Algebra was first described by the Persian mathematician Muhammad ibn Musa al-Khwarizmi around 830 CE. He called it Al-Jabr, a term that can mean “completion” or “balancing.” In his important book, al-Khwarizmi explained how to work with unknown quantities. He used the Arabic term ash-shai’, meaning “the unknown thing,” for an unknown variable. The word algorithm also comes from the Latinized form of his name. Algebra later spread from the Islamic world to Europe, with Spain playing an important role. Spanish does not have the “sh” sound found in Arabic, so some scholars used the Greek letter chi (χ) to represent this sound when translating mathematical ideas. Here is what uppercase and lowercase Chi look like:

In 1961, MIT meteorologist Edward Lorenz was running weather calculations on an old computer. When he repeated a calculation, he got very different results, even though he thought he had used the same data. He later discovered that he had entered the numbers with different precision: six decimal places the first time and three the second time. This small difference produced a completely different result. Lorenz showed that chaotic systems can be extremely sensitive to their starting conditions. A very small change at the beginning can lead to a very different outcome later. This idea became known as the butterfly effect. After this discovery, Lorenz became increasingly interested in mathematics and shifted much of his research from meteorology to mathematics.