Newtonian Physics and Classical Economics Albert Einstein came of age in a world where the classical physics of Sir Isaac Newton still reigned. Two features of Newton's worldview are pertinent to understanding the classical economics that Keynes meant to attack. The first is that Newton's physics presupposes an absolute separation of space and time. The position of any particle in space can be defined, by means of a system of coordinates, with respect to any observer or any fixed reference point. Motion is the displacement of the particle from one position to another.
Velocity is motion, divided by the number of ticks on a clock that it takes for the motion to occur.
The clock that is used to measure velocity lies, in a conceptual sense, outside the universe itself. In other words, all observers of an event, provided they were equipped with accurate timepieces, no matter where they might be, would always agree on the exact time that the event occurred. Newton imagined time as an absolutely regular phenomenon that could not depend on the location of the clock or be affected by its movement or any other physical force. Gravity in Newton's system is the basic force exerted by one massive body on any other. Gravity produces the acceleration of a particle in space, according to the position and mass of all other particles in the universe that exert gravitational force.