A Theory of Everything (That Matters)

A Short Guide to Einstein, Relativity and the Future of Faith

Alister E McGrath

• Publisher: Hodder Faith
• Year: 2019
• ISBN:
  9781529377972
• Topic: Theology & Religion
• Subtopic: Religion

On 29th May 1919, British astronomers tested Einstein's theory of relativity by measuring the path of the stars travelling near the sun during an eclipse. On 7th November 1919, the results of that experiment were announced in London, proving Einstein's theory of relativity. A Theory of Everything (that Matters) has been written in celebration of this 100th anniversary. With the confirmation of Einstein's theories at the beginning of the twentieth century, our understanding of the universe became much more complex. What does this mean for religious belief, and specifically Christianity? Does it mean, as so many people assume, the death of God? In A Theory of Everything (that Matters) Alister McGrath - Professor of Science and Religion at Oxford University - explores these questions, giving an overview of Einstein's thought and scientific theories, including his nuanced thinking on the difference between the scientific enterprise and beliefs outside its realm. This groundbreaking book is for anyone intrigued by Einstein as one of the twentieth century's most iconic figures, who wants to know what his theories mean for religion, and who is interested in the conversation between science and religions more broadly. 'An excellent study of Einstein's theories in relation to his beliefs about God' - starred review in PUBLISHERS WEEKLY

Part One

A Revolution in Science

II

The Old World: Newton’s Clockwork Universe

Let’s return to that headline in The Times of November 1919, announcing the verification of Einstein’s theory of relativity: ‘Newtonian Ideas Overthrown’. Just what were these ideas, and how were they ‘overthrown’ by Einstein? What difference does this make? And how does their development help us understand how the natural sciences work? Let’s begin by reflecting a little on what science is all about.

Thinking about Science

At one level, the natural sciences are about the patient and scrupulous accumulation of observations – whether we are talking about the movements of planets, the behaviour of ants or the patterns of rainfall in a region of the Andes. Yet science is about more than harvesting countless observations. It is a quest for understanding in which we try to discern the deeper patterns and structures of our universe that cause it to behave in certain ways. Science aims to go behind our observations and figure out what deeper truths underlie what we can see of our world.

It’s an idea explored in the writings of the great Renaissance philosopher and scientist Francis Bacon (1561–1626), who compared ‘natural philosophers’ to bees. (The word scientist did not come into use until the 1830s.) Why bees? Because bees do more than just gather pollen; they ‘transform and digest’ what they collect and convert it into something new – honey. In the same way, the scientist both gathers observations and then transforms these by weaving them together into a theory – a way of understanding our world.

The word theory is widely used in science to refer to ways of understanding our world. It comes from the Greek word theoria, meaning ‘a way of beholding’ or ‘contemplation’. A theory is like a lens that allows us to see through and beyond the world of appearances to grasp something deeper and more fundamental that lies behind it. Like a set of spectacles, a theory allows us to see things in focus, helping us grasp the way in which seemingly disconnected observations are actually part of something greater. Over time, certain theories gain widespread acceptance, becoming a settled part of the furniture of our minds. We get so used to these ideas that they seem natural and self-evidently true. So what happens if they turn out to be wrong? What if a familiar and trusted way of understanding ourselves and our world proves fallible and unreliable? What if a new theory comes along and is shown to be far superior to what we have been used to?

Let’s take an example – the movement of the planets. Even in the ancient world, people noticed that some of the objects in the night sky seemed to move around. Names were given to the five star-like objects that moved against the background of the fixed stars: Mercury, Venus, Mars, Jupiter and Saturn. So what explained the movement of these ‘wandering stars’? In the second century, the astronomer and mathematician Ptolemy of Alexandria set out a way of understanding the heavenly bodies that would be accepted by most people for more than a thousand years. For Ptolemy, the sun, moon and planets all revolved in circular orbits at different distances around the Earth.1 It was a neat model, and it worked reasonably well, partly because, before the invention of the telescope in the sixteenth century, observations of planetary movements weren’t very accurate.

But in the sixteenth century, awkward questions arose as increasingly accurate measurements of the movements of the planets became possible. The Polish astronomer Nicolaus Copernicus published a book arguing that the sun – not the Earth – stood at the centre of the known universe. The Earth now had to be seen as simply one among many other planets. Copernicus’ theory was wrong in several respects – for example, he believed that the planets revolved in circular orbits around the sun at uniform speeds. It needed correction before it could provide more reliable predictions of the movement of the planets against the fixed stars of the night sky.

Johannes Kepler corrected those errors through his close study of the movement of the planet Mars in the early seventeenth century. He pointed out that the Earth and other planets actually revolved in elliptical orbits around the sun at variable speeds. Yet Kepler couldn’t explain why this was the case. In many ways, Kepler’s achievement was simply to set out the rules that seemed to govern planetary motion. It remained a mystery as to why they should behave in this way in the first place. Kepler was unable to offer a theory that accounted for the existence and form of these rules. A bigger picture of the solar system was required to explain this.

As if on cue, the English mathematician and natural philosopher Isaac Newton (1643–1727) stepped up to the plate and ushered in a new and deeper way of understanding our universe.

