I was thinking about the immediate ways that physicists had for checking the validity of Newton's theory of gravitation in the time Newton published it. An obvious way would be to check if it predicts what is stated by Kepler's laws. Does anyone know if this was made? Do you know of other tests they carried out? BTW, I found this text http://radio.astro.gla.ac.uk/a1dynamics/ellproof.pdf showing that the theory "predicts Kepler first law", but it seems to be too complicated for being worked out at that time.