What Is the Nature of Time?
A few years ago researchers interested in the subjective perception of time arranged to have volunteers harnessed to a platform, raised a hundred feet into the air, and dropped into a net at an amusement park in Dallas, Texas. Before any of the twenty participants had a turn, they observed someone else being dropped. After this preview they were asked to shut their eyes and imagine the fall. They were told to press a button at the moment when they pictured the person beginning to drop, and again when they pictured the person landing. Then each subject took the plunge themselves. Afterward, they were asked to imagine their own fall and as before to press a button at the beginning and the end. The subjects’ mental playbacks of their own experience lasted significantly longer than both their imagined experience of others, and the actual experience. The researchers had expected this because people who have endured brief dangerous events, such as violent attacks and car accidents, often report that the events seem to have occurred in slow motion. But our memory of an event depends on two neural systems—that governing our perception of the event, and that governing its recording and recall from our memory. So one might ask, Do we really perceive dangerous events in slow motion, or do we just remember them that way? Do we have a single sense of time that becomes distorted, or does the clock of our perception of the event run at its usual pace, but the clock of our memory of the event slow down?
To investigate that issue the subjects were given a wristwatch that flashed random numbers and told to read the digits during their fall. The catch was that the digits flashed just a bit too quickly for them to make out—that is, too fast to make out in ordinary circumstances. If the stretching of time that affects the memory of such events also affects perception, the falling subjects would see the numbers as flashing more slowly, and be able to read them. But the subjects couldn’t read the numbers. Their memories recorded the events in slow motion but their perception clock was unaltered.
Perception and memory clocks are not our only measure of time. We seem to have many internal clocks, underpinned by different neural mechanisms. Much of our feeling for time comes from the clocks built into our bodies and visible in our environment. The principal clock in our environment, the rhythm of day and night, light and dark, is intimately connected to at least one clock in our bodies, the circadian rhythm. Living things—even unicellular organisms—have this biological rhythm that runs on a sleeping and waking cycle of about one day. In many animals this is governed by a biochemical process in which certain proteins accumulate, enter cell nuclei, degrade, and cycle back to their original state. The process is more complex in humans, and takes place in a part of our brain called the hypothalamus. In all animals the twenty-four-hour clock is only approximate. Human beings living in total darkness will have sleep/waking cycles lasting about twenty-five hours, while mice and fruit flies kept in darkness have cycles that are somewhat less than twenty-four. But under normal conditions, these biological clocks are reset each day, in humans when photoreceptors in the eyes and skin cells pick up light from the sun. Animals have other built-in bodily rhythms that run on much shorter cycles, such as the in and out of respiration and the pumping of our hearts, as well as certain wave patterns that occur in our brains. It is through all these internal clocks that we feel the passage of time.
The multiplicity of biological clocks leads to some interesting illusions—for example, in one experiment subjects were fooled into thinking that a flash of light preceded their pressing a key when actually it came afterward. Biologists and neuroscientists are interested in understanding the subjective aspects of our sense of time, and the physical, chemical, and biological mechanisms that produce them, and indeed these are fascinating topics. But although your own memory clock might slow when you’re tossed off a platform, for the rest of the universe it is business as usual. And so physicists, unlike biologists and neuroscientists, or saints and sages, ponder time’s mysteries from a less personal standpoint.
The starting point for physicists is to examine what we mean by time. Human language excels at capturing human feelings, but we shouldn’t let our language define our concept of reality. If you haven’t thought much about it, time is hard to define. It is an abstract concept derived and distilled from our experience. We describe the motion of projectiles and planets employing time, but time isn’t a material object. One can think of time as one thinks of space, as a coordinate that enables us to label events. The event of the opening of the heliport atop the World Trade Center has the coordinates 40 degrees 43 minutes north latitude, 74 degrees 1 minute west longitude, 1,350 feet above ground level, and the year 1972. From this point of view we can consider the universe as a four-dimensional space akin to the three-dimensional space we see around us. But time not only labels the moments events take place and orders them; it also assigns events a duration.
