The fourth dimension is time, as defined by Einstein in regards to the Theories of Relativity. The Spatial dimensions are those of height, length, and depth. The fourth dimension can be related to a hypercube, much as the first dimension is related to a line, the second two lines connected at perpendicual angles to one another, and the third dimension being a cube. The fourth dimension is(sometimes) associated with the space-time continuum.
It is truly inane to travel to a universe that is based only upon the fourth dimension, as that woould include only time, and no being could truly exist.
by John the Redeemer June 12, 2006