Superstring theory is a theory in 10 dimensions. There are 5 different flavours of supersting theory and for a while much confusion over why this was

the case. In 1995 Edward Witten created M-theory and explained that all versions of the theory were equivalent if they were considered as

approximations to an 11 dimensional theory. This theory is M-theory and it is the current hot favourite for the

theory of everything. In a series of lectures to the

public (slides available from the Institite of Theoretical

Physics Santa Barbra) Witten suggests that the M stands

for Magic or Mystery.