Physicists theorize that collisions of subatomic particles in turn produce new particles as a result of the collision, including a graviton that escapes from the fourth dimension, or brane, leaking off into a five-dimensional bulk. The fifth dimension is difficult to directly observe, though the Large Hadron Collider provides an opportunity to record indirect evidence of its existence. The Kaluza–Klein theory today is seen as essentially a gauge theory, with the gauge being the circle group. The other 10 dimensions are compacted, or 'rolled up', to a size below the subatomic level. M-theory suggested a potentially observable extra dimension in addition to the ten essential dimensions which would allow for the existence of superstrings. Superstring theory then evolved into a more generalized approach known as M-theory. The Kaluza–Klein theory experienced a revival in the 1970s due to the emergence of superstring theory and supergravity: the concept that reality is composed of vibrating strands of energy, a postulate only mathematically viable in ten dimensions or more. While not detectable, it would indirectly imply a connection between seemingly unrelated forces. Under his reasoning, he envisioned light as a disturbance caused by rippling in the higher dimension just beyond human perception, similar to how fish in a pond can only see shadows of ripples across the surface of the water caused by raindrops. To explain why this dimension would not be directly observable, Klein suggested that the fifth dimension would be rolled up into a tiny, compact loop on the order of 10 -33 centimeters.

Although their approaches were later found to be at least partially inaccurate, the concept provided a basis for further research over the past century. German mathematician Theodor Kaluza and Swedish physicist Oskar Klein independently developed the Kaluza–Klein theory in 1921, which used the fifth dimension to unify gravity with electromagnetic force. Much of the early work on five-dimensional space was in an attempt to develop a theory that unifies the four fundamental interactions in nature: strong and weak nuclear forces, gravity and electromagnetism. Whether or not the universe is five-dimensional is a topic of debate. If interpreted physically, that is one more than the usual three spatial dimensions and the fourth dimension of time used in relativistic physics. In mathematics, a sequence of N numbers can represent a location in an N-dimensional space. A 2D orthogonal projection of a 5-cubeĪ five-dimensional space is a space with five dimensions. For alternate planes of existence in fiction, see fourth dimension in literature.

For the musical group, see The 5th Dimension. This article is about mathematical spaces having five dimensions.

4d shapes explained