Galileo never dropped any balls from the Tower of Pisa. He never spent time in a dungeon. And he didn't prove that the earth revolved around the sun. These are just 3 of many myths we are told about Galileo. The myths have even duped famous scientists such as Neil DeGrasse Tyson, Carl Sagan, Bertrand Russell, Stephen Hawking and others. Knowing science doesn't mean you know it's history. Hopefully, this page will help readers separate fact from fiction.
Bertrand Russell tells a good story but there is no reason to believe any of it is true. Neither Galileo nor any of his contemporaries mentioned the Tower of Pisa story during Galileo's lifetime. The source of the myth is Galileo's first biographer, Vincenzo Viviani. Viviani is not considered a credible source because of other errors in the biography. There is documented evidence of two Tower of Pisa experiments during Galileo's time, neither conducted by Galileo. One of the experiments was done by Vicenzio Renieri, a Roman Catholic monk and professor at the University of Pisa. Renieri was a friend of Galileo's and reported it immediately to Galileo ( see Galileo's Contemporaries ). Another experiment was done by Giorgio Coresio, another University of Pisa professor. Even if Galileo had actually performed the experiment, it wouldn't have been considered novel. Several free fall experiments from towers had been conducted before the suggested date of Galileo's mythical experiment (these include experiments by Simon Stevin, Giuseppe Moletti, Varchi, John Philoponus). John Philoponus had conducted his experiment about 1000 years before Galileo was born. The image below is taken from a book on the lives of great scientists (Story-Lives of Great Scientists,Rowbotham).
This myth of "Eppur si muove' is so common that it traps unsuspecting authors even at the most prestigious news sources. Early biographies of Galileo never mentioned the event. The first mention of the myth in the English language was by Giuseppe Baretti in 1757, more than a century after Galileo's death. Records of Galileo's trial do not reference any similar statements being said by Galileo.
Carl Sagan evokes a frightening image of Galileo's experience at the hands of the Inquisition. Fortunately, we have a floor plan of the large 5-room suite in the Palace of the Inquisition that had been assigned to Galileo(see image below) [_1_] . It was larger than the average American home (approximately 230 sq. m. or 2500 sq. ft.). Two of the rooms overlooked the Vatican Gardens. It included a room for the personal valet that had been provided by the Inquisition. The ante room (similar to a waiting room) allowed Galileo's valet to greet visitors before ushering them to meet him. Galileo was given two choices for food, eat his meals with the Cardinals of the Inquisition or to have his favoured Tuscan food and wine provided to him by the Tuscan Embassy. He chose the food and wine from the Tuscan Embassy ( see Galileo's Battle for the Heavens ).
What if no one invented the scientific method, as many historians of science believe ( see Nobody Invented the Scientific Method ). Firstly there is no agreement on exactly what the scientific method is. But even if you use the definitions typically taught in grade school there is a problem. The scientific method is a specific approach to inductive reasoning. There was continuous discussion of inductive methods similar to the scientific method from the time of the Greeks, and through the early and late middle ages by Greek, Islamic and Christian scholars. Galileo's first important position was at the University of Padua. The University was already an important center for the development of inductive reasoning techniques (the double regress) which was very similar to the scientific method (see Medieval Methodologists).
The PBS documentary's educational materials manage to get it wrong about both Galileo and Newton in one sentence (see Fathers of the Telescope). Astronomers switched from using Galilean designs to Keplerian designs very shortly after Galileo's death (see Timeline of the Telescope). Keplerian astronomical refractors dominated until the late nineteenth century [_2_] . In the twentieth and twenty-first century the most important telescopes were almost exclusively Cassegrain reflecting telescopes. Laurent Cassegrain was a Catholic priest from Isaac Newton's time (see Reflecting on History) . Kepler never actually made a telescope of his design but his contemporaries amongst the Jesuits did (see Jesuits and the Early Telescope).
Galileo is important to the history of telescopes because he was responsible for making the use of telescopes in astronomy respectable and that he very quickly raised the bar on telescope manufacturing. Galileo's telescopes were 20X and 30X power versus the 3X power of the original Dutch telescopes. Regardless, Galileo's preferred design had a very serious design flaw. As you increase the power of a Galilean telescope the field of view decreases to the point where the telescope becomes useless. That is why the popularity of the Galilean design barely outlived Galileo himself . The image below shows a view of the moon from a 20X Keplerian telescope and a 20X Galilean telescope. The bubble in the middle of the moon is the field of view of a Galilean telescope.
