1. The Scientific Revolution (17 th Century) I.Two Major Themes II.Celestial Dynamics and Terrestrial Mechanics A.Johannes Kepler B.Galileo Galilei III. The Mechanical Philosophy A.Rene Descartes B.William Harvey IV.Isaac Newton

2. I. Two Major Themes A. The universe is mathematically ordered 1. Nature in geometric terms 2. Description B. Mechanical philosophy 1. Nature is a machine 2. Explanation C. Different goals – often in conflict solution: solution: "Nature and Nature's Laws lay hid in Night God said, Let Newton be! and all was Light." God said, Let Newton be! and all was Light." Alexander Pope

3. II, Celestial Dynamics and Terrestrial Mechanics The Revolution 1. De Revolutionibus Orbium Coelestium (1543): 50 years later 2. The revolutionaries: Kepler and Galileo A. Johannes Kepler (1571 – 1630) 1. Life 2. Mysterium Cosmographicum (1596) a. Why did God chose 6 planets? b. Answer: 5 platonic solids

4. A. Johannes Kepler (1571 – 1630) 3. Tycho Brahe (1546 – 1601) a. Life b. Aristotle’s celestial spheres crystalline crystalline perfect, unchangeable perfect, unchangeable quintessence = the aether quintessence = the aether circular motion circular motion c. Tycho’s observations very precise (no telescopes) very precise (no telescopes) evidence against celestial spheres evidence against celestial spheres “new” star (supernova) 1572 “new” star (supernova) 1572 comet 1577 comet 1577 beyond orbit of Mars beyond orbit of Mars motion non-circular motion non-circular

5. A. Johannes Kepler (1571 – 1630) d. Tycho Brahe’s model of the universe 4. Kepler and the foundation of celestial mechanics a. No celestial spheres b. Celestial obey same laws as terrestrial c. Kepler focuses on Mars

6. A. Johannes Kepler (1571 – 1630) 5. Astronomia Nova (1609) Kepler’s 3 laws of planetary motion Kepler’s 3 laws of planetary motion 1. Law of orbits The orbit of every planet is an ellipse with the sun at one The orbit of every planet is an ellipse with the sun at one of the foci of the focifoci

7. A. Johannes Kepler (1571 – 1630) 2. Law of areas A line joining a planet (or comet) and the Sun sweeps out equal areas in A line joining a planet (or comet) and the Sun sweeps out equal areas in equal intervals of time equal intervals of time movie of Kepler’s first two laws movie of Kepler’s first two lawsmovie of Kepler’s first two lawsmovie of Kepler’s first two laws

8. A. Johannes Kepler (1571 – 1630) 3. Law of periods The ratio of the squares of the revolutionary periods for The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their two planets is equal to the ratio of the cubes of their semimajor axes. semimajor axes.semimajor semimajor

9. A. Johannes Kepler (1571 – 1630) 6. Sun has magnetic pull on planets (no animistic forces) 7. Results of Kepler’s model simplicity simplicity no circles/ epicycles/ equants no circles/ epicycles/ equants destroys Copernican system destroys Copernican system problems: problems: no evidence no evidence it works! it works! no stellar parallax no stellar parallax

10. B. Galileo Galilei (1564 – 1642) 1. Life 2. The motion problem Aristotle: every motion requires a mover Aristotle: every motion requires a mover projectiles: medium moves it along projectiles: medium moves it along Middle ages: impetus theory Middle ages: impetus theory moving body acquires impetus moving body acquires impetus Galileo’s solution: inertia Galileo’s solution: inertiainertia body in motion moves with body in motion moves with uniform velocity forever uniform velocity forever in a circle! in a circle!

