Here is presented the first of two additional instalments to what was initially envisaged to be a series of three papers, namely “Temporal Mechanics (A): Time-Space Constants”, “Temporal Mechanics (B): Time-space Circuits”, and “Temporal Mechanics (C): Time-Space Manifolds”, here as Time-Space Metrics and in a subsequent paper as Time-Space Logistics. The importance of this fourth paper in this series of five upholds the need to detail what is recognized as an underlying theme through its three lead-up papers, namely time-space metrics being integral to the ideas of time-space constants, time-space circuits, and time-space manifolds, and what those “metrics” are, how those “metrics” can be demonstrated to exist from the microscopic scale (and elementary particle level) to the macroscopic scale (cosmological distances). Here therefore will be communicated the idea of a principle of relativity that conveys how the small scale relates with the large scale, how the elementary particle level works on a cosmological scale, and how that transference of metrics can be properly and consistently accounted for in the context of the previously presented time-space constants, circuits, and manifolds. In demonstration of these metrics will be derived the age of the perceived universe and the distance of the closest star to Sol, using the a priori metrics of Temporal Mechanics.