Newtonian model
The law of gravity:
Drawbacks
There is instantaneous action at a distance. But, according to special theory of relativity, no information can be transmitted faster than the speed of light; but if newton’s law was an accurate model, you would have a gravitational telegraph which can transmit information instantaneously.
Modeling spherical objects
An important special case. If sphere is symmetric in density, it turns out that using point mass located at the center of the sphere is an equally accurate model.
Model objects close to planetary surface
Model: Acceleration due to gravity is constant: relative change in r is insignificant.
Air resistance, terminal velocity.
Curvature in space-time model
Mass curves space-time. Objects move through this curved space-time.
Gravitational waves
An object osscilating in a small pace causes waves in space-time.
Evidence of existance: Massive stars revolving around each other moving closer to each other, loosing energy; matches theoretical prediction of energy dissipated as gravitational waves.