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.
These images are both beautiful and revolutionary. Catholic dogma asserted that the Moon and the other heavenly bodies were perfect, unblemished spheres. Previous astronomers who had viewed the Moon, either with the naked eye or through telescopes, had drawn a two-dimensional blotchy surface, but Galileo saw the patterns of light and dark differently. His training in chiaroscuro revealed to him an alien lunar landscape of mountain ranges and craters.
‘I have been led to the conclusion that … the surface of the Moon is not smooth, even and perfectly spherical – as the great crowd of philosophers have believed about this and other heavenly bodies – but, on the contrary, to be uneven and rough and crowded with depression and bulges. And it is like the face of the Earth itself, which is marked here and there with chains of mountains and depths of valleys.’
Galileo shared the watercolours with his long-standing friend from Florence, the artist Cigoli, who was inspired to represent this new and radical view of the Moon in the grandest of settings. Built in the year 430 by Pope Sixtus III, the Pauline Chapel in Rome documents the changing artistic styles and techniques used to represent the natural world across many centuries; a place filled with shifting examples of how the three-dimensional world can be represented on a two-dimensional surface. Covering the dome
of the Pauline Chapel is Cigoli’s final masterpiece – a striking fresco depicting a familiar scene of the Virgin Mary bathed in a shaft of golden light surrounded by cherubs and angels. The fresco depicts Mary over what was, for the first time, a detailed, textured and cratered moon. The Vatican named it the Assumption of the Virgin, unaware perhaps of the philosophical challenge it represented. Here was art representing scientific knowledge – a type of knowledge radically different to historical or scriptural authority, based on observation rather than dogma and presented unashamedly in a grand setting for all in Rome to see. It is undoubtedly true that Galileo didn’t intend to challenge the very theological foundations of the Church of Rome by observing the Moon through a telescope. But scientific discoveries, however innocuous they may seem at first sight, have a way of undermining those who don’t much care for facts. Reality catches up with everyone eventually.
With his depictions of the Moon completed, Galileo turned his ever more powerful lenses to other celestial bodies. Between 7 and 13 January 1610, he became the first human to observe Jupiter’s four largest moons – Io, Europa, Ganymede and Callisto – now known as the Galilean Satellites. For Galileo, this was further evidence to support the work of Copernicus and the physical reality of the heliocentric model. If moons were orbiting Jupiter, Galileo reasoned, it was impossible to argue that the Earth was at the centre of the universe, because heavenly bodies existed that did not circle the Earth.
Galileo published these observations in the spring of 1610 in ‘The Starry Messenger’, and from his correspondence with Kepler his irritation with the discontent it caused amongst philosophers was clear. ‘My dear Kepler, I wish that we might laugh at the remarkable stupidity of the common herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the Moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth.’
To Galileo’s mind, absolute confirmation of Copernicus’s heliocentric model was provided by his studies of Venus. Beginning in September 1610, Galileo observed Venus over the course of months and, like the Moon, he observed that Venus had phases. Sometimes the planet was lit completely by the Sun, but at other times only a crescent appeared to be illuminated. The only plausible explanation for this observation was that Venus was orbiting the Sun. This was surely final compelling evidence of a solar system with the Sun at its heart and the planets orbiting around it.
It wasn’t that simple, of course. Galileo, in what was certainly an ill-judged move, decided to move beyond reporting his scientific observations and instead champion a particular theological and philosophical interpretation of the data – namely that the Church was wrong and that the Earth was most definitely not the centre of the universe. This he seems to have done because he wanted to be famous, and famous he became. Copernicus’s De revolutionibus was banned until ‘corrected’ (the full version was not removed from the banned list until 1758!) and Galileo ordered not to repeat his ‘foolish and absurd’ conclusions. Galileo didn’t keep quiet, and he achieved his historical notoriety by being put under house arrest in 1633, where he stayed for the remainder of his life.
