They might be varying very slowly, perhaps by only a few parts per million over the age of the Universe. Or, it might be that they are only constant in some statistical or average sense. Since these possibilities cannot be excluded except by assumption or prejudice there needs to be a detailed experimental study of constants and their constancy. Physicists became interested in determining the values of the constants of Nature with greater and greater accuracy and devising ways of checking whether they were truly constant. This quest for the evaluation of the constants of Nature had seemed to some to be the ultimate goal of physics. For, amusingly, at the end of the nineteenth century, it was widely believed that all the interesting discoveries had already been made in physics and all that remained was to measure with greater and greater accuracy – an enterprise of polishing rather than of discovery or revolution. Caricaturing this hubris, Albert Michelson wrote in 1894 that there was a view abroad that

‘The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is remote … Our future discoveries must be looked for in the sixth place of decimals.’52

Even Planck had been influenced by these views. As a student in 1875 he recalled that his tutor advised him to work in biology because all the important problems of physics were solved and the subject was fast approaching completeness. Ironically, Planck was the leader in creating the new quantum view of reality that was then followed by Einstein's assaults on our conceptions of space, time and gravity. Far from being near to completion, physics had barely begun.

ABOUT TIME

‘The old believe everything: the middle-aged suspect everything: the young know everything.’

Oscar Wilde53

One of the paradoxes of our study of the Universe around us is that as our descriptions of its workings become more precise and successful so they also become increasingly remote from everyday human experiences. The most accurate predictions that we can make are not about the workings of banks or the vagaries of consumer choice and voter intent, they are about elementary particles and astronomical systems of spinning stars. This is exactly the opposite to what would be expected if our descriptions of the world were strongly biased by input from the human mind rather than being in some sense acts of discovery. It need not have been like this. We have only to look at our attempts to understand the complexities of human behaviour to recognise a strong subjective element. The reliability of our conclusions generally falls as we deal with situations farthest from our own experience and individuals least like ourselves.

By contrast, our unravelling the existence of constants of Nature behind the realities described by laws of change and invariance has enabled us to formulate standards by which we can judge whether things are big or small, young or old, heavy or light, hot or cold, by reference to an absolute standard. When we say that the Universe has been expanding for 13 billion years, does that mean it is old ? It sounds very old against the fleeting span of a human lifetime, or when compared with the day or the year that derive from the motions of the Earth. But, then again, the Universe might be going to expand for trillions of years, or perhaps even forever. By those standards it is very young. Natural units tell us that in a well-defined sense the Universe is very old already, about 1060 Planck times old. Life on Earth didn't appear until after the Universe was 1059 Planck times old. We were a late arrival.

chapter three
Superhuman
Standards

‘Brother Mycroft is coming round.’

A. Conan Doyle1

EINSTEIN ON CONSTANTS

‘What I'm really interested in is whether God could have made the world in a different way; that is, whether the necessity of logical simplicity leaves any freedom at all.’

Albert Einstein2

Albert Einstein did more than any other scientist to create the modern picture of the laws of Nature. He played a major role in creating the correct perspective upon the atomic and quantum character of the small-scale world of matter, showed how the speed of light introduced a relativity into each observer's view of space, mass and time, and singlehandedly found the theory of gravity that superseded the classic picture created by Isaac Newton 250 years before. He was always fascinated by the way in which some things must always look the same, no matter how the viewer is moving. The prime example that he displayed was the speed of light moving in a vacuum. No matter how fast the source of a light beam is moving relative to you, after it emits its light you will always measure the light to have the same speed relative to you.

This is completely unlike any everyday motion at low speed that we are familiar with. Launch a missile at 500 kilometres per hour from a train that is moving in the same direction at 100 kilometres per hour and the missile will be found to move at 600 kilometres per hour relative to the ground. But fire a light beam from a train moving at the speed of light (300,000 kilometres per second) and it will be found to move at the speed of light relative to the ground. The speed of light is a special constant of Nature. It is the benchmark against which we can judge whether motion is ‘fast’ or ‘slow’ in some absolute sense.