Relativity

The space-time continuum reconciled Maxwell's equations with Newton's laws of motion.

In 1900, Isaac Newton's theory of gravity and James Clerk Maxwell's equations of electromagnetism were thought to explain almost everything. Unfortunately these two theories could not be worked together without modifying one of them.

Maxwell's equations described light waves that travelled at a constant speed, regardless of how the light source moved. Newton's laws of motion suggested that the motion of the source should affect the speed of light.

Most scientists tried to change Maxwell's equations. They suggested that there was an "ether" through which light waves travelled and that the speed of light given by Maxwell was relative to this ether. Unfortunately, no-one could detect this ether!

Einstein came up with a more radical solution to this contradiction. He proposed that the speed of light remained constant, but that the way we perceive space and time change!

Once the way different observers measure intervals of space and time is taken into account, the speed of light becomes a constant regardless of the motions of either the source or the observer.