|Newton (1642-1727) used
a new type of reflecting telescope, as well as other
instruments, to observe and calculate the orbits of planets and
satellites that would be the basis for his laws of motion and
gravity. He could now see more than any scientist before him. Newton's
law of motion would take astronomy to a new scientific level.
Newton's first law of motion may be stated simply that a body remains
at rest or continues to move with constant velocity in a
straight line unless it is acted on by an unbalanced outside
force. The second law of motion states that the change of speed or
direction of a body (acceleration) is directly proportional
to the external force producing the change. The third law of motion is
that every action has an opposite and equal reaction.
Sir Isaac Newton, 1689