The Universe Within

by Neil Turok

  Maxwell’s theory did much more. Slowly the realization dawned that it contradicted the two most hallowed frameworks in physics: Newton’s theory of forces, motion, and gravity, and the equally firmly established theory of heat. As Maxwell’s equations were studied, it was noticed by the Dutch physicist Hendrik Lorentz that they possessed a symmetry connecting space and time, which would open the door to Einstein’s unification of space, time, mass, energy, and gravity, and plant the seed for the study of the entire evolving cosmos.

  Likewise, Maxwell’s theory opened the door to quantum theory. In trying to reconcile Maxwell’s description of electromagnetic radiation with the theory of heat, Max Planck and then Albert Einstein discovered an inconsistency so drastic that, in time, it would overturn the entire classical picture of the world. Maxwell’s theory emerged from this collision in a new form: as a quantum field theory. In taking this form, it set the pattern for all of twentieth-century physics.

  We are still struggling with the implications of the quantum revolution. Our intuition is based on the classical picture of the world, a picture founded upon Newton’s and Maxwell’s discoveries, in which particles and fields have a definite existence and move around in space according to absolutely deterministic laws. But, as I will describe in the next chapter, that picture is gone, and a more mysterious, quantum conception of reality has emerged, incorporating a greater degree of possibility and giving us a greater role.

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  I HAVE TITLED THIS work The Universe Within because I want to celebrate with you our progress towards understanding nature at its most basic level. In subsequent chapters we will follow the journey physics has taken, from the quantum world to the cosmos to the unification of all known physics in a single equation. It is a story of fun, yearning, determination, and, most of all, humility and awe before nature.

  Science is all about people. They may work in labs and scribble strange formulae, but they are driven by the same natural curiosity we are all born with: to explore and discover our world and what we can do. Some people are blessed with unusual mathematical abilities or physical insight; others make great discoveries through sheer persistence, careful planning, or just good luck. Science is, above all, a human activity. It is all about making the most of the marvellous gift of life.

  When Usain Bolt smashed the world sprint records in Beijing in 2008, and again in Berlin in 2009, we all celebrated. Wasn’t it fantastic to see seemingly impossible limits breached? In the same way, we should celebrate the even more remarkable achievements of Maxwell and Einstein and their modern counterparts. The world needs more people who are capable of making great discoveries, and they can come from anywhere. They are examples of our human nature and spirit, and we should all draw inspiration from their success.

  Much of science is complicated and technical. Many of its ideas are difficult, but scientists can and must become much better at explaining what they are doing, and why. And society needs to appreciate far better how science brought us here, and where it might take us.

  Reconnecting science to society has a deeper purpose than developing the next marketable technology. It is about the kind of society we want to create, a society in which there is optimism, confidence, and purpose. Scientists need to know why they are doing science, and society needs to know why it supports them.

  The technologies we rely on today are all based on past discoveries. We need new breakthroughs and we need to find more intelligent ways of using the knowledge we already possess. The billions of young minds on our planet need to be carefully nurtured and encouraged. Each one is a potential Faraday, Maxwell, or Mandela, capable of transforming the world.

  A new world is now beckoning. As I’ll describe in the next chapter, quantum physics has revealed that the behaviour of the universe, and the way in which we are involved with it, is stranger than anyone could have expected. On the horizon are technologies and understanding beyond anything we have experienced so far. We are being challenged to rise to the next level of existence, the next stage in the evolution of ourselves and of the universe. Witnessing all the changes wrought by classical physics, we can only imagine what our quantum future holds — and what we will do with it.

  TWO

  OUR IMAGINARY REALITY

  “Theoretical physicists live in a classical world, looking out into a quantum-mechanical world.”

  — John Bell30

  “Describing the physical laws without reference to geometry is similar to describing our thoughts without words.”

  — Albert Einstein31

  THE SCHOOL OF ATHENS, by Raphael (click to see photo), is one of the most breathtaking paintings of the Italian Renaissance. It represents a key moment in human history: the flowering of free thinking in Classical Greece. Somehow, the people of the time were able to look at the world with fresh eyes, to set aside traditional superstitions and beliefs in dogma or high authority. Rather, through discussion and logical argument, they began to figure out for themselves how the universe works and what principles human society should be based upon. In doing so, they changed Western history forever, forming many of the concepts of politics and literature and art that underlie the modern world.

  Raphael’s picture is full of philosophers like Aristotle, Plato, and Socrates engaged in discussion. There is also the philosopher Parmenides, in some ways the ancient Greek version of Stephen Hawking. Like Hawking, Parmenides believed that at its most fundamental level, the world is unchanging, whereas Heraclitus, also in the portrait, believed that the world is in ceaseless motion as a result of the tension between opposites. There are mathematicians too. At front right is Euclid, giving a demonstration of geometry, and at front left is Pythagoras, absorbed in writing equations in a big book. Beside Parmenides is Hypatia, the first woman mathematician and philosopher. The whole scene looks like a sort of marvellous university — which I, for one, would have loved to attend — full of people exploring, exchanging, and creating ideas.

