Isaac Newton

Sir Isaac Newton (1642-1727) was an English physicist and mathematician. One of his most famous accomplishments was formulating the theory of gravity. The Doctor once claimed that he sat in Newton's tree dropping apples onto his head, then explained gravity to him over dinner. (DW: The Pirate Planet)

Newton coined the phrase, "For every action, there is an equal and opposite reaction." When the Doctor quoted this to Romana, she concluded that Newton invented punting. (DW: The Five Doctors)

When the Doctor and Nyssa were arrested for forgery, Isaac Newton drew a series of interesting conclusions from a series of well-worn coins that the Doctor accidentally passed. (BFA: Circular Time)

At some point the Doctor took Newton on a trip to planet Practas Seven, but according to the Doctor, Newton didn't take the experience very well and "sat in a corner and whimpered". (IDW: Final Sacrifice)


 * It's unknown whether the trip to Practas Seven was a one-off event or if Newton actually travelled with the Doctor as a companion.