The ("N"th) Dimension(s)
While working on a publication, with an imminent deadline, on a topic I am supposed to be a bit of an expert on, it occurred to me I should confirm the meaning of the word "dimension".
Thank goodness for wikipedia! Simply because I enjoy learning, I used wikipedia since I general find this encyclopedia more educational than a dictionary. It saved me from the embarrassment of using some of my old notes that glibly referred to just 3 physical dimensions and assert that Time should be thought of as the 4th dimension. Now all I have to do is re-write my drafts, which I hope will be a lot less work that writing responses to the inevitable challenges that would result from being (only a bit, I hope) "out of date".Amplify’d from en.wikipedia.org
Dimension
From Wikipedia, the free encyclopedia
In mathematics and physics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify each point within it.[1][2] Thus a line has a dimension of one because only one coordinate is needed to specify a point on it. A surface such as a plane or the surface of a cylinder or sphere has a dimension of two because two coordinates are needed to specify a point on it (for example, to locate a point on the surface of a sphere you need both its latitude and its longitude). The inside of a cube, a cylinder or a sphere is three-dimensional because three co-ordinates are needed to locate a point within these spaces.
[edit] Dimension of a vector space
The dimension of a vector space is the number of vectors in any basis for the space, i.e. the number of coordinates necessary to specify any vector. This notion of dimension (the cardinality of a basis) is often referred to as the Hamel dimension or algebraic dimension to distinguish it from other notions of dimension.
[edit] Time
A temporal dimension is a dimension of time. Time is often referred to as the "fourth dimension" for this reason, but that is not to imply that it is a spatial dimension. A temporal dimension is one way to measure physical change. It is perceived differently from the three spatial dimensions in that there is only one of it, and that we cannot move freely in time but subjectively move in one direction.
The equations used in physics to model reality do not treat time in the same way that humans commonly perceive it. The equations of classical mechanics are symmetric with respect to time, and equations of quantum mechanics are typically symmetric if both time and other quantities (such as charge and parity) are reversed. In these models, the perception of time flowing in one direction is an artifact of the laws of thermodynamics (we perceive time as flowing in the direction of increasing entropy).
Read more at en.wikipedia.orgThe best-known treatment of time as a dimension is Poincaré and Einstein's special relativity (and extended to general relativity), which treats perceived space and time as components of a four-dimensional manifold, known as spacetime, and in the special, flat case as Minkowski space.