There are many problems with choosing Galileo as the "First Modern Scientist" or the "Father of Modern Science". Tim O'Neil outlines some of these problems in "Why is Galileo considered the "Father of Modern Science"? . Galileo's use of observation and carefully designed experiments to prove his points was not unique in his time. The various free fall experiments conducted by Galileo's contemporaries all exhibit good design. For instance, when Galileo was only 12 years old, Giuseppe Moletti (a professor at the University of Padua) conducted a free fall experiment by dropping balls from a tower. Moletti, like others of his time, knew about controls. He controlled for shape, material and volume (see Galileo's Predecessors). Galileo's use of mathematics to describe natural events also wasn't unique. The use of mathematics in the study of motion was already widespread throughout Europe and had been for more than two centuries ( see The Oxford Calculators). We know that Galileo had been exposed to this previous work from his own notes as a student [_3_] . Galileo did champion the use of actual physical experiments in his writings. Although he talked the talk, Galileo didn't always walk the walk. He often fell back on "Mind Experiments" instead of actual physical experiments to argue his points. The use of mind experiments to support arguments was common amongst renaissance scientists. Galileo didn't always describe the experiments such that they could be easily replicated. In fact, there is still some controversy over whether some of the experiments he described were real physical experiments or just mind experiments.
The best model being argued during Galileo's day was Kepler's model, the one that is taught in grade schools today. Galileo's preferred model was the Copernican. Galileo felt that Kepler was so erratic that it was best to ignore his work completely (see Galileo's Contemporaries). The Keplerian model already had one major success before Galileo's Dialogue of Two Chief World Systems when it successfully predicted the Transit of Mercury (see Gassendi and the Transit of Mercury). The image below is Gassendi's drawing of the transit. In this experiment, the Copernican model faired badly, performing even worse than the Ptolemaic model. The Copernican Model did not fit with observations any better than any of the competing models, including the ancient Ptolemaic Model. This has been confirmed by modern computer-based statistical analysis. The Copernican Model may have been more simply calculated, but this wasn't as important as it may seem. Users of the models would be working from pre-calculated tables not the models themselves.
Galileo made observations with his telescope that were better explained by the sun-centered Copernican model than the earth-centered Ptolemaic model. These observations include the phases of Venus and retrograde motion of planets. Retrograde motion is when a planet exhibits a pattern of motion that includes a reversal in direction. This showed up the flaws in the Ptolemaic system but didn't prove Copernicus' model was correct. Other models being discussed at the time were geo-heliocentric, which means that some planets revolved around the sun and some around the earth. These included the Tychonic and the Capellan models. Both these models did not have these flaws from the Ptolemaic model. They had a theoretical advantage over the Copernican model in that they accommodated for the lack of stellar parallax. If the earth really did revolve around the sun, there should be evidence of stellar parallax, and none was observed ( see Copernicus and Stellar Parallax ). Another obvious problem for scientists of the time is that if Galileo was correct, you should expect the Copernican Model to predict planet positions better than earth centered models; it didn't. Galileo also presented a disastrous support for heliocentrism based on tides, but in his world there was only one tide per day. Scientists are very demanding of any proof of a theory. Centuries later, scientists rejected Alfred Wegener's Continental Drift Theory even though he probably had stronger support for his theory than Galileo did for his (see Wegener and Continental Drift).
Not everyone during Galileo's time was a blind follower of Greek thinkers such as Aristotle and Ptolemy. In fact, attacking Aristotle and Ptolemy was already a blood sport before Galileo was born. These great men were attacked based on theory, observation and experiment. Tyson is wrong about nobody saying "Show me!". There were many free fall experiments before Galileo's experiment. These started about 1000 years before Galileo (John Philoponnus) but there were many in the sixteenth and early seventeenth century (Varchi, Borro, Buonamici,Moletti, Mazzoni, Harriot, Stevin, Coresio, Renieri).
When science commentators discuss the blind faith put in Aristotle, they ignore what happened in the century before Galileo's birth; European mariners crossed the equator and rounded the Cape of Good Hope, and Europeans colonized the Western Hemisphere. Aristotle and Ptolemy had written extensively on Geography, Meteorology and Biology. The observations by the mariners and Spanish Jesuit naturalists based in South America showed how disastrously wrong both Aristotle and Ptolemy could be on all of these subjects (see Galileo's Contemporaries). The maps below show a Ptolemaic map from before Columbus' voyage and a Spanish map from about 3 decades after his voyage.
