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Hayashi, Chusiro

‘big bang’ universe contraction

(1920– ) Japanese astrophysicist.

Educated at Kyoto and Tokyo, Hayashi returned to Kyoto in 1954 and taught there throughout his career. In 1948 the ‘Big Bang’ theory offered an explanation for the relative abundance of the chemical elements in the universe, using in part the idea due to in 1946 that thermonuclear reactions would occur in the very hot and dense first stages of the ‘Big Bang’. In these conditions they assumed that neutrons could combine with protons. In 1950 Hayashi modified ‘Big Bang’ theory by calculating that within the first 2 s the temperature would be above 10 10 K, which is above the threshold for the formation of electron–positron pairs from photons. Working through the consequences of these ideas, he and others showed that they would lead to a fixed hydrogen:helium ratio in stars, with only small amounts of heavier elements. This was the first of the many variants on the ‘Big Bang’ idea, whose common feature is that the universe began as an explosive event from some primordial state, with space itself expanding along with the matter in it. The concept is broadly accepted by cosmologists, but whether it will ultimately be followed by contraction and repetition (ie an oscillating universe) or by limitless expansion, or by a violent final contraction (the ‘Big Crunch’) remains an open question.

Hayden, Palmer(1890–1973) - Painter, Life as Serviceman and Fledgling Artist, The Renaissance Artist Paints Seascapes [next] [back] Hawley, Monte (1901–1950)

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