We've all heard of relativity, but what is it? How does it relate to light and motion? So we've all heard of relativity, right? But... what is relativity? And how does it relate to light? And motion?

It stands among the most famous theories ever created, but the general theory of relativity did not spring into being with a single, astonishing paper like the special theory of relativity in 1905.

Pedro Ferreira looks back at how Einstein himself and a panoply of other physicists have framed the theory. Until very recently, relativists were few and often self-taught. General relativity still ...