Free The Perfect Theory by Pedro G. Ferreira

light. When measured with a spectrometer, these wavelengths appear as a series of lines like a bar code. This bar code is known as an object’s spectrum.
    Slipher used his equipment at the Lowell Observatory in Flagstaff, Arizona, to measure the spectra of nebulae scattered all over the sky. He then compared his measured spectra with what he would have obtained if he had measured an object made of the same elements sitting on his desk in his office. (The spectra for the elements making up the nebulae were perfectly well known so he didn’t actually need to repeat the experiment in his office.) He found that his measurements of the nebulae’s spectra were all displaced relative to what he expected. The bar codes were shifted either to the left or to the right.
    The shift in the spectra implied that the measured objects were in motion. When a source of light is moving away from an observer, the wavelengths in its spectrum appear to stretch. The net effect is that light will look redder. Conversely, if a source of light is moving toward the observer, its spectrum is shifted to shorter wavelengths and will look bluer. This effect, known as the Doppler effect, is something you have probably experienced in the context of sound. Imagine a speeding ambulance coming down the street toward you—the pitch of its siren changes as it passes by, shifting to a lower pitch as it moves away. This same effect in light enabled Slipher to figure out how things were moving in the universe.
    Slipher’s results weren’t altogether surprising. He expected things to move around, buffeted by the gravitational pull of nearby objects. In fact, one of his first measurements seemed to indicate that one of the brighter nebulae, Andromeda, was moving closer to us: its light was blueshifted. But Slipher was systematic and recorded spectra of a few more nebulae. What he found was puzzling—almost all the nebulae seemed to be drifting away from us. There was a trend.
    In 1924, a young Swedish astronomer named Knut Lundmarktook Slipher’s data and made a rough guess of how far away from us the different nebulae were. Lundmark still couldn’t tell exactly how far away each nebula was and wasn’t entirely sure about his results. But lying there in front of him was the telltale trend—the farther away the nebulae were, the quicker they seemed to move.
    Now, in 1927, the Abbé Lemaître had rederived the trend that appeared in de Sitter’s model and that Slipher seemed to see in the data. Indeed, his calculations predicted that measuring the redshifts
and
distances of faraway galaxies should reveal a linear relation between the two. Plotted on a graph, with distance on the horizontal axis and redshift on the vertical axis, the galaxies should all fall approximately on a straight line. Unaware of Friedmann’s work, Lemaître wrote up his results for his doctorate and published them in an obscure Belgian journal. He included his calculations and a short section discussing the observational evidence, working out the slope of the linear relation that Eddington, Weyl, and he himself had found. The observational evidence for expansion was tentative and contained large errors, but it was tantalizing how everything seemed to fit together.
    To Lemaître’s utter dismay, his work was completely ignored by relativity’s leading theorists, including Eddington, his former adviser. When Lemaître met Einstein at a conference later that year, Einstein was unimpressed by Lemaître’s work. Einstein graciously pointed out to Lemaître that his work merely replicated Alexander Friedmann’s findings. While Einstein had conceded that Friedmann’s calculations were correct, he clung to his belief that these strange expanding solutions were a mathematical curiosity, unrepresentative of the real universe, which he knew to be static. He concluded his appraisal of Lemaître’s work with a dismissive