Simplify the following text for a Grade 6 native English-speaking person.
Original: Sir Fred Hoyle FRS ( 24 June 1915 -- 20 August 2001 ) was an English astronomer and mathematician noted primarily for his contribution to the theory of stellar nucleosynthesis and his often controversial stance on other cosmological and scientific mattersâ '' in particular his rejection of the `` Big Bang '' theory , a term originally coined by him as a jocular , perhaps disparaging , name for the theory which was the main rival to his own .
Simplified: Sir Fred Hoyle ( 24 June 1915 â `` 20 August 2001 ) was an English astronomer .