Isaac Newton and the Laws of Nature

Newton set out his proposals for classical mechanics and gravitational theory in his Philosophiae Naturalis Principia Mathematica (‘Mathematical Principles of Natural Philosophy’), now usually referred to simply as Newton’s Principia, in 1687. His massive intellectual achievement was summed up by one of the leading poets of his age, Alexander Pope:

Nature and nature’s laws lay hid in night;

GOD said, Let Newton be! and all was light.

So who was Newton? And what was his achievement? Newton developed most of his important work while he was professor of mathematics at Cambridge University. By careful observation, Newton set out a series of principles that governed the behaviour of objects on Earth and then argued that these same principles applied to the motion of the moon around the Earth and the planets around the sun. This is the point made in the famous story of Newton and the apple.

This well-known story exists in several forms. The version of the story I was told back in the late 1950s was that Newton was sitting in his garden when an apple fell on his head – happily inflicting no permanent damage! Then, in a moment of devastating intellectual illumination, Newton invented his theory of gravity. It’s a wonderful story. And, like so many of these stories, there is an element of truth. Yet there’s also a lot of exaggeration.

One account of this incident was written down by John Conduitt, who became Newton’s assistant at the Royal Mint, which Newton directed in his later years:

In the year 1666 [Newton] retired again from Cambridge to his mother in Lincolnshire. Whilst he was pensively meandering in a garden it came into his thought that the power of gravity (which brought an apple from a tree to the ground) was not limited to a certain distance from Earth, but that this power must extend much further than was usually thought. Why not as high as the Moon said he to himself & if so, that must influence her motion & perhaps retain her in her orbit, whereupon he fell a calculating what would be the effect of that supposition.2

This account was written down sixty years after the event. Scholars can hardly be blamed for wondering if Newton might have creatively embellished the story through retelling it over time, perhaps to conceal the fact that another British scientist – Robert Hooke – had developed a similar idea in the 1670s.3

The story of Newton’s apple was given a surprising religious twist by the French antireligious philosopher Voltaire, who saw the apple as a symbol of science displacing religion as the cornerstone of human wisdom. Drawing on the tradition that the ‘forbidden fruit’ in the Garden of Eden was an apple, Voltaire suggested that Newton’s scientific discovery ushered in a new era in human history and self-understanding.4

Newton, of course, did not see his achievement in these terms. He rather saw himself as clarifying the deeper logic of the universe, discerning certain ‘laws of nature’ that he considered to reflect the wisdom of God as creator. Newton argued that the mysterious and undetectable force he named gravity was the explanation for both an apple falling to the Earth and the moon orbiting around the Earth. Newton had no idea what caused gravity in the first place and refused to speculate about its origins. ‘It is enough that gravity does really exist, and . . . abundantly serves to account for all the motions of the celestial bodies.’5

Initially, Newton’s demonstration of the regularity of these laws of nature was seen as confirming the Christian belief in a God who had created an ordered universe and endowed humanity with the power of reason to discover those laws. Yet some were not so sure. Newton might well have shown that the universe was like a well-designed machine – cold, impersonal and mechanical. But where was there any sense of beauty or joy? Furthermore, God now seemed to be pointless. Having constructed the universe and set it going, God is left without any significant role. God might retire or even die, but the universe would continue to function according to the laws by which God had caused it to function. Newton, perhaps unwittingly, had laid the groundwork for a self-sustaining and self-regulating universe, with no place for God.6

Newton on Space

Newton had demonstrated that the planets moved around the sun and that the moon moved around the Earth according to certain ‘laws of nature’ that could be expressed mathematically. But what did they move through? Newton introduced the idea of space – a vast, empty container that enclosed the sun, planets and stars. This naturally raised some important questions, most obviously the question of what this ‘space’ was made of. As with gravity, Newton refused to speculate on this question. Space was like an enormous box through which all objects moved in straight lines until some force caused their trajectory to curve. Like gravity, space could not itself be observed. Yet, again like gravity, it made sense of everything else that we observe. For Newton, both gravity and space were legitimate scientific inferences from an observable phenomenon to the unobservable entity that best explains it.7

Newton recognised that space and time were not things we observe directly but were rather inferences from those observations. However, many of his interpreters began to think of these as self-evident truths, things so obviously correct that they did not require justification or defence. Einstein would later express his concern about the ease with which such provisional concepts came to be seen as necessarily true and praised the German physicist Ernst Mach for insisting that scientific concepts arise out of experience:

Concepts, which have proved useful in the ordering of things, easily acquire such a degree of authority over us that we forget their earthly origin. We take them as unchangeable givens. They come to bear the stamp of necessities of thought, of a priori givens. The path of scientific advance is often made impassable for a long time through such mistakes.8

So what was the significance of Newton’s theories? Basically, Newton was able to demonstrate that a vast range of observational data could be explained on the basis of a simple set of universal principles, such as his laws of motion and the force of gravity. Newton’s theories worked well within the comfort zone of our intuitions about the classical world. Yet when we move away from this narrow world, we encounter the strange world of the very small and very fast – the world which Einstein later made his own.

Newton on Light

As we shall see, one of Einstein’s most significant contributions to modern science concerned the nature of light. So what did Newton have to say on this question? In his Opticks (1704), Newton took the view that a beam of light consisted of a series of rapidly moving small particles or ‘corpuscles’ (from the Latin term corpuscula, ‘small bodies’). Rays of light were actually beams of tiny particles. Not e...