Question

To which astronomer and cosmologist is what became known as the "big bang theory", the currently leading cosmological theory as modified by George Gamow, attributed?

Answer 1

Georges Lemaître
Expanding models of the universe had been considered by several scientists, including by Hubble and de Sitter; Lemaître's theory in 1927 was designed to be testable, and explained the observed redshift of galaxies and the linear relation between distances and velocities.