5.5 Classical physics and the exorcism of time
At first sight, classical physics appears to lend support to the commonsense view of time – that only present events exist; past events have ceased to exist, and future ones do not yet exist. In Newtonian physics time is linear and uniform with physical reality restricted to present events and things.
However, on closer examination we find that classical physics treats time as entirely external to and independent of the physical world. In spite of its apparent ontological priority, the present has no special status in the Newtonian scheme. Indeed, far from explaining or integrating time into its theories, the first priority of classical physics appears to have been to eliminate it from consideration. Classical physics is characterised by the quest for laws that do not vary with time (or make no reference to time). This bias amounts to what Ilya Prigogine has described as an exorcism of time (Prigogine and Stengers, 1984:291f.) from classical physics.
This is not to suggest that physicists made a conscious decision to exclude time from consideration. Rather such an exclusion follows naturally (and unconsciously) from certain philosophical and theological assumptions that were widespread in seventeenth- and eighteenth-century
One of these assumptions was the sharp division of reality into two incommensurable realms. On the one hand, there is res cogitans: the intelligible realm, the province of subjectivity, of mind, soul and spirit (and, hence, of religion and supernature). On the other hand, there is res extensa: the material realm, the province of nature and science. According to Descartes, the entities of res extensa possessed no other properties besides spatial extension. It was a passive world amenable to the physicists’ ideal of quantification.
The significance of this dualism for a physical account of time becomes clear in the light of the very close association between time and mind. As Genevieve Lloyd puts it, ‘we cannot think consciousness without thinking time, or time without thinking consciousness . . . if we take away the thought of consciousness, time also vanishes’ (Lloyd, 1993: 2). The Cartesian elimination of mind from physical reality could only result in a similar elimination of time or, at least, its reduction to an external parameter. As a result, classical physics became the observation of a world characterised only by extension from the vantage point of a quasi-divine spectator, namely, from eternity.
Another factor affecting the classical physical treatment of time was the dominant interpretation of eternity in Christian theology. This tended to be treated either as timelessness or a present that does not pass away. Typical is the following passage from Boethius (470-5—524):
Embracing the infinite lengths of past and future, it [God’s knowledge] considers everything as if it were going on now in a simple mode of awareness. So, if you want to weigh the presentness with which he discerns everything, you will more rightly judge it to be not a foreknowledge as of the future, but the knowledge of a never failing instant. Hence it is called pro-vidence rather than pre-vision, because it looks forth from a position far removed from things below as if from the highest summit of things. (Quoted in Sorabji, 1983:256)
Boethius portrays God’s view of history as that of an observer on a mountain-top viewing the countryside all laid out equally below. Time is likened to space. From God’s (true) perspective there is no passage of time in creation. And it was to these heights that the classical physicist aspired.
5.6 Relativity and the rediscovery of time
As physicists became more confident of their ability to model the world, they set their sights beyond the very simple mechanical phenomena that had been the foundation of Newtonian dynamics. Thus the idea of unvarying or time-free physical laws began to come under pressure during the nineteenth century with the development of thermodynamics. The more complex phenomena associated with heat transfer were simply not amenable to the same treatment as, say, a simple pendulum. As the Ancients realised, ignis mutat res – fire changes things. And change is a fundamental aspect of the commonsense view of time.
However, it is not thermodynamics that is commonly associated with the rediscovery of time in physics but Einstein’s theory of relativity – the answer to the first of Lord Kelvin’s clouds. Published in 1905, Albert Einstein’s innocuously entitled paper ‘On the electrodynamics of moving bodies’ was first and foremost an attempt to explain anomalies arising from attempts to apply Maxwell’s Theory of Electromagnetism to moving bodies. The velocity of light appears in that theory as a universal constant – but relative to what: the source, the intervening medium or the observer?
Drawing on our experience of objects moving at low speeds, we might expect the velocity of light to be constant relative to its source. However, this is not borne out by observation (e.g. it would significantly affect observations of binary star orbits). Thus attention turned to the second option: the velocity of light is constant relative to the intervening medium – absolute space – the aether. If so, it should be possible to detect the aether by looking for variations in the velocity of light caused by the Earth’s motion relative to the aether. Failure to do so was one of the clouds that worried Lord Kelvin.