A few years before Galileo was born, Domingo de Soto, a Roman Catholic priest, published a physics text that stated the objects in free fall undergo constant acceleration obeying the "times square law". This was Galileo's Law of Free Fall. The book was tremendously successful and had gone through 8 printings before Galileo had graduated from university (see Galileo's Predecessors). The behaviour of objects undergoing constant acceleration had been discussed for centuries before Galileo (see The Oxford Calculators). The "times square rule" and "Galileo's Odd Number Rule' had been proposed by the Parisian doctors (e.g. Nicole Oresme ) centuries before as well. Galileo never experimentally discovered the law of free fall; he experimentally proved it.
While some of the elements of the law of free fall had been around centuries, Galileo's experiment to prove the law was brilliant. The main problem Galileo faced was finding a timing mechanism that was accurate in the seconds range and slowing down the process of free fall so that it could more easily and accurately be measured. Mechanical clocks of the time didn't even have minute hands. Galileo opted for a carefully calibrated water clock (if it drips at a fixed frequency, the volume of water dripped is proportional to time) and to slow down the experiment by rolling balls down an inclined plane instead of dropping balls from a tower. This approach was accurate enough to prove the law.
While Galileo's experiment was accurate enough to prove the law, it wasn't accurate enough to determine the acceleration due to gravity ( small "g" ). That would be left to his contemporaries amongst the Jesuits. They developed a pendulum timing mechanism by having teams of Jesuits count the oscillations of pendulums of various lengths over a 24 hour period. The goal was to get a pendulum length that would generate 86400 oscillations in a day (since there are 86400 seconds in a day). They used an easily recognizable night-time celestial event to start and stop the timing. When they found a pendulum that oscillated at close to 86400 times a day, they used it to time balls falling from one of the tallest towers in Europe, the Torre Asinelli in Bologna. Their work pointed to an acceleration due to gravity of 914 cm/sec/sec versus the actual value of about 981 cm/sec/sec. Galileo's value was about 467 cm/sec/sec (see Galileo's Contemporaries). The image below is a view from the top of the Torre Asinelli; the smaller tower below is just a few meters shorter than the Tower of Pisa.
Thermometers must have a scale in order to measure differences in temperature. Galileo invented a thermoscope that gave an indication of the temperature but didn't have a scale. It was Santorio Santorio who invented the thermometer in 1612.
This is one of those myths that was manufactured from thin air. No documentary evidence from Galileo's time has been found to support it. Instead, the documentary evidence supports the thesis that the Cardinals from Galileo's time were early adopters of telescope technology. Galileo's first public demonstration of his telescope was to the Doge of Venice in August of 1609. By that time, Cardinal Borghese of Rome had already acquired a telescope from artisans in Northern Europe [_4_] . After the demonstration in Venice, Galileo started building telescopes for others. Many of his clients were Cardinals.
Cardinals were Galileo's perfect client. He didn't want his telescopes getting into the hands of mathematicians or scientists, since that could mean more competition for astronomical discoveries. The more powerful princes and dukes might have court mathematicians or astrologers. The Emperor of the Holy Roman Empire was not able to get a Galilean telescope. This is likely because his court mathematician was Johannes Kepler. The Emperor complained to the Tuscan ambassador as to why he shouldn't get priority over the Cardinals [_5_] . Eventually Kepler was able to borrow a telescope from the Catholic Archbishop of Cologne.
An alternative myth replaces 'Cardinals' with 'Aristotelian professors'. This is questionable too. There was a letter from Galileo to Kepler about learned people who do not wish to try out the telescope, but it doesn't mention names. Galileo's colleague and friend, Cremonini, told him that he would not look through the telescope, after looking through it. He complained that it gave him a headache. Given the questionable quality of the optics from that time, this is believable. The only professor known to refuse to try out Galileo's telescope was Giulio Libri.
After Galileo's trial there was no change in his ability to receive the sacraments of the church [_6_] . When he moved back to Florence due to illness, he made a special request that he be allowed to be carried to a local church to attend Mass on feast days. It was approved. Galileo's contemporary, Johannes Kepler, was excommunicated from the Lutheran church in 1619.
