Multiple time dimensions
Encyclopedia
The possibility that there might be more than one dimension of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

has occasionally been discussed in physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

.

Physics

Special relativity
Special relativity
Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...

 describes spacetime
Spacetime
In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...

 as a manifold
Pseudo-Riemannian manifold
In differential geometry, a pseudo-Riemannian manifold is a generalization of a Riemannian manifold. It is one of many mathematical objects named after Bernhard Riemann. The key difference between a Riemannian manifold and a pseudo-Riemannian manifold is that on a pseudo-Riemannian manifold the...

 whose metric tensor
Metric tensor
In the mathematical field of differential geometry, a metric tensor is a type of function defined on a manifold which takes as input a pair of tangent vectors v and w and produces a real number g in a way that generalizes many of the familiar properties of the dot product of vectors in Euclidean...

 has a negative eigenvalue. This corresponds to the existence of a "time-like" direction. A metric with multiple negative eigenvalues would correspondingly imply several timelike directions, i.e. multiple time dimensions, but there is no consensus regarding the relationship of these extra "times" to time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 as conventionally understood.

Nonetheless, theories with more than one dimension of time have sometimes been advanced in physics, whether as a serious description of reality or just as a curious possibility. Itzhak Bars
Itzhak Bars
Itzhak Bars is a theoretical physicist at the University of Southern California in Los Angeles. In 2007, Bars presented a theory concerning the fundamental laws of physics. According to Bars' theory, time may not have only one dimension , but may have two separate dimensions instead.Humans normally...

's work on "two-time physics"http://physics.usc.edu/~bars/twoTph.htm, inspired by the SO(10,2) symmetry of the extended supersymmetry structure of M-theory
M-theory
In theoretical physics, M-theory is an extension of string theory in which 11 dimensions are identified. Because the dimensionality exceeds that of superstring theories in 10 dimensions, proponents believe that the 11-dimensional theory unites all five string theories...

, is the most recent and systematic development of the concept (see also F-theory
F-theory
F-theory is a branch of string theory developed by Cumrun Vafa. The new vacua described as F-theory were discovered by Vafa, and it also allowed string theorists to construct new realistic vacua — in the form of F-theory compactified on elliptically fibered Calabi-Yau four-folds...

).

Philosophy

An Experiment with Time
An Experiment with Time
An Experiment with Time is a long essay by the Irish aeronautical engineer J. W. Dunne on the subjects of precognition and the human experience of time. First published in March 1927, it was very widely read, and his ideas promoted by several other authors, in particular by J. B. Priestley. Other...

by J.W. Dunne (1927) describes http://sprg.ssl.berkeley.edu/~jmcd/book/revs3/aewt.html an ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

 in which there is an infinite hierarchy of conscious minds, each with its own dimension of time and able to view events in lower time dimensions from outside. His theory was often criticised as exhibiting an unnecessary infinite regress
Infinite regress
An infinite regress in a series of propositions arises if the truth of proposition P1 requires the support of proposition P2, the truth of proposition P2 requires the support of proposition P3, .....

.

The conceptual possibility of multiple time dimensions has also been raised in modern analytic philosophy
Analytic philosophy
Analytic philosophy is a generic term for a style of philosophy that came to dominate English-speaking countries in the 20th century...

.http://philosophy.uwaterloo.ca/people/weinstein.html

The English philosopher John G. Bennett
John G. Bennett
John Godolphin Bennett, was a British mathematician, scientist, technologist, industrial research director, and author. He is perhaps best known for his many books on psychology and spirituality, and particularly the teachings of G.I. Gurdjieff...

 posited a six-dimensional Universe with the usual three spatial dimensions and three time-like dimensions that he called time, eternity and hyparxis. Time is the sequential chronological time that we are familiar with. The hypertime dimensions called eternity and hyparxis are said to have distinctive properties of their own. Eternity could be considered cosmological time or timeless time. Hyparxis is supposed to be characterised as an ableness-to-be and may be more noticeable in the realm of quantum processes.

The conjunction of the two dimensions of time and eternity could form a hypothetical basis for a Multiverse cosmology with parallel universes existing across a plane of vast possibilities. The third time-like dimension hyparxis could allow for the theoretical existence of sci-fi possibilities such as time travel, sliding between parallel worlds and faster-than-light travel.

While Bennett has put forward some curious speculation, his ideas stop at some subjective aspects of the perception of time which does not place them on a fully scientific basis. The question of measurement, how one would measure these hypothetical extra time-like dimensions, is left unaddressed.

In fiction

The Number of the Beast
The Number of the Beast (novel)
The Number of the Beast is a science fiction novel by Robert A. Heinlein published in 1980. The first edition featured a cover and interior illustrations by Richard M. Powers...

by Robert A. Heinlein
Robert A. Heinlein
Robert Anson Heinlein was an American science fiction writer. Often called the "dean of science fiction writers", he was one of the most influential and controversial authors of the genre. He set a standard for science and engineering plausibility and helped to raise the genre's standards of...

 (1980) features a six-dimensional cosmology
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 in which there are three time dimensions, denoted t, tau (Greek
Greek alphabet
The Greek alphabet is the script that has been used to write the Greek language since at least 730 BC . The alphabet in its classical and modern form consists of 24 letters ordered in sequence from alpha to omega...

 τ
Tau
Tau is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.The name in English is pronounced , but in modern Greek it is...

) and teh (Cyrillic
Cyrillic alphabet
The Cyrillic script or azbuka is an alphabetic writing system developed in the First Bulgarian Empire during the 10th century AD at the Preslav Literary School...

 cursive т).

The Ware Tetralogy
Ware Tetralogy
The Ware Tetralogy is a series of four science fiction novels by author Rudy Rucker: Software , Wetware , Freeware and Realware . The first two books both received the Philip K. Dick Award for best novel...

 by Rudy Rucker
Rudy Rucker
Rudolf von Bitter Rucker is an American mathematician, computer scientist, science fiction author, and philosopher, and is one of the founders of the cyberpunk literary movement. The author of both fiction and non-fiction, he is best known for the novels in the Ware Tetralogy, the first two of...

 features aliens
Extraterrestrial life in popular culture
In popular cultures, "extraterrestrials" are life forms — especially intelligent life forms— that are of extraterrestrial origin .-Historical ideas:-Pre-modern:...

 called Metamartians who "are from a part of the cosmos where time
is two-dimensional".http://www.rudyrucker.com/pdf/realwarenotes.pdf

In Diane Duane
Diane Duane
Diane Duane is an American science fiction and fantasy author. Her works include the Young Wizards young adult fantasy series and the Rihannsu Star Trek novels.-Biography :...

's Star Trek
Star Trek
Star Trek is an American science fiction entertainment franchise created by Gene Roddenberry. The core of Star Trek is its six television series: The Original Series, The Animated Series, The Next Generation, Deep Space Nine, Voyager, and Enterprise...

novel, The Wounded Sky
The Wounded Sky
The Wounded Sky is a 1983 Star Trek novel by Diane Duane, featuring James T. Kirk as captain of the USS Enterprise. The author would four years later adapt the novel's plot for the teleplay of the first season Star Trek: The Next Generation episode "Where No One Has Gone Before".-Plot:The...

, the Hamalki physicist K't'lk states that time has three dimensions, called "inception," "duration," and "termination."

See also

  • Dimension
    Dimension
    In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...

  • Hyperspace
    Hyperspace
    Hyperspace may refer to:*in mathematics and general science** A Euclidean space of dimension greater than three, see fourth dimension and higher dimensions ** Space of any dimension, whether lower, higher, or...

  • Space-time#Privileged character of 3+1 spacetime
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