Newton & Galileo -- motion
- i.e. the ratio a3/P2 = 1 for planets but = 0.96 x 10-3 for Jupiter’s satellites
- Newton would show this implies the mass of Jupiter is 0.96 x 10-3 times the mass of the Sun!
Motion of bodies
- Aristotle:
- All bodies tend to fall (natural motion) toward center of Earth
- Any other motion requires a force to sustain
- Galileo studied just how bodies did fall
- hard to do because no clocks existed! Used his pulse as clock!
- measured period of pendulum
- in his case a swinging light fixture
- period independent of amplitude of swing demo
- same period for large and small angles of swing
- Rather than timing free fall (too fast) measured balls rolling down inclined planes demo