Scientific Revolution II - Galileo Galilei

1. Galileo Galilei (1564-1642)

   1. Born in Pisa to a cloth merchant-musician father

   2. Studies medicine and mathematics

   3. Serves as professor of mathematics at Universities of Pisa (briefly) and Padua (1589-1609)

   4. 1609 - learns about newly invented telescope, builds his own

   5. 1610 - publishes The Starry Messenger at 46, gains fame and recognition as a scientist

2. Galileo the icon

   1. Remembered as first true modern scientist, or at very least, one of the first

   2. Seen also as martyr for science against ignorance and religious dogma

   3. Reality is more complex than that, however

3. The Starry Messenger (Siderius nucius), 1610

   1. The beginnings of telescopic astronomy

      1. Galileo seems to be the first person to point his telescope at the stars - at least the first to publish

      2. 40 page pamphlet announces a number of extraordinary discoveries

         1. Mountains and craters on the moon

         2. Four new "planets" circle around Jupiter

         3. There were many stars could not be seen with the naked eye

         4. While the moon and planets appeared larger in the telescope, the stars only seemed brighter, implying enormous distance

      3. Proof of Copernicus?

         1. Ptolemaic system said everything in the heavens was perfect - but Moon clearly was not

         2. Many had expressed doubts that the Moon could circle the Earth while the Earth circled the Sun

            1. but here were four moons around Jupiter

            2. Clearly, not everything directly circled the Earth

         3. New stars and moons meant the ancients didn't know everything

         4. If the stars were circling the Earth, yet they were so extraordinarily distant, then they would have to be going unfathomably fast

   2. Galileo, Renaissance career man

      1. Starry Messenger is a classic example of how scholars and artists advanced their careers in the Renaissance

      2. Galileo dedicated the book to the powerful ruler of Florence, Cosimo de Medici, Duke of Tuscany

      3. Named the new moons of Jupiter the "Medician stars" - we call them the Galilean satellites (Io, Europa, Ganymede, and Callisto.)

      4. Parlayed this flattery and his new fame into a job as court mathematician and philosopher to the Medicis

      5. Left the University behind for a more lucrative and individualistic position as an independent researcher working for a patron - the ideal Renaissance career path

4. Further telescopic discoveries - Letter on Sunspots, 1613

   1. Sums up various discoveries made from 1610 to 1613

   2. Venus goes through phases like the Moon - hard to explain under Ptolemy, easy under Copernicus (and Tycho)

   3. Sunspots

      1. Another observer, David Fabricus, beat him to publication

      2. Implied that the Sun was not unchanging, unlike the claims of the Aristotelian-Ptolemaic system

      3. Some critics suggested these were only small planets near the Sun - would take some time to resolve

   4. Rings of Saturn

      1. In Galileo's weak telescope, he saw "twins," two small globes attached to Saturn (1610)

      2. Again, this demonstrated that not everything in the heavens was a perfect sphere

      3. By 1612, the "twins" had disappeared!

      4. Would not be till 1659 that Chrstiaan Huygens shoed that they were rings, not globes, that "disappeared" when they were edge on to the Earth

5. Conflict with the Church

   1. By 1616, Catholic Church had decided heliocentrism was a problem, and Galileo narrowly avoided being condemned.

   2. Galileo ordered not to "hold or defend" a belief in heoliocentrism, but he could still discuss it.

   3. Publishes Dialogue Concerning the Two Chief World Systems in 1632, as a conversation between a supported of heolicentrism and geocentrism.

   4. The geocentric defender was called Simplicus, seemed foolish, and used some wording the Pope himself had used.

   5. Galileo convicted of heresy in 1633, condemned to house arrest

   6. Would do important wok on gravity, inertia, mechanical physics and number theory before his death in 1642.