259 --> 00:20:48.180 a triangle is one half base times height. Since 00:20:48.180 --> 00:20:51.720 the base is time, t, and the height is the final 00:20:51.720 --> 00:20:54.640 velocity, which is acceleration times time, the 00:20:54.640 --> 00:20:58.039 area, or distance d, is proportional to t squared. 00:20:58.500 --> 00:21:01.200 He showed how this geometrical proof perfectly 00:21:01.200 --> 00:21:03.619 matched his experimental data from the inclined 00:21:03.619 --> 00:21:06.019 planes. It's important to give context to his 00:21:06.019 --> 00:21:08.539 predecessors, though, as the idea of unequal 00:21:08.539 --> 00:21:10.759 weights falling at the same speed wasn't entirely 00:21:10.759 --> 00:21:14.920 new. His rigor was... Yes, that's a key point. 00:21:15.279 --> 00:21:17.799 The Roman philosopher Lucretius, as early as 00:21:17.799 --> 00:21:21.099 60 BC, had a similar suggestion. John Philipponus 00:21:21.099 --> 00:21:23.039 in the 6th century made related observations. 00:21:23.519 --> 00:21:26.460 And in the 14th century, Nicola Resme had derived 00:21:26.460 --> 00:21:28.619 the time -squared law for uniformly accelerated 00:21:28.619 --> 00:21:31.359 change conceptually. And Domingo de Soto's work 00:21:31.359 --> 00:21:33.900 in the 16th century. De Soto suggested that bodies 00:21:33.900 --> 00:21:35.700 falling through a homogenous medium would be 00:21:35.700 --> 00:21:38.920 uniformly accelerated. But he did not have Galileo's 00:21:38.920 --> 00:21:41.299 theoretical or experimental rigor. And we have 00:21:41.299 --> 00:21:44.220 to mention the 1586 Delft Tower experiment by 00:21:44.220 --> 00:21:46.369 Simon. Stephen. What did he do? He dropped two 00:21:46.369 --> 00:21:48.150 lead balls of different weights but identical 00:21:48.150 --> 00:21:50.450 size and confirmed they hit the ground simultaneously. 00:21:51.250 --> 00:21:54.130 But while successful, Stephen relied on audio 00:21:54.130 --> 00:21:57.349 feedback hearing them hit. Galileo relied on 00:21:57.349 --> 00:22:00.210 precise, reproducible, mathematical confirmation. 00:22:01.009 --> 00:22:03.490 That's the difference. Moving beyond acceleration, 00:22:04.009 --> 00:22:07.069 Galileo laid the crucial groundwork for modern 00:22:07.069 --> 00:22:10.609 concepts of inertia and relativity. Let's start 00:22:10.609 --> 00:22:12.839 with the principle of relativity. or Galilean 00:22:12.839 --> 00:22:15.579 invariance. This is a powerful conceptual leap. 00:22:15.960 --> 00:22:18.200 Galileo established the basic principle that 00:22:18.200 --> 00:22:20.579 the laws of physics are the same in any system 00:22:20.579 --> 00:22:22.660 moving at a constant speed in a straight line, 00:22:22.819 --> 00:22:25.380 regardless of how fast or in what direction that 00:22:25.380 --> 00:22:28.220 system is moving. This idea made heliocentrism 00:22:28.220 --> 00:22:30.980 physically plausible. Because if the Earth is 00:22:30.980 --> 00:22:33.319 spinning and moving at thousands of miles per 00:22:33.319 --> 00:22:35.839 hour, why don't objects fly off it? Why don't 00:22:35.839 --> 00:22:38.559 we feel it? Exactly. His principle explained 00:22:38.559 --> 00:22:40.930 why we don't feel the Earth moving. The laws 00:22:40.930 --> 00:22:43.369 of motion and the forces acting within our local 00:22:43.369 --> 00:22:45.609 frame are independent of the uniform motion of 00:22:45.609 --> 00:22:48.470 the frame itself. This was foundational for Newton's 00:22:48.470 --> 00:22:51.309 first law and, centuries later, for Einstein's 00:22:51.309 --> 00:22:53.470 special theory of relativity. The thought experiment 00:22:53.470 --> 00:22:56.150 he devised in a dialogue concerning the two chief 00:22:56.150 --> 00:22:59.390 world systems is still taught today. It's so 00:22:59.390 --> 00:23:02.430 clear. It is a model of clarity. He asks you 00:23:02.430 --> 00:23:04.730 to imagine being shut in the main cabin of a 00:23:04.730 --> 00:23:07.920 ship. Inside, you have flies flying, butterflies 00:23:07.920 --> 00:23:10.960 flitting, water dripping into a bowl, and fish 00:23:10.960 --> 00:23:13.539 swimming in a tank. He states that if the ship 00:23:13.539 --> 00:23:15.980 is standing still, you observe a certain internal 00:23:15.980 --> 00:23:19.039 behavior. Then, if the ship proceeds with any 00:23:19.039 --> 00:23:21.099 speed you like, provided the motion is uniform 00:23:21.099 --> 00:23:24.180 and linear, you will discover not the least change 00:23:24.180 --> 00:23:26.880 in all the effects named. You cannot determine, 00:23:27.059 --> 00:23:30.019 using only internal observations, whether the 00:23:30.019 --> 00:23:33.000 ship is moving or stationary. this is the essence 00:23:33.000 --> 00:23:35.900 of galilean invariance it was a devastating answer 00:23:35.900 --> 00:23:38.920 to the argument that if the earth moved