In special relativity, let v be the velocity of a moving particle and c the speed of light. Then the quantity is defined by
In general relativity, the parameter measures a superposition of gravitational effects. Measurements
obtained from tracking the Viking lander space probe to Mars give the value
Lorentz Transformation, Eric Weisstein's World of Math Pseudorapidity, Rapidity, Relativistic Gamma, Special Relativity
