Abstract

The concept of potential energy and the principle of energy conservation arose first in the middle of the nineteenth century when Newton's 'Principia' was already 170 years old. Quite remarkably, physics had progressed without much thought being given to energy. All this changed with Helmholtz 1847 epoch-making lecture on the conservation of energy, a principle which crossed the borders between all branches of science.

The first important papers dealing with potential energy were published by F.E. Neumann in 1845 and 1847. A potential energy paradox is pointed out. Positive and negative potential energy do not add algebraically! We have to conclude that positive and negative potential energy are two different kinds of energy which might as well have been named "red" and "green" energy.