On electrodynamics of moving objects is the first paper on special relativity published by Albert Einstein in the Yearbook of Physics on June 30th, 1905.

Einstein mainly discussed two "physical events" in "On Electrodynamics of Moving Objects": First, the frequency of light emitted by a moving object will change with the change of the moving speed of the object; First, the speed of the clock carried by a moving object will also change with the speed.

See: /view/20 17 13.htm for details.