Free The Perfect Theory by Pedro G. Ferreira Page B

nebulae. The fainter they were, the farther away they would be. But he was battling with an instrument that wasn’t really set up to do these kinds of measurements. It would take him two or three days to get a spectrum, while other telescopes could already do it in a few hours.
    While Humason looked for redshifts, Hubble focused on determining distances. He measured the amount of light each nebula was emitting and compared the results. From this, he could get a rough idea of how far away the objects were, comparing to his measurement of the distance of Andromeda. He then combined his measurements of distance with Slipher’s and Humason’s measurements of redshifts to look for a linear relation between the two, the telltale sign of the de Sitter effect.
    By January of 1929, Hubble and Humason had redshifts for forty-six nebulae. Of these, Hubble had distances for twenty-four, the closer ones for which Slipher had measured the redshifts. He plotted them on a graph: the
x
axis denoted the distances and the
y
axis denoted the apparent velocities determined by the observed redshifts. There was still a lot of scatter, but it looked better than Lundmark’s or Lemaître’s attempts, and there was a distinct trend: the farther away the nebulae were, the larger the redshift.
    Hubble submitted for publication, without Humason, a short paper, “A Relation Between Distance and Radial Velocity Among Extragalactic Nebulae,” plotting out his data. Lundmark had been there before him, but althoughHubble mentioned Lundmark’s work in passing, he hyped the importance of his own result. In his last paragraph he wrote, “The outstanding feature, however, is the possibility that the velocity-distance relation may represent the de Sitter effect, and hence the numerical data may be introduced into discussions of the general curvature of space.” In a short, modest paper submitted on the same day, Humason published his measurements of redshift and distance to a nebula that was twice as distant as all the ones that Hubble had considered in his paper. It also seemed to lie along the redshift relation that Hubble was finding. There it was, the de Sitter effect.
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    Although Lundmark and Lemaître had been there before, Hubble’s discovery of the linear relationship between redshift and distance was the catalyst that brought cosmology together. In the years that followed Hubble’s seminal paper of 1929, the ideas of Einstein, de Sitter, Friedmann, and Lemaître, which had been fermenting during the previous decade or so, would finally be reconciled into one simple picture. And even though the evidence for the recession of galaxies was already sitting in Slipher’s data and Lundmark’s and Lemaître’s tentative analyses, it was Hubble’s and Humason’s papers that convinced astronomers that the de Sitter effect might be real.
    A year after Hubble’s paper was submitted, Eddington wrote up a discussion of the de Sitter effect and Hubble’s observations in
The Observatory,
the same journal that had published his pacifist pleas during the dark days of the Great War. The Abbé Lemaître, firmly ensconced at the University of Louvain, read Eddington’s article and was nonplussed. There was no mention of his work—his far simpler model of an expanding universe had been forgotten. Lemaître immediately sent Eddington a letter, describing his work from 1927 in which he had shown that there were other solutions to Einstein’s equations in which the universe expanded. At the end of his letter, he added,“I send you a few copies of the paper. Perhaps you may find occasion to send it to de Sitter. I sent him also at the time but probably he didn’t read it.” Eddington was mortified. His “brilliant” and “clear-sighted” student had kept him up-to-date with his forays in relativity, yet Eddington had simply dismissed and forgotten his