Between the Third Dimension, which is where we are right now, and the Fifth Dimension, which was a popular group back in the 70s, lies the Fourth Dimension. And the existence of this fourth spatial dimension could be proven using a satellite scheduled to be launched next year. Although still in they-think-it-exists stage, the 4th dimension could give rise to thousands of mini-black holes within our own solar system. 

Black holes of various masses are thought to have been generated by the Big Bang as elementary particles. If Einstein's theory of general relativity is correct, the smallest of "primordial" black holes should have dissipated by now through a quantum process called Hawking radiation.

Alternative theories say these small black holes could still exist because of the existence of the 4th dimension which is lacking in theory of general relativity. "That [extra spatial dimension] changes the rate at which black holes radiate, so you can slow down the evaporation quite substantially," says Charles Keeton, a physicist at Rutgers University.

Keeton and colleague Arlie Petters at Duke University have calculated how many of these tiny black holes should exist based on the Randall-Sundrum braneworld model. The braneworld model states the 3D universe we live in is floating within a larger universe with an extra spatial dimension.

According to the physicists' calculations, there could be thousands of black holes the mass of a small asteroid in the solar system, "the nearest ones would lie well inside Pluto's orbit," says Keeton. The researchers say these black holes may soon be detected. They say gamma-ray bursts (GRBs), believed to be caused by the violent deaths of massive stars or the collisions of dense stellar corpses, have the right period to provide such a test.

While telescopes are unable to probe the high-energy gamma rays required to test this theory, in August 2007, NASA 's Gamma Ray Large Area Space Telescope (GLAST) satellite will be able to do so. "If we do see the signal, then the strongest conclusion we can draw is that primordial black holes exist," says Keeton. "If it is below some limit, you could say such a black hole cannot exist in general relativity because it would have evaporated by now. What we think is exciting is that we can make a specific prediction for an astronomical measurement that would open the door to studying the fourth dimension."

We heard that, as soon as the existence of the 4th dimension is proven, Pixar Animation Studios will release Toy Story in 4D.