birds 00:23:38.920 --> 00:23:41.460 flying upward would be instantly left behind 00:23:41.460 --> 00:23:44.380 as the ground rushed away beneath them in fact 00:23:44.380 --> 00:23:46.940 the birds the air and you on the ground all share 00:23:46.940 --> 00:23:49.460 the same state of uniform motion and this line 00:23:49.460 --> 00:23:52.039 of reasoning also birthed the concept of inertia 00:23:52.589 --> 00:23:55.849 Yes. He concluded that objects retain their velocity 00:23:55.849 --> 00:23:58.869 in the absence of friction or resistance. This 00:23:58.869 --> 00:24:01.369 fundamentally contradicted the Aristotelian view, 00:24:01.529 --> 00:24:03.930 which held that movement required a continuous 00:24:03.930 --> 00:24:06.609 mover, and that objects naturally sought a state 00:24:06.609 --> 00:24:10.029 of rest. Galileo said no, remove the impediments, 00:24:10.109 --> 00:24:13.269 and the object keeps moving perpetually. There's 00:24:13.269 --> 00:24:15.390 a crucial nuance here, though, regarding the 00:24:15.390 --> 00:24:18.130 type of perpetual motion he envisioned. That's 00:24:18.130 --> 00:24:21.529 vital for a deep dive audience. Galileo posited 00:24:21.529 --> 00:24:23.569 that a particle projected along a horizontal 00:24:23.569 --> 00:24:27.109 plane without friction will move along this same 00:24:27.109 --> 00:24:29.789 plane with a motion which is uniform and perpetual. 00:24:30.390 --> 00:24:33.569 However, his conceptual framework was still tied 00:24:33.569 --> 00:24:35.930 to the perfect circles of the Copernican system. 00:24:36.269 --> 00:24:38.230 So he thought the motion would be circular. He 00:24:38.230 --> 00:24:40.650 believed that this perpetual, unimpeded motion 00:24:40.650 --> 00:24:43.309 would be circular, describing a great circle 00:24:43.309 --> 00:24:45.349 around the center of the Earth consistent with 00:24:45.349 --> 00:24:47.630 a planetary orbit. And that's where Newton later 00:24:47.630 --> 00:24:51.230 stepped in and formalized the concept. Yes, it 00:24:51.230 --> 00:24:53.470 was Isaac Newton who later clarified the principle, 00:24:53.730 --> 00:24:57.049 recognizing that truly perpetual motion in the 00:24:57.049 --> 00:24:59.730 absence of forces must be in a straight line. 00:25:00.509 --> 00:25:03.329 Galileo's insight was the radical step of idealization, 00:25:03.509 --> 00:25:06.630 of conceptualizing a frictionless world. But 00:25:06.630 --> 00:25:09.410 Newton provided the final, correct, geometrical 00:25:09.410 --> 00:25:11.890 description of inertia. Before we move to his 00:25:11.890 --> 00:25:14.069 conflict with the church, quickly summarize his 00:25:14.069 --> 00:25:16.329 other physics insights regarding acoustics and 00:25:16.329 --> 00:25:18.579 light. In acoustics, he was one of the first 00:25:18.579 --> 00:25:20.980 to truly link the pitch of sound to the physical 00:25:20.980 --> 00:25:23.759 concept of frequency. He did this by scraping 00:25:23.759 --> 00:25:26.500 a chisel across a plate, noting the regularity 00:25:26.500 --> 00:25:28.279 of the scratches, and connecting the spacing 00:25:28.279 --> 00:25:30.460 of those skips directly to the resulting musical 00:25:30.460 --> 00:25:33.759 pitch. So he identified frequency as the measurable 00:25:33.759 --> 00:25:36.039 characteristic of pitch. He did. And regarding 00:25:36.039 --> 00:25:38.900 the pendulum, as we noted earlier, he later confirmed 00:25:38.900 --> 00:25:41.099 that the square of the pendulum period varies 00:25:41.099 --> 00:25:43.519 directly with its length, an insight fundamental 00:25:43.519 --> 00:25:46.039 to clock design. And his attempt to measure the 00:25:46.039 --> 00:25:48.039 speed of light, which was an almost impossibly 00:25:48.039 --> 00:25:51.099 difficult task for the 17th century. In his 1638 00:25:51.099 --> 00:25:53.720 work, he described a methodology using two observers 00:25:53.720 --> 00:25:56.059 positioned at some distance, less than a mile 00:25:56.059 --> 00:25:58.299 in his attempt, each holding a lantern with a 00:25:58.299 --> 00:26:01.480 shutter. Observer one opens his shutter. Observer 00:26:01.480 --> 00:26:03.759 two, upon seeing the light, immediately opens 00:26:03.759 --> 00:26:06.559 his own. The time delay between observer one 00:26:06.559 --> 00:26:08.559 opening his shutter and seeing the second light 00:26:08.559 --> 00:26:11.420 indicates the round -trip time. Given the incredible 00:26:11.420 --> 00:26:14.400 speed of light, what was his conclusion? He reported 00:26:14.400 --> 00:26:17.279 the result was inconclusive. The time delay was 00:26:17.279 --> 00:26:19.700 simply too short for human reaction and the crude 00:26:19.700 --> 00:26:21.940 timing instruments to differentiate between an 00:26:21.940 --> 00:26:24.940 instantaneous appearance and an extremely rapid 00:26:24.940 --> 00:26:27.619 