Amanda Gefter says every book and article she consulted gave the same answer to the question “What does the M in M-theory mean?”: “nobody knows” (19 April, p 47). She finally tracks down Edward Witten, who reveals: “the M stood for magic, mystery or membrane, according to taste” – as he did in my New Scientist article “Theory of Everything” (Instant Expert, 4 June 2011).
In the period between the superstring revolution of 1984 and the M-theory revolution of 1995, membranes were taboo. One string theorist announced that “I want to cover up my ears every time I hear the word membrane” and some organisers of the annual superstring conferences even banned the use of the “M-word”. My colleague Paul Townsend, one of the membrane pioneers, compared this with the theatrically superstitious calling Macbeth the “M-Play”.
The myth that no one knows what M stands for is just a smokescreen designed to obscure the red faces of those who ridiculed membranes (later called M-branes) but were then forced to admit they form a vital part of M-theory. Even now, Dean Rickles promises that his A Brief History of String Theory: From dual models to M-theory explores how M-theory came into being, but mentions “M-branes” nowhere in the book and “membranes” only in a footnote, referring to them in the text as “higher-order strings”.
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