Monsignor Georges Henri Joseph Édouard Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer at the Catholic University of Leuven. He sometimes used the title Abbé or Monseigneur. Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, which he called his 'hypothesis of the primeval atom'.[1][2][3]
Lemaître was a pioneer in applying Einstein's theory of general relativity to
cosmology. In a 1927 article that preceded Hubble's landmark article by two
years, Lemaître derived what became known as Hubble's law and proposed it as a
generic phenomenon in relativistic cosmology. Lemaître also estimated the
numerical value of the Hubble constant. However, the data used by Lemaître did
not allow him to prove that there was an actual linear relation, which Hubble
did two years later.
Wikipedia