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For the past 500 years, mathematicians and scientists have used symbols, the crucial one being the equals sign. Unusually, we know who invented it and why. Robert Recorde, in 1557, wrote in his treatise, “The Whetstone of Witte”: “To avoide the tediouse repetition of these woordes: is equalle to: I will sette as I doe often in woorke use, a paire of paralleles, or gemowe lines of one lengthe: bicause noe .2. thynges, can be moare equalle.” This wonderful bit of mathematical history, quaintly recorded, comes from Ian Stewart, writing in the Feb. 13, 2012 online issue of New Scientist.