"The missing link," by Ian Stewart. New Scientist, 9 November 2002, pages 30-33.
When mathematicians found a way to usefully interpret the idea of the square root of -1, now universally denoted as i, they soon realized that the number system it generates is extremely useful in physics. In analogy with that number system, which can be thought of as two-dimensional, mathematicians discovered the octonions, which form an eight-dimensional number system. In a surprising twist, researchers are now finding that the octonions play an important role in the new branch of physics known as string theory. The article suggests as further reading on this topic "The octonions," by John Baez, published in 2002 in the Bulletin of the AMS.
--- Allyn Jackson