- Japanese physicist
whose research in 1950 exposed a fallacy in the 'hot Big Bang' theory
proposed two years earlier by Ralph Alpher and others. Hayashi has published
many papers on the origin of the chemical elements in stellar evolution
and on the composition of primordial matter in an expanding universe.
Hayashi was born and educated in Kyoto, where he became professor of
physics 1957.
Hayashi pointed out that in the Big Bang earlier than the first two
seconds, the temperature would have been greater than 1010K, which is
above the threshold for the making of electron-positron pairs. This
radically altered the timescale proposed in the 'hot Big Bang' theory.
He also showed that the abundance of neutrons at the heart of the Big
Bang did not depend on the material density but on the temperature and
the properties of the weak interreactions. Provided the density is great
enough for the reaction between neutrons and protons to combine at a
rate faster than the expansion rate, a fixed concentration of neutrons
will be incorporated into helium nuclei, however great the material
density is - producing a plateau in the relationship between helium
abundance and material density.
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