motion. It was an ingenious experiment design, 00:26:27.740 --> 00:26:30.079 but technologically way ahead of its time. All 00:26:30.079 --> 00:26:32.400 this scientific momentum led him straight into 00:26:32.400 --> 00:26:35.500 the defining confrontation of his life. Yet the 00:26:35.500 --> 00:26:37.819 catalyst for the conflict was ironically the 00:26:37.819 --> 00:26:40.720 one thing he got profoundly wrong. His theory 00:26:40.720 --> 00:26:45.089 of the tides. A strategic failure, yes. By 1615, 00:26:45.210 --> 00:26:48.210 the intellectual debate was intense. Cardinal 00:26:48.210 --> 00:26:50.829 Bellarmine, a respected theologian, requested 00:26:50.829 --> 00:26:54.589 a true physical demonstration for heliocentrism, 00:26:54.589 --> 00:26:56.829 not just mathematical arguments that might be 00:26:56.829 --> 00:26:59.589 considered convenient fictions. Galileo believed 00:26:59.589 --> 00:27:01.849 his mechanical explanation of the tides was that 00:27:01.849 --> 00:27:04.230 physical proof. What was his mechanical explanation? 00:27:04.759 --> 00:27:07.579 Galileo's idea was purely inertial. He proposed 00:27:07.579 --> 00:27:09.880 that tides were caused by the sloshing of water 00:27:09.880 --> 00:27:12.119 in the seas as a result of the Earth's rotation 00:27:12.119 --> 00:27:14.759 on its axis and its simultaneous revolution around 00:27:14.759 --> 00:27:17.240 the sun. He reasoned that at certain points on 00:27:17.240 --> 00:27:19.299 Earth, these two motions would briefly combine, 00:27:19.559 --> 00:27:22.279 causing acceleration and a buildup of water, 00:27:22.420 --> 00:27:24.640 a high tide. And at other points, they'd subtract, 00:27:24.960 --> 00:27:27.880 causing a low tide. Exactly. But the flaw in 00:27:27.880 --> 00:27:29.920 this mechanical proof was immediate and profound. 00:27:30.160 --> 00:27:32.559 The fatal flaw was that this theory only implies 00:27:32.559 --> 00:27:35.490 one high tide per day. One. Yet the Atlantic 00:27:35.490 --> 00:27:37.809 Ocean and the Mediterranean Sea both clearly 00:27:37.809 --> 00:27:41.349 exhibit two high tides daily. Galileo tried desperately 00:27:41.349 --> 00:27:43.930 to account for the twice -daily tides by attributing 00:27:43.930 --> 00:27:46.490 the secondary tide to minor incidental causes 00:27:46.490 --> 00:27:48.890 like the specific shape and depth of the sea 00:27:48.890 --> 00:27:51.730 basin. And he completely dismissed the correct 00:27:51.730 --> 00:27:54.750 moon -related cause, didn't he? He vehemently 00:27:54.750 --> 00:27:57.109 rejected the idea that the moon caused the tides. 00:27:57.509 --> 00:28:00.109 If we connect this to the deeper context of the 00:28:00.109 --> 00:28:02.529 era, he disliked the lunar influence because 00:28:02.529 --> 00:28:05.809 it seemed to imply an occult, magical, or action 00:28:05.809 --> 00:28:08.829 at a distance for something mystical outside 00:28:08.829 --> 00:28:11.230 the realm. of observable mechanical physics. 00:28:11.589 --> 00:28:13.829 He wanted a mechanical explanation. He preferred 00:28:13.829 --> 00:28:17.450 his, albeit flawed, rational mechanical explanation 00:28:17.450 --> 00:28:20.809 over the more accurate, but seemingly inexplicable, 00:28:20.809 --> 00:28:23.849 influence of the moon, an idea his contemporary 00:28:23.849 --> 00:28:26.750 Kepler had already proposed. So he was left arguing 00:28:26.750 --> 00:28:29.930 for a flawed physical proof, while his true evidence 00:28:29.930 --> 00:28:32.470 lay in the astronomical observations that challenged 00:28:32.470 --> 00:28:34.890 scripture. Meanwhile, the Jesuit community was 00:28:34.890 --> 00:28:37.269 already deeply alienated thanks to intellectual 00:28:37.269 --> 00:28:39.829 sparring. That leads us to the comet's controversy. 00:28:40.190 --> 00:28:42.609 This was a nasty academic feud that began in 00:28:42.609 --> 00:28:45.910 1618 with the Jesuit father, Horacio Grassi. 00:28:45.950 --> 00:28:47.910 Grassi argued that the comets observed that year 00:28:47.910 --> 00:28:50.329 were fiery celestial bodies farther away than 00:28:50.329 --> 00:28:53.029 the moon. Galileo, writing through his pupil 00:28:53.029 --> 00:28:55.950 Mario Guducci in Discourse on Comets, attacked 00:28:55.950 --> 00:28:58.390 Grassi's position and gratuitously insulted the 00:28:58.390 --> 00:29:00.950 Jesuits. And his subsequent reply, the Essayer 00:29:00.950 --> 00:29:04.910 from 1623, was a masterpiece of rhetorical warfare. 00:29:05.500 --> 00:29:07.980 The Essayer is often considered Galileo's scientific 00:29:07.980 --> 00:29:10.640 and rhetorical peak. It wasn't just about comments. 