Astronomy Picture of the Day

Explanation: Does our universe have higher but unusual spatial dimensions? This idea has been gaining popularity to help explain why vastly separated parts of our universe appear so similar, and why the geometry of our universe does not seem to result naturally from the amounts of matter it seems to contain. The idea is also prevalent in modern attempts to combine gravity and quantum mechanics that include M-theory (formally string theory) and Randall-Sundrum theory. Such models involve branes and bulks and frequently attempt to explain, among other things, why some quantum energies and the measured cosmological constant are so small. Above, a dynamic three-dimensional drawing (two spatial plus one time) of a four-dimensional depiction of a five-dimensional cube (a hypercube with four spatial dimensions is also known as a tesseract) is shown. Donning red-blue glasses will give the best multi-dimensional perspective.