Hyperfine transitions in cesium are used to define the SI unit for this quantity, which undergoes dilation at relativistic speeds.
This quantity is the only physically-meaningful axis of a Feynman diagram. Detailed balance describes conditions under which systems are reversible in this variable. All physical laws are believed to be invariant under charge conjugation, parity inversion, and reversal of this variable. Loosely speaking, virtual particles are permitted by the form of the Heisenberg uncertainty principle that relates energy to this quantity. Hyperfine transitions in cesium are used to define the SI unit for this quantity, which undergoes dilation at relativistic speeds. The change in position per unit change in this is velocity. For 10 points, name this dimension which is not space.
This quantity is the only physically-meaningful axis of a Feynman diagram.
time