00:29:10.859 --> 00:29:14.880 It was his polemical manifesto, elegantly articulating 00:29:14.880 --> 00:29:17.079 the primacy of experimentation and mathematical 00:29:17.079 --> 00:29:20.579 reasoning over blind adherence to ancient Aristotelian 00:29:20.579 --> 00:29:23.720 authority. His wit was razor sharp. It was hugely 00:29:23.720 --> 00:29:25.940 successful politically, at least initially. Oh, 00:29:25.940 --> 00:29:29.140 yes. The new pope, Urban VIII, a former friend 00:29:29.140 --> 00:29:31.920 and admirer of Galileo, was delighted by the 00:29:31.920 --> 00:29:34.559 book's style and had it read aloud to him. However, 00:29:34.759 --> 00:29:37.980 its biting satire and direct attacks cemented 00:29:37.980 --> 00:29:39.960 the permanent alienation of many influential 00:29:39.960 --> 00:29:42.799 Jesuit scholars, particularly those at the Collegio 00:29:42.799 --> 00:29:45.039 Romano who were critical players in the Inquisition. 00:29:45.099 --> 00:29:47.740 He won the battle, but was losing the war. The 00:29:47.740 --> 00:29:50.079 core conflict, the one the Church couldn't ignore, 00:29:50.220 --> 00:29:53.059 was the incompatibility of heliocentrism with 00:29:53.059 --> 00:29:55.250 certain interpretations of Scripture. That's 00:29:55.250 --> 00:29:57.349 the religious opposition, rooted in biblical 00:29:57.349 --> 00:30:00.349 passages implying a fixed earth, like Psalm 104 00:30:00.349 --> 00:30:03.589 .5, which suggests the earth should not be moved 00:30:03.589 --> 00:30:06.730 forever. However, we must stress that the opposition 00:30:06.730 --> 00:30:09.289 was also powerfully scientific by the standards 00:30:09.289 --> 00:30:11.450 of the time. And the champion of the scientific 00:30:11.450 --> 00:30:14.349 opposition was Tycho Brahe. Brahe's argument 00:30:14.349 --> 00:30:17.339 was geometrically powerful. If the Earth truly 00:30:17.339 --> 00:30:20.640 moved, we should observe an annual stellar parallax, 00:30:20.680 --> 00:30:23.539 a tiny shift in the apparent position of nearby 00:30:23.539 --> 00:30:26.539 stars as the Earth moves across its orbit. Since 00:30:26.539 --> 00:30:29.299 no parallax was measured, Brahe concluded the 00:30:29.299 --> 00:30:32.039 Earth must be stationary. Copernicans correctly 00:30:32.039 --> 00:30:34.480 argued that the stars were simply too distant 00:30:34.480 --> 00:30:37.019 for the parallax to be measurable with 17th century 00:30:37.019 --> 00:30:39.619 instruments. But Brahe had a very clever counter 00:30:39.619 --> 00:30:42.039 -argument to that. The star size argument. This 00:30:42.039 --> 00:30:45.200 was popularized by Francesco Ngole in his 1616 00:30:45.200 --> 00:30:47.640 anti -Copernican essay, which was directed at 00:30:47.640 --> 00:30:50.740 Galileo. Ngole used Brahe's specific geometry. 00:30:51.480 --> 00:30:54.019 If the stars were as incredibly distant as required 00:30:54.019 --> 00:30:56.519 to hide the parallax, given their observed angular 00:30:56.519 --> 00:30:59.039 size through early telescopes, they would have 00:30:59.039 --> 00:31:01.440 to be physically implausibly large. How large 00:31:01.440 --> 00:31:03.690 are we talking? Engoli argued that the stars 00:31:03.690 --> 00:31:06.150 would have to be so vast they would surpass or 00:31:06.150 --> 00:31:08.349 equal the size of the orbit circle of the Earth 00:31:08.349 --> 00:31:11.710 itself. This contradiction observed size versus 00:31:11.710 --> 00:31:14.670 required distance was mathematically sound based 00:31:14.670 --> 00:31:17.309 on the instruments available. Galileo tried to 00:31:17.309 --> 00:31:19.650 counter this by re -measuring the stars and finding 00:31:19.650 --> 00:31:22.130 they were much smaller points of light. But he 00:31:22.130 --> 00:31:24.130 didn't realize that the apparent size he and 00:31:24.130 --> 00:31:26.900 others were measuring was spurious. Exactly. 00:31:27.019 --> 00:31:30.000 It was caused by the optical phenomenon of diffraction 00:31:30.000 --> 00:31:32.319 around the aperture of the telescope. So this 00:31:32.319 --> 00:31:34.720 was a legitimate scientific hurdle, not just 00:31:34.720 --> 00:31:37.480 a theological one. The traditionalists had a 00:31:37.480 --> 00:31:39.700 strong scientific case unless one could prove 00:31:39.700 --> 00:31:41.819 that the apparent size of stars was being distorted 00:31:41.819 --> 00:31:44.240 by the instrument itself. The crisis reached 00:31:44.240 --> 00:31:48.130 ahead in 1616. That year, an inquisitorial commission 00:31:48.130 --> 00:31:51.509 formally declared heliocentrism foolish and absurd 00:31:51.509 --> 00:31:54.269 in philosophy and formally heretical since it 00:31:54.269 --> 00:31:56.890 explicitly contradicts in many places the sense 00:31:56.890 --> 00:32:00.009 of Holy Scripture. Cardinal Bellarmine formally 00:32:00.009 --> 00:32:03.130 ordered Galileo to abandon completely the opinion 00:32:03.130 --> 00:32:05.750 that the sun stands still and the earth moves. 