a brief biography of the equals sign
Like Roald Dahl and Catherine-Zeta Jones, the equals sign was born in Wales.
It was 1557—not that long ago, in the scheme of things. Just a few years before the birth of Shakespeare. In fact, the Danish prince and the Scottish king captivated the public long before their humble Welsh neighbor reached wide renown.
The early equals sign was a lovely but ungainly thing, a long pair of parallels that its inventor called Gemowe Lines:
Over the centuries, this stilt-legged creature shortened into the compact and tidy symbol we know today.
And before that? Well, mathematicians simply spelled out equalities with the phrase “is equal to.”
10 is equal to 7 + 3.
8 x 9 is equal to 72.
And of course, a2 + b2 is equal to c2.
The equals sign offered a way to avoid the tedious repetition of these words. Or, as Robert Recorde, the father of the symbol, put it: to auoide the tedioufe repetition of thefe woords.
An equals sign, then, is a verb. It’s the mathematical equivalent of “to be”—just as common, just as concise, and just as powerful.
But that’s not what kids see, is it?