What Hath Befallen Gravity?

Topic 4

Newton’s rules for the study of natural philosophy

1. Simplicity

2. Generality

3. Experimental verification

4. Theories are tentative

Three Approaches to Forces

A. Action at a distance

-no mechanism

B. Field Description

-space changed by body

C. Particle Exchange

-emitted or removed

Flat Space vs. Spherical Space

Effect of Acceleration

Principle of Equivalence

• Downward pull of gravity can be duplicated by an upward acceleration

Curvature of Space

Deflection of Light

Orbital Precession

Gravitational Red Shift

Black Hole

Particle Exchange

Expanding Universe