00:32:05.890 --> 00:32:08.150 And Copernicus' book was banned. De revolutionis 00:32:08.150 --> 00:32:10.769 was banned until corrections could be made, yes. 00:32:11.589 --> 00:32:14.109 Galileo remained silent on the issue for years. 00:32:14.750 --> 00:32:17.289 focusing on his non -controversial work, until 00:32:17.289 --> 00:32:19.970 his friend, Mafio Barberini, took the papacy 00:32:19.970 --> 00:32:22.150 as Urban VIII. And that gave him an opening. 00:32:22.430 --> 00:32:24.990 It gave him confidence, but the pope laid down 00:32:24.990 --> 00:32:27.789 a specific condition. Any discussion of the two 00:32:27.789 --> 00:32:30.750 systems must be impartial. This led to the publication 00:32:30.750 --> 00:32:33.109 of Dialogue Concerning the Two Chief World Systems 00:32:33.109 --> 00:32:36.109 in 1632, published with official authorization. 00:32:36.589 --> 00:32:39.170 The structure of the book, however, was Galileo's 00:32:39.170 --> 00:32:41.509 ultimate undoing. It was a political disaster 00:32:41.509 --> 00:32:44.180 disguised as philosophy. The book is presented 00:32:44.180 --> 00:32:47.160 as a conversation among three people, Salviati, 00:32:47.240 --> 00:32:49.900 the Copernican supporter, Segreto, the intelligent, 00:32:50.079 --> 00:32:52.640 neutral layperson, and Simplicio, the defender 00:32:52.640 --> 00:32:56.279 of the geocentric Aristotelian view. Simplicio. 00:32:56.319 --> 00:32:58.720 The name itself was perceived as a massive insult. 00:32:58.920 --> 00:33:01.359 While Galileo claimed the name honored a famous 00:33:01.359 --> 00:33:04.559 6th century Aristotelian commentator, the name 00:33:04.559 --> 00:33:07.200 Simplicio carries the immediate connotation of 00:33:07.200 --> 00:33:10.730 simpleton in Italian. But even worse, and critically, 00:33:11.150 --> 00:33:14.150 Pope Urban VIII had specifically requested that 00:33:14.150 --> 00:33:17.089 Galileo include an argument emphasizing that 00:33:17.089 --> 00:33:20.049 no human ingenuity could fully comprehend God's 00:33:20.049 --> 00:33:23.230 plan, and therefore one should not assert a cosmological 00:33:23.230 --> 00:33:26.329 model as absolute truth. And where did Galileo 00:33:26.329 --> 00:33:29.069 put that papal argument? He placed the Pope's 00:33:29.069 --> 00:33:32.009 preferred, cautious argument directly into the 00:33:32.009 --> 00:33:34.589 mouth of the ridiculed character Simplicio in 00:33:34.589 --> 00:33:37.410 the final lines of the book. This action caused 00:33:37.410 --> 00:33:39.769 Urban VIII to feel personally humiliated and 00:33:39.769 --> 00:33:43.069 betrayed. It instantaneously alienated his most 00:33:43.069 --> 00:33:45.250 powerful protector and guaranteed his trial. 00:33:45.470 --> 00:33:49.309 The trial followed in 1633. Galileo was called 00:33:49.309 --> 00:33:51.990 before the Inquisition. The key charge was violating 00:33:51.990 --> 00:33:55.190 the 1616 instruction. Despite arguing he had 00:33:55.190 --> 00:33:57.029 only presented the ideas for discussion, he was 00:33:57.029 --> 00:33:58.910 forced under threat of torture, though the torture 00:33:58.910 --> 00:34:01.210 was not administered, to formally admit that 00:34:01.210 --> 00:34:02.950 the dialogue gave the impression of defending 00:34:02.950 --> 00:34:05.390 Copernicanism. What was the final verdict and 00:34:05.390 --> 00:34:10.389 sentence? On June 26, 1633, he was found vehemently 00:34:10.389 --> 00:34:13.650 suspect of heresy, a status that required public 00:34:13.650 --> 00:34:16.630 repudiation of the error. He was forced to publicly 00:34:16.630 --> 00:34:19.889 recant and abjure, curse, and detest his opinions. 00:34:20.170 --> 00:34:22.670 His sentence of formal imprisonment was immediately 00:34:22.670 --> 00:34:25.409 commuted to house arrest, first under the Archbishop 00:34:25.409 --> 00:34:27.670 of Siena, and then for the rest of his life at 00:34:27.670 --> 00:34:30.590 his villa in Arsetri. All of his past and future 00:34:30.590 --> 00:34:32.409 works were strictly forbidden from publication. 00:34:33.070 --> 00:34:34.769 And what about the famous legend, And Yet It 00:34:34.769 --> 00:34:37.590 Moves, Y Pussy Mauve? It's a wonderful legend. 00:34:37.670 --> 00:34:39.670 It captures the defiance we imagine he felt. 00:34:39.829 --> 00:34:41.829 However, the earliest known written account of 00:34:41.829 --> 00:34:44.010 him uttering the phrase dates from a full century 00:34:44.010 --> 00:34:46.730 after his death. The often cited evidence, a 00:34:46.730 --> 00:34:48.730 painting purportedly showing the phrase written 00:34:48.730 --> 00:34:51.190 on a prison wall, was later traced to an artist 00:34:51.190 --> 00:34:55.030 in 1837. It is likely apocryphal, but the spirit 00:34:55.030 --> 00:34:56.869 of the quote certainly reflects his personal 00:34:56.869 --> 00:34:59.110 convictions. It is truly remarkable that while 00:34:59.110 --> 00:35:01.269 under permanent house arrest, silenced by the 00:35:01.269 --> 00:35:03.150 church and suffering from debilitating health, 00:35:03.369 --> 00:35:05.869 Galileo produced his magnum opus on mechanics. 