by Mark English
There is the physics of time, and then there is time as we experience it. Natural languages provide quite complex mechanisms for expressing the latter, but it would be a mistake to think that they could ever provide adequate tools for dealing with the former. Physicists cannot dispense with ordinary language, of course, but any satisfactory understanding or articulation of the physical nature of time obviously requires a good knowledge of physics.
There are however some important facts about time which were discovered in the 20th century which can be known and accepted by anyone, including those without any training in theoretical physics. For example, we know by experiment that synchronized clocks do not stay synchronized under certain circumstances (relating to motion and exposure to gravitational fields). If two clocks are synchronized at a given place and one of them is sent off on a journey in space and then brought back, the space-travelling clock will register significantly less time having passed than the other clock. And a clock exposed to a stronger gravitational field than another clock with which it has been synchronized will register less time having passed than the other clock when the clocks are reunited.
These facts have important implications for how we think about time. This becomes clear if you substitute living human bodies for mechanical clocks. An astronaut who travels on a long space journey and returns to earth will be younger than her twin who remained at home.
A natural interpretation of the end result is that time (from the point of view of the stay-at-home) has passed more slowly for the astronaut, and (from the point of view of the astronaut) has passed more quickly for her twin. But such claims need to be clearly distinguished from claims about the other person’s experience.
We do, of course, experience periods when time seems to pass more quickly or slowly than normal. The former tends to be associated with pleasant or absorbing activities and the latter with pain or boredom. And we have the sense that time in general and especially longer periods of time pass more quickly as we age. But these are, and are clearly understood to be, subjective phenomena.
Moreover, fast and slow are intrinsically relational ideas. If last year seemed to rush by, it is only by comparison with how we remember previous years. And a slow motion or time-lapse photography-based film can only be identified as such by contrast to the pace of events in the real world with which we are familiar.
There is another sense in which time can be said to go faster or slower. Different kinds of nervous and perceptual systems run on different time scales. For example, we find flies and many small animals very hard to catch. Their perceptual and motor systems run faster than ours. It is as if to them we are lumbering giants living in a slow-motion world.
The claims about time having passed more quickly for the stay-at-home twin and more slowly for the astronaut should not be taken as these sorts of claims. Quite obviously, they do not relate to the experience of time passing or the experience of aging. Nor should they be seen as adding anything to the basic facts. But the claims are not meaningless. They represent, as I understand them, perspectival views and constitute a natural – and quite harmless – gloss or commentary on the facts.
Has the astronaut traveled to the future? In a sense, she has. Certainly, whenever natural language is applied to areas like this it has the potential to mislead. But a knowledge of and respect for the basic science coupled with an awareness that natural language expressions can be read and interpreted in different ways will minimize misunderstanding and confusion.
I am not questioning the adequacy of ordinary language for ordinary communication nor its adaptability and flexibility in the face of technological change and development. There is, however, often a tension between a scientific perspective and a commonsense perspective. The latter is inevitably shaped by language as well as by other inherited modes of thought.
Applying a language that evolved to deal with certain limited sets of possibilities to situations which involve contingencies that transcend these limits inevitably poses problems. And these problems are all the greater if we are dealing not just with incremental technological developments but with ideas, circumstances and possibilities that are radically new and which lack analogues in the world within which language originally evolved. It is hardly surprising, therefore, that our languages – at a basic and structural level – are ill-equipped to deal satisfactorily with the issue under discussion.
The limitations of natural language to which I am drawing attention apply only to some types of language use; specifically to those that involve the application of ordinary language to certain kinds of theoretical question (such as the nature of time).When it comes to the ordinary social world, and our perceptions of time, language works just fine.
There is great variation in the way different languages deal with time. Some languages are tenseless (e.g. Burmese, Vietnamese, Thai, Malay and most varieties of Chinese) and have other ways of dealing with time but in most languages, the grammatical category of tense plays a central role. The category of tense interacts with aspect and mood in complex ways that vary from language to language, allowing precise, time-related distinctions to be made. The complexity and sophistication of the grammatical structures involved testify to the importance that a command of the subtleties of time (and perspectives on time) have played in human thought and interaction over many millennia.
Tense is relational. The time of the event or state denoted by the verb is indicated in relation to some other temporal reference point or points. In the case of absolute tense, the temporal reference point (or deictic center) is the “now” of the speaker; the moment of utterance. (“It was raining.” “It has been raining.” “It is raining.” “It will rain.”)
More complicated cases involve absolute-relative tense. This involves reference to a time that is related to a temporal reference point which is not the moment of utterance; this temporal reference point is, in turn, related to the moment of utterance. So you are in effect juggling three points or periods in time. The main kinds of absolute-relative tense are future perfect, past perfect, future-in-future and future-in-past.
The future perfect, for example, involves reference to a time located before a contextually determined temporal reference point that must be located in the future relative to the moment of utterance. (“He will no doubt have forgotten about it by the morning.”) The past perfect involves a time in the past relative to a reference point which is itself in the past relative to the moment of utterance. (“I had hoped to find her at home but she wasn’t there.”)
The inferences involved in conditional sentences are often time-based. Past perfect tense is often involved. (“Had he been here when you passed, you would have seen him.”) Or the future perfect. (“If she completes the task by tomorrow afternoon, she will have proven herself.”) Note that a particular view or “map” of the structure of past, present and future is implicit in these forms of expression, and the logic of the sentences rests upon a shared understanding of this time “map.”
In addition to these and similar grammatical structures, there are also many common idiomatic expressions that pertain to how we experience time. Such expressions are almost invariably metaphorical. Crucially, they are generally taken as such, and are not seen as literal or metaphysical or proto-scientific claims. The same can be said for many common expressions about the natural world which, taken literally, are in conflict with a scientific understanding but which, used in the normal way, are perfectly acceptable. (Sun rising, wind blowing, etc..)
Time doesn’t literally “pass” or “flow”. Fine. But these and similar expressions capture something of our experience of time. Time seems at times to rush or race; at times to drag.
All of these experiences involve the mechanisms of memory and various systems within the body which keep track of time at various scales.
The focus here, however, is on how our experiences of, and facts about, time may be articulated, not on how these experiences are generated within the nervous system.
NOTE: At various points in this piece, implicit reference is being made to an essay entitled “The Fallacy of Time Travel” by Ronald Green which was published on this site late last year.