Einstein's theory of relativity encompasses both special relativity and general relativity. Together these describe the structure of spacetime including insights into energy, gravitation and time dilation. Wolfram|Alpha includes numerous formulas and tools for calculating the effects of relativistic motion, gravitational distortion and other effects of relativity.
Compute the effects of special relativity on length, time and other physical properties.
Use general relativity to calculate time dilation and the properties of black holes.