Issac Newton (1700) — made the seminal and universal discovery of how things interact with each other.  (Brown's theory shows that all forces are Newtonian interactions.)

• No force - then no change of motion
• Forces occur in equal-opposite pairs 
• For each force there is an acceleration divided by mass (for both forces of every pair)

James Clerk-Maxwell (1865) — unified electricity and magnetism

Albert Einstein (1900) —

• Recognized that magnetic force doesn’t depend upon absolute motion 
• Proposed connecting space and time to solve magnetic problem but thought Newton's Laws were incorrect at high speeds
• Developed a theory of gravity by connecting mass, space, and time
• Tried, unsuccessfully, to unify gravitation and electromagnetisms

Recent Researchers (2000) — Trying to unify physics using n-dimensional spaces (n>3)