Today is
Pi Day, dedicated to that familiar mathematical number
π. The number (3.14159 etc), the ratio of a circle's circumference to its diameter, has been around for millennia but only got its familiar name and symbol in 1706. The inventor of
π? A Welsh mathematician and friend of Isaac Newton and Edmund Halley, William Jones.
Jones was born in Llanfihangel, Anglesey in 1675 and educated at a charity school, but as an adult moved to London. Interested in navigation, he was for a while mathematics master on a battleship: he brought back a pair of scissors as plunder! Back in London, he wrote
A whole compendium on the new art of navigation and became part of the circle of leading mathematicians and natural philosophers. Thanks to his impressive archive of manuscripts, Jones was appointed to a Royal Society committee to investigate the invention of calculus; he later became Vice-President of the Royal Society.
Until Jones came up with his simple but brilliant notation, the number had been represented by the letter 'p' (for perimeter). It was generally known as 'the Ludolphian number', a rather clunky name for such an essential concept. However, when Jones wrote a maths textbook, he used the more elegant Greek letter; later writers including
Euler followed his example, and the rest is history.
Find out more: you can watch a half-hour lecture on Jones's life here.
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