11. B. Galileo Galilei (1564 – 1642) 2. The motion problem motion and the Earth’s rotation motion and the Earth’s rotation ball dropped from a height ball dropped from a height if Earth in motion, ball should drop to the west if Earth in motion, ball should drop to the west observation: ball drops straight down observation: ball drops straight down Galileo: all objects on Earth share its motion Galileo: all objects on Earth share its motion 3. Galileo versus Aristotle A: cause of natural motion; cause of forced motion A: cause of natural motion; cause of forced motion G: no natural place; motion is just a state G: no natural place; motion is just a state object is indifferent to its place object is indifferent to its place rest and motion degrees of the same rest and motion degrees of the same

12. B. Galileo Galilei (1564 – 1642) Projectile motion Projectile motion practical advantage: better war machines practical advantage: better war machines Weights Weights Aristotle: objects with different weights fall at different Aristotle: objects with different weights fall at different velocities velocities Galileo: objects with different weights fall at same Galileo: objects with different weights fall at same velocities (under ideal conditions) velocities (under ideal conditions)

13. B. Galileo Galilei (1564 – 1642) 4. Galileo’s astronomical observations invention of telescope: Hans Lippershey (1608) invention of telescope: Hans Lippershey (1608) Galileo’s telescopes Galileo’s telescopes 1609: Galileo looks at the heavens 1609: Galileo looks at the heavens observations observations moon is not perfect; earthy moon is not perfect; earthy moons of Jupiter moons of Jupiter sunspots sunspots

14. B. Galileo Galilei (1564 – 1642) phases of Venus phases of Venus Galileo claims observations prove Copernican system Galileo claims observations prove Copernican system

15. B. Galileo Galilei (1564 – 1642) 5. Galileo’s “scientific” method Galileo’s world of ideals Galileo’s world of ideals Galileo stuck in the past Galileo stuck in the past the Universe created perfectly by perfect Creator the Universe created perfectly by perfect Creator therefore, all motion must be circular therefore, all motion must be circular

16. B. Galileo Galilei (1564 – 1642) 6. Galileo and the Church the Reformation the Reformation Martin Luther (1483 – 1546) Martin Luther (1483 – 1546) 95 theses (1517) 95 theses (1517) the Counter- Reformation (1560) the Counter- Reformation (1560) the Inquisition the Inquisitionthe Inquisitionthe Inquisition

17. B. Galileo Galilei (1564 – 1642) 6. Galileo and the Church Galileo’s social skills Galileo’s social skills “The Bible teaches the way to go to heaven, not the way the heavens go.” G: the Church should reinterpret the Bible G: the Church should reinterpret the Bible 1616: De Revolutionibus banned (“foolish and absurd … and 1616: De Revolutionibus banned (“foolish and absurd … and formally heretical”) formally heretical”) 1616: Galileo forbidden to hold, defend, or teach the 1616: Galileo forbidden to hold, defend, or teach the Copernican system Copernican system

18. B. Galileo Galilei (1564 – 1642) 6. Galileo and the Church Dialogue Concerning the Two World Systems (1629) Dialogue Concerning the Two World Systems (1629) Ptolemaic versus Copernican (Brahe and Kepler ignored) Ptolemaic versus Copernican (Brahe and Kepler ignored) three men having a dialogue three men having a dialogue Church gives official approval Church gives official approval problems problems 1. Biased towards Copernican system 2. Pope’s statements put in mouth of Simplicio Result: Galileo summoned to Rome to face trial for heresy Result: Galileo summoned to Rome to face trial for heresy

19. B. Galileo Galilei (1564 – 1642) 6. Galileo and the Church The Trial of Galileo (1633) The Trial of Galileo (1633)The Trial of GalileoThe Trial of Galileo prosecution by the Inquisition prosecution by the Inquisition in opposition to Scripture in opposition to Scripturein opposition to Scripturein opposition to Scripture lack of evidence lack of evidence

20. B. Galileo Galilei (1564 – 1642) 6. Galileo and the Church Galileo made to renounce Copernican system Galileo made to renounce Copernican system house arrest house arrest Dialogue banned Dialogue banned 1638: Galileo writes Discourses 1638: Galileo writes Discourses 7. The legacy of Galileo Sentence Sentence Galileo pardoned Galileo pardoned