Human Universe. Andrew Cohen

1934, the Princeton physicist Howard Percy Robertson catalogued all of the possible solutions to Einstein’s equations given a uniform distribution of matter throughout the cosmos – a perfect Copernican principle according to which no place in the cosmos is special or significant. The models containing matter tend to describe either an expanding or contracting universe, and therefore suggest a quite wonderful thing: there may have been a day without a yesterday. Einstein’s equations contain within them a scientific creation story, even though their author himself resisted it.

      The story of Einstein’s Theory of General Relativity, and its subsequent application to the whole universe, delivers a compelling narrative illustrating the power of physics. The theory, inspired by thinking about a man falling off a roof, predicts that there was a moment of creation. No experimental measurements are required and no observations need be made other than that things fall at the same rate in a gravitational field. There are multiple layers of irony here! The idea that such progress towards answering the most profound questions about our origins can be made by thinking alone is almost Aristotelian: a partial throwback to the lofty authority of the classical world that Bruno, Copernicus and Galileo did so much to overturn. That the equations seem to describe a universe with a necessary moment of creation, lending support, at least in Lemaître’s eyes, to the notion of a creator, would also appear to bring us full circle and back to Borman, Lovell and Anders and the creation stories of old. Indeed, Pope Pius XII, on hearing about the new cosmology, said ‘True science to an ever increasing degree discovers God, as though God was waiting behind each door opened by science’. Einstein, to his deep chagrin, having thrown a blanket of rational thought across a landscape of mythology, appeared to have replaced one creation story with another.

      To finish the story of our magnificent relegation, let me briefly address these points. The theoretical prediction of an expanding universe does of course require experimental verification, and this came rapidly. On 15 March 1929, Edwin Hubble published a paper entitled ‘A relation between distance and radial velocity among extra-galactic nebulae’, in which he reported his observation that all galaxies beyond our local group are rushing away from us. Moreover, the more distant the galaxy, the higher its speed of recession. This is precisely what an expanding universe as predicted by Einstein’s theory should look like. In 1948, Alpher, Bethe and Gamow published a famous paper (with the coolest author list in the history of physics) which showed how the observed abundance of light chemical elements in the universe could be calculated assuming a very hot, dense phase in the early history of the universe. Modern calculations of these abundances are extremely precise, and agree perfectly with astronomical observations. Perhaps most compellingly of all, the afterglow of the Big Bang, known as the Cosmic Microwave Background Radiation, also predicted by Alpher and Herman in 1948, was discovered by Penzias and Wilson in 1964. We will have much to say about the Cosmic Microwave Background in the following chapters; for now, it is sufficient to say that the discovery that the universe is still glowing at a temperature of 2.7 degrees above absolute zero was the final evidence that convinced even the most sceptical scientists that the Big Bang theory was the most compelling model for the evolution of the universe.