00:35:06.130 --> 00:35:08.630 It speaks volumes about his singular dedication 00:35:08.630 --> 00:35:12.469 to knowledge. While confined at Arcetri, he secretly 00:35:12.469 --> 00:35:15.329 compiled and refined the theoretical and experimental 00:35:15.329 --> 00:35:17.550 work on motion he had been developing for decades 00:35:17.550 --> 00:35:20.269 into discourses and mathematical demonstrations 00:35:20.269 --> 00:35:24.289 relating to two new sciences in 1638. And because 00:35:24.289 --> 00:35:26.909 of the ban, the manuscript had to be smuggled 00:35:26.909 --> 00:35:30.360 out of Italy. Yes, to Leiden in Holland for publication. 00:35:30.699 --> 00:35:33.599 This work essentially defined the field of classical 00:35:33.599 --> 00:35:36.119 physics and kinematics for the next generation. 00:35:36.400 --> 00:35:39.099 Absolutely. The work is divided into four days 00:35:39.099 --> 00:35:41.559 of conversation. The first three days focus on 00:35:41.559 --> 00:35:43.719 the strength of materials, a massive contribution 00:35:43.719 --> 00:35:46.639 to engineering and kinematics. He details his 00:35:46.639 --> 00:35:48.880 experiments on acceleration, derived his time 00:35:48.880 --> 00:35:50.880 -squared law, and established the trajectory 00:35:50.880 --> 00:35:53.980 of projectiles as parabolic arcs. That structural 00:35:53.980 --> 00:35:56.000 engineering element often gets overlooked in 00:35:56.000 --> 00:35:58.329 favor of the astronomy. It shouldn't. The first 00:35:58.329 --> 00:36:00.250 two sections on the strength of materials were 00:36:00.250 --> 00:36:02.949 highly innovative. He proved that scaling up 00:36:02.949 --> 00:36:05.170 a structure proportionally does not maintain 00:36:05.170 --> 00:36:07.829 the same relative strength. He discussed how 00:36:07.829 --> 00:36:10.130 the size limitations on structures like ships 00:36:10.130 --> 00:36:12.789 or towers are related to the square cube law, 00:36:12.969 --> 00:36:16.329 explaining why giants cannot exist. This established 00:36:16.329 --> 00:36:18.469 the foundational theory for fracture mechanics 00:36:18.469 --> 00:36:20.809 and structural engineering. And Einstein praised 00:36:20.809 --> 00:36:23.369 it. Albert Einstein, reflecting on the historical 00:36:23.369 --> 00:36:26.170 significance, later called Galileo the father 00:36:26.170 --> 00:36:29.090 of modern physics, specifically citing the achievement 00:36:29.090 --> 00:36:31.969 of two new sciences. It's crucial to remember 00:36:31.969 --> 00:36:34.570 that he remained the practical polymath and entrepreneur 00:36:34.570 --> 00:36:37.670 even into his later years. His engineering genius 00:36:37.670 --> 00:36:41.449 was constant. Between 1595 and 1598, he developed 00:36:41.449 --> 00:36:44.010 and sold hundreds of his improved geometrical 00:36:44.010 --> 00:36:46.929 and military compasses. This sector instrument 00:36:46.929 --> 00:36:49.309 allowed gunners to quickly calculate the proper 00:36:49.309 --> 00:36:51.250 charge of gunpowder for different cannonballs 00:36:51.250 --> 00:36:54.110 and angles and allowed surveyors to perform complex 00:36:54.110 --> 00:36:56.590 geometric calculations on the spot. He wasn't 00:36:56.590 --> 00:36:58.949 just selling the tool, he was selling the expertise. 00:36:59.690 --> 00:37:02.750 Yes, he was marketing a complete solution. He 00:37:02.750 --> 00:37:05.210 sold the instrument, published detailed instruction 00:37:05.210 --> 00:37:07.789 manuals for its use, and often offered a full 00:37:07.789 --> 00:37:10.050 course of instruction to wealthy patrons, sometimes 00:37:10.050 --> 00:37:13.389 charging 120 lira for the training. His early 00:37:13.389 --> 00:37:16.110 horsepower water pump also underscores his focus 00:37:16.110 --> 00:37:19.809 on applied, income -generating science. His work 00:37:19.809 --> 00:37:21.949 in optics extended beyond the telescope, too. 00:37:22.250 --> 00:37:25.010 Indeed. He was using a compound microscope by 00:37:25.010 --> 00:37:28.030 1624, refining it for observations in biology 00:37:28.030 --> 00:37:30.530 and minute details. It's a point of interest 00:37:30.530 --> 00:37:33.050 that the name microscope itself was coined by 00:37:33.050 --> 00:37:35.590 Giovanni Faber, a member of the Accademia dei 00:37:35.590 --> 00:37:38.829 Lincei in 1625, creating a linguistic analogy 00:37:38.829 --> 00:37:41.329 with Galileo's earlier perfected instrument, 00:37:41.610 --> 00:37:44.090 the telescope. He even had a mechanical insight 00:37:44.090 --> 00:37:46.690 that predates modern lubrication theory. The 00:37:46.690 --> 00:37:49.639 caged ball bearing. Galileo described the use 00:37:49.639 --> 00:37:52.420 of a caged ball bearing to reduce friction. While 00:37:52.420 --> 00:37:54.539 many attribute the formal patent or innovation 00:37:54.539 --> 00:37:57.500 to later engineers, Galileo's description proves 00:37:57.500 --> 00:37:59.539 he understood the critical principle of isolating 00:37:59.539 --> 00:38:01.619 rolling elements to prevent them from rubbing 00:38:01.619 --> 00:38:04.280 against each other, ensuring smooth motion. His 00:38:04.280 --> 00:38:06.880 life ended tragically under restriction, yet 00:38:06.880 --> 00:38:09.780 his physical remains caused a final post -mortem 00:38:09.780 --> 00:38:13.699 scandal. Galileo died on January 8, 1642, aged 00:38:13.699 --> 00:38:17.079 77, having become completely blind a few years 00:38:17.079 --> 00:38:20.860 earlier in 1638. His patron, the Grand Duke of 00:38:20.860 --> 00:38:23.940 Tuscany, Ferdinando II, planned a grand gesture, 00:38:24.260 --> 00:38:27.440 a marble mausoleum in the Basilica of Santa Croce 00:38:27.440 --> 00:38:30.159 next to his ancestors. But the shadow of the 00:38:30.159 --> 00:38:32.880 Inquisition still held sway. Pope Urban VIII, 00:38:33.019 --> 00:38:35.880 still politically constrained by the 1633 verdict, 00:38:36.019 --> 00:38:38.440 protested vehemently, and the Grand Duke's plans 00:38:38.440 --> 00:38:42.360 were blocked. Galileo was instead buried discreetly 00:38:42.360 --> 00:38:45.280 in a small side room of the Basilica. It wasn't 00:38:45.280 --> 00:38:48.480 until 1737 that he was reburied in the main body 00:38:48.480 --> 00:38:51.099 of Santa Croce. And that reburial created a strange 00:38:51.099 --> 00:38:53.920 act of reverence or perhaps morbid souvenir collection. 00:38:54.280 --> 00:38:56.420 During the transfer of his remains, three fingers 00:38:56.420 --> 00:38:58.900 and a tooth were removed. One of those fingers, 00:38:58.980 --> 00:39:01.179 an index finger, is now displayed at the Museo 00:39:01.179 --> 00:39:03.460 Galileo in Florence, pointing heavenward in a 00:39:03.460 --> 00:39:05.719 silent, symbolic tribute to the man who pointed 00:39:05.719 --> 00:39:07.920 humanity toward the stars. It took centuries 00:39:07.920 --> 00:39:09.679 for the church to lift the sanctions against 00:39:09.679 --> 00:39:13.110 his work. The process was glacial. The ban on 00:39:13.110 --> 00:39:15.809 reprinting his works was slowly lifted in 1718. 00:39:16.469 --> 00:39:19.809 The general prohibition against advocating heliocentrism 00:39:19.809 --> 00:39:22.230 was gradually removed from the Index of Prohibited 00:39:22.230 --> 00:39:25.329 Books. But all official opposition to the Copernican 00:39:25.329 --> 00:39:27.789 system finally disappeared from the Index only 00:39:27.789 --> 00:39:31.110 in 1835. And the final, formal acknowledgement 00:39:31.110 --> 00:39:33.690 of error occurred in the late 20th century. Yes. 00:39:33.889 --> 00:39:36.469 Pope John Paul II addressed the Pontifical Academy 00:39:36.469 --> 00:39:39.909 of Sciences in 1992, acknowledging that the Inquisition 00:39:39.909 --> 00:39:42.360 had erred. He stated that the theologians involved 00:39:42.360 --> 00:39:44.960 in the case did not recognize the formal distinction 00:39:44.960 --> 00:39:47.860 between the Bible and its interpretation, mistakenly 00:39:47.860 --> 00:39:49.900 taking metaphorical scriptural language about 00:39:49.900 --> 00:39:52.860 the Earth's stability as literal scientific fact. 00:39:53.139 --> 00:39:55.699 His legacy encompassing the Galilean moons, the 00:39:55.699 --> 00:39:57.639 Galileo spacecraft, and the establishment of 00:39:57.639 --> 00:40:00.340 mathematical physics is absolutely colossal. 00:40:00.480 --> 00:40:03.079 Stephen Hawking once noted that Galileo probably 00:40:03.079 --> 00:40:05.300 bears more of the responsibility for the birth 00:40:05.300 --> 00:40:08.440 of modern science than anybody else. His impact 00:40:08.440 --> 00:40:11.239 wasn't just in his discoveries. but in his methodology. 00:40:11.659 --> 00:40:14.980 He showed that observable evidence, rigorously 00:40:14.980 --> 00:40:18.019 tested and mathematically described, must trump 00:40:18.019 --> 00:40:21.039 ancient authority, even when that authority is 00:40:21.039 --> 00:40:23.539 backed by the most powerful institutions on earth. 00:40:23.739 --> 00:40:26.659 So what does this life of contradiction, invention, 00:40:26.920 --> 00:40:30.130 and ultimate persecution mean for us now? We've 00:40:30.130 --> 00:40:32.170 seen Galileo marry mathematics and experiment, 00:40:32.469 --> 00:40:35.530 defining fundamental kinematics and forcing humanity's 00:40:35.530 --> 00:40:38.349 worldview to shift from earth -centered to sun 00:40:38.349 --> 00:40:40.269 -centered, not through philosophy, but through 00:40:40.269 --> 00:40:43.309 verifiable, reproducible evidence. His core contribution 00:40:43.309 --> 00:40:45.550 was establishing the modern idea that physical 00:40:45.550 --> 00:40:47.329 reality is intelligible through mathematics. 