all such spiral nebulae were moving away from the Earth, he failed to reach the conclusion that this meant the universe was expanding.
Around the same time, Slipher was making his observations, Friedmann, the Soviet physicist, explained how Einstein's General Relativity Theory might prove that the universe was expanding. Einstein's theory updated and revised Newton's gravitational laws, for conditions where enormous mass and energy existed. Newton concluded that gravity was a force between two masses; Einstein argued, correctly as it was proved by later experiments, that gravity was the warping of space and time caused by mass. While Newton's model of gravity was not consistent with the Big Bang theory-since there was no mass in the primordial state of heat and density at the beginning of time-Einstein's allowed for the possibility of gravity itself coming into being, though, ironically, Einstein himself held to a static view of the universe when he came up with his General Relativity Theory.
Roughly a decade after Friedmann developed his models out of Einstein's General Relativity Theory-models that, while published, generally got overlooked by other physicists - a Belgian physicist and astronomer Georges LemaГ®tre, independently coming up with the same theories as Friedmann, used them to reach the conclusion that had eluded Slipher-that receding nebulae meant the universe was expanding. In 1931, LemaГ®tre also hypothesized that the universe must have begun with a single atom, an idea that came to be called the "cosmic egg" theory. American astronomer Edwin Hubble, the first to realize that nebulae were in fact other galaxies, also confirmed that the galaxies all seemed to be moving away from us simultaneously. Extrapolating backward, Hubble believed that they all had emerged from the same high-density place, exploding outward in a kind of initial fireball. Hubble made his findings by noting shifts in the light spectrum of distant galaxies that fit in with the Doppler effect.
Despite such findings, a competing theory emerged in the years after World War II,. The "steady state" model, advocated by British astronomer Frederick Hoyle, held that new matter was created as the universe expanded. A confirmed atheist, Hoyle rejected the "cosmic egg" theory as it seemed to imply the existence of a creator. Ironically, it was Hoyle who, in the 1950s, coined the term "Big Bang," using it in a radio interview to ridicule LemaГ®tre's ideas. To reconcile his constant universe idea and the observed fact that galaxies were moving away from each other, Hoyle hypothesized that new galaxies came into being as older ones grew apart. While later discounted, Hoyle's work was useful in explaining how matter and energy came into existence, a key component of the Big Bang theory.
Confirmation of the Big Bang Theory
For two decades the two theorie...
