One of several blogs I keep an eye on is the aptly-named Math With Bad Drawings (though, actually, I think the drawings do have a certain charm and they are in any case done with pedagogical rather than aesthetic intent). This blog is by an American mathematician (hence the mis-spelling of maths :) ) and consists of illustrated essays on a variety of mathematical topics.
I was recently flicking back through the archives of this blog and came across an interesting post that I didn’t notice when it first appeared, last December, even though I was following the blog by then (I guess it was pretty close to Christmas, which is generally a pretty busy time when it’s easy to skip over blog posts). It is a post that describes itself as a brief biography of the equals sign (=).
You may be thinking that this isn’t the most enthralling of subjects and, although a mathematician myself (with a fairly keen interest in mathematical notation and history to boot), I’d be inclined to agree with you. However, here’s the exciting thing I learned from the post: the equals sign was invented in Wales (*).
The article doesn’t actually contain all that much information about the early history of the sign, though it has some fascinating stuff about its meaning and usage, as well as related symbols like > and <. There was just enough detail to enable me to hit Wikipedia and do a quick Google search for other sites to cross-check the facts (not very extensive research, I know, but probably sufficient to establish that Ben, the author of the MWBD blog, wasn’t just making it up).
Apparently the first recorded use of the equals sign was in a book called The Whetstone of Witte, by Welsh mathematician Robert Recorde, published in 1557. It is believed that Recorde invented this sign; before this, people used to just write “is equal to” (or words to that effect) when they wanted to indicate equality, so the sign was definitely a very convenient shorthand.
The same book is also credited with introducing the plus (+) and minus (-) signs to the English speaking world, though they (unlike =) were already known in other parts of the world so presumably Recorde became acquainted with them through perusing literature in other languages, or perhaps corresponding with other mathematicians, rather than re-inventing them independently. In any case, the book definitely had a significant impact on the development of mathematical notation – and the importance of having good notation for being able to develop mathematical ideas should not be underestimated.
(*) Actually, my statement that “the equals sign was invented in Wales” is probably not quite accurate (the original article phrases it as “the equals sign was born in Wales”, which is little better). Robert Recorde was indeed Welsh (born in Tenby, Pembrokeshire) but he seems to have spent most of his adult life in Oxford, Cambridge and London (where he was a physician as well as a mathematician) so it’s more likely that the equals sign was born/invented in one of those places. Still, I think it’s fair to credit it as a Welsh invention.