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Galilean Science

Rob Iliffe Galilei (1564-1642)

• Born in Pisa, son of musician . • Enrolled for a medical degree but soon dedicated himself to mathematics, becoming Professor of Mathematics at Pisa in 1589. • After three years he became Prof. of Mathematics at the prestigious University of Padua, • thus becoming senior mathematician in the Venetian Republic. • While at Pisa he showed extraordinary confidence, setting out to dismantle the fundamental presuppositions of Aristotelian science, • Notably the doctrine of the 4 elements and their ‘natural’ places. Contra Aristotle

• In a number of writings in the 1590s Galileo attacked the Aristotelian claim that the 2 ‘heavy’ elements (earth and water) naturally sought to move down towards the centre of the earth, • While the lighter elements (Air and Fire) sought to rise to the heavens. • Instead, he argued that there was only one principle of motion (‘gravitas’ or ‘heaviness’) that was downward; • And only one sort of matter; if objects rose to the air it was because they had been ‘displaced ‘ by heavier objects. Inclined planes

• Galileo started a new research programme in c. 1603, measuring the actions of and balls rolling on inclined planes. • Having studied ‘natural’ accelerations from the mid-1590s, he began to integrate time and acceleration into his work on falling bodies. • ‘Odd-number’ (total distance fallen is proportional to the square of time taken) rule, discovered c. 1605, was the first mathematization of an Aristotelian qualitative motion - • The successive distances travelled in each second (1, 3, 5, 7, etc.) implied a constant acceleration, • But Galileo refused to speculate on its cause. Galileo and the Telescope • A ‘far-seeing device’ was announced at Frankfurt fair in 1608, devised by Hans Lippershey (Middelburg) • Galileo worked with technicians to improve the instrument through 1609 and turned it to the heavens at the end of 1609 • Starry Messenger (1610) announced the existence of mountains on Moon, satellites of Jupiter and resolved stars in the Milky Way, each of which was remarkable. • He dedicated the book to the new Duke of Tuscany, Cosimo II, • An action that was part of a larger effort to gain a position as a major scholar at the Medici court.

Back of envelope notes on satellites of Jupiter, Jan. 14-25, 1611 Impact of

• Sidereus Nuncius caused a sensation and made him famous. • In 1610, having named the Jovian moons the ‘Medician satellites’, he was made Royal Mathematician at the Medici Court in Florence, • Slightly later obtaining the additional title of ‘Philosopher’. • Although lacking a telescope himself, Kepler responded to the work immediately in an essay, assuming • (a) what Galileo had not made completely explicit, namely that the work was generally supportive of the heliocentric position, and • (b) that Galileo had given decisive evidence for life on the Moon. Image of ‘Domingo Gonsales’ flying to the Moon powered by giant swans (gansas); from Francis Godwin, The Man in the Moone (1638)

Christian Huygens’s Cosmotheoros (1698) Letters on (Istoria e Dimostrazioni intorno alle Macchie Solari) (1613) • Published in Italian (and thus a broader audience) under auspices of the , Galileo unambiguously announced his commitment to Copernicanism for the first time. • Work was response to a series of letters by Jesuit , who argued that the spots were small bodies (like the Medicean satellites!) orbiting the Sun. • Galileo’s work provided evidence that -- contra Aristotle -- the Sun had its own motion, • and more generally, via identification of ‘maculae’ on the solar surface, that the heavens were not perfect. Galileo’s drawings of phases and change in visible size of Venus, 1612 (he discovered this in 1610).

He published his results in the work on sunspots; it was decisive evidence against geocentrism but not against Tycho’s geoheliocentrism Roman adventures, 1613-15

• Jesuit astronomers at the Collegio Romano had repeated Galileo’s observations within a few months, • but in early 1613, a number of Dominicans began to preach against Galileo and Copernican ideas, • Arguing that natural philosophers had no authority to explain away geocentric passages in the Bible. • After writing to his ex-student (a Benedictine Abbot) on the relationship between science and religion, • In 1615 Galileo wrote an inflammatory defence of Copernicanism to Cosimo’s mother the ‘Grand duchess’ Christina, arguing (with the help of friends) that was compatible with Scripture. Condemnation

• In 1615 Galileo went to Rome, where Cardinal Roberto Bellarmino was asked to adjudicate on the issue between Galileo and his opponents. • Bellarmino initially stated that Galileo should treat heliocentrism as a hypothetical and not a real situation, since it was not a matter of faith; • There had not yet been a conclusive demonstration of its truth. • However, the Inquisition pronounced on the matter in February 1616. calling it ‘foolish and absurd in philosophy, and formally heretical’. • Bellarmino told Galileo that he was not to ‘hold, teach or defend’ the doctrine in any manner. • The Congregation banned all Copernican books on 5 March. (Il Saggiatore) 1623

• Ostensibly a book on the nature of comets, in which Galileo peculiarly argued (against Tycho and some Jesuit astronomers) that they were optical illusions whose cause lay in the terrestrial atmosphere. • More than this, it was a major exposition of a new scientific method, in which Galileo drew on Copernicus to claim that the universe was written in mathematical characters, • And that one needed to use mathematics to decipher it. • It was dedicated to the family of his friend Maffeo Barberini, who had just been elected Pope Urban VIII; • Barberini apparently read it with great pleasure.

