time axis

mathematical representation of the succession in time according to the space-time model of instantaneous events along a unique axis Note 1 to entry: According to the theory of special relativity, the time axis depends on the choice of a spatial reference frame. Note 2 to entry: In IEC 60050-113:2011, 113-01-03, time according to the space-time model is defined to be the one-dimensional subspace of space-time, locally orthogonal to space. [SOURCE:IEC 60050-113:2011, 113-01-07, modified — The words “according to the space-time” have been added; the phrase “special theory of relativity” has been changed to “theory of special relativity” for clarity; Note 2 to entry has been added.]