Thus, in Minkowski’s 4-geometry, we are not now to think of the space-time as being simply built out of a succession of 3-surfaces, each representing what we think of as ‘space’ at various different times (Fig. 2.10). For that interpretation, each of these 3-surfaces would describe a family of events all of which would be taken to be simultaneous with one another. In special relativity, the notion of ‘simultaneous’ for spatially separated events does not have an absolute meaning. Instead, ‘simultaneity’ would depend upon some arbitrarily chosen observer’s velocity.
