“I wanna go back and do it all over
But I can’t go back I know
I wanna go back ’cause I’m feeling so much older
But I can’t go back I know”

—Popular song by Eddie Money
(1986, CBS Inc.)

Mostly we take space for granted so long as we have enough of it. But what about time? The Romans said “tempus fugit” and said it all, or at least most of it. It is difficult to say more without getting tautological; but we can say that time has only duration so it must be one-dimensional. The natural division of time into past, present, and future, which we often picture as a straight line with a point marking the present, the past stretching back along the line, and the future stretching ahead, expresses time’s one dimensional nature.

What about space and time? How are they related? A tough question; it’s fair to ask if it is meaningful. Is there any reason to expect them to be related? Common sense suggests that, indeed, they must be linked together somehow. For instance, when we make an appointment to meet someone we state not only a place, but also a time.

But as to what the relationship might be, this is much less clear. The fact that Isaac Newton did not get it right suggests that the situation is far from straightforward. Only at the beginning of this century, stimulated by the discoveries of 19th-century physics, did physicists realize exactly how time fits into the scheme of things. The world doesn’t consist of a three-dimensional space with time as a separate unrelated entity, but is a fusion of space and time in which time is the fourth dimension. Hermann Minkowski, who first discussed the properties of unified space-time, opened his address to the 1908 Assembly of German Natural Scientists and Physicians with a clear statement: “The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.”

Minkowski did much more than merely state that time is the fourth dimension. He tamed time by showing how to convert an interval of time into an equivalent of space and so put things on a quantitative footing, like a good scientist should. He demonstrated that the conversion factor is the speed of light. Thus an interval of time is equivalent to the distance that light travels during that time. Because of light’s enormous speed (186,000 miles per second), a little time is “worth” an immense distance—one second corresponds to 186,000 miles, for example. We all know that “time is money,” but nobody says that “distance is money,” so perhaps, in a way, folk wisdom anticipated Minkowski.

The establishment of the relationship between time and space does not imply that time is a type of space. It isn’t. Time and space by themselves “are doomed to fade away into mere shadows” in Minkowski’s eloquent phrasing, but nonetheless they are separate shadows; time is time, and space is space.

Developments since Minkowski’s time have confirmed his space-time description of the world. Einstein’s theory of general relativity, which is a theory of gravity, adopts Minkowski space-time as an essential preliminary ingredient. Einstein did not “explain” gravity any more than Newton “explained” gravity, but he did provide a better description of gravity. Einstein’s theory does everything that Newton’s does, and then some.

Einstein did not modify or extend Newtonian theory but took an entirely new approach in which Newton’s gravitational force is superseded by curvature of space-time. From Einstein’s viewpoint the apple didn’t fall on Newton’s head because of a gravitational force between the apple and the Earth, but because the mass of the Earth curves space-time in the Earth’s vicinity, and the apple’s falling was a manifestation of this curvature. The space-time that is being curved by the Earth’s presence is Minkowski space-time. In outer space, far away from massive bodies like the Earth, apples don’t fall off apple trees because space-time assumes the undistorted, or “flat” form of Minkowski space-time.

When Einstein proposed the general theory of relativity in 1916, science, technology, and mankind’s exploration of the universe were still so primitive that there was almost no overlap between the theory’s predictions and observation. In fact the only point of contact was a peculiarity in the orbit of the planet Mercury.

Mercury, Earth, and the other planets all pursue elliptical orbits around the Sun. Thus, as a planet orbits the Sun, it moves from a point of closest approach to the Sun, called perihelion, out to a point of greatest distance, called aphelion, and then back to perihelion. In the case of Mercury the difference between its perihelion and aphelion distances from the Sun—29 million versus 43 million miles—is nontrivial and is a result of the little planet’s pronouncedly elliptical orbit. Somewhat surprisingly. Mercury’s orbit is not fixed.

