Conservation principles

In antiquity ‘self-evident’ principles were used to argue for the conservation of certain quantities. The concept of quantitative conservation laws, such as those of mass and energy, is of much later origin. Even prior to the development of modern mechanics, symmetries were employed to solve some dynamical problems. The relation between conserved quantities and symmetries has come to play a central role in the physical sciences. Conservation laws may reflect as much about the way the human mind organizes the phenomena of the world as they do about physical reality itself.