Note 1 — PART II The General Theory of Relativity

Minkowski found that the Lorentz transformations satisfy the following simple conditions. Let us consider two neighbouring events, the relative position of which in the four-dimensional continuum is given with respect to a Galileian reference-body K by the space co-ordinate differences and the time-difference dt. With reference to a second Galileian system we shall suppose that the corresponding differences for these two events are . Then these magnitudes always fulfil the condition1.