What Is Time?

It is my belief that if we want to talk of time in a more profound sense we must determine what kind of time we are talking about. One encyclopedia defines time as “the period during which an action or event occurs; also, a dimension representing a succession of such actions or events. Time is one of the fundamental quantities of the physical world, being similar in this respect to length and mass.” By another definition, time is a continuum in which one event follows another from the past through to the future. Both definitions are physical, so let us take a look at how physicists perceive time.

 Physicists’ Time

       Under The Theory of Relativity and Quantum Mechanics above we have touched on some of the scientific concepts of time, concepts which have undergone considerable change, especially during the last century, and which still need careful thought. According to one theory, the Hartle-Hawking no-boundary hypothesis, time had a beginning. As Stephen Hawking asserts, time came into being together with or rather preceded Big Bang. In the words of Hawking: “… when quantum mechanics is taken into account, there is the possibility that the singularity may be smeared out and that space and time together only form a closed four-dimensional surface without boundary or edge, like the surface of the Earth but with two extra dimensions … Asking what happened before the Big Bang is like asking for a point one mile north of the North Pole.”  and further “…the beginning of time would have been a point of infinite density and infinite curvature of space. All known laws of science would break down at such a point. To talk of time at this point, the singularity, is meaningless.”

“Time” as such does not exist any more than the past and the future. Einstein taught us that what he calls time are local phenomena, belonging to particular reference frames such as the Earth. Within that frame an infinite succession of events occurs, practically simultaneous with their being observed by a theoretical observer. The physical world is replete with periodical events, some of them of infinitely short duration (one “revolution” of an electron round the nucleus), others lasting one revolution of Earth round itself, others one revolution of Earth round the Sun etc. etc. Time does not exist in a system in chaotic movement because 'time' is meaningless without periodic change. If this is correct, then time did not exist during the first dozens of seconds after Big Bang, because the elementary particles present then were in chaotic movement – due to the extremely high temperatures reigning.

 Physical time is defined in terms of change and is measured by motion in space. We humans have agreed on registering physical time by counting specific periodically repeating phenomena by making a one-to-one correlation between our clocks and the event under observation. Physical time is synonymous with the counting of cyclic events. Each of these cyclic phenomena is a different clock. In the course of evolution we humans have chosen the kind of clock which suited our technological level and our needs at the time. Today, the second is defined as the duration of  9,192,631,770 cycles of one type of radiation produced by the cesium 133 atom. These clocks are all based on the assumption that each period is identical with the previous and the following, that each swing of the pendulum is identical with the previous one and the next one, and that each pulse from the cesium 133 atom is identical with the next. We are convinced (but we can never be sure) that without our presence all these cyclic events of different duration will continue to happen for eternities, also within other reference frames. 

Without us humans to count, maybe there is no time. This will probably not bother the infinitely many interrelated or simultaneously occurring, periodic or chaotic events of all magnitudes and durations within our observable universe. But if the universe continues to expand at an accelerating rate, maximum entropy will result. Molecules will stop jiggling, stars will be dead cold and everything will reach the same temperature of – 273º. In fact, nothing will move and time will cease to exist.

What Einstein so cleverly saw was that there could be no universal counting of events; each belonged to its own reference frame, and in order to get from one frame to another we must use the Lorenz transformation equations plus the invariance of light-speed as a yardstick. In Relativity, there is no such thing as a universally agreed past, present and future. In space-time, this concept is meaningless.

 Everyday Time

       The way we use the word ‘time’ presents a hotch-potch of often contradictory statements and usages. But this, together with the clock, is what provides our lives with the indispensable practical framework. We can beat time or kill it, save it or lose it, and it can stand still. Expressions like “How time flies!”, “How slowly time goes”, and “Time hung heavy on his hands”, do not say anything about time but only about our mental recording and neural manipulation of chains of events. The complaint “Goodness, how time flies” or ”How fast time goes” is usually heard after the experience of a concentrated course of events in which the person has engaged him- or herself emotionally. The opposite, “Time hung heavy on his hands” or “How slowly time goes!” is heard, conversely, when the engaging events are beeing far apart, and the feeling will be reinforced if the person expects a joyful, exciting, frightening or merely interesting event later.

All these statements can be re-written and communicated without mentioning the word “time” and without loss of meaning, and none of them actually refer to time as a measurable entity. So how can we explain that time goes fast or slowly? We all know what is meant, and we Westerners all know that the phrases refer to our mental experience of time while real time runs at the speed of 60 seconds per minute. Surely my aerobics instructor also knows that, but she causes a lot of confusion when she shouts “And now double time” and half of the group doubles the rhythm while the other half slows down to half pace. (She does not make life easier for us when later she suddenly shouts “Double time” and lets it mean exactly what it means!).

The Psychology of Time

      To the psychologist time is related to consciousness. Like most lower animals a newborn child lives in an eternal present, but within a few weeks it learns to associate present events with future consequences. Time and memory have entered its life. At the age of about a year and a half the child can talk of objects and events which are not present. At the age of two it can find a hidden object after a delay. Gradually, consciousness is developing.

