| M-theory - Wikipedia, the free encyclopedia |

| | In the early 1990s, it was shown that the various superstring **theories** were related by dualities, which allows physicists to relate the description of an object in one string **theory** to the description of a different object in another **theory**. |

| | The **theory** of electromagnetism was also in such a state in the mid-19th century; there were separate **theories** for electricity and magnetism and, although they were known to be related, the exact relationship was not clear until James Clerk Maxwell published his equations. |

| | The Type IIA string **theory** and the Type IIB string **theory** are connected by T-duality; this means, essentially, that the IIA string **theory** description of a circle of radius R is exactly the same as the IIB description of a circle of radius 1/R. This is a profound result. |

| en.wikipedia.org /wiki/M-theory (1914 words) |