An ordinary spacetime plot must let distant regions run off the page. A Penrose diagram uses a conformal rescaling to bring an unbounded geometry into a finite range while preserving light cones and causal order. Metric scale is sacrificed so causal structure can be seen.

The boundaries labelled future, past, null or spatial infinity belong to a conformal completion, an auxiliary geometry used to study the original spacetime. They are not locations made physically reachable by drawing them nearby. The page holds a causal map, not a scale model of an entire universe.

For a black-hole spacetime, the diagram can place exterior region, event horizon and interior in one causal picture. The horizon is locally an ordinary null surface, yet globally it marks a limit: signals sent from inside cannot reach future null infinity.

Popular accounts say that space and time "swap roles" at a Schwarzschild horizon. That phrase depends on a particular coordinate description and can mislead. The diagram makes the safer statement visible: future-directed paths inside have different causal destinations. A singular boundary, where the classical spacetime description fails, is drawn as an edge rather than a place an observer can inhabit.

Every event in a relativistic spacetime has a local light cone separating possible causal influence from spacelike separation. A conformal diagram keeps that ordering legible across a large or unbounded region. It can show that two areas belong to one solution while remaining causally unable to exchange signals.

This is where the archive's metaphor must stop short of mechanism. The drawing may invite reflection on relation and separation, but it is not a "higher view" in which lives or universes blur into one. Its power comes from preserving distinctions with unusual clarity.

The page's edges are mathematically classified. Light rays may end at future null infinity; massive idealized observers may approach future timelike infinity; spatial infinity captures another limiting direction. Different spacetimes have different conformal boundaries.

A Big Bang or black-hole singularity can also appear as a boundary, but drawing it does not make it a known physical object or settle what replaces general relativity there. The finite page offers a disciplined kind of wonder: infinity can be compared without being domesticated, and the unknown remains labelled rather than filled in.