1. A Revolution In Science - Empirical • A dramatic change in ideas or practices. • Any complete circle made around something such as a planet orbiting another body.

2. A Revolution In Science - Empirical • Nicholas Copernicus (1473 – 1543): A Catholic cleric who was also a mathematician, astronomer, all around scholar. He was educated at Krakow Academy (now Jagiellonian University). • He was born in Prussia a part we know as Poland.

3. A Revolution In Science - Empirical • He was a serious thinker of his day. • What he did was to start a revolution in the Western world with respect to scientific thought. • He did not make lots of friends in the church.

5. A Revolution In Science - Empirical • Copernicus proposed that the planets rotate around the Sun. He did not know why or if it was really true. • Copernican Principle = Earth removed from any position of great cosmic significance. Nicolai Copernici Torinensis De Revolutionibus Orbium Coelestium Libri VI Heliocentric as opposed to geocentric

6. A Revolution In Science - Empirical 1. There is no one center of all the celestial circles or spheres. 2. The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. 3. All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe. 4. The ratio of the earth's distance from the sun to the height of firmament is so much smaller than the ratio of the earth's radius to its distance from the sun that the distance from the earth to the sun is imperceptible in comparison with the height of the firmament. 5. Whatever motion appears in the firmament arises not from any motion of the firmament, but from the earth's motion. The earth together with its circumjacent elements performs a complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged. 6. What appear to us as motions of the sun arise not from its motion but from the motion of the earth and our sphere, with which we revolve about the sun like any other planet. The earth has, then, more than one motion. 7. The apparent retrograde and direct motion of the planets arises not from their motion but from the earth's. The motion of the earth alone, therefore, suffices to explain so many apparent inequalities in the heavens.

7. A Revolution In Science - Empirical • Galileo Galilei (1564 – 1642): A physicist, mathematician, astronomer, and philosopher. He was the key player in the Scientific Revolution. • Born in Tuscan, Italy.

8. A Revolution In Science - Empirical • Galileo Galilei provided support for the idea of Copernicus through his observations. • 1610- Sidereus Nuncius (The Starry Messenger) • 1632- Dialogo sopra I due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems)

9. A Revolution In Science - Empirical • Other publications: • 1590 – Pisan De Motu (On Motion) • 1596 - La Billancetta (The Little Balance) • 1606 – Le Operazioni del Compasso Geometrico et Militar

10. A Revolution In Science - Empirical • Tycho Brahe (1546 – 1601): He was a Danish nobleman who was an astronomer and alchemist. • He had an estate on the island of Hven and built a research institution known as Uraniborg.

11. A Revolution In Science - Empirical • Tycho made many important observations and key recordings of the locations of celestial objects. • He observed SN 1572 in 1572! • What a nose! • From 1600 till his death in 1601 he had an assistant.

12. A Revolution In Science - Empirical • Johannes Kepler (1571-1630): He was a German mathematician, astronomer, and astrologer.

13. A Revolution In Science - Empirical • He produced two major works: Astronomia nova (1609)

14. A Revolution In Science - Empirical • He produced two major works: Harmonices Mundi (1619). • This is the one work that affects all of science.

15. A Revolution In Science - Empirical • Kepler took the next step in understanding the physics of our solar system and the motion of planets. He deduced three empirical rules or laws. • Empirical = the quest to first note and then accurately describe patterns in nature.

16. A Revolution - Kepler’s Laws • I. The orbital paths of the planets are elliptical (not circular), with the Sun at one focus. • Shape and size of planetary orbits: Semimajor axis = the length of the long axis or the ellipse’s size. Eccentricity of an ellipse = the ratio of the distance between the foci to the length of the major axis.

18. A Revolution - Kepler’s Laws • II. “Law of Equal Areas” The line connecting a planet to the Sun sweeps out equal areas in equal times, regardless of where the planet is in its orbit. • An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal intervals of time. • The speed of a planet changes as it goes around its orbit.

20. A Revolution - Kepler’s Laws • III. The square of the period of a planet’s orbit, measured in years, is equal to the cube of the semimajor axis of the planet’s orbit, measured in AU. Harmonic Law • The square of a planet’s orbital period is proportional to the cube of its semi-major axis. • (Pyears)2 = (AAU)3 • How long it takes a planet to orbit the Sun = period. This law states the relationship between the period of a planet’s orbit (P) and its distance from the Sun (A).

21. A Revolution - Kepler’s Laws • Kepler simply described the orbits of the planets, he did not explain why they are the way they are.

22. A Revolution - End of Empirical Approach • Up to this point in the lecture we have been discussing the Empirical Approach or Empirical Observations. • We have been discussing the what! • Now we will begin to explain the why and how of the observations.

23. A Revolution - Newton’s Laws • Sir Isaac Newton (1642-1723) - Set the foundation for Classical Mechanics. Laws were published in 1687. Known as the Laws of Motion.

24. A Revolution - Newton’s Laws • I. Newton’s First Law • Objects at rest stay at rest, objects in motion stay in motion. • Every body continues in a state of rest or in a state of uniform motion in a straight line unless it is compelled to change that state by a force acting on it.

25. A Revolution - Newton’s Laws • The tendency of an object to keep moving in the same direction or remain at rest is known as inertia. • One measure of an object’s inertia is its mass - essentially the total amount of matter it contains or what determines an object’s resistance to a change in motion. • The greater the mass, the greater the force needed to change the object.

26. A Revolution - Newton’s Laws • II. Newton’s Second Law • If there is an unbalanced force acting on an object, then the object’s motion does change. • When a force F acts on a body of mass m, it produces in it an acceleration a equal to force divided by mass • a=F/m or F = ma

27. A Revolution - Newton’s Laws • III. Newton’s Third Law • For every action or force there is an equal and opposite reaction or force.