Recent developments in theoretical physics have generated a new hypothesis for the origin of dark matter.

It has long been known that there are 4 basic forces that generate all matter and energy. weak nuclear force, strong nuclear force, electromagnetic force, and the gravitational force. Gravity stands out in that it is far weaker than any of the other three fundamental forces. This may be due to gravity propogating into other dimensions outside of our basic four.

The recent work of Paul Townsend, professor at the Department of Applied Mathmatics and Theoretical Physics at Cambridge, developed the overspecific superstring theory into the new p-brane theory (also see M-theory). From this it has been hypothesized that we humans live in a universe that is a p-brane, in other words it has more than four dimensions. The reason that we do not see these other dimensions is because they may be curled up really really small. Imagine a really thin piece of paper. It would look to be 2-dimensional unless you looked really closely and then you could see its third dimension curled up tightly.

Shadow Branes
This idea of a p-brane universe with multiple dimensions is intruguing because it is experimentally testable in the next generation particle accelerators, and it may explain dark matter. Famous physicist Stephen Hawking hypothesizes about the existence of a nearby "shadow" brane, similar to our own in his book The Universe in a Nutshell. Gravity would be able to travel through other dimensions onto this brane while other particles and energies would be limited to our own brane. Dark matter then could be mass residing on the nearby brane. "In the brane world scenario, planets may orbit a dark mass on a shadow brane because the gravitational force propogates into the extra dimensions" (Hawking, 185). The way in which gravity propogates into the extra dimensions would account for the weakness of gravity compared to the other forces.

The shadow brane hypothesis would explain why we haven't been able to detect dark matter other than by it's gravitational influence. In large galaxies the outlying stars shouldn't be travelling as fast as they are from the experimentally determined amount of mass in their galaxy. There is missing mass evaluated as dark matter which may reside on a shadow brane. "We would not see a shadow galaxy on a shadow brane because light would not propagate through the extra dimensions. But gravity would, so the rotation of our galaxy would be affected by dark matter, matter we cannot see" (Hawking, 188).

Hawking, Stephen. The Universe in a Nutshell (Bantam Doubleday Dell Pub, November 6, 2001.)