In physics and mathematics, a sequence of N numbers can be understood to represent a location in an N-dimensional space.
Abstract five-dimensional space occurs frequently in mathematics, and is a 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 [unreliable source?]. 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 dimension. 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.
In popular usage, the "fifth dimension" is often used to refer to unexplored or unknown aspects of the universe, and not necessarily to the mathematical concept of a 5-dimensional space. For example, the opening narration of The Twilight Zone begins: "There is a fifth dimension, beyond that which is known to man." In the fictitious universe of DC Comics, the "fifth dimension" is said to be the place from which Mister Mxyzptlk comes. In 1966, The Byrds released an album titled Fifth Dimension, using the fifth dimension as a metaphor for unexplored and unknown aspects of the universe and oneself. The 5th Dimension is the name of an American vocal music group popular in the late 1960s and early 1970s. In Hindu philosophy, the fifth dimension of love of the Divine is termed by the Gaudiya Vaisnavas as turyatita, the dimension of the soul's Soul. The original Doctor Who episode hints at the 5th dimension being key to the abilities of the TARDIS.
Other uses of the "fifth dimension" are closer to its mathematical meaning. For example, the novel The Boy Who Reversed Himself features 4-dimensional and 5-dimensional spaces, using the mathematical fact that a 3-dimensional object can be turned into its mirror image if additional spatial dimensions were available for it to rotate through. The characters in Madeleine L'Engle's novel A Wrinkle In Time use the fifth dimension as a "dimensional shortcut" to travel through space. A similar concept appears in the Powerpuff Girls episode Bring Back Jojo, where a creature unable to see higher dimensions takes a dimensional shortcut through a fifth dimension to travel through time. The Red Dwarf episode "Parallel Universe" refers to the fifth dimension as the space in which multiple four-dimensional spaces exist.
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'Borrowing' more material.
standready on Sat Jan 14, 2012 10:48 pm