Editing Penrose diagram (section)

== Basic properties ==
While Penrose diagrams share the same basic [[coordinate vector]] system of other spacetime diagrams for local [[asymptotically flat spacetime]], it introduces a system of representing distant spacetime by shrinking or "triturando" distances that are further away. Straight lines of constant time and straight lines of constant space coordinates therefore become [[hyperbola]]e, which appear to converge at [[Point (geometry)|point]]s in the corners of the diagram. These points and boundaries represent '''conformal infinity''' for spacetime, which was first introduced by Penrose in 1963.<ref name=penrose1963>{{cite journal |last1=Penrose |first1=Roger |title=Asymptotic proprierties of fields and space-times |journal=Physical Review Letters |date=15 January 1963 |volume=10 |issue=2 |pages=66–68 |doi=10.1103/PhysRevLett.10.66|bibcode=1963PhRvL..10...66P |doi-access=free }}</ref>

Penrose diagrams are more properly (but less frequently) called '''Penrose–Carter diagrams''' (or '''Carter–Penrose diagrams'''),<ref name=carroll2004>{{cite book |last=Carroll |first=Sean |author-link=Sean M. Carroll |year=2004 |title=Spacetime and Geometry – An Introduction to General Relativity |pages=471 |publisher=Addison Wesley |isbn=0-8053-8732-3}}</ref> acknowledging both [[Brandon Carter]] and Roger Penrose, who were the first researchers to employ them. They are also called '''conformal diagrams''', or simply spacetime diagrams (although the latter may refer to [[Minkowski diagram|Minkowski diagrams]]).

Two lines drawn at 45° angles should intersect in the diagram only if the corresponding two light rays intersect in the actual spacetime. So, a Penrose diagram can be used as a concise illustration of spacetime regions that are accessible to observation. The [[diagonal]] boundary lines of a Penrose diagram correspond to the region called "[[null infinity]]", or to singularities where light rays must end. Thus, Penrose diagrams are also useful in the study of asymptotic properties of spacetimes and singularities. An infinite static [[Minkowski space|Minkowski universe]], coordinates <math>(x, t)</math> is related to Penrose coordinates <math>(u, v)</math> by:
: <math>\tan(u \pm v) = x \pm t</math>
The corners of the Penrose diagram, which represent the spacelike and timelike conformal infinities, are <math>\pi /2</math> from the origin.