  An odd figure is peering over Pythagoras’s shoulder and scribbling in a notebook. He looks as if he is cheating, and in some ways he is: he has one eye on the mathematics and the other on the real world. This is Anaximander, who some consider to be the world’s first scientist.32 He lived around 600 B.C. in Miletus, then the greatest Greek city, in the eastern Aegean on the coast of modern Turkey. At that time, the world was dominated by kings and traditional rulers with all kinds of mystical and religious beliefs. Yet somehow Anaximander, his teacher Thales, and his students — and the thinkers who followed — trusted their own powers of reason more than anyone had ever done before.

  Almost every written record of their work has been lost, but what little we know is mind-boggling. Anaximander invented the idea of a map — hence quantifying our notion of space — and drew the first known map of the world. He is also credited with introducing to Greece the gnomon, an instrument for quantifying time, consisting of a rod set vertically in the ground so that its shadow showed the direction and altitude of the sun. Anaximander is credited with using the gnomon, in combination with his knowledge of geometry, to accurately predict the equinoxes.33

  Anaximander also seems to have been the first to develop a concept of infinity, and he concluded, although we do not know how, that the universe was infinite. He also proposed an early version of biological evolution, holding that human beings and other animals arose from fish in the sea. Anaximander is considered the first scientist because he learned systematically from experiments and observations, as when he developed the gnomon. In the same way he was taught by Thales, he seems to have taught Pythagoras. Thus was built the scientific tradition of training students and passing along knowledge.

  Just think of these phenomenal achievements for a moment, and imagine the transformations they eventually brought about. How often have you arrived in a strange city or neighbourhood without a map or a picture of your location? With nothing but your immediate surroundings, w
ith no mental image of their context, you are lost. Each new turn you take brings something unexpected and unpredictable. A map brings a sense of perspective — you can anticipate and choose where you want to go and what you want to see. It raises entirely new questions. What lies beyond the region shown in the map? Can we map the world? And the universe?

  And how would you think of time without a clock? You could still use light and dark, but all precision would be lost in the vagaries of the seasons and the weather. You would live far more in the present, with the past and the future being blurred. The measurement of time opened the way to precise technologies, like tracking and predicting celestial bodies and using them as a navigational tool. Yet even these matters were probably not Anaximander’s primary concerns. He seems to have been more interested in big questions, such as what happened if you traced time back into the distant past or far forward into the future.

  What about Anaximander’s idea that the universe is infinite? This seems plausible to us now, but I distinctly remember that when I was four years old, I thought the sky was a spherical ceiling, with the sun and stars fixed upon it. What a change it was when I suddenly realized, or was told, that we are looking out into an infinite expanse of space. How did Anaximander figure that out? And what about his idea that we arose from fish in the sea? His ideas suggested above all a world with potential. If things were not always as they are now, they might be very different in the future.

  It was no accident that these beginnings of modern science occurred around the same time as many new technologies were being invented. Nearby, on the island of Samos, Greek sculptor and architect Theodorus developed, or at least perfected, many of the tools of the building trade: the carpenter’s square, the water level, the turning lathe, the lock and key, and the craft of smelting.

  Hand in hand with these developments was a flowering of mathematics, philosophy, art, literature, and, of course, democracy. But the civilization of ancient Greece was fleeting. Throughout its existence, it was ravaged by wars and invasions: the Greco-Persian Wars, the war between Athens and Sparta, the invasion by Alexander the Great, and the chaos following his death. Finally, there was the triumph of Rome and then its decadent decline, which snuffed out civilization in Europe for a millennium. The great libraries of the ancient world, like the one at Alexandria, were lost. Only fragments and copies of their collections survived.

  In the fifteenth century, Aldus Manutius, Italy’s leading printer, made it his personal mission to reproduce cheap and accurate pocket editions of the ancient classics and make them widely available. In this way, the ideas of ancient Greece directly seeded the Renaissance and the Scientific Revolution that followed.

  MORE THAN FOUR HUNDRED years later, we come to a modern counterpart of Raphael’s masterpiece: a black-and-white photograph of the Fifth Solvay International Conference on Electrons and Photons, held in Brussels in 1927 (click to see photo).

  Towards the end of the nineteenth century, physicists had felt they were close to converging on a fundamental description of nature. They had Newton’s laws of mechanics; Maxwell’s theory of electricity, magnetism, and light; and a very successful theory of heat founded by Maxwell’s friend William Thomson (Lord Kelvin), among others. Physics had provided the technical underpinning of the Industrial Revolution and had opened the way to global communication. A few small details remained to be wrapped up, like the inner structure of the atom. But the classical picture of a world consisting of particles and fields moving through space and time seemed secure.

  Instead, the early twentieth century brought a series of surprises. The picture became increasingly confused and was only resolved by a full-scale revolution between 1925 and 1927. In this revolution, the physicists’ view of the universe as a kind of large machine was completely overturned and replaced by something far less intuitive and familiar. The Fifth Solvay Conference was convened just as this new and abstract representation of the world had formed. It might be considered the most uncomfortable conference ever held in physics.