Although the planets are all much less massive than the Sun and therefore have correspondingly tiny gravitational influences, each planet exerts its own small gravitational effect on the others, and each planet, in its turn, responds to the combined gravitational effects of all the other planets. Thus a planet’s orbit is calculated as if it is alone in orbit around the Sun—the gravitational master of the solar system—and then the small gradual changes due to the presence of the other planets are calculated as departures, or “perturbations,” from the simplified one-planet-on-its-own picture. One effect of the other planets’ gravitation is that Mercury’s orbit slowly rotates in its own plane. This means that successive orbits of Mercury do not exactly repeat each other but build-up a rosette-like pattern. Astronomers, who use the direction from the Sun to a planet’s perihelion as one of the measures that fix the orientation of the planet’s orbit, see this as a progressive change of Mercury’s perihelion, which they label “precession of perihelion.”

In the second half of the 19th century it became apparent that Mercury’s perihelion was precessing slightly faster than expected, and by the start of this century thorough analysis of Mercury’s orbit had shown that its anomalous perihelion precession was 43 arcseconds per century. (A circle is divided into 360 degrees; a degree into 60 arcminutes; and an arcminute into 60 arcseconds.) The effect, which corresponds to completion of a full circle in three million years, was of minute proportions. Not only did the 19th-century celestial mechanics notice the discrepancy, but they measured it accurately—a tribute to the keenness of their instruments and calculations (all done by hand). As the innermost planet of the solar system. Mercury lies closest to the Sun and therefore, of all the planets, it experiences the greatest curvature of space-time that the solar system has to offer, so it was no coincidence that it was the first planet to betray noticeable non-Newtonian behavior.

In spite of the slightness of Mercury’s deviation from good Newtonian form, it had prompted astronomers to advance a variety of explanations for the puzzle. None of them, however, had much observational basis or any general acceptance.

It was at this point that Einstein and his general theory of relativity arrived on the scene. The physicist Clifford Will describes things as follows:

In November, 1915, while struggling to put the finishing touches on the general theory, Einstein was well aware of the problem of Mercury, and it was one of the first calculations he carried out using the new theory. To his delight, he found a precession of 43 arcseconds per century! He later wrote, “for a few days I was beside myself with joyous excitement,” and told a colleague that the discovery had given him palpitations of the heart.

Since then, the development of science and mankind’s exploration beyond the Earth have provided new tests of Einstein’s theory. The most demanding of these experiments involved the American Viking soft-lander on Mars. Accurate measurements of the time taken for radio signals to travel from Earth to the Viking space-probe on the Martian surface and back to Earth have shown that the Sun’s curvature of space-time in the inner solar system agrees with the general relativity prediction to one part in a thousand.

This success was a success not only for Einstein but also for Minkowski. Einstein’s theory presupposed Minkowski’s flat space-time—because gravity curves space and time together, not separately, any description of gravity as a curvature of space-time can be successful only if Minkowski put space and time together successfully in the first place.

Einstein’s theories of relativity are, at their core, theories of invariance, not relativity. “Invariance” in his theories says that the particular situation of the observer should not affect his description of physical laws. The laws of physics, as perceived by an observer cruising along the highway in a limousine and another observer sitting at the side of the highway, should be the same. This simple but very powerful idea guided Einstein toward both his theories of so-called relativity. Arnold Sommerfield, the distinguished physicist and colleague of Einstein, remarked that: “Relativity theory is accordingly an Invariantentheorie of the Lorentz group. The name relativity theory was an unfortunate choice: the relativity of space and time is not the essential thing, which is the independence of laws of nature from the viewpoint of the observer.”

In 1987, and in the same vein, physicist David Jackson wrote: “The whole worldview of modern theoretical physics can be traced back to the fundamental postulate or idea that physical phenomena do not change just because you happen to be moving by, instead of standing still, when observing them.”

The misnomer of Einstein’s theories has caused the widespread impression that they somehow support a universal relativism. They do not. The parallel between the worlds of physical science and human conduct is a very dubious one, and, if it is made, it argues in favor of absolutism, not relativism.

But what about time? Although science has successfully unified space and time, nonetheless time remains utterly different from space. It flows. Time can be multiplied by any constant you choose, but it won’t stop flowing.

Where does this flow come from? Is it something happening in the external world, or is it something imposed on the world by the mind? Is time a river or is life a journey?

