It is generally accepted that the Pythagoreans in the sixth century BCE were the first to recognise and accept that the earth is a sphere. Of course recognising and accepting that the earth is a sphere immediately prompts other questions, one of the first being just how big a sphere is it? Picard’s determination of the size of the earth would go on to play a significant role in the history of physics. The size of the earth that he had used in his calculation had been wrong. [The photos showing the monuments marking the ends of Picard’s baseline are taken from Paul Murdin, Full Meridian of Glory: Perilous Adventures in the Competition to Measure the Earth, Copernicus Books, 2009]