  In 1925, the young German prodigy Werner Heisenberg launched quantum theory with a call to “discard all hope of observing hitherto unobservable quantities, such as the position and period of the electron,” and instead to “try to establish a theoretical quantum mechanics, analogous to classical mechanics, but in which only relations between observable quantities occur.”34 Heisenberg’s work replaced the classical picture of the electron orbiting the atomic nucleus with a far more abstract, mathematical description, in which only those quantities that were directly observable in experiments would have any literal interpretation. Soon after, in 1926, the Austrian physicist Erwin Schrödinger found an equivalent description to Heisenberg’s, in which the electron was treated as a wave instead of a classical particle. Then, in early 1927, Heisenberg discovered his famous uncertainty principle, showing that the central concept in Newton’s classical universe — that every particle had a definite position and velocity — could not be maintained.

  By the time the physicists got to Brussels for the Solvay Conference, the classical view of the world had finally collapsed. They had to give up any notion of making definite predictions because there was, in a sense, no longer a definite world at all. As Max Born had realized in 1926, quantum physics could only make statements about probabilities. But it wasn’t even a case of little demons playing dice in the centre of atoms: it was far stranger than that. There was an elegant mathematical formalism governing the world’s behaviour, but it had no classical interpretation. No wonder all the physicists at Solvay are looking so glum!

  Front and centre in the photo, of course, is Einstein. Next to him, with his legs crossed, is Dutch physicist Hendrik Lorentz. And then there is Marie Curie — the only woman in the picture and also the only one among them to win two Nobel prizes. Curie, with her husband Pierre, had shown that radioactivity was an atomic phenomenon. Their discovery was one of the first hints of the strange behaviour in the subatomic world: radioactivity was finally explained, a year after the Fifth Solvay meeting, as the quantum mechanical tunnelling of particles out of atomic nuclei. Next to Curie is Max Planck, holding his hat and looking sad. Planck had been responsible for initiating the quantum revolution in 1900 with his suggestion that light carries energy in packets called “photons.” His ideas had been spectacularly confirmed in 1905, when Einstein developed them to explain how light ejects electrons from metals.

  In the middle of the next row back, between Lorentz and Einstein, is Paul Dirac, the English genius and founder of modern particle physics, with Erwin Schrödinger standing behind him. Werner Heisenberg is standing at the back, three in from the right, with the German-British mathematician Max Born sitting in front of him. Heisenberg and Born had together developed the matrix mechanics formulation of quantum theory, which Dirac had brought to its final mathematical form. Next to Born is the Danish physicist Niels Bohr, a towering figure who had extended Planck’s quantum idea to the hydrogen atom and who had since played the role of godfather to quantum theory. Bohr founded the Institute for Theoretical Physics of the University of Copenhagen and became its director. There, he mentored Heisenberg and many other physicists; it became a world centre for quantum theory. Heisenberg would later say, “To get into the spirit of the quantum theory was, I would say, only possible in Copenhagen at that time [1924].”35 Bohr was responsible for developing what became the most popular interpretation of quantum theory, known as the Copenhagen interpretation. On Heisenberg’s right is Wolfgang Pauli, the young Austrian prodigy who had invented the Pauli exclusion principle, stating that two electrons could not be in the same state at the same time. This principle, along with the quantum theory of spin that Pauli also developed, proved critical in understanding how electrons behave within more complicated atoms and molecules. Dirac, Heisenberg, and Pauli were only in their mid-twenties and yet at the forefront of the new developments.

  The participants came from a wide range of back
grounds. Curie was more or less a refugee from Poland. 36 Einstein himself had worked at a patent office before making his sensational discoveries in 1905. He, Born, Bohr, their great friend Paul Ehrenfest (standing behind Curie in the photo), and Pauli’s father were representatives of a generation of young Jews who had entered maths and science in the late nineteenth century. Before that time, Jews had been deliberately excluded from universities in western Europe. When they were finally allowed to enter physics, maths, and other technical fields, they did so with a point to prove. They brought new energy and ideas, and they would dispel forever any notion of intellectual inferiority.

  So there we have many of the world’s leading physicists meeting to contemplate a revolutionary new theory — and to figure out its repercussions for our view of the universe. But they seemed none too happy about it. They had discovered that, at a fundamental level, the behaviour of nature’s basic constituents is truly surreal. They just don’t behave like particles or billiard balls or masses sliding down planes, or weights on springs or clouds or rivers or waves or anything anyone has ever seen in everyday life. Even Heisenberg saw the negative side: “Almost every progress in science has been paid for by a sacrifice; for almost every new intellectual achievement, previous positions and conceptions had to be given up. Thus, in a way, the increase of our knowledge and insight diminishes continually the scientist’s claim on ‘understanding’ nature.” 37 On the other hand, objectively speaking, the 1920s were a golden age for physics. Quantum theory opened up vast new territories where, as Dirac told me when I met him many years later, “even mediocre physicists could make important discoveries.”

  It would take most of the remainder of the twentieth century for physicists to fully appreciate the immense opportunities that quantum physics offers. Today, we stand on the threshold of developments through which it may completely alter our future.