      Psychological as well as physiological evidence indicate that our the biological clocks keep track of the progression of time, each in its own way but all the time synchronizing the biological processes with the outside world. Most of the clocks work autonomously but some, like our breath and pulse, may be controlled consciously. Both breath and pulse influence our sensation of the duration of time. But it may be easily disrupted; under the influence of certain drugs the sense of time may either shorten or drag out. Depressants like barbiturates and opiates make time seem shorter: “I felt I had lived an entire life in a single day” would be a typical remark from someone under the influence of opium. Stimulants like caffeine or amphetamine, which speed up metabolism, make time seem longer. “Time was stretched to an extent that it almost ceased to exist” is a typical remark from someone under the influence of amphetamine.

     The experience of time is frequently, if not always, culturally determined; primitive people have a very vague attitude towards clocks. The Hopi Indians have no words to define linear time. Their verbs have no past and future tenses: they live in a kind of perpetual present, which encompasses all events that ever happened. Muslims say they always carry the past with them. Yogis claim they through their disciplines can achieve liberation from any sensation of the flow of time. They call this state Moksha. Buddhists say they can reach a similar state through contemplation and call it Satori, or Nirvana. Several Christian mystics claim to have reached meditative states of release from the treadmill of mundane life, but to physicists time is just a mathematical entity like the three space dimensions that we assume emerged with the BB 13.7 billion years ago. Could it be after all that time does not exist? Or that at least the perception of the passage of time is an illusion?

The cosmologist Paul Davies says “…to talk of  the past or the future is as meaningless as referring to the up or the down…[which are only spatial directions just as past and future are just temporal directions] …we do not really observe the passage of time. What we actually observe is that the later states of the world differ from earlier states that we still remember.” and “…Two events that occur at the same moment if observed from one reference frame may occur at different moments if viewed from another… [It is impossible] to confer special status on the present moment, for whose “Now” does that moment refer to?…The most straightforward conclusion is that both past and future are fixed. For this reason, physicists prefer to think of time as laid out in its entirety, a timescape, analogous to a landscape, with all past and future events located there together.  It is a notion sometimes referred to as block time. … In short, the time of the physicist does not pass or flow.”

Yet our daily experience tells us that time flows; what happened yesterday is fixed and cannot be altered; what will happen tomorrow we can only speculate about, and it is our present that conveys upon us our sense of reality. In the present, reminiscences of the immediate past are stored in the short term memory from which they may be retrieved - and are perhaps retrieved almost incessantly – maybe to give us the sensation that the past is with us. But the retrieved is not identical with the stored; what was stored is in a sense already lost. The normal brain immediately seems to begin sorting and censoring the input, expunging useless or contradictory parts, placing the rest in chronological order and assigning those deemed to have emotional or survival value to their respective brain centers. No doubt consciousness also contributes to the sensation of the flow of time; we as thinking beings can consciously dig back into our memory the better to establish the chronology. To quote Paul Davies again: “Consciousness may involve thermodynamic or quantum processes that lend the impression of living moment by moment.” And the English mathematical physicist Roger Penrose has suggested that large-scale quantum activities are occurring in the brain, and it is not inconceivable that they are somehow connected with the way in which we perceive the present.

Thus when an event is recalled, it has most certainly already been edited. The stronger attention given to or emotion experienced at the time of the event, the deeper it etches itself on the brain and the longer it will remain in the memory bank, but as time passes, the event undergoes further cataloguing, censoring and editing, the stronger the more often it is recalled. But our cultural and intellectual background and our language also tend to tinge it. We remember what we want to or are taught to remember. And the event rarely or never recalled will weaken until it fades into oblivion.

How are the events given their chronological places in the brain? We do not carry a cerebral video recorder with us which replays past events in the correct order, though it is probable that our biological clock plays a role. It could clock in and stamp each discrete memory bit and pass this temporal information on to the registrar of events in the brain. How this happens is not yet known. But psychologists, neurophysiologists and even linguists from all over the world are researching into these subjects because many suspect that the entire neural system is involved in how we experience the arrow of time, as suggested in the above quote by Paul Davies.

Considering that practically all the cells in the body except those of the brain and heart are replaced in the course of twenty years (some of them even daily), and that you are henceforth biologically a new person, is it not amazing that we can maintain the feeling of identity: of being something absolutely singular and private!

Some Philosophies of Time

       The exact sciences look with suspicion on all philosophy, especially within its own specialty; however, both cosmology and quantum physics have reached a level of understanding which in itself is virtually identical with philosophy. They speak of a beginning and a possible end to the universe, they point out the limits to the comprehension to be reached by any observer; and they launch and reject hypotheses about the character and constitution of the universe and of matter, about spontaneous creation of matter (e.g. Fred Hoyle’s steady state universe) and swollowing up of matter in black holes, all of it of the highest philosophical relevance. But long before science reached its present level, philosophers and authors had given birth to a large number of models and speculations about the inner essence of time and the universe; it has a history together with and apart from that of physics but seems now to be having a renaissance again, being courted by the physicists. Here, you can read about some of the philosophies.

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(The Japanese/Chinese character in the background reads “toki” in Japanese, which means “time”)

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