Aristole:
    The foremost Greek scientist of the fourth century BC.  Studied motion and divided it into 2 parts: natural motion and violent motion.

Copernicus:
    Astronomer during the 16th century AD.  Developed the heliocentric theory.

Galileo:
    Formost scientist of the late Italian Renaissance.  He was persecuted and arrested for supporting Copernicus's theories.  One of his greatest contributions to physics was to discredit the idea that force (a push or pull) was necessary to keep an object moving.  He argued that only when friction is present is a force needed to keep and object moving.  If you roll a ball on a frictionless surface, then it will continue to roll infinitely.

Newton:
    Wrote Principia Matmatica in 1687.  It is the most influencial book of science ever written.  Invented calculus to do physics.  An apple never hit the man on his head.  Responsible for the 3 laws of motion.

    Newton's First Law of Motion

Every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted upon it.

An object at rest tends to stay at rest.  An object in motion tends to stay in motion in a straight line unless acted upon by an unbalanced force.

    Mass is NOT weight or volume.
    Mass is the quantity of matter in an object.  More specifically, mass is a measure of the inertia that an object exhibits in response to any effort made to start it, stop it, or otherwise change its state of motion.
    Weight is the force of gravity on an object.
    Volume is a measure of space.

This means that you would weigh differently on Earth and the moon, but your mass would remain the same.  Mass is measured in kilograms and weight is measured in newtons or pounds.

    The net force on an object is the sum of all the forces acting on an object.  It is measured in vectors.  Equilibrium is achieved when the net force on an object equals zero.