Einstein with Edwin Hubble, in 1931, at the Mount Wilson Observatory in California, looking through the lens of the 100-inch telescope through which Hubble discovered the expansion of the universe in 1929. Courtesy of the Archives, Calif Inst of Technology.
In 1917, just after Albert Einstein’s general theory of relativity was issued—but quiet two years earlier he would turn out to be a worldwide personality as we know— Albert Einstein elected to tackle not only the origin but the whole universe. For anybody else, this might appear a remarkably ambitious and difficult task, but this was THE ALBERT EINSTEIN. Albert Einstein initiated his study of understanding the whole universe by relating his field equations of gravitation to what he considered to be the whole universe. The field equations extended Newton’s theory of gravity to realms where speeds approach that of light and masses are incredibly very huge. One important point to be noted here is, his math was well improved than he desired to trust. In other words his equations expressed that the universe could not stay fixed: it had to either expand or contract under all circumstances. Einstein elected to ignore what his math was telling him.
This story of Albert Einstein’s key to this problem is the maligned “cosmological constant” (alsocalled lambda), which is well identified in the entire history of science. But this story has a not the same ending than everybody assumed: Albert Einstein late in life reverted to considering his condemned lambda. And his conversion predicted lambda’s use in an unpredicted new situation, with huge significance to a key conundrum in modern physics and cosmology i.e. dark energy.
The Irish physicist Cormac O’Raifeartaigh was checking papers at the Einstein Archives at the Hebrew University in Jerusalem in late 2013 when he discovered a handwritten document by Einstein that researchers had never considered wisely before. The discovered paper, named “Zum kosmologischen Problem” (“About the Cosmological Problem”), had been mistakenly placed as a draft of extra paper, which was published by Albert Einstein in 1931 in the records of the Prussian Academy of Sciences. This paper was actually his determined effort to resurrect the cosmological constant which he had vowed not ever to use for a second time.
In a paper just filed on the electronic physics source ArXiv, O’Raifeartaigh and coworkers display that in the initial 1930s (the supposed date is 1931, but this is unclear), Albert Einstein was still trying to return to his analysis of 1917 of a universe with a cosmological constant. Albert Einstein composed (the authors’ transformation from the German): “This difficulty [the inconsistency of the laws of gravity with a finite mean density of matter] also arises in the general theory of relativity. However, I have shown that this can be overcome through the introduction of the so-called “λ–term” to the field equations… I showed that these equations can be satisfied by a spherical space of constant radius over time, in which matter has a density ρ that is constant over space and time.” But Albert Einstein was now attentive of Hubble’s discovery of the expansion of the universe: “On the other hand, Hubbel’s [sic*] exceedingly important investigations have shown that the extragalactic nebulae have the following two properties 1) Within the bounds of observational accuracy they are uniformly distributed in space 2) They possess a Doppler effect proportional to their distance”
And so Albert Einstein suggested a review of his model, still with a cosmological constant, but at that time the constant was liable for the conception of new matter as the universe expanded (that’s because Albert Einstein assumed that in an expanding universe, the whole concentration of matter had to still stay constant): “In what follows, I would like to draw attention to a solution to equation (1) that can account for Hubbel’s facts, and in which the density is constant over time.” And: “If one considers a physically bounded volume, particles of matter will be continually leaving it. For the density to remain constant, new particles of matter must be continually formed in the volume from space.” Albert Einstein attains this property by the use of his old cosmological constant, λ (lambda): “The conservation law is preserved in that by setting the λ-term, space itself is not empty of energy; as is well-known its validity is guaranteed by equations (1).” So Albert Einstein hang onto using his rejected lambda, even though he invented it for a non-expanding universe. If the universe expands as presented by Hubble, Albert Einstein appears to be saying, then I still want my lambda—now to preserve the universe from becoming less dense as it enlarges in volume.
Nearly two decades later, a related “steady state” universe would be offered by Hermann Bondi, Fred Hoyle and Tommy Gold, in papers distributed in 1949. But these published models of the universe are not supported by modern theories. A theory of modern cosmology is that as the universe will expand a great deal (after an unbelievably lengthy period of time), it will convert into very thinly occupied, reasonably than dense, with lost photons and electrons whooshing alone through huge areas of vacuum.
*It’s exciting that Einstein constantly misspells the name of Edwin Hubble (“Hubbel”). Had he not yet met Hubble in person? Well we don’t know. The spelling mistake does point at the statement that Hubble’s discovery was not yet so intensely recognized so that his name would be well known by all researchers.