Edwin Hubble was already famous by 1924 but that year he became a celebrity. A few years earlier he had met Grace Burke, daughter of a California millionaire. Grace was already married when Hubble fell in love with her but in 1921 she was widowed when her husband, a geologist, fell down a vertical mineshaft to his death. Grace and Edwin renewed their relationship and were married in 1924. Hubble was working at the Mt. Wilson observatory about 15 miles from Los Angeles at the time. With his marriage into money he gained entry to parties where movie stars and politicians mingled. Hubble was gregarious and outgoing and soon the likes of Douglas Fairbanks and Cole Porter visited the Mt. Wilson observatory where Hubble regaled them with stories.
Hubble had heard of Slipher’s and others’ discoveries that the majority of galaxies are moving away from us. He took it as his duty as the world’s foremost astronomer to solve this problem. The 100-inch Mt. Wilson telescope was 17 times more powerful than Slipher’s. Hubble spent countless hours staring through it at the night sky. With his assistant Milton Humason he set about measuring the speed of the receding galaxies.
What they discovered was the first observational evidence to support Lemaitre’s and Friedmann’s theory that the universe is not static but is expanding. Hubble plotted the distance of dozens of galaxies against their speed and discovered a linear relation. In other words, if a galaxy was twice as far from earth as another, the first was moving twice as fast. Instead of traveling at random speeds and in random directions, virtually all galaxies were traveling at speeds proportional to their distance and moving away from the Milky Way.
By running the movie in reverse, so to speak, Hubble showed that last year all galaxies were closer to us than now, a hundred years ago they were closer still. Moreover, and this was the incredible part, since the velocity was in proportion to the distance, the more distant galaxies would arrive at the beginning point at the same time as the nearer ones. A galaxy three times as far away moved three times as fast, so, assuming that the relative speeds were constant, there was a time in the distant past when all galaxies were gathered together in one region of the universe.
Hubble’s findings weren’t conclusive proof of the Big Bang (it still had not been so named) and Einstein and others still favored a steady state view of the universe. But it did give ammunition to the expanding universe proponents and put the burden on the steady-staters to reconcile their view with this indisputable evidence of galactic movement.
Hubble’s discovery gave rise to what is known as Hubble’s Law. This isn’t an exact law like gravity but is more of a rule of thumb. What it does is allow the distance of a galaxy to be calculated by knowing its speed, or its speed to be calculated if the distance is known. The most profound implication of Hubble’s Law is that the age of the universe can be calculated. Using Hubble’s Law and the speed of various galaxies led to a conclusion that the universe is 1.8 billion years old.
The only problem with this age is that geologists have calculated the age of the Earth at around 4 billion years. How can the Earth be older than the universe that contains it? While Hubble’s discovery gave credence to a time of beginning or creation of the universe, it posed internal inconsistencies.
Nevertheless, Hubble had a showman’s sense of when to leave the stage. Rather than stay around after his prime, he stepped down at the top of his game. He did not get involved in the next Great Debate
over the steady-state vs. expanding universe. He luxuriated in his celebrity status as the man who had expanded the universe from the Milky Way to a perhaps infinite number of galaxies, who had shown that all these galaxies are racing away from us and who, though he might not acknowledge it himself, had nurtured the seed of the notion that the universe began at a finite time in the past, thus giving some objective evidence that Genesis’ statement “let there be light” is more than just a poetic description.