## Maximal Extension of Schwarzschild Metric in Physical Review 119, No. 5, September 1960, pp.1743–1745

Lancaster: American Physical Society, 1960. 1st Edition. FIRST EDITION IN ORIGINAL WRAPS OF “KRUSKAL’S DISCOVERY OF THE FULL CLASSICAL SPACETIME STRUCTURE OF THE SIMPLEST TYPE OF BLACK HOLE IN GENERAL RELATIVITY” (Wikipedia). This work spurred a renaissance in a study of the physics of black holes.

In this paper, Kruskal presents his “Kruskal coordinates” – an innovation that facilitated the mathematical study of the interior of black holes. Krukal’s methodology allows the solutions of the equations of general relativity to be singular at the center of a black hole but finite in other parts -- including the event horizon.

Kruskal’s created a “very complete space-time diagram which allows us to represent on a plane the central regions of the Schwarzschild black hole” (Luminet, Black Holes, 168). Problematically, the Schwarzchild solution had only been able to describe “the region exterior to the horizon of the black hole” (Wikipedia). Kruskal’s introduction of “a single set of coordinates that were non-singular everywhere outside the physical singularity” (Lambourne, Relativity, 191).

This work led Kruskal to the astonishing discovery that the interior of the black hole looks like a "wormhole" connecting two identical, asymptotically flat universes. This was the first real example of a wormhole solution in General Relativity (Wikipedia). Item #492

CONDITION & DETAILS: First edition in original wraps. Lancaster: American Physical Society. Slight wear and light creasing at the edges of the wraps. Very good condition.

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