One of the first clocks used in physics, at least according to legend, was the pulse of Galileo, who used that rhythm to time the swing of a chandelier in the cathedral of Pisa. Today we use more reliable clocks, like the natural oscillations of atoms. For example, when an atom jumps from a higher energy state to a lower energy state, radiation is emitted. That radiation oscillates with a frequency determined by the difference in energy between the states. The radiation corresponding to the transition between two particular energy levels of the cesium-133 atom passes through exactly 9,192,631,770 cycles each second. I can say “exactly” here with confidence because since 1967 that has been, according to the International System of Units, the definition of a second. And so if we say the crystal in a quartz watch vibrates 32,768 times per second, we mean that if we started counting the oscillations of the crystal and the radiation simultaneously, at the precise moment the cesium radiation had gone through 9,192,631,770 cycles, the quartz crystal would be reaching its 32,768th vibration. This highlights an important related concept that is crucial to the definition of time as duration: the concept of synchrony. We measure the time one process takes by comparing it to some other standard process—like the ticks of a stopwatch—that has a concurrent beginning and ending.
This nice intuitive picture of time works well in everyday life, but between 1905 and 1916, Albert Einstein showed that it is only an approximation of the way nature really works. The approximation is perfectly fine if you don’t measure time too accurately, and you consider objects that are moving much slower than the speed of light, and that are in gravitational fields not much stronger than those we experience on Earth. But in truth, Einstein showed, those concepts upon which our ideas of clocks are based, especially synchrony, and even the fixed order of events, depend on the state of the observer—by which he did not mean the emotional state.
The fact that two events one perceives as simultaneous can, from the perspective of another observer, occur at different times, probably sounds somewhere between strange and wrong. It might help to look at the same effect with regard to space. Suppose a person standing in the aisle of an airplane bounces a ball on the floor. That passenger would report that the ball hit the floor at the same spot, over and over again. To an observer on the ground, however, the ball would not be returning to the same spot, but rather tracing a line across the sky at over 500 miles per hour. Both observers are right, from their own perspective. Analogously, different observers may disagree about whether events happen at the same time, and if the observers are moving fast enough relative to each other, that disparity can be noticeable. This is an important point for our later discussion of the nature of reality, so we’ll come back to it then.
The inability of moving observers to agree on simultaneity means that clocks can disagree, and that different observers can disagree on the duration of events. The referees working for the Guinness World Records 2010 watched as the world’s fastest hot dog eater downed sixty-six hot dogs in twelve minutes, but observers flying past at great speed would have measured the feast as having taken much longer. According to relativity, each clock measures its own local flow of time, and observers who are moving relative to each other, or are experiencing differing gravitational fields, will in general find that their clocks do not agree.
One can think of a clock as a kind of odometer for time. An odometer measures the distance you travel in journeying from one event to another, while a clock measures the duration that elapses between events. The distance an odometer measures depends on both the difference in the spatial coordinates of the two events—such as their latitude and longitude—and the path the odometer takes to get from one event to the other. According to relativity, the time a clock will measure between events also depends on the path the clock takes between the events. For example, suppose two fifteen-year-old twins watched the World Trade Center dedication in 1972, after which one was snatched up by aliens and whisked off on a very fast rocket ride, perhaps even passing near (but not too near) the powerful gravitational field of a black hole. If the abducted twin was returned to Earth and reunited with her sister at the dedication of a World Trade Center Memorial in 2013, the Earthbound sister would be fifty-six while the abducted twin might be just sixteen. Between the abduction and the reunion the odometer of the Earthbound twin would have registered many miles, and her clock an elapsed time of forty-one years. Her sister’s odometer would have registered many more miles—but her clock, perhaps only one year—between the same two events. Einstein showed that there is no contradiction in this; it is just the way time works. This effect was confirmed by experiment in 1971, in which a very accurate atomic clock was flown around the world and compared to an identical earthbound clock. The effect of the clock’s motion at those relatively slow speeds, however, amounted to a difference of only about 180 billionths of a second per circuit.
Since an hour spent in a moonlight stroll with a loved one does not feel the same as an hour spent justifying your work to a nasty boss, we are lucky to have our reliable cesium atoms, whose light will pass through 33,093,474,372,000 cycles each hour regardless of our state of mind. Though the biologist, the neuroscientist, and the physicist will all conclude that time depends on the observer, they mean it in different ways. To a physicist, time depends only on motion and gravity, and we have mathematical formulas that account for the relevant factors. These allow physicists to translate back and forth among different observers’ clocks, without any bias that might arise from the observers’ feelings entering into the physicists’ formulas.