Einstein’s extraordinary proposal was to treat the velocity of light as constant relative to the observer while, at the same time, insisting that ‘the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good’ (Einstein, 1923:37f.) – his principle of relativity. These apparently irreconcilable postulates allowed Einstein to develop an alternative to
’s laws of motion that effectively dissolved the anomalies that had troubled his predecessors. Newton
However, the new theory required a redefinition of the concept of simultaneity. In a Newtonian world there would be universal agreement that two events had occurred simultaneously. According to Einstein, one observer moving relative to another would not agree with the second that the two events were simultaneous. A corollary of this disagreement is that there can be no universal present moment – what is present to me may be past to one observer and still to come for another! Thus the principle of relativity rules out the possibility of a Newtonian universal ‘now’. The universe may not be thought of as a succession of instantaneous spaces. Space and time are simply not separable in the manner envisaged by Newtonian physics.
5.7 Relativity and the spatialisation of time
Ironically, Einstein’s revolution in our treatment of space and time is often interpreted as supporting the classical view of temporal passage as extraneous to physics. Many physicists maintain that the connection between time and space established by Einstein is of such a kind that time should be thought of as analogous to space – a fourth spatial dimension. For them, reality consists of the entire collection of events that ever have been or ever will be – past, present and future taken together in a static block (sometimes called the stasis theory of time). If so, our perception of time as passing is an artefact of human psychology rather than a physical reality. The following quotations are typical:
The objective world simply is. It does not happen. Only to the gaze of my consciousness crawling upward along the lifeline of my body does a section of this world come to life as a fleeting image. (Weyl, 1949:166)
relativity physics has shifted the moving present out from the superstructure of the universe, into the minds of human beings, where it belongs. (Davies, 1974:2f.)
[The physicist] does not regard time as a sequence of events which happen. Instead, all of past and future are simply there, and time extends in either direction from any given moment in much the same way as space stretches away from any particular place. (Davies, 1990:124)
What these assertions (and many others like them) fail to make clear is that this is an interpretation of the special theory of relativity. It is not that relativity theory has somehow proven Boethius’ analogy between time and space to be the case. Rather these physicists are reading relativity in the light of that analogy. Indeed it is an interpretation about which Einstein himself was ambivalent. On occasions he certainly wrote in a similar vein. However, when faced with Meyerson’s critique of this interpretation, Einstein agreed that ‘The element of spatial distance and the element of duration remain distinct in nature, distinct even in the formula giving the square of the world interval of two infinitely near events’ (Einstein  quoted in Capek, 1976:366f.).
5.8 Time and space
What are the implications of accepting a strong analogy between time and space?
It would, to say the least, be odd to entertain the notion that the things and events located in some regions of space were somehow more real than those located elsewhere. By analogy, then, we must deny that present events are more real than past or future events. In other words, events at every temporal location must be equally real. All things and events coexist timelessly. I am ignorant of the events of 2010 only because of my location in 2004 (just as I am ignorant of events in
Exeter while revising this chapter in Glasgow). All future events are there to be read off as and when we reach the right spatio-temporal location. Nor do past events pass away into oblivion – they remain (timelessly) in spatio-temporal locations to which I (the conscious observer moving through spacetime) no longer have access.
If this is so, then we must admit the validity of certain strange locutions. For example, few people living in November 2004 would quibble with the assertion that ‘Tony Blair is alive and well, and living in
Downing Street’. But the theory that all entities and events exist timelessly (a ‘stasis’ view of time) requires us also to accept such assertions as ‘John F. Kennedy is (timelessly) alive and well and living in 1958’. Of course, oddity does not imply that this is invalid. However, it does highlight the fact that this view of time is strongly counterintuitive.
5.8.1 Spacelike time and determinism
We generally believe the past to be determinate. For example, we may not have access to all the details of the Napoleonic Wars but we do know that a joint Anglo-Prussian force finally defeated Napoleon’s army at the Battle of Waterloo. It simply is the case that this happened – nothing can change the fact (not even the most inspired historical reinterpretation). Conversely it is our experience that the future is not determinate in this sense. We do not know what the future will bring. However, we can make predictions based upon past trends and present knowledge. Our predictions generally take the form of a range of possibilities. We further believe that in certain cases it is possible to influence the outcome by acting in certain ways.
