ylem ,
n :
(astronomy, cosmology, physics, now chiefly historical) In the Big Bang theory, the hot and dense plasma which made up the cosmos at the time of recombination in an early stage of its expansion and cooling, when the first atoms formed and photons decoupled. The ylem is regarded as the source of the cosmic microwave background. George Gamow, who co-authored the 1948 paper with Ralph Asher Alpher and Hans Bethe which first used the term ylem in this context, died on this day in 1968.
