So it's kind of like the pythagoras triangle, except it's kind of got two hypotenueses and only one regular side (or three regular sides and two hypoteneuses if you take the three spatial dimensions as three dimensions); that is the area of the square of one side (the distance) minus the area of the square of either of the other two sides (the distance light has travelled, and the interval) leaves the area of the square of the remaining side.

Interesting concept.