In direct contradiction of our experience of past and future, the spatial treatment of time asserts that future events are determinate in precisely the same way as past events. Advocates of this approach are quick to point out the mind-dependence of the experience described above. They argue that the apparent indeterminacy of the future is entirely explicable in terms of our psychological limitations. There is a merely psychological arrow of time that denies us access to knowledge of events which are located at spatio-temporal locations later than our own.
However, this has interesting physical implications. As we shall discuss in 5.11–5.14, quantum mechanics is usually taken to imply indeterminacy – future states of the universe cannot be totally predicted, even in theory, from the present state. But on a ‘stasis’ view where all future events are (timelessly) determinate, the most obvious candidate for an adequate interpretation of quantum mechanics would be some kind of hidden-variables theory, one in which the apparent indeterminacy of the quantum world is underpinned by a more fundamental determinism [see 5.13 (ii)]. Thus all uncertainty about the future is merely a product of our ignorance. Alternatively, we may opt for a many-worlds interpretation in which all possible future events are equally real but isolated from each other in parallel universes (see 5.13 (iii)).
5.8.2 Spacelike time and causality
To say that A causes B is to say that A has some (significant) role in bringing B into existence. In our common understanding (with its implicit dependence upon a process theory of time), temporal location is usually implicated in such statements. A temporal relation of ‘earlier than’ is generally assumed to be a necessary but not sufficient condition for asserting a causal relation. Thus, when faced with the challenge to ‘Discuss the influence of James Joyce upon William Shakespeare’, an English undergraduate will either lapse into blank incomprehension or reinterpret it in postmodern terms as a request to explore the impact of Joyce’s work upon all subsequent readings of Shakespeare.
If the stasis theory is correct, there is no warrant for our habit of attempting to explain the present in terms of the past. Temporal location should have no more significance for our investigations of causes than spatial location. And, if there really were a strong analogy between time and space, we might expect the cause of some event to lie in one particular direction rather than another!
In reality, of course, we observe a systematic distinction between past, present and future that is quite unlike the characteristics of space. On the face of it, time and space are distinct even though intimately related.
However the difficulties created by a spacelike view of time are by no means insuperable. One way out might be to assert the timelessness of all causal relations. There is clear precedent for such a move in the classical understanding of divine causality. Another (possibly preferable) option might be to relate causality not to temporal location as such but rather to the physical factors that lead to the apparent distinctions between past and future.
5.9 Space, time and theology
Is time essentially spacelike with all that implies for our understanding of freedom and causation? Or is it the fundamental determinant of being and non-being? Contrary to popular belief, the new physics does not adjudicate between the rival interpretations of time that have been touched on in this section.
Both interpretations are open to theologians. Indeed both have appeared in Christian theology, albeit under very different guises. By and large theologians have tended to adopt a more or less commonsense view of created time. Thus Emil Brunner is typical when he comments that,
Everyone knows that time passes away. Everyone knows that the moment which was just now and is now gone never more returns. What men of all times and countries have been conscious of as the painful experience of time is the unceasing flow of the time stream, transience, the irreversibility and inexorability of this movement from the ‘not yet’ to the ‘now’ and onwards to the ‘no longer’ . . . The flow of time is inseparably bound up with transience, mortality, the not lingering, the not being able to return to what has once been, and just that constitutes the linearity of time. (Brunner, 1953:43)However, when the same theologians try to imagine what the passage of created time might look like from God’s perspective, the answer they often come up with is akin to the stasis theory of time described above, as though God were looking down on the four-dimensional space-time diagram that relativistic physicists draw. Polkinghorne has repeatedly rejected this view of God, insisting that there is a temporality to the divine experience (1989:Ch.7, 2004: 104-10). Willem B. Drees however questions whether relativity offers any time that could be thought of as God’s time (1996:261-66). The debate over the nature of time initiated by contemporary interpretations of relativity theory reveals a long-standing inconsistency in Christian theology with respect to time. For further discussion of different theories of time, especially of ‘the block universe’, a technical term for the ‘stasis’ view we have described, see Isham and Polkinghorne (1993:135–44) and DeWeese (2004).