Of all the branches of physics, mechanics has the most scientific and practical consequences.
Newton is generally considered the greatest scientist who has yet lived because he invented the theoretical scientific approach, invented a new mathematics (calculus) and because his work has had such an impact on future (i.e. present-day) science and technology. A further reason for his greatness is that his laws overthrew centuries of careful thought about motion by some very intelligent people (chief among them Aristotle).