The End of Time: The Next Revolution in Physics

Newton’s time is absolute. It flows with perfect uniformity for ever and nothing in the world affects its flow. Space, too, is absolute. Newton conceived of space as a limitless container. It stretches from infinity to infinity like a translucent block of glass, through which, nevertheless, objects can move unhindered. Space is a huge arena; time is a clock in the grandstand. Both are more fundamental than things. Newton could imagine an empty world but not a world without space and time. Many philosophers have agreed with him. So does the proverbial man in the pub, convinced that space goes on for ever and that ‘there must have been time before the Big Bang’.

At any instant, all the things in the Newtonian world are at definite positions. His absolute space performs two distinct roles. As in the discussion above, it binds, or holds, things together, in one instant. But it also places them in a container. Imagine taking two-dimensional snapshots of a table in a room. Paint out the background room, and you could still reconstruct the form of the three-dimensional table, but you would not know where to place it. Newton insisted that the things in the world in any instant have a definite place, and he posited absolute space as a kind of room to provide that place. His fixed container persists through time. We could take real snapshots of the things in the world (Figure 1). Ideally, these snapshots should be three-dimensional, like space, and show all things relative to each other and their positions in absolute space, just as snapshots of a soccer match show the players, ball and referee on the pitch with its markings. The grandstand clock records the time.

According to Newton, all bodies move through absolute space in accordance with definite laws of motion which govern the speed and direction of the bodies in that space as measured by absolute time. The laws are such that if the motions of the bodies are known at some instant, the laws determine all the future movements. All the world’s history can be determined from two snapshots taken in quick succession. (If you know where something is at two closely spaced instants, you can tell its speed and direction. Two such snapshots thus encode the future.)

Figure 1 As explained in the text, Newton conceived of space as a container, or arena, and time as a uniform flow. The difficulty is that both are invisible. This diagram attempts to represent the way he thought about space and time. The blank white of the page is a two-dimensional substitute for the invisible three-dimensional space, and the effect of the flow of time is mimicked by supposing that it triggers light flashes at closely spaced equal intervals of time. These flashes illuminate the objects in absolute space at the corresponding instants of time just as strobe lighting illuminates dancers in a darkened room. In this computer-generated perspective view, the vertices of a triangle represent the positions of three mass points as they move through absolute space. The triangles formed by the points at successive instants are shown.

Newton’s picture is close to everyday experience. We do not see absolute space and time, but we do see something quite like them – the rigid Earth, which defines positions, and the Sun, whose motion is a kind of clock. Newton’s revolution was the establishment of strict laws that hold in such a framework.

LAWS AND INITIAL CONDITIONS

These laws have a curious property. They determine motions only if certain initial conditions are combined with them. Newton believed that God ‘set up’ (created) the universe at some time in the past by placing objects in absolute space with definite motions; after that, the laws of motion took over. The statement that Newton’s is a clockwork universe is a bit misleading. Clocks have one predetermined motion: the pendulum of the grandfather clock simply goes backwards and forwards. The Newtonian universe is much more remarkable, being capable of many motions. However, once an initial condition has been chosen, everything follows.

Thus, there are two disparate elements in the scientific account of the universe: eternal laws, and a freely specifiable initial condition. Einstein’s relativity and major astronomical discoveries have merely added to this dual scheme the exciting novelty of a universe exploding into being about fifteen billion years ago. The initial condition was set at the Big Bang.