1. What Hath Befallen Gravity? Topic 4

2. Newton’s rules for the study of natural philosophy 1.Simplicity 2.Generality 3.Experimental verification 4.Theories are tentative

5. Three Approaches to Forces A.Action at a distance -no mechanism B.Field Description -space changed by body C.Particle Exchange -emitted or removed

10. Flat Space vs. Spherical Space

11. Effect of Acceleration

12. Principle of Equivalence Downward pull of gravity can be duplicated by an upward acceleration

13. Curvature of Space

14. Deflection of Light

15. Orbital Precession

16. Gravitational Red Shift

17. Black Hole

18. Particle Exchange

20. Expanding Universe