The Emergence of the Big Bang Theory
But if the universe truly was expanding, why was it doing so? By the late 1940's, two theories had emerged to account for the expansion of the universe.
Three British astrophysicists—Hermann Bondi, Thomas Gold, and Fred Hoyle—developed the steady state theory. According to this theory, the universe has always existed and has always looked essentially the same, except that galaxies constantly move away from each other. In the growing empty regions between them, new stars and galaxies are formed from matter that somehow pops into existence from the vacuum of space.
A different scenario was presented by the big bang theory, whose most outspoken proponent was the Russian-American physicist George Gamow. The big bang theory held that the universe began in a huge explosion of matter and energy at some moment in the far distant past. Matter created in this “primeval fireball” later came together to form the stars and galaxies.
In 1948, Gamow predicted that even though the universe had greatly expanded and cooled since the big bang, the explosion's leftover energy would still exist as very faint microwaves (high frequency radio waves) throughout space. Detecting this cosmic background radiation would lend strong support to the big bang theory.
Gamow's prediction was not confirmed until the 1960's. In 1965, two researchers at Bell Telephone Laboratories in Holmdel, N.J.—Arno A. Penzias and Robert W. Wilson—were working with a large horn shaped antenna designed for satellite communications. They detected a persistent hiss from wherever in the sky they pointed the antenna. That hiss was the sound of the cosmic background radiation.
With Penzias and Wilson's discovery, the big bang theory became widely accepted as the correct explanation for the origin of the universe. Although the theory has been refined, with details added by physicists studying matter on the smallest levels, the “big picture” of our cosmos being born in a moment of fiery energy appears to be correct. We live in a universe that has been here for a limited amount of time and that is evolving toward a future we have yet to determine.