﻿Symm & conservation

# Symmetries & conservation laws

Noether's theorem
Emmy Noether discovered the relation between physical laws of conservation and symmetries in 1915.

 Conservation law of Related symmetry Explanation momentum translation symmetry in space Executing an experiment 'here' gives the same result as executing it 'there', provided that the conditions are identical. energy translation symmetry in de tijd Executing an experiment 'earlier' gives the same result as executing it 'later', provided that the conditions are identical. electrical charge translation symmetry along the potential-axis Electrical voltage is a potential difference. The absolute value of the voltage cannot be measured, because in an electrical system, everything happens in the same way after adding a constant potential everywhere.(In an electrical circuit any point can be chosen to be connected with earth or ground, by definition the zero voltage.) mass translation symmetry along the gravitational energy-axis In a gravitational system (for example, in the planetary system) gravity energy is not defined. Only gravitational energy differences can be calculated. The planets would move identically if a constant energy is added to the gravitational energy formula. In practice, in an infinitely distant point the gravitational energy is chosen to be zero by definition. angular momentum rotation symmetry in space