1. The problem statement, all variables and given/known data How does the scalar product of displacement four vector with itself give the square of the distance between them? 2. Relevant equations (Δs)2= Δx.Δx ( s∈ distance, x∈ displacement four vector) or how ds2=ηαβdxαdxβ 3. The attempt at a solution Clearly I am completely new to the subject, thus I have no idea about it.