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Penrose, Sir Roger

black hole mass holes

(1931–) British theoretical physicist: major contributor to theories on black holes.

Son of a distinguished geneticist and expert on mental defects, Penrose studied at University College, London, and Cambridge. After posts in London, Cambridge and the USA he became professor of applied mathematics at Birkbeck College, London (1966), and Rouse Ball Professor of Mathematics in Oxford (1973).

Penrose revealed many of the properties of black holes by his research. Black holes occur when large stars collapse and reach a density such that even light (photons) cannot escape from the intense gravitational attraction. The ‘event horizon’ marks the region within which light cannot escape and Penrose proved that a space-time singularity (a point, having mass but no dimensions) arises at the centre of a black hole, and Penrose established that event horizons always prevent us from observing these singularities from the outside. They also argued, in 1970, that the universe must have begun as a singularity, from which the ‘Big Bang’ developed.

However, if a black hole is rotating but uncharged, (a Kerr black hole) it possesses a region around it in which matter will always be broken into one mass that falls inside the hole and the remainder, which is ejected. Curiously, the ejected mass-energy must exceed that of the original matter, so that the Kerr black hole has lost mass-energy on accreting matter. Overall, Penrose’s research adds much to our knowledge of gravitation, and he added to the efforts to formulate a satisfactory quantum theory of gravity, which are as yet unsuccessful.

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