|Einstein in 1931|
Image: Wikimedia Commons
Historian Harry Nussbaumer's paper argues that Einstein ignored observational evidence his "Cosmological Constant" was wrong, and instead only admitted he was wrong when he personally came to the conclusion that his model of the universe was unstable. Nussbaumer culled through stacks of the physicist's diary entries, drafts of speeches and even newspaper articles, looking for the source of his conversion.
When Einstein was developing the theory of general relativity in 1915, he was faced with a serious problem; His equations indicated that there was no way the universe could exist. At the time, everyone thought the universe was static, that stars didn't move very much and the idea of galaxies was unheard of. According to his equations based on that understanding of the universe's density, gravity should pull everything in the universe together into a single conglomerated mish-mash.
To compensate, he introduced the cosmological constant to counteract gravity. There was no observational evidence for it or any real theoretical scientific backing, but it kept the universe from collapsing in on itself, so it was an effective fudge factor.
However it was wrong, and in April of 1931 Einstein published a paper where he renounced it and said that he agreed with astronomers who said the universe was expanding, effectively countering the pull of gravity, and the cosmological constant was a mistake.
How Einstein reached that conclusion has however been the stuff of myth.
|The galaxies in this photo that appear redder are|
farther away and moving away at a tremendous speed.
However, Nussbaumer argues, Einstein was not as impressed with Hubble as common lore holds. Einstein, from his interactions with other physicists, already superficially knew most of what Hubble was saying about the redshift of distant galaxies, and his meeting with the astronomer added nothing really new. Plus, the idea of redshift was so new, no one was sure that's what they were seeing.
On February 4, Einstein gave a seminar about astronomy where he mentioned the work of the astronomers at the Wilson Observatory. He commended their work, but was conservative about how their observations might affect his equations, speculating that likely the universe was still static, but he might have to refigure his equations slightly.
Despite that modest answer, headlines across the country lit up, claiming that Einstein had been converted to a believer in an expanding universe. Hubble's own hometown newspaper the Springfield Daily News headlined "Youth Who Left Ozark Mountains [Hubble] to Study Stars Causes Einstein to Change His Mind."
Even to this day, that narrative is often repeated. Walter Isaacson's acclaimed biography Einstein: His Life and Universe, implies as much and author Denis Brian writes in Einstein: A Life, "Einstein was Tremendously Impressed... [N]ow he could hardly deny the spectacular evidence."
Except Einstein wasn't so impressed. His diary from that time period hardly mentions Hubble at all. A week later when he was at another seminar, this one specifically on redshifted galaxies he offered a much more nuanced and qualified view. He said it could be an expanding universe, or from a universe that expanded and contracted, or perhaps even that distant light got "tired" and redder the farther it traveled. His beliefs were starting to change, but it was hardly the instant conversion often talked about. When asked how he could explain the redshifts, he said "I don't know the answer."
|Today's accepted version of the expanding universe.|
Over the next few months he reviewed the published literature on the expanding universe problem. His opinion continued to evolve and in mid-March he sat down and started writing a paper for the Prussian Academy of Sciences where he finally renounced the cosmological constant. In putting it together he only made oblique referenced the works of Hubble and whose last name he habitually misspelled as "Hubbel," indicating that he may not have read any of Hubble's papers.
Though Hubble's observations were immensely important to science they were not as important to Einstein. He never liked his cosmological constant not just because it was hackneyed, but because it had to be impossibly perfectly balanced for a static universe to even exist. He finally came around to the idea of a dynamic universe without the constant only after a he found a workaround for the age of the universe. He cited "inhomogeneities" in matter distribution of the universe as possibly affecting the equations for the age of the universe.
Einstein was a relatively late comer to the idea of a dynamic universe. Many in the field had either already accepted that explanation by the time his paper was published. The paper itself contained no new science, but was important historically for being the point when Einstein finally admitted that his own cosmological constant was cosmological claptrap.
Nussbaumer's research was recently accepted to the journal European Physical Journal - History.