Many historians characterise Galileo as a bit of an egotistical social climber who brought it all on himself, which is partly true and yet also desperately unfair. He was undoubtedly a great scientist and a supremely talented astronomical observer. In particular, he was the first to clearly state the principle of relativity which lies at the heart of Newton’s laws of motion; namely that there is no such thing as absolute rest or absolute motion. This is why we don’t feel the movement of the Earth around the Sun, and why Aristotle et al. were misled into reading far too much into their stationary feelings. In the hands of Albert Einstein, the principle of relativity can be generalised to freely falling objects in a gravitational field, and this ultimately leads to modern cosmology and the Big Bang theory. But we are jumping ahead again. The purpose of recounting the story of Galileo is not to attack the easy target of the Inquisition (which nobody expects). Rather, it is to highlight the fact that the smallest and most modest of scientific observations can lead to great philosophical and theological shifts that in turn can have a tremendous impact on society. Galileo, by looking through a telescope, doing some drawings and thinking about what he saw, helped to undermine centuries of autocratic idiocy and woolly thinking. In doing so, he got himself locked up, but also bridged the gap between Copernicus and Kepler, and paved the way for Isaac Newton and ultimately Albert Einstein to construct a complete description of the universe and our place within it.
THE HAPPIEST THOUGHT OF MY LIFE
Scientific progress, then, is often triggered by rather innocuous discoveries or simple realisations. There is a terrible cliché about scientists exhibiting a ‘childlike’ fascination with nature, but I can’t think of a better way of putting it. The sense in which the cliché rings true is that children are occasionally in the habit of focusing on a very small thing and continuing to ask the question ‘Why?’ until they get an answer that satisfies their curiosity. Adults don’t seem to do this as much. Good scientists do, however, and if I have a thesis in this chapter then it is as follows: by focusing on tiny but interesting things with honesty and clarity, great and profound discoveries are made, often by flawed human beings who don’t initially realise the consequences of their investigations. The absolutely archetypal example of such an approach can be found at the beginning of Einstein’s quest to replace Newton’s Theory of Gravity.
Einstein is most famous for his equation E=mc2, which is contained within the special theory of relativity he published in 1905. At the heart of the theory is a very simple concept that dates all the way back to Galileo. Put simply, there is no way that you can tell whether you are moving or not. This sounds a bit abstract, but we all know it’s true. If you are sitting in a room at home reading this book, then it feels the same as if you are sitting in an aircraft reading this book, as long as there is no turbulence and the aircraft is in level flight. If you aren’t allowed to look out of the window, then nothing you can do in the room or on the plane will tell you whether or not you are ‘sitting still’ or moving. You might claim that your room is self-evidently not moving, whereas a plane obviously is because otherwise it wouldn’t take you from London to New York. But that’s not right, because your room is moving in orbit around the Sun, and indeed it is spinning around the Earth’s axis, and the Sun itself is in orbit around the galaxy, which is moving relative to other galaxies in the universe. Einstein discovered his famous equation E=mc2 by taking this seemingly pedantic reasoning seriously and asserting that NO experiment you can ever do, even in principle, using clocks, radioactive atoms, electrical circuits, pendulums, or any physical object at all, will tell you whether or not you are moving. Anyone has the absolute right to claim that they are at rest, as long as there is no net force acting on them causing them to accelerate. You are claiming it now, no doubt, if you are reading this book sitting comfortably on your sofa. Pedantry is very useful sometimes, because without Einstein’s theory of special relativity we wouldn’t have E=mc2, we wouldn’t really understand nuclear or particle physics, how the Sun shines or how radioactivity works. We wouldn’t understand the universe.
Something important bothered Einstein after he published his theory in 1905, however. Newton’s great achievement – the all-conquering Universal Law of Gravitation – did not fit within the framework of special relativity, and therefore one or the other required modification. Einstein’s response to this problem was typically Einsteinian: he thought about it very carefully, and, in November 1907, whilst sitting in his chair in the patent office in Bern, he found the right thread to pull. Looking back at the moment in an article written in 1920, Einstein described his idea with beautiful, and indeed child-like, simplicity.
I am well aware that you might object quite strongly to this statement, because it appears to violate common sense. Surely an object falling under the action of the gravitational force is accelerating towards the ground, and therefore cannot be said to be ‘at rest’? Good, because if you think that then you are about to learn a valuable lesson. Common sense is completely worthless and irrelevant when trying to understand reality. This is probably why people who like to boast about their common sense tend to rail against the fact that they share a common ancestor with a monkey. How, then, to convince you that Einstein was, and indeed still is, correct?
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