The Mysterious Universe

September 01, 2012

After the great discoveries of Sir Isaac Newton and his successors, to many people in the eighteenth century it seemed that they lived in a world so clear and orderly in its character that it was devoid of any hint of mystery. The universe appeared to be no more than a gigantic piece of clockwork mechanism whose Creator, if there was one, was simply the Cosmic Clockmaker who had set it all going and then stood back to watch what happened as it ticked away. Even human beings were considered by many to be merely complex automata. A Frenchman, de la Mettrie, wrote a famous book Man the Machine.

There was always something highly questionable about this mechanical view. If humans are simply machines - that is automata merely mouthing sounds - what makes their speech have rational content and be more than just gobbledygook? In fact the notion of a mechanical universe has not survived, for the twentieth century saw the death of the idea of mere mechanism. The universe has been found to be something altogether more subtle and more supple than that. Four fundamental discoveries brought about this revolution. The first was the discovery of quantum physics, the fact that the physical world, though seeming so clear and orderly on the scale of everyday phenomena, is in fact cloudy and fitful at its subatomic roots. We cannot predict with certainty that a radioactive nucleus will decay in the next hour, but we can only calculate the probability that it might do so. The nature of this subatomic unpredictability could be either epistemological (an unavoidable ignorance of some of the causal factors that in fact determine outcomes) or ontological (the presence of a real indeterminacy in physics' account of process). In fact, it has been shown that either possibility can be adopted with the same empirical consequences resulting. The choice between the two interpretations, therefore, cannot be settled by science, but it requires also an act of metaphysical decision. Our notions of physical causality are constrained by physics but not determined by it. Consequently science has not established the causal closure of the world on its reductionist terms alone. Of course, the exchange of energy between constituents is certainly part of the causal story, but it need not be the whole story. It is perfectly possible to take with appropriate seriousness all that science can truly tell us without being driven to deny our experience of the exercise of human agency or, indeed, belief in divine providential action within the open grain of created nature.

Quantum entities have been found to behave in ways that seem impossible and absurd in terms of everyday understanding. The most famous example is given by the nature of light, which sometimes behaves as if it is composed of waves and sometimes as if it is made up of tiny particles, called photons. Since a wave is spread out and lapping and a particle is something like a little bullet, this wave/particle duality seems at first sight to be totally unintelligible. However, after about 25 years of intellectual struggle the physicists came to make sense of this mysterious fact. They did so through discovering the deeper mystery of quantum mechanics. In quantum theory, entities can have properties that are mixtures of what commonsense would say could never be mixed together. A billiard ball is either 'here' or it is 'there', but an electron can be in a state which is a mixture of both 'here' and 'there' simultaneously — a 'middle term' of a kind unanticipated by Aristotle, so that a new kind of logic holds in the quantum world. It turns out that it is just this kind of ambiguous mixing which permits light sometimes to look like waves and sometimes to look like particles. A wavelike state is composed of an indefinite number of particles. Yet, despite more than eighty years of exploration and exploitation, there are still unresolved problems in quantum theory, principally concerned with how the combination of unpicturable and elusive quantum constituents can give rise to the picturable and controllable world of everyday experience.

The second great twentieth-century discovery arose from Albert Einstein's formulation of the theory of relativity, which showed that the character of space and time is much more subtle than Newton had supposed. For example, our experience of time is influenced by the state of our motion through space. A picturesque example of this fact is given by the story of the so-called 'twin paradox'. If one twin stays on Earth and the other goes off on a space-jouney to some distant star and back, on his return the travelling twin will be found to be younger than his stay-at-home sibling, a kind of behaviour which has been verified experimentally with elementary particles (though not with twins!).

Relativity's revelation of an intimate connection between space and time is an illustration of the third great discovery: namely that the universe is deeply relational in its character. The most striking example of this is provided by what is called quantum entanglement. When two quantum entities, such as two electrons or two photons, have once interacted with each other, they can become so mutually entangled that, however far they may subsequently separate, they retain a power of instantaneous mutual influence on each other. If one stays here and the other goes `beyond the Moon', as we conventionally say, acting on the one here will produce an instantaneous change in the state of the other. Einstein pointed out this implication of quantum mechanics, but he thought it was so 'spooky' that it must mean that there was something wrong with the theory. However, subsequent experiments have clearly demonstrated that this 'togetherness in separation' is indeed a property of nature. It seems that even the subatomic world cannot be described simply atomistically.

