An introduction to Einstein’s Theory for a lay audience. The only preparation needed is an open mind. Albert Einstein described Relativity as a “popular explosion” of his famous theory. Written in 1916, it introduced the audience to the remarkable perspective that had overturned theoretical physics.

The theory of relativity, or simply relativity, generally encompasses two theories of Albert Einstein: special relativity and general relativity.

Concepts introduced by the theories of relativity include: Measurements of various quantities are relative to the velocities of observers. In particular, space and time can dilate. Spacetime: space and time should be considered together and in relation to each other. The speed of light is nonetheless invariant, the same for all observers.

The term “theory of relativity” was based on the expression “relative theory” used by Max Planck in 1906, who emphasized how the theory uses the principle of relativity.