Famous politicians can get it wrong about Galileo, too. Galileo did not argue against a flat earth because he didn't have to. Medieval scholars, like the Greeks before them, believed in a spherical earth. And this knowledge went beyond the scholars, since there were many references to a spherical world in important popular literature from the middle ages. The myth probably originated as part of a propaganda war between Protestants and Catholics in the Early Modern Period to portray the Catholic Church as backward. The myth was taken up by several nineteenth century authors to support the thesis that the church and science conflict. The history of the Flat Earth myth is discussed in detail in Inventing the Flat Earth by Jeffrey Burton Russell.
Popular myths die hard. Although Jeffrey Burton Russell soundly thrashed the Flat Earth Myth, the news hasn't reached everyone. Generations living today grew up being taught the Flat Earth Myth as fact. They would have no reason to doubt that they were being taught the truth when they graduated, so they would have no reason to revisit what they were taught. That is why it is so easy to find famous figures in recent times who believed or believe the myth. These include Neil deGrasse Tyson (Flat Earth Tweets), George Bush Sr. [_7_] and Barack Obama ( Obama Speech 2012). This is another reminder that the best place to get your history of science is from a historian, not a scientist, TV personality or politician.
During Galileo's stay in Arcetri he lived in a casa da signore, a landowner's villa. The villa, Villa Il Gioella, was named The Jewel because of the beautiful view. The villas in the hills surrounding Florence had been used for centuries by the rich of Florence to escape the oppressive summer heat of the city. Often, the villas would be larger than the owner's homes back in Florence. The location of the villa was considered very desirable since it made Galileo one of the closer neighbours to the summer palace of the Medicis. There is speculation that Galileo entertained guests regularly at the villa because his wine cellar had the equivalent of 1200 or more bottles (more than 5 large casks). Even Galileo, with his great love of wine, couldn't consume that much wine. Detailed knowledge of the size, layout and contents of Villa Il Gioella during Galileo's lifetime are known through the letters from his daughter and an inventory taken by his son on his death [_8_] .
This is another myth that seems to have originated from Vincenzo Viviani's biography. There was no reference to the myth during Galileo's lifetime. The chandelier that supposedly sparked Galileo's great discovery wasn't even installed in the cathedral until after his student days. Galileo didn't pay serious attention to the isochronicity of pendulums until much later in his career. In 1614, Santorio Santorio, developed a device called a pulsilogium which used a pendulum to time a patient's pulse. Galileo was not the type who would sit idly by if he felt someone was getting credit for something he rightly deserved [_9_] . Galileo never challenged Santorio's priority.
This myth is very common on the internet, in books, and even university course notes. Apparently, by moving the center of the universe from earth to the sun, Copernicus and Galileo were diminishing man's importance in the universe. Today, being at the centre of things means you are more important. You are in the inner circle! But Galileo and Copernicus both died more than 350 years ago. 350 years ago the people of Europe didn't think that way. Earth was in the centre because it was base and coarse. In Inferno, the great medieval poet, Dante, placed the lowest pit of hell at the earth's center. The earth's centre and hell would therefore have been the center of the universe. Thomas Aquinas described a medieval cosmology where the earth was at the centre, being the most material and coarse. The inner circle wasn't such a great place to be in the middle ages or early modern period. The trap that peddlers of this myth fall into is presentism. They assume that the attitudes of times past were the same as the present.
Galileo did not blind himself. He wasn't that dumb. There were ways to project images from telescopes that were completely safe and even if you didn't use these devices you can view the sun at sunrise and sunset with relative safety . The Jesuits at the time were using camera obscura (a prototype of the camera that could take any view and project it onto a two-dimensional surface (see Jesuits and the Telescope). Galileo is known to have used projection devices as well.
The reason that opthamologists and medical historians don't believe Galileo had sun-blindness is that Galileo's symptoms didn't fit the disease. Sun-blindness is also known as solar retinopathy. With solar retinopathy, Galileo would have been centrally blind because the sun would have burned the small spot on the retina where vision is very sharp (the macular). He would have retained his peripheral vision. There is no indication that Galileo was centrally blind.
One thesis is that Galileo had a congenital disease of the sinus where mucus buildup would force one or both eyeballs downwards and outwards. The portrait done of Galileo (in his lifetime) by the realist portrait artist, Ottavio Leoni, shows just that [_10_] . Another thesis on Galileo's blindness is that he had simple glaucoma, which is a distinct possibility, since Galileo went blind very late in life.