Exploring Newton's Laws and Galileo's Discoveries in Motion and Gravity

1. Great Idea #2: Newton’s universal laws of motion and gravity predict the behavior of objects on Earth and in space.

2. How Do Objects Move? Key Idea: One set of laws describes motions on Earth and in space • Universal laws of motion • The universal law of gravity Key Terms: • Force • Uniform Motion • Acceleration • Weight vs. Mass

3. What evidence do you have that the universe is predictable?

4. Newgrange, Ireland:5,000-year old “passage tomb”

7. Winter Solstice

8. Stonehenge • On the Salisbury Plain of southern England

11. Summer Solstice

12. What evidence do you have that the universe is predictable?“Aristotelians considered that knowledge about nature could be won by pure thought, and that experiment was, in a way, a rather trivial and pedestrian proceeding.”British Historian, Neville Andrade

13. What evidence do you have that the universe is predictable?Oxford College—ca.1500

14. What evidence do you have that the universe is predictable?“Galileo had thought [the discoveries of the telescope] would provide irrefutable proof to any man in good faith. … But a few months were enough to undeceive him. Certain doctors steadfastly refused to look through the telescope. … Some did look and professed to see nothing; most of them, however, said that they had never gotten around to looking through it, but that they knew already that it would show nothing of philosophical value” Historian of Science, Giorgio de Santilliana

15. A Hierarchy of Scientific Ideas • Fact (a confirmed observation) • Hypothesis (an educated guess) • Law (a predictive mathematical description of nature) • Theory (a well established explanation of nature)

16. The Idealized Scientific Method

17. John Snow (1813-1858) He used the scientific method to discover that contaminated water at the Broad Street Pump was the source of a deadly cholera outbreak in London. His research saved countless thousands of lives.

18. Measurements and Observations • How would you measure a star’s position? • Compass – direction to an object (degrees from North) • Protractor w/ straw (degrees from horizon) • Plot changes from night to night • Planets (Mars) display retrograde motion • Patterns emerge

20. Ptolomy’s Model of the Solar System • Model of the universe with Earth at the center (13-volume Almagest) • Epicycle (wheels within wheels) • Why is it important? • Navigation • Astrology • Lasted 1500 years

21. Dead White Males • Nicolas Copernicus (1473-1543) • Sun-centered solar system • Tycho Brahe (1546-1601) • Meticulous measurements of planet positions • Johannes Kepler (1571-1630) • Mathematical analysis of planetary orbits • Galileo Galilei (1564-1642) • Founder of experimental physics

23. Ptolomeic vs. Copernican models • Earth- vs. Sun-centered • Perfect circles (still need epicycles) Ptolomy Copernicus

25. Tycho Brahe (1546-1601) • Personality—Tycho’s nose • Observed a new star • Showed heavens can change over time • Designed and used new astronomical instruments • Collected data on planetary movements

27. The Quadrant

28. Tycho Brahe (1546-1601) • Uncertainty • before Tycho

29. Tycho Brahe (1546-1601) • Uncertainty • before Tycho

30. Tycho Brahe (1546-1601)

32. Johannes Kepler (1571-1630) • Mathematician • Assistant to Tycho Brahe • Inherited his notebooks • Traditional ideas of the solar system are wrong (Kepler’s Laws)

33. Kepler’s Laws of Planetary Motions First Law: Planets have elliptical orbits

34. Elliptical orbits

35. Kepler’s Laws Second Law: Orbits sweep out equal areas in equal times

36. Kepler’s Laws Third Law: Distant orbits take longer. (Average orbital radius)3 = k (orbital period)2 R3/P2 = constant

38. Galileo Galilei (1564-1642) • Mathematician and musician • Improved the telescope

39. Galileo Galilei (1564-1642) • Mathematician and musician • Improved the telescope • Observational astronomy

40. Galileo Galilei (1564-1642) • Mathematician and musician • Improved the telescope • Observational astronomy • Founder of experimental science • Arrogant and contemptuous of others • Published in Italian (vernacular) promoting Copernican view • Heretic (threatened with torture) so he recanted

42. Galileo – The Founder ofExperimental Science Galileo studied the relationship among distance, time, velocity and acceleration He observed that objects accelerate while falling:

43. Galileo’s Discoveries • Constant acceleration • Balls on a plane: v = at • Freefall • Constant acceleration at g • g = 9.8 m/s2 = 32 feet/s2 • Distance traveled (d) = ½at2

44. Speed, Velocity, and Acceleration • Speed = distance traveled over time • Velocity = speed with direction • Equation for speed: • Acceleration = rate of change of velocity • Equation for velocity:

45. Galileo’s Laws of Motion • Trajectories are parabolas • All objects fall at the same velocity • Distance of fall = k(Time)2 Remember Kepler (1571-1630) • Orbits are ellipses • Equal areas in equal times • (Radius)3 = k(Time)2 Now on to Sir Issac Newton (1642-1727)

47. Sir Issac Newton (1642-1727) • Born prematurely • Abandoned by his mother • Forced to run family farm • Sent to Cambridge University • Made fundamental advances in several scientific fields

48. x Cambridge

49. Issac Newton’s – Plague Years (1665-1666) • Calculus

50. Issac Newton’s – Plague Years (1665-1666) • Calculus 2. Laws of optics • Broke white light into colored light