A Penrose diagram, also known as a Penrose-Carter diagram or causal diagram, can be used to visualize spacetime with a symmetry, so the relevant properties the whole thing by considering a lower-dimen...A Penrose diagram, also known as a Penrose-Carter diagram or causal diagram, can be used to visualize spacetime with a symmetry, so the relevant properties the whole thing by considering a lower-dimensional part of it. For example, for a spacetime that is spherically symmetric, then we can reduce the four-dimensional to a two-dimensional one, with each point representing a two-sphere.