Science gives a clear answer. Life is an immense journey of the spirit; what we see as the flow of time is a consequence of our spirits’ flight through time. When we consider the external world as a four-dimensional proposition, then time’s flow and associated conventions, such as past, present, and future, evaporate. (No criticism of humble, and often easily dismissed, convention is intended. Rather, it is suggested that convention is the stuff of life.) Mathematician Hermann Weyl described the four-dimensional situation as follows: “The objective world simply is, it does not happen. Only to the gaze of my consciousness, crawling upward along the life line of my body, does a section of this world come to life as a fleeting image in space which continuously changes in time.”

This seems a little unreal, but, nonetheless, it is an inescapable implication of the way space and time go together. Weyl’s use of the word “crawling,” however, may be questioned on grounds of insufficient dynamism. If one second is the time equivalent of 186,000 miles of distance, then evidently the mind doesn’t crawl through time, but moves along lickety-split.

Neither Weyl nor science were the first to see life this way. “Man springs out of nothing, crosses time, and disappears forever in the bosom of God” was Tocqueville’s view of life. And Rilke said: “L’avenir est fixe, cher Monsieur Kappus, c’est nous qui sommes toujours en mouvement dans l’espace infini.” He wrote this in 1904—four years before Minkowski’s 1908 lecture identifying time as the fourth dimension and 22 years before Weyl’s writings—so, although Rilke’s words are astonishingly similar to Weyl’s, they are a poet’s independent statement rather than an echo of science’s nascent rumblings of discovery.

Although the notion that “the objective world simply is, it does not happen,” has a hard strangeness, its implication that the flow of time is much more subjective than objective is not so strange when we think about it.

Undoubtedly our experience of time takes place on multiple levels. A biological clock must be a foundation stone and very likely our mind is able to read this clock better than is generally supposed. Many people know the experience of wanting to wake up in the morning at a certain time, but, for some reason, not being able to use an alarm clock. “I must wake up at 7:00,” they say to themselves before going to sleep, and come the morning, presto, they wake up within a couple of minutes of 7:00. But the flow of time is much more than a matter of biological clocks. At the mind’s higher levels, where life is actually lived, where we love and hate, have successes and failures, the flow of time becomes a very subjective business—a matter of spirit, of passion, and of emotion.

When our spirit is aroused it grips the fabric of time very differently than when it is relaxed. When we are positively engaged with the external world, we stride through time. If we are in love and in the company of our loved one, on an adventure with friends, or within sight of a long-sought-after objective, time seems to zip by so that we don’t even notice it. But when we are negatively engaged with the world—if circumstances become threatening—our spirit dawdles, and time drags. Most people know how five minutes in the dentist’s chair can seem like five hours of mundane existence elsewhere. And the presence of the threat of violent death almost freezes time. In Life and Fate, Vasily Grossman, who was a World War II war correspondent, describes the hellish fighting at Stalingrad: “The distortion of the sense of time during combat is something still more complex. . . . And as for hand-to-hand fighting—that takes place quite outside time.”

These examples of time’s elasticity in life as we experience it, as the bittersweet adventure it is, square with a flow of time that springs from the mind, not the external world. The view is far from new. It bubbles under the surface of ordinary language, often bursting into the open in everyday sayings, such as: “Life is a journey, not a destination.”

What is new is that the description of life as an active journey now rests on the sure quantitative foundation of exact empirical science. Science has no idea what consciousness is, but, whatever it is, movement through time must be its key aspect. We can no more stop our headlong rush into the future and continue to live than an airplane can stop its motion through the air and stay in the sky.

The implications of this, however, have not sunk in to the scientific or the medical or the general awareness. Sleep, for instance, is a subject where, very likely, the realization that life is an odyssey of the spirit will aid understanding.

Articles about sleep in learned journals or encyclopedias suggest that it is a mysterious business—its purpose unknown. For example. Dr. Allan Rechtschaffen of the University of Chicago, who has pursued sleep’s secret with studies of crocodiles, rats, and humans, says: “Perhaps sleep does not have a function. . . . Perhaps we should accept our failure to isolate a specific function for sleep as evidence for nonexistence of a function. But it is hard to believe that we spend almost one-third of our lives in a behavioral state that has no function at all.”

