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We know of x, y, and z dimensions. We also know of "time"... Another dimension we are aware of, which is a "non-physical dimension" called a "temporal dimension". Now, we all look at "time" as a "single dimension". We all know "time"... has 3 different aspects to it (past, present, and future).

What if time is constructed of "multiple dimensions"?

Is "time" actually a singular dimension or is it just a hologram of the past, present, and future?

Hologram: a three-dimensional image formed by the interference of light beams from a laser or other coherent light source.

Michael Ecklund
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  • Time is just a coordinate like the other three spatial coordinates; nothing special right? –  Jun 01 '16 at 17:00
  • @MAFIA36790 Kinda right, apart from the fact we are (severely) limited in moving around in that co-ordinate : ) –  Jun 01 '16 at 17:47

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Suppose you are standing upright aligned with the $z$ axis and facing along the $y$ axis, then the $x$ axis is to the left of you, at your position and to the right of you. But we don't say there are three $x$ axes. The $x$ axis simply comes in from $-\infty$ from your left, through your position and then off away to $+\infty$ on your right.

In exactly the same way the time axis comes from your past, through your position and off into your future. The time axis is a single axis just like the three spatial axes.

Community
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John Rennie
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Itzhak Bars proposes a two-time physics. This means the spacetime(s) metric is of the form $$ ds^2 = dt^2 + du^2 - dx^2 - dy^2 - dz^2. $$ The anti-de Sitter spacetime is a subspace of this type of metric as well, where a constant surface is a hyperboloid. A hyperboloid in 5 dimensional space times is given by $$ t^2 + u^2 - x^2 - y^2 - z^2 = 1. $$

The Lorentz symmetry of spacetime has the orthogonal group structure $SO(3,1)$, and if there were two-times the structure of the spacetime would be $SO(3,2)$. Anti-de Sitter spacetime is a subspace of a five dimensional spacetime with two-times. This is $AdS_4 = SO(3,2)/SO(3,1)$. The quotient can be interpreted as meaning the five dimensional spacetime equivalent under Lorentz generators.

Lawrence B. Crowell
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Time is not a combination of a past, present, and future dimensions, but rather a one-dimensional axis, where the past and future are dependent on the present for definition, and the present is a particle's position in time. In the theory of relativity, a particle has position $(x,y,z,t)$, where $(x,y,z)$ is the particle's position in space, and $t$ is the particle's position in time. The past of the particle is defined as all values of $t$ less the particle's $t$ value, the present is the particle's $t$ value, and the future is any $t$ value greater then the particle's $t$ value.

John Dumancic
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