At Cologne, on 21 September 1908, Hermann Minkowski delivered an address to the 80th assembly of German Natural scientists and Physicians. He began with the following words:

'The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and herein lies their strength. They are radical Henceforth space by itself and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.'