Conventionally, we think that we sleep because we are tired. When we say this we mean the physical fatigue that follows an active day, and we look on sleep as a natural respite. H.G. Wells expresses this view in “The War of the Worlds” when he describes the differences between Martians and humans: “Their physiology differed strangely from ours, their organisms did not sleep, any more than the heart of man sleeps. Since they have no extensive muscular mechanism to recuperate, that periodical extinction was unknown to them.”

But if we keep the flight of the spirit that we know as life in mind, then the speculation that sleep’s first purpose must be to rest the spirit, not the body, suggests itself. After all, it is the spirit, not the body, that moves through time; the body is the home in which the spirit dwells. One second of time is equivalent to 186,000 miles, so the 16 waking hours of a typical day are equivalent to 24,000 billion miles, or II round trips to Jupiter. Would you be puffed-out after making 11 nonstop round trips to Jupiter without any artificial aid whatsoever? You bet. Martians probably need sleep too.

The ravages of an epidemic that swept Europe and America in the 1920’s reveal the close links between sleep, the flow of time, and life. This dreadful disease, a sleeping disorder known as encephalitis lethargica or sleeping sickness, first appeared in Europe in 1917, spread to America, and then faded away, so that by 1927 it had disappeared. In its wake the disease left five million victims of whom one third died. Those who succumbed died in a deep coma or in an agonized sleeplessness beyond sedation.

Most survivors were devastated. All sorts of neurotic and psychotic disorders, including extreme and exaggerated forms of Parkinson’s disease, dogged them. The neurologist Oliver Sacks, who has devoted himself to the clinical observation, care, and treatment of these people, describes their postepidemic fate: “The illness started to cool or congeal, and states of immobility and arrest. Parkinsonian, catatonic, melancholic, apathetic, started to roll in a great sluggish tide over the survivors, enveloping them in singular and scarcely accessible states of trance, abeyance, or stillness. Patients so affected were put away in chronic hospitals, nursing homes, lunatic asylums, special colonies—and totally forgotten.”

The most unfortunate survivors never returned to life—for the most part they merely existed. In 1966, Dr. Sacks took charge of a group of postencephalitic patients at a suburban New York hospital, one of the very few remaining such groups in the world. He found that they were “motionless and speechless all day in their chairs, totally lacking energy, impetus, initiative, motive, appetite, affect or desire; they registered what went on about them without active attention, and with profound indifference” and concluded that lack of will “forms the empty heart of such states.”

Clearly the inability to sleep made the disease’s victims physically lethargic, but the crucial effect was the victims’ loss of will; their loss of spirit. No longer able to sleep, their spirits had no respite from their flights through time so they became exhausted and went into suspension.

Treatment of these patients with L-DOPA, a drug used for the relief of Parkinson’s syndrome, brought dramatic recovery. The patients regained their animation and interest in themselves and the world. “One patient, who had been totally transfixed physically and mentally for over thirty years, intensely rigid, completely motionless and mute, showed no reaction whatever as the dose was built up, and then suddenly—in the space of five seconds or less—’awoke,’ jumped to her feet, ran down the corridor, and burst into voluble conversation with the dumbfounded nursing staff on her ward. . . . The first awakenings nearly always gave intense and unmixed joy to the patients.” Sadly, many of these recoveries were not sustained. Although some patients enjoyed an enduring restoration to life, others tended to develop more or less severe behavior disorders within a few months of their awakening, in spite of continued treatment with L-DOPA.

Encephalitis lethargica robbed its victims not only of their spirits, but also their sense of time. In the most extreme cases they entered a timeless state devoid “of all sense of history and happening.” After “awakening,” one patient was full of allusions and stories all relating to 1926, “her last year of real life before her illness closed round her.” When asked about this, “she said she knew perfectly well that it was 1969 and she was 64, but that she felt as if it was 1926 and she was 21, and that she couldn’t imagine what it was like being older than 21.”

Existence is an eventless drifting on the currents of time, while life is a flight through time. Encephalitis lethargica’s ghastly effects suggest that sleep, far from being a functionless waste of time, makes the difference between existence and life; it is the key that transforms us from time’s tumbleweeds into time’s eagles.

