Human Universe. Andrew Cohen

that have transformed our perspective. Aside from their scientific merit, such images assume great cultural significance because of the ideas they generate and the philosophical and ideological challenges they pose. They also carry with them, in the shadows, personal stories. Someone would have taken a photograph of Andromeda, someday, and discovered what Hubble did. But Hubble took this one, and his story therefore becomes inextricably intertwined with it. Some don’t like their history presented in this way, but science is richer when its stories include people as well as ideas; curiosity is, after all, a human virtue. Hubble may never have taken the photograph had he followed through on a promise to his father to practise law. Reading jurisprudence at Queen’s College, Oxford, as one of the first Rhodes Scholars, Hubble aimed to fulfil his father’s wishes, but John Hubble died before Edwin finished his degree. The death of his father encouraged Edwin to ditch law and revisit his childhood passion for astronomy. He left Oxford for the University of Chicago, joined the Yerkes Observatory and received his PhD in 1917 with a thesis entitled ‘Photographic Investigations of Faint Nebulae’. After brief service in the US Army at the end of World War One, Hubble obtained a position at the Mount Wilson Observatory. He found himself at the controls of the largest, most powerful telescope on the planet, and with the knowledge and good sense to point it at the most intriguing and controversial object in the night sky: Andromeda. Just like Curtis before him, Hubble could make out distinct features within the misty patch, but the newly commissioned 100-inch Hooker telescope allowed him to see much more detail. On 5 October 1923 he took a 45-minute exposure, found three unidentified specks that he assumed were new novae and marked them all with an ‘N’.

      To confirm his findings Hubble needed to compare this plate with previous images of Andromeda taken at Mount Wilson. The following day he made the journey down to the basement archive where the observatory’s collection of images was catalogued and stored. To Hubble’s delight, two of the specks were indeed newly discovered novae – what we now know to be the bright nuclear flares of white dwarf stars as they accrete gas and dust from a nearby companion. But it was the third speck that he found most interesting when he compared it to previous images. As Hubble scanned back through the Mount Wilson catalogue he discovered that the star had been captured before; in some plates it appeared brighter, whereas in others it appeared dim or not present at all. Hubble immediately grasped the importance of his discovery. The third speck was a Cepheid variable, the type of star Henrietta Leavitt had studied two decades earlier. In one of the most famous corrections in scientific history, Hubble crossed out the letter ‘N’ and replaced it in red ink with the letters ‘VAR’ followed by a very understated exclamation mark.

      Hubble had discovered a cosmic yardstick in Andromeda, and it was a trivial matter to calculate the distance. The new star varied with a period of 31.415 days, which, following Leavitt, implied its intrinsic brightness was 7000 times that of our Sun, and yet it appeared so dim in the night sky that it was invisible to all but the most powerful of telescopes. Hubble’s initial calculations revealed that the star was over 900,000 light years away from Earth, a staggering distance when the size of our own galaxy was estimated to be no more than 100,000 light years across. Hubble, with the help of Leavitt’s ruler, laid the Great Debate to rest. Andromeda, the distant patch of light in the night sky, is a galaxy; an island, according to current estimates, of a trillion suns. Current measurements put the giant spiral at a distance of 2.5 million light years from the Milky Way, one of around 54 galaxies gravitationally bound together to form our galactic neighbourhood known as The Local Group.

       THE POLITICAL RAMIFICATIONS OF REALITY, OR ‘HOW TO AVOID GETTING LOCKED UP’

      What is science? There are many answers, and whole academic careers are devoted to a complex analysis of the historical and sociological development of the subject. To a working scientist, however, I think the answer is quite simple and illuminating because it reveals a lot about how scientists see themselves and what they do. The great (an overused adjective, but not in this case) physicist Richard Feynman gave a characteristically clear and simple description in his Messenger Lectures delivered at Cornell University in 1964: ‘In general, we look for a new law by the following process: First we guess it. Then we – now don’t laugh, that’s really true – then we compute the consequences of the guess to see what, if this is right, if this law that we guessed is right, to see what it would imply. And then we compare the computation results to nature, or we say compare to experiment or experience, compare it directly with observations to see if it works. If it disagrees with experiment, it’s wrong. In that simple statement is the key to science. It doesn’t make any difference how beautiful your guess is, it doesn’t make any difference how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it’s wrong. That’s all there is to it.’

      Why do I like this so much? The reason is that it is modest – almost humble in its simplicity – and this, in my opinion, is the key to the success of science. Science isn’t a grandiose practice; there are no great ambitions to understand why we are here or how the whole universe works or our place within it, or even how the universe began. Just have a look at something – the smallest, most trivial little thing – and enjoy trying to figure out how it works. That is science. In a famous BBC Horizon film broadcast in 1982 called ‘The Pleasure of Finding Things Out’, Feynman went further: ‘People say to me, “Are you looking for the ultimate laws of physics?” No, I’m not. I’m just looking to find out more about the world and if it turns out there is a simple ultimate law which explains everything, so be it; that would be very nice to discover. If it turns out it’s like an onion with millions of layers and we’re just sick and tired of looking at the layers, then that’s the way it is … My interest in science is to simply find out more about the world.’

      The remarkable thing about science, however, is that it has ended up addressing some of the great philosophical questions about the origin and fate of the universe and the meaning of existence without actually setting out to do so, and this is no accident. You won’t discover anything meaningful about the world by sitting on a pillar for decades and contemplating the cosmos, although you may become a saint. No, a truly deep and profound understanding of the natural world has emerged more often than not from the consideration of much less lofty and profound questions, and there are two reasons for this. Firstly, simple questions can be answered systematically by applying the scientific method as outlined by Richard Feynman, whereas complex and badly posed questions such as ‘Why are we here?’ cannot. But more importantly, and rather more profoundly, it turns out that the answers to simple questions can overturn centuries of philosophical and theological pontificating quite by accident. Reputations count for naught in the face of observation. The famous story of Galileo’s clashes with the Inquisition at the height of the Copernican debate, which he certainly did not expect (nobody does), is the archetypal example.

      Galileo began his university career with the study of medicine, but his imagination was captured by art and mathematics. Between studying Medicine in Pisa and returning to his hometown in 1589 to become Professor of Mathematics, Galileo spent a year in Florence teaching perspective and in particular a technique called chiaroscuro. Chiaroscuro is the study of light and shadow, and how it can be used to create a sense of depth by accurately representing the way that light sources illuminate objects. Chiaroscuro was one of the most important new artistic techniques to emerge during Galileo’s time, allowing a new sense of realism to be portrayed on canvas.

      Although Galileo spent only a brief time in Florence, the skills he acquired had a great impact on his scientific work. In particular, his carefully developed ability to understand the delicate play of light on three-dimensional shapes, when applied to his later astronomical studies, played an important role in undermining the Aristotelian cosmological edifice which formed a cornerstone of the teachings of the Roman Catholic Church.

      The small and seemingly innocuous theological thread on which Galileo unwittingly tugged was made available to him on a visit to Venice in 1609, when he purchased the lenses required to build his first telescope. One of the first objects he turned his ‘perspective tube’ towards was the Moon. With the mind of a mathematician and the eye of an artist, Galileo drew a series of six watercolours representing what he saw.