In 1916, Arthur Eddington, a war-weary British astronomer, opened a letter written by an obscure German professor named Einstein. The neatly printed equations on the scrap of paper outlined his world-changing theory of general relativity. Until then Einstein's masterpiece of time and space had been trapped behind the physical and ideological lines of battle, unknown.
Einstein's name is now synonymous with 'genius', but it was not an easy road. He spent a decade creating relativity and his ascent to global celebrity owed much to against-the-odds international collaboration, including Eddington's globe-spanning expedition of 1919 - two years before they finally met. We usually think of scie