|Albert Einstein at Mount Wilson Observatory in 1931, with Edwin Hubble (centre) and Walter Adams.|
A manuscript that lay unnoticed by scientists for decades has revealed that Albert Einstein once dabbled with an alternative to what we now know as the Big Bang theory, proposing instead that the Universe expanded steadily and eternally. The recently uncovered work, written in 1931, is reminiscent of a theory championed by British astrophysicist Fred Hoyle nearly 20 years later. Einstein soon abandoned the idea, but the manuscript reveals his continued hesitance to accept that the Universe was created during a single explosive event.Evidence for the Big Bang first emerged in the 1920s, when US astronomer Edwin Hubble and others discovered that distant galaxies are moving away and that space itself is expanding. This seemed to imply that, in the past, the contents of the observable Universe had been a very dense and hot ‘primordial broth’.
But, from the late 1940s, Hoyle argued that space could be expanding eternally and keeping a roughly constant density. It could do this by continually adding new matter, with elementary particles spontaneously popping up from space, Hoyle said. Particles would then coalesce to form galaxies and stars, and these would appear at just the right rate to take up the extra room created by the expansion of space. Hoyle’s Universe was always infinite, so its size did not change as it expanded. It was in a ‘steady state’.
The newly uncovered document shows that Einstein had described essentially the same idea much earlier. “For the density to remain constant new particles of matter must be continually formed,” he writes. The manuscript is thought to have been produced during a trip to California in 1931 — in part because it was written on American note paper.
It had been stored in plain sight at the Albert Einstein Archives in Jerusalem — and is freely available to view on its website — but had been mistakenly classified as a first draft of another Einstein paper. Cormac O’Raifeartaigh, a physicist at the Waterford Institute of Technology in Ireland, says that he “almost fell out of his chair” when he realized what the manuscript was about. He and his collaborators have posted their findings, together with an English translation of Einstein’s original German manuscript, on the arXiv preprint server (C. O’Raifeartaigh et al. Preprint athttp://arxiv.org/abs/1402.0132; 2014) and have submitted their paper to the European Physical Journal.
“This finding confirms that Hoyle was not a crank,” says study co-author Simon Mitton, a science historian at the University of Cambridge, UK, who wrote the 2005 biography Fred Hoyle: A Life in Science. The mere fact that Einstein had toyed with a steady-state model could have lent Hoyle more credibility as he engaged the physics community in a debate on the subject. “If only Hoyle had known, he would certainly have used it to punch his opponents,” O’Raifeartaigh says.
Albert Einstein Archives, Hebrew University of Jerusalem, Israel
Einstein’s correction to his erroneous calculation.
Although Hoyle’s model was eventually ruled out by astronomical observations, it was at least mathematically consistent, tweaking the equations of Einstein’s general theory of relativity to provide a possible mechanism for the spontaneous generation of matter. Einstein’s unpublished manuscript suggests that, at first, he believed that such a mechanism could arise from his original theory without modification. But then he realized that he had made a mistake in his calculations, O’Raifeartaigh and his team suggest. When he corrected it — crossing out a number with a pen of a different colour — he probably decided that the idea would not work and set it aside.
The manuscript was probably “a rough draft commenced with excitement over a neat idea and soon abandoned as the author realized he was fooling himself”, says cosmologist James Peebles of Princeton University in New Jersey. There seems to be no record of Einstein ever mentioning these calculations again.
But the fact that Einstein experimented with the steady-state concept demonstrates his continued resistance to the idea of a Big Bang, which he at first found “abominable”, even though other theoreticians had shown it to be a natural consequence of his general theory of relativity. (Other leading researchers, such as the eminent Cambridge astronomer Arthur Eddington, were also suspicious of the Big Bang idea, because it suggested a mystical moment of creation.) When astronomers found evidence for cosmic expansion, Einstein had to abandon his bias towards a static Universe, and a steady-state Universe was the next best thing, O’Raifeartaigh and his collaborators say.
Helge Kragh, a science historian at Aarhus University in Denmark, agrees. “What the manuscript shows is that although by then he accepted the expansion of space, [Einstein] was unhappy with a Universe changing in time,” he says.
Nature 506, 418–419 (27 February 2014) doi:10.1038/506418a