The fourth discovery was that the universe has been very different in the past to what we see today. The unfolding of cosmic history has had a truly formative effect on the nature of the present, so that the latter's character cannot be fully understood without taking into account its origin in the past. We know that our universe originated in the fiery event of the Big Bang, some 13.7 billion years ago. Initially it was a very simple world, an almost uniform, expanding ball of energy, which is just about the simplest physical system one could think of. Yet that apparent simplicity was already endowed with a vast potentiality. The laws of nature which operated were `fine-tuned' in character in a way that was essential if they were to permit the eventual evolution of the rich complexity of carbon-based life. An example of this fine-tuning is provided by the process of the generation of carbon itself. The only place in the universe where this vital element can be fowled is in the interior nuclear furnaces of the stars (we are people of stardust, formed of the ashes of dead stars!). This process is exceedingly delicate and it is only possible because the nuclear forces involved have very specific properties. If these properties had been only slightly different, the universe would have been condemned to a sterile history. As far as we know, life only appeared in the universe when it was about 10 billion years old, and intelligent life only yesterday in cosmic terms, but the universe was pregnant with the possibility of life from the start.

In summary, we live in a universe which is subtle and supple in its physical nature, deeply relational in its character and endowed with an inbuilt fertility of which we ourselves are the most striking expression known to us. (The human brain is far and away the most complex system we have ever encountered in our exploration of the universe.) Perhaps the deepest mystery of all is that we have been able to discover these facts. The universe is profoundly intelligible to our enquiry, rationally transparent despite often displaying properties which seem counterintuitive in terms of everyday expectation. (Just think of wave/particle duality.) And the mystery is even deeper than that, for it has turned out that the key to unlocking these cosmic secrets is provided by the seemingly abstract subject of mathematics. Time and again in fundamental physics, the successful theories turn out to be expressed in terms of equations which carry the unmistakable character of mathematical beauty (involving properties such as economy and elegance). The universe is not only rationally transparent but it is also rationally beautiful. Scientists are privileged to enjoy the experience of wonder at the marvellous order of the world disclosed to their enquiry.

The profound intelligibility of the universe is a significant and mysterious fact.

Those who are imbued with a deep thirst for understanding through and through will not be content to treat it simply as a fortunate accident. We are driven to ask why the world is so beautifully and fruitfully ordered? Addressing this issue will take us beyond science itself, for it is simply content to exploit the wonderful resources thus provided but it is not in a position to explain their origin. I believe that the most satisfying and comprehensive understanding of cosmic intelligibility and fertility is afforded by the theological insight that the universe is a divine creation. I have been describing a world which in its wonderful order is, so to speak, shot through with signs of mind and I believe that this is because the Mind of the Creator lies behind this wonderful order. It has proved accessible to us because we are, to use an ancient and powerful phrase, creatures made in the image of our Creator. That fact that the initial ball of energy that sprang out of the Big Bang has been able to evolve to become the home of saints and scientists is an expression of the beneficent purposes of its Creator. The deep relationality with which nature is endowed can be seen by the Christian as a pale reflection of the Triune nature of the Creator.

Thus I find that placing science within the wider context of a theological understanding is persuasive and deeply intellectually satisfying. Far from science and religion being at odds with each other, they are complementary rather than conflicting. I like to say that I am 'two-eyed', viewing reality with both the eye of science and the eye of religious insight. I believe that with this binocular vision I can see further and deeper than I could with either eye on its own.

One final point remains to be made. I have commented on the unexpected, indeed often counterintuitive, character of many of these fundamental scientific discoveries. Who in 1899 would have supposed wave/particle duality to be a coherent possibility? J. B. S. Haldane once said about quantum theory that it had shown us, not only that the world is queerer than we thought, but queerer than we could have thought without the nudge of nature pushing us in an unexpected direction. Consequently the natural question for a scientist to ask about a proposition, both within science and beyond it, is not 'Is it reasonable?', as if we were confident beforehand of the shape that reason had to take, but rather 'What makes you think that might be the case?' This is a question both open and demanding, not excluding surprising possibilities but requiring, if something strange is being asserted, that there to be motivating evidence offered in its support. I am entirely happy to approach my religious beliefs in a similar spirit of the quest for truth to be attained through well-motivated belief. But that is another story.

The Rev Dr John Polkinghorne is an eminent physicist and theologian, and Fellow of Queen's College, Cambridge.