(idea) by 95% fat free Sat Apr 21 2001 at 12:39:29

Given a metric gab, the formal definition of a light cone based as some point xc is

    LC(xc) = {yc|gab(ya-xa)(yb-xb) = 0}
For the Lorentzian metric in three dimensions (diagonal(11,-1)), this indeed is a (double) cone.

I like it!