When we humans slow down to smell the roses, the betadamascenone molecules that carry the smell continue their motion unaffected by our subjective feelings. But when the Earth exerts its gravitational pull, it does affect the clocks in the GPS systems that tell you how to get to the nearest florist. That’s how nature works, and it is nature’s gift—random as it may have been—that we evolved into beings with minds that can comprehend the difference.
Eternity is in love with the productions of time.
—WILLIAM BLAKE
Time gives spirituality a golden opportunity. People need a new way to live where time hasn’t become a kind of psychological enemy. Deadlines press upon us. There are only so many hours in the day. No matter how fast we move, all of us are running out of time. Religion hasn’t helped, because it tends to be grim about our time on Earth. What could be more depressing than the Puritan doctrine of “Sin in haste, repent at leisure”? If spirituality can free us from time’s psychological downside, everyday life would be transformed.
Leonard is at pains to precisely define and measure time. He also hits upon a favorite point made by science, that subjectivity is unreliable. If you are a physicist collecting data on hadrons, bosons, and the like, you don’t get to say, “My measurement changed because I have a migraine.” But people don’t use subjectivity to measure time; we use it to experience time. There is no other way. Time in all its aspects comes to us through our nervous system, as an experience in consciousness. Being conscious of time isn’t abstract and objective. It’s personal and participatory. And once we know how we participate in time, we will have an important clue about how to participate in the timeless.
The timeless? At this point I can imagine a wave of doubt coming from the reader, even a sympathetic reader. I’m not challenging the accuracy of the cesium-133 atomic clock, because there is no need to do so. Any aspect of time, including Einstein’s relative time, is a by-product of the timeless; in the preuniverse there is no time. Our very source is the realm of timelessness. The story of how time sprang from eternity is the real mystery, and it’s one that spirituality can solve. When you and I can experience the timeless, then phrases like “eternal life,” “the immortal soul,” and “a transcendent God” aren’t just wishful thinking. When we look at it closely, eternity doesn’t mean a long, long, long time. It means a reality where time is not present. But how do we actually get there?
Let’s establish a point where spirituality and science agree. Time is relative. It isn’t fixed. We don’t need Einstein to confirm this, because everyday life already does. Depending on the state of consciousness you are in, the flow of time changes. In deep sleep there is no experience of time. In dreams, time is completely fluid: an epoch can pass in a moment, or a passing moment can last an epoch. (A story about the Buddha has it that he shut his eyes for a few moments, and yet inside he was experiencing thousands of years past.) Leonard stepped off this train before it left the station. He argues that time coming to us “through our senses” isn’t the same as “the workings of the inanimate universe.” But there is much more to consciousness than the five senses. Birds, bees, and snow leopards would see a mountain, the sky, or the moon in different ways because those creatures possess unique nervous systems.
If you change the nervous system, the idea of objectivity breaks down. This holds true not just for animals but for us, too. In recent experiments Buddhist monks were shown to have brain waves in the gamma region that were twice as fast as the norm: 80 cycles per second instead of 40 cycles. Gamma waves are thought to be the brain’s way of holding the world together as a conscious experience. So Buddhist monks, by receiving twice the number of signals per second, are twice as awake, or conscious. Other people, operating on half-wakefulness, are sleepy and dull by comparison.
We can match this finding to other experiences. Quarterback Joe Namath reported that when he was “in the zone,” time seemed to stand still. The ball left his hand as if in slow motion, while at the same time the roar of the crowd disappeared, and he knew, with certainty, exactly where the ball would go; he even knew it would be caught. In other words, time cannot be detached from personal experience, which in turn means that no two people experience time in exactly the same way.
Subjective time, far from being an illusion, meshes quite well with post-Newtonian physics, where the notion of an objective observer was undercut long ago by relativity. If a space traveler’s starship begins traveling near the speed of light, his time, as observed by someone standing back on Earth, slows down. This is a basic principle in relativity. Yet even as time became slower than molasses on a winter’s day, as observed from Earth, the space traveler would register the clocks around him ticking off seconds, minutes, and hours in normal fashion. Likewise, since the gravitational field gets more and more powerful in the vicinity of a black hole, a faraway observer would see a space traveler’s time seem to slow down until it virtually stopped altogether as the traveler approached the black hole’s horizon—