masses in the Universe
- showed gravity force was radial
- radial forces can apply no torques
- string can only apply a radial force
K III follows from vcircular = sqroot(GM/r)
- Period of orbit is given by P = 2?r/vcircular
- square both sides and substitute GM/r for vcircular2
- use a (i.e. semi-major axis) for r
- solve for a3
- use units of AU for a, years for P, and solar masses for M
- M1P2 = a3
- Military Police = arrest, as simple as 1, 2, 3
- This is K III for orbits around the sun
- the orbits of the Galilean satellites imply the mass of Jupiter is 0.96 x 10-3 times the sun’s mass
- can be used to measure masses throughout the Universe