Penrose diagram
From Freepedia
In theoretical physics, a Penrose diagram (named for mathematical physicist Roger Penrose) is usually a two-dimensional diagram that captures the causal relations between different points in spacetime. Slanted lines at an angle of 45° correspond to light rays. Locally, the metric on a Penrose diagram is conformally equivalent to the actual metric in spacetime.
Penrose diagrams are more properly (but less frequently) called Carter-Penrose diagrams (or Penrose-Carter diagrams), acknowledging both Brandon Carter and Roger Penrose, who were the first researchers to employ them.
