His universal law of gravitation explained many things, including the action of tides & the motion of comets
To test his hypothesis of universal gravitation, Newton wrote 
Flamsteed to ... so in natural philosophy the investigation of difficult things by the 
method of... [DOC] [TLE] Newton's Principia and the Genesis of Universal Gravitation [PAR] In England, Isaac Newton developed a universal theory of gravitation that would 
... To explain motion Descartes introduced the concept of vortices.