MadSci Network: Science History
Query:

Re: About when did the sign for '=' appear in history and what was the conseque

Date: Thu May 17 15:34:25 2001
Posted By: Mark Huber, Post-doc/Fellow, Statistics, Stanford University
Area of science: Science History
ID: 989864035.Sh
Message:

When did the sign for "=" appear in history, and did it lead to any dramatic changes in mathematics?


The equals sign, "=", was believed to have been invented by Robert Recorde an Englishman who lived in the 1500's. Certainly the earliest known printed use of the equals sign is in his 1557 book, The Whetstone of Witte. In it, Recorde explains that he uses two parallel lines to mean equals "because no 2 things could be more equal". Well, actually he wrote in sixteenth century English, so what appears in the book is, "bicause noe 2 thynges can be moare equalle". This link leads to a picture of the page of his book where he introduces the equals sign. Notice that the equals sign as he wrote it is much longer than the two short lines that we use today. The original was more like ===== than =.

Before the invention of the equals sign, people would simply abbreviate the word instead of using a symbol. An Englishman might write eq. as shorthand for equals, or if he was educated enough to use Latin, ae, short for the Latin word aequalis. Plus (+) and minus (-) symbols would also be abbreviated, so 5 + 4 – 2 = 7 might be written as 5 p. 4 m. 2 ae 7. You can see some of the problems with this method. Different languages would have different abbreviations, and deciphering an equation could be quite difficult. While the introduction of the equals sign itself wasn't a tremendous step forward, the idea that there should be a universal language for mathematics was very helpful. It meant that a Swedish mathematician and a French mathematician (or an Italian banker and an English merchant) could communicate their work to one another without the need for a translator. By the 1600's, all of the symbols we use today for arithmetic and algebra were in place.

This process did not stop there. New mathematics is being invented every day, and requires the invention of new symbols. This page tells what is known about the origin of many mathematical symbols, such as p (the concept goes back to the Greeks, but the use of the symbol only goes back to 1706). In my own field of research, in the last few years the Greek letter capital delta D has come to represent the maximum degree of a graph. Trust me, after you have written "the maximum degree of the graph" a few dozen times having a symbol on hand makes you want to thank those early Renaissance thinkers who first started building our modern language of mathematics.

Mark Huber


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