The appreciation of life as a flight of the spirit through time may be novel and interesting; however, it may also seem to be rather exotic. Nonetheless, it has important consequences. We will conclude with consideration of one of them.

A feature of 20th-century Western civilization is the rationalist mentality—the low-grade, logical-positivist tone—of its intellectual and cultural elites. The general assumption, usually unstated, is that everything of importance in the external world and the life of the mind has been, or soon will be, put on a rational basis. Even God is expected to fall within the rationalist scope.

“How do you reconcile God’s goodness and infinite power with suffering?” is one form of questioning God’s design. Russian Communists of the 1920’s, for example, argued that there could be no God because if there were. He would have arranged for the large Siberian rivers to flow south and water the arid lands of central Asia, instead of flowing north into the frozen Arctic wasteland.

The scientist, and winner of the Nobel Prize for Medicine, Sir Peter Medawar puts it somewhat less crudely: “Nowhere is this incongruence [between transcendent answers and the world of experience] more apparent than in the problem of evil and of reconciling the idea of a benevolent God with the natural dispositions and events that are so difficult to reconcile with it.”

In a recent conversation, Sidney Hook asked: “Is it expecting too much to ask that at some point as adults we would be blessed with the understanding to see the justice, if it exists, in the succession of events over which He rules so that not a sparrow falls to the ground without the Father knowing?” He amplified that if, perchance, he were to wake up in God’s presence, he would say: “Lord, you didn’t give me enough evidence.”

A world in which God’s design were intellectually accessible, a world where the Siberian rivers flowed south, would be very satisfying in many ways; it would also, of necessity, be a straitjacket. The human heart can feel God’s presence, but to expect that human reason should be able to grasp His design is extremely unreasonable—and quite arrogant and silly. Among other things, it leaves no scope for mankind’s further development.

The Earth is five billion years old. If we assume that the evolution of the Sun into a red giant will set the upper limit on the Earth’s age, then it has about another five billion years to go. This does not necessarily set the upper limit on mankind’s future. The possibility of travel to other stars with planetary systems of their own and the attendant prospect of migration to the solar systems of future generations of stars as yet unborn pushes this limit a factor of 10 or 20 further into the future. In this context mankind is extremely young; the species has just been born, and an enormous avenue of time beckons. Although many vicissitudes may lie along the way, it is reasonable to hope that mankind will travel down this avenue. Couple this prospect with a recollection of mankind’s growth and achievements during the last 2,000 or 3,000 years and it is clear that the potential future growth of mankind’s horizons, including his intellectual horizons, lies beyond our wildest imaginings.

A boundless prospect? Yes. But some reflection suggests that if God’s design—even in only very hazy outline—lay within the grasp of 20th-century intellectuals, the future would look a lot more like a dead end. The discoveries and intellectual developments to come would uncover the plan in more and more detail, until, finally, it lay fully revealed. As God’s plan, not any old plan, it would, in some sense, be a bedrock plan and therefore unchangeable. Life’s meaning; the future, on timescales short and long; all would become transparent to human intellect. Everything—events small and large, in the near future or the distant future—would be predictable.

But in this place where everything was predictable, nothing could “happen” in the real sense of the word. As God’s plan became fully accessible to the human intellect so the flow of time would dissipate and, ultimately, with the arrival of “full understanding,” it would evaporate completely. It is hard to see how people in this dreaded state would differ from the zombies who survived encephalitis lethargica. In such a world only the children and the stupid would actually live.

Consideration of the flow of time and the big picture suggest that Balzac got it right when he said: “I believe in the incomprehensibility of God.”

So, is this a call to abdicate from reason? A call to abandon individual responsibility and surrender to fatalism?

No, it isn’t. As we travel along time’s avenue we must use the light of intellect to show us the way. But we must remember that it is passion, not intellect, that powers us through time. The intellect is the handmaiden of the passions, and reason is only part, a small part, of intellect.

Our conjectures about time suggest that Western civilization’s rationalist emphasis is overdone and misguided. It mistakes a secondary aspect of human nature for something primary and, as a result, it discusses many vital questions backwards.