The 5th Dimension
In physics and mathematics, a sequence of N numbers can be understood to represent a location in an N-dimensional space. When N=5, the space consisting of all locations with a nonzero fifth number is called the fifth dimension.
Abstract five-dimensional space occurs frequently in mathematics, and is a perfectly legitimate construct. Whether or not the real universe in which we live is somehow five-dimensional is a topic that is debated and explored in several branches of physics, including astrophysics and particle physics.
In physics, the fifth dimension is a hypothetical extra dimension beyond the usual three spatial dimensions and one time dimension of Relativity. The Kaluza-Klein theory used the fifth dimension to unify gravity with the electromagnetic force; e.g. Minkowski space and Maxwell’s equations in vacuum can be embedded in a 5-dimensional Riemann curvature tensor (Embedding.pdf eq. 37). Kaluza-Klein theory now is seen as essentially a gauge theory with gauge group the circle group. M-theory suggests that space-time has eleven dimensions, seven of which are “rolled up” to below the subatomic level. Physicists have speculated that the graviton, a particle thought to carry the force of gravity, may “leak” into the fifth or higher dimensions which would explain how gravity is significantly weaker than the other three fundamental forces.
In 1993 the physicist Gerard ‘t Hooft put forward the holographic principle, which explains that the information about an extra dimension is visible as a curvature in a spacetime with one fewer dimensions. For example, holograms are three-dimensional pictures placed on a two-dimensional surface, which gives the image a curvature when the observer moves. Similarly, in general relativity, the fourth dimension is manifested in observable three dimensions as the curvature of path of a moving infinitesimal (test) particle. Hooft has speculated that the fifth dimension is really the spacetime fabric.
Since 2006, author Rob Bryanton has been advancing the idea that the fifth dimension is also our universe’s probability space, meaning that the fifth dimension contains the full amount of possibilities that could happen within the parallel universes of Everett’s Many Worlds Interpretation. This idea requires an acceptance that time is just one of the two possible directions in the fourth spatial dimension (as per the concept of time reversal symmetry), which makes this idea the subject of controversy at present.
Via Wikipedia.
