Look up Newton's laws on Wikipedia Newton's three laws are

First Law

If no external force acts on a particle, then it is possible to select a set of reference frames, called inertial reference frames, observed from which the particle moves without any change in velocity.

**Second Law**

Observed from an inertial reference frame, the net force on a particle is proportional to the time rate of change of its linear momentum. Momentum is the product of mass and velocity. This law is often stated as F = ma (the force on an object is equal to its mass multiplied by its acceleration).

**Third Law**

Whenever A exerts a force on B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line.

Einstein came up with E=mC^{2} or energy = mass x speed of light squared. He proves this by using thought experiments.

HOWEVER - Einstein may not have been the one to come up with it. His first wife, also a theoretical physicist, may have been the originator. I watched a show about his papers, which after the death of his long time secretary, became the property of an Israeli University recently. The program was on the Discovery Science Channel. If you give me a minute or two to look for it, I will try to find a reference or a link to that program.

Forgive me, I never learned to type so I'm still slow. I am up to about 20 words per minute, though!