Curiously, however, a number of scientists, while they accepted Einstein’s theory of relativity and the calculations on which it was based, never accepted the cosmological constant, and the correction on which it was based. Alexander Friedmann, a young Russian scientist, was the first man to cause Einstein to think again (‘cosmological constant’ was actually his term). Friedmann’s background was brutish. His mother had deserted his father – a cruel, arrogant man – taking the boy with her. Convicted of ‘breaking conjugal fidelity,’ she was sentenced by the imperial court to celibacy and forced to give up Alexander. He didn’t see his mother again for nearly twenty years. Friedmann taught himself relativity, during which time he realised Einstein had made a mistake and that, cosmological constant or no, the universe must be either expanding or contracting.44 He found this such an exciting idea that he dared to improve on Einstein’s work, developing a mathematical model to underline his conviction, and sent it to the German. By the early 1920s, however, Arthur Eddington had confirmed some of Einstein’s predictions, and the great man had become famous and was snowed under with letters: Friedmann’s ideas were lost in the avalanche.45 Undaunted, Friedmann tried to see Einstein in person, but that move also failed. It was only when Friedmann was given an introduction by a mutual colleague that Einstein finally got to grips with the Russian’s ideas. As a result, Einstein began to have second thoughts about his cosmological constant – and its implications. But it wasn’t Einstein who pushed Friedmann’s ideas forward. A Belgian cosmologist, Georges Lemaître, and a number of others built on his ideas so that as the 1920s advanced, a fully realised geometric description of a homogeneous and expanding universe was fleshed out.46
A theory was one thing. But planets and stars and galaxies are not exactly small entities; they occupy vast spaces. Surely, if the universe really was expanding, it could be observed? One way to do this was by observation of what were then called ‘spiral nebulae.’ Nowadays we know that nebulae are distant galaxies, but then, with the telescopes of the time, they were simply indistinct smudges in the sky, beyond the solar system. No one knew whether they were gas or solid matter; and no one knew what size they were, or how far away. It was then discovered that the light emanating from spiral nebulae is shifted toward the red end of the spectrum. One way of illustrating the significance of this redshift is by analogy to the Doppler effect, after Christian Doppler, the Austrian physicist who first explained the observation in 1842. When a train or a motorbike comes toward us, its noise changes, and then, as it goes past and away, the noise changes a second time. The explanation is simple: as the train or bike approaches, the sound waves reach the observer closer and closer together – the intervals get shorter. As the train or bike recedes, the opposite effect occurs; the source of the noise is receding at all times, and so the interval between the sound waves gets longer and longer. Much the same happens with light: where the source of light is approaching, the light is shifted toward the blue end of the spectrum, while light where the source is receding is shifted toward the red end.
The first crucial tests were made in 1922, by Vesto Slipher at the Lowell Observatory in Flagstaff, Arizona.47 The Lowell had originally been built in 1893 to investigate the ‘canals’ on Mars. In this case, Slipher anticipated finding redshifts on one side of the nebulae spirals (the part swirling away from the observer) and blueshifts on the other side (because the spiral was swirling toward earth). Instead, he found that all but four of the forty nebulae he examined produced only redshifts. Why was that? Almost certainly, the confusion arose because Slipher could not really be certain of exactly how far away the nebulae were. This made his correlation of redshift and distance problematic. But the results were nonetheless highly suggestive.48
Three years elapsed before the situation was finally clarified. Then, in 1929, Edwin Hubble, using the largest telescope of the day, the 100-inch reflector scope at Mount Wilson, near Los Angeles, managed to identify individual stars in the spiral arms of a number of nebulae, thereby confirming the suspicions of many astronomers that ‘nebulae’ were in fact entire galaxies. Hubble also located a number of ‘Cepheid variable’ stars. Cepheid variables – stars that vary in brightness in a regular way (periods that range from 1—50 days) – had been known since the late eighteenth century, but it was only in 1908 that Henrietta Leavitt, at Harvard, showed that there is a mathematical relationship between the average brightness of a star, its size, and its distance from earth.49 Using the Cepheid variables that he could now see, Hubble was able to calculate how far away a score of nebulae were.50 His next step was to correlate those distances with their corresponding redshifts. Altogether, Hubble collected information on twenty-four different galaxies, and the results of his observations and calculations were simple and sensationaclass="underline" he discovered a straightforward linear relationship. The farther away a galaxy was, the more its light was redshifted.51 This became known as Hubble’s law, and although his original observations were made on twenty-four galaxies, since 1929 the law has been proven to apply to thousands more.52
Once more then, one of Einstein’s predictions had proved correct. His calculations, and Friedmann’s, and Lemaître’s, had been borne out by experiment: the universe was indeed expanding. For many people this took some getting used to. It involved implications about the origins of the universe, its character, the very meaning of time. The immediate impact of the idea of an expanding universe made Hubble, for a time, almost as famous as Einstein. Honours flowed in, including an honorary doctorate from Oxford, Time put him on its cover, and the observatory became a stopping-off place for famous visitors to Los Angeles: Aldous Huxley, Andrew Carnegie, and Anita Loos were among those given privileged tours. The Hubbies were taken up by Hollywood: the letters of Grace Hubble, Edwin’s wife, written in the early thirties, talk of dinners with Helen Hayes, Ethel Barrymore, Douglas Fairbanks, Walter Lippmann, Igor Stravinsky, Frieda von Richthofen (D. H. Lawrence’s widow), Harpo Marx and Charlie Chaplin.53 Jealous colleagues pointed out that, far from being a Galileo or Copernicus of his day, Hubble was not all that astute an observer, and that since his findings had been anticipated by others, his contribution was limited. But Hubble did arduous spadework and produced enough accurate data so that sceptical colleagues could no longer scoff at the theory of an expanding universe. It was one of the most astonishing ideas of the century, and it was Hubble who put it beyond doubt.
At the same time that physics was helping explain massive phenomena like the universe, it was still making advances in other areas of the minuscule world, in particular the world of molecules, helping us to a better understanding of chemistry. The nineteenth century had seen the first golden age of chemistry, industrial chemistry in particular. Chemistry had largely been responsible for the rise of Germany, whose nineteenth-century strength Hitler was so concerned to recover. For example, in the years before World War I, Germany’s production of sulphuric acid had gone from half that of Britain to 50 percent more; its production of chlorine by the modern electrolytic method was three times that of Britain; and its share of the world’s dyestuffs market was an incredible 90 percent.
The greatest breakthrough in theoretical chemistry in the twentieth century was achieved by one man, Linus Pauling, whose idea about the nature of the chemical bond was as fundamental as the gene and the quantum because it showed how physics governed molecular structure and how that structure was related to the properties, and even the appearance, of the chemical elements. Pauling explained the logic of why some substances were yellow liquids, others white powders, still others red solids. The physicist Max Perutz’s verdict was that Pauling’s work transformed chemistry into ‘something to be understood and not just memorised.’54