00:40:47.769 --> 00:40:50.829 He was a master of idealization, conceptualizing 00:40:50.829 --> 00:40:53.369 motion in a vacuum, or conceptualizing a system 00:40:53.369 --> 00:40:56.309 free from resistance, and then using that idealization 00:40:56.309 --> 00:40:58.510 to build theories he could test in the real world 00:40:58.510 --> 00:41:00.739 using his his ingenious experimental setups. 00:41:00.920 --> 00:41:04.099 And his literary works, like the Essayer and 00:41:04.099 --> 00:41:07.500 the Dialogue, were equally revolutionary. demonstrating 00:41:07.500 --> 00:41:10.219 how scientific argument could be conveyed, not 00:41:10.219 --> 00:41:12.860 just through dry equations, but through rhetorical 00:41:12.860 --> 00:41:15.659 mastery and conversational force. He was trying 00:41:15.659 --> 00:41:18.159 to change not just what people believed, but 00:41:18.159 --> 00:41:21.239 how they believed it. He sought to shift trust 00:41:21.239 --> 00:41:24.880 from authority to observable, demonstrable fact. 00:41:25.360 --> 00:41:28.659 That required both genius in the lab and brilliance 00:41:28.659 --> 00:41:31.260 with a pen. And it's a story of genius that continues 00:41:31.260 --> 00:41:33.880 right up until his final moment, even when his 00:41:33.880 --> 00:41:36.409 work was forbidden. The poignant anecdote about 00:41:36.409 --> 00:41:39.369 his personal library perfectly captures the fragility 00:41:39.369 --> 00:41:41.809 of knowledge in the face of institutional suppression. 00:41:42.190 --> 00:41:44.730 While under house arrest at his villa, Il Giolo, 00:41:44.869 --> 00:41:46.929 he relied on visitors to smuggle in the latest 00:41:46.929 --> 00:41:49.289 scientific texts from northern Europe, ensuring 00:41:49.289 --> 00:41:51.190 he remained current despite the official ban 00:41:51.190 --> 00:41:54.130 on his own publications. His library was substantial, 00:41:54.449 --> 00:41:57.550 containing nearly 600 volumes. Yet, after his 00:41:57.550 --> 00:42:00.309 death, his priceless papers and books were scattered. 00:42:00.699 --> 00:42:02.639 They fell to his daughter -in -law, Sestilia, 00:42:02.900 --> 00:42:05.639 who simply did not grasp their intellectual value. 00:42:06.360 --> 00:42:08.960 Although his former student, Vincenzo Viviani, 00:42:09.139 --> 00:42:11.579 tried to collect them for publication, the project 00:42:11.579 --> 00:42:15.139 failed. Servants and heirs oblivious to the profound 00:42:15.139 --> 00:42:18.179 historical and scientific significance sold many 00:42:18.179 --> 00:42:20.659 of the volumes, sometimes literally for waste 00:42:20.659 --> 00:42:24.559 paper. Imagine the humiliation. The manuscript 00:42:24.559 --> 00:42:27.519 detailing the birth of modern physics being sold 00:42:27.519 --> 00:42:30.510 by weight for recycling. It's the ultimate indignity, 00:42:30.510 --> 00:42:32.969 but also a profound testament to the risk of 00:42:32.969 --> 00:42:36.449 suppressing ideas. It wasn't until around 1750, 00:42:36.650 --> 00:42:39.530 a century after his death, that a dedicated scholar, 00:42:39.809 --> 00:42:42.530 the Florentine senator Giovanni Battista Clemente 00:42:42.530 --> 00:42:45.110 Danelli, began piecing the archive back together. 00:42:45.550 --> 00:42:47.769 He heard rumors of the scattering and diligently 00:42:47.769 --> 00:42:49.949 purchased the remaining manuscripts and books 00:42:49.949 --> 00:42:52.469 from shopkeepers and heirs, saving Galileo's 00:42:52.469 --> 00:42:54.750 physical archive from total disintegration. The 00:42:54.750 --> 00:42:57.010 knowledge had to be literally rescued scrap by 00:42:57.010 --> 00:42:59.110 scrap from the trash heap of history because 00:42:59.110 --> 00:43:01.150 the prevailing authorities had failed to recognize 00:43:01.150 --> 00:43:03.429 its worth and had instead chosen to suppress 00:43:03.429 --> 00:43:05.989 it. It's the physical manifestation of the long 00:43:05.989 --> 00:43:08.469 arc of scientific truth prevailing over established 00:43:08.469 --> 00:43:11.179 dogma. Understood. Consider this then as you 00:43:11.179 --> 00:43:13.699 reflect on Galileo's life. Even after his physical 00:43:13.699 --> 00:43:15.460 body was interred and his written words were 00:43:15.460 --> 00:43:18.159 banned, the knowledge he produced had to be literally 00:43:18.159 --> 00:43:20.719 rescued piece by piece by later generations. 00:43:21.039 --> 00:43:23.960 What ideas, backed by verifiable evidence, are 00:43:23.960 --> 00:43:26.119 we overlooking or suppressing today, either due 00:43:26.119 --> 00:43:28.579 to convenience, tradition, or authority, that 00:43:28.579 --> 00:43:29.980 will need to be similarly rescued tomorrow?