Dialogue on the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo) (1632) • Galileo’s most famous text, a brilliantly written dialogue set over 4 days, aimed at a broad audience. • In ‘days’ one and two of the dialogue, Galileo tried to solve problem (which Copernicus had failed to address) of what the real motions were of objects on the face of the Earth. • Solution was that ‘natural’ terrestrial motion was circular, • i.e. in whatever frame of reference one was in, all unimpeded moving objects tended to move in a circular direction around the surface of the earth. On Day Three, Galileo’s character Salviati made the Aristotelian character Simplicio utter ridiculous comments about the Aristotelian system, one of which infuriated the Pope.

The 4th Day concerned Galileo’s demonstration of Copernicanism based on his (faulty) explanation of the motion of the tides; this was supposed to be the long-awaited ‘demonstration’ of the physical reality of heliocentrism. Trial and House Arrest

• Galileo’s work was published at a time when the Catholic Church was suffering a series of losses in the 30 Years’ War, • And Urban VIII, displeased by the Dialogo and under pressure from the Spanish to act against heresies, now moved against his one-time friend. • In 1633 Galileo was ordered to stand trial on suspicion of heresy for ‘holding as true the false doctrine’ of Copernicanism. • He was found guilty and forced to ‘abjure, curse and detest’ Copernicanism, • Sentenced to house arrest in Arcetri near Florence, where he stayed for the rest of his life. Discourses and Mathematical Demonstrations on (Discorsi e dimostrazioni matematiche intorno a due nuove scienze (1638) • This was published in Amsterdam in 1638 and became Galileo’s most significant work. • In the First Two days of the dialogue Galileo attempted to give a science of matter from a mathematical perspective, • and to show that mathematical principles of motion that are the core of belong to the science of . • Days 3 and 4 include a number of famous claims, such as the notion that all objects would fall at the same rate, if not impeded. • And new anti-Aristotelian arguments, showing its internal incoherence. The Mathematization of Natural Philosophy

• Galileo’s mathematical approach to natural philosophy was deeply influential for many, inc. for Christiaan Huygens and Isaac Newton. • However, his work was criticized by many, including René Descartes, for paying insufficient attention to the physical causes of natural phenomena (the traditional goal of natural philosophy). • Moreover, even for his supporters it was extremely difficult to prove the odd-number rule by repeated experiments. • And thus to show that this cosmos, as opposed to a perfect Platonic off-world, was essentially written in mathematical characters. Bibliography 1)

• S. Bedini, Galileo and the Measure of Time, (Florence, 1967) • M. Biagioli, Galileo, Courtier, (Chicago, 1993) • M. Buccianti et al. Il telescopio de Galileo, (Torino, 2012) • S. Drake, Galileo at Work: His Scientific Biography, (Chicago, 1978) • P. Galluzzi, Momento: Studi Galileani, (Rome, 1979) • J. Heilbron, Galileo, (Oxford, 2010) • A. Koyré, Etudes Galileennes, (Paris 1939) • The Cambridge Companion to Galileo • T. Mayer, ed., The Trial of Galileo, 1612-33 (Ontario 1992) • P. Palmieri, Re-enacting Galileo’s Experiments: Rediscovering the Techniques of Seventeenth-Century Science, (Lewiston, NY, 2008) Bibliography (2) • J. Renn, J. P. Damerow, P. & S. Rieger, S., ‘Hunting the White Elephant: When and How did Galileo Discover the Law of Fall?’, in Renn (ed.), Galileo in Context, (Cambridge 2002), 29–149. • E. Reeves, Galileo’s Glass Works: The telescope and the mirror, (Cambridge, 2008) • M. Segré, In the Wake of Galileo, (New Brunswick, 2008) • T. Settle, “Galileo and Early Experimentation,” in R. Aris, et al. (eds.), Springs of Scientific Creativity, (Minneapolis: 1983), pp. 3–20. • W. Shea & M. Artigas, 2003, Galileo in Rome: The Rise and fall of a Troublesome Genius, (Oxford, 2003). • W. Wallace, Galileo and his Sources: The Heritage of the Collegio Romano in Galileo’s Science, (Princeton, 1984).