How old was Isaac Newton when in 1666 he formulated the theory of universal gravity?

The laws are: (1) Every object moves in a straight line unless acted upon by a force. (2) The acceleration of an object is directly proportional to the net force exerted and inversely proportional to the object's mass. (3) For every action, there is an equal and opposite reaction.

Brits! Who remembers the old public information film...."Sir Isaac Newton told us why, an apple falls down from the sky. A brick, a bolt, a bar, a cup, invariably fall down, not up. And from this fact it's very plain, most other objects do the same" ? Health and Safety back in the day! Good old 1970s!