The Ascent of Man (23 page)

In the winter of 1713 a group of disgruntled Tory writers formed themselves into a literary society. Until Queen Anne died the next summer, it met often in the rooms in St James’s Palace of her physician, Dr John Arbuthnot. The society was called the Scriblerus Club, and set out to ridicule the learned societies of the day. Jonathan Swift’s attack
on the scientific community in the third book of
Gulliver’s Travels
rose out of their discussions. The group of Tories, who later helped John Gay to satirise the government in
The Beggar’s Opera
, also helped him in 1717 to write a play
Three Hours After Marriage
. There the butt of the satire is a pompous, ageing scientist under the name of Dr Fossile. Here are some typical scenes from the play
between him and an adventurer, Plotwell, who is having an affair with the lady of the house.

The first topic of fun, naturally, is alchemy; the technical jargon is quite correct throughout.

The scientific references come quick and fast now: to the troublesome problem of finding the longitude at sea, to the invention of fluxions or the differential calculus,

It seems irreverent to us that Newton should have been subject to satire in his lifetime, and subject to serious criticism too. But the fact is that every theory, however majestic, has hidden assumptions which are open to challenge and, indeed, in time will make it necessary to replace
it. And Newton’s theory, beautiful as an approximation to nature, was bound to have the same defect. Newton confessed it. The prime assumption he made is this: that he said at the outset, ‘I take space to be absolute’. By that he meant that space is everywhere flat and infinite as it is in our own neighbourhood. And Leibniz criticised that from the outset, and rightly. After all, it is not even probable
in our own experience. We are used to living locally in a flat space, but as soon as we look in the large at the earth, we know it not to be so overall.

The earth is spherical; so that the point at the North Pole can be sighted by two observers on the equator who are far apart, yet each of whom says, ‘I am looking due North’. Such a state of affairs is inconceivable to an inhabitant of a flat
earth, or one who believes that the earth is as flat overall as it seems to be near him. Newton was really behaving like a flat-earther on a cosmic scale: sailing out into space with his foot-rule in one hand and his pocket-watch in the other, mapping space as if it were everywhere as it is here. And that is not necessarily so.

It is not even as if space has to be spherical everywhere – that
is, must have a positive curvature. It might well be that space is locally lumpy and undulating. We can conceive of a kind of space that has saddle-points in it, over which massive bodies slide in some directions more easily than in others. The motions of the heavenly bodies must still be the same, of course – we see them and our explanations must fit them. But the explanations would then be different
in kind. The laws that govern the moon and the planets would be geometrical and not gravitational.

At that time they were all speculations far in the future, and even if they had been uttered, the mathematics of the day could not cope with them. But thoughtful and philosophic minds were aware that, in laying out space as an absolute grid, Newton had given an unreal simplicity to our perception
of things. In contrast, Leibniz had said the prophetic words, ‘I hold space to be something purely relative, as time is’.

Time is the other absolute in Newton’s system. Time is crucial to mapping the heavens: we do not know in the first place how far away the stars are, only at what moment they pass across our line of sight. So the mariner’s world called for the perfection of two sets of instruments:
telescopes and clocks.

First, then, improvements in the telescope. They were now centred in the new Royal Observatory at Greenwich. The ubiquitous Robert Hooke had planned that when he was rebuilding London with Sir Christopher Wren after the Great Fire. The sailor trying to fix his position – longitude and latitude – off a remote shore from now on would compare his readings of the stars with
those at Greenwich. The meridian of Greenwich became the fixed mark in every sailor’s storm-tossed world: the meridian, and Greenwich Mean Time.

Second as an essential aid to fixing a position was the improvement of the clock. The clock became the symbol and the central problem of the age, because Newton’s theories could only be put to practical use at sea if a clock could be made to keep time on
a ship. The principle is simple enough. Since the sun rounds the earth in twenty-four hours, each of the 36o degrees of longitude occupies four minutes of time. A sailor who compares noon on his ship (the highest position of the sun) with noon on a clock that keeps Greenwich time therefore knows that every four minutes of difference place him one degree further away from the Greenwich meridian.

The government offered a prize of £20,000 for a time-keeper that would prove itself accurate to half a degree on a voyage of six weeks. And the London clock-makers (John Harrison, for instance) built one ingenious clock after another, designed so that their several pendulums should, between them, correct for the lurch of the ship.

These technical problems set off a burst of invention, and established
the preoccupation with time that has dominated science and our daily lives ever since. A ship indeed is a kind of model of a star. How does a star ride through space, and how do we know what time it keeps? The ship is a starting point for thinking about relative time.

The clock-makers of the day were aristocrats among workmen, as the master-masons had been in the Middle Ages. It is a nice reflection
that the clock as we know it, the pacemaker strapped to our pulse or the pocket dictator of modern life, had since the Middle Ages fired the skill of craftsmen too, in a leisurely way. In those days the early clock-makers wanted, not to know the time of day, but to reproduce the motions of the starry heavens.

The universe of Newton ticked on without a hitch for about two hundred years. If his
ghost had come to Switzerland any time before 1900, all the clocks would have chimed hallelujah in unison. And yet, just after 1900 in Berne, not two hundred yards from the ancient clocktower, a young man came to live who was going to set them all by the ears: Albert Einstein.

Time and light first began to go awry just about this time. It was in 1881 that Albert Michelson carried out an experiment
(which he repeated with Edward Morley six years later) in which he fired light in different directions, and was taken aback to find that however the apparatus moved, always he came out with the same speed of light. That was quite out of keeping with Newton’s laws. And it was that small murmur at the heart of physics which first set scientists agog and questioning, about 1900.

It is not certain
that the young Einstein was quite up-to-date about this. He had not been a very attentive university student. But it is certain that by the time he went to Berne he had already asked himself, years earlier as a boy in his teens, what our experience would look like seen from the point of view of light.

The answer to the question is full of paradox, and that makes it hard. And yet, as with all
paradox, the hardest part is not to answer but to conceive the question. The genius of men like Newton and Einstein lies in that: they
ask transparent, innocent questions which turn out to have catastrophic answers. The poet William Cowper called Newton a ‘childlike sage’ for that quality, and the description perfectly hits the air of surprise at the world that Einstein carried in his face. Whether
he talked about riding a beam of light or falling through space, Einstein was always full of beautiful, simple illustrations of such principles, and I shall take a leaf out of his book. I go to the bottom of the clocktower, and get into the tram he used to take every day on his way to work as a clerk in the Swiss Patent Office.

The thought that Einstein had had in his teens was this: ‘What would
the world look like if I rode on a beam of light?’ Suppose this tram were moving away from that clock on the very beam with which we see what the clock says. Then, of course, the clock would be frozen. I, the tram, this box riding on the beam of light would be fixed in time. Time would have a stop.

Let me spell that out. Suppose the clock behind me says noon when I leave. I now travel 186,000
miles away from it at the speed of light; that ought to take me one second. But the time on the clock, as I see it, still says ‘noon’, because it takes the beam of light from the clock exactly as long as it has taken me. So far as the clock as I see it, so far as the universe inside the tram is concerned, in keeping up with the speed of light I have cut myself off from the passage of time.

That
is an extraordinary paradox. I will not go into its implications, or others that Einstein was concerned with. I will just concentrate on this point: that if I rode on a beam of light, time would suddenly come to an end for me. And that must mean that, as I approach the speed of light (which is what I am going to simulate in this tram), I am alone in my box of time and space, which is more and more
departing from the norms round me.

Such paradoxes make two things clear. An obvious one: there is no universal time. But a more subtle one: that experience runs very differently for the traveller and the stay-at-home – and so for each of us on his own path. My experiences within the tram are consistent: I discover the same laws, the same relations between time, distance, speed, mass and force,
that every other observer discovers. But the actual values that I get for time, distance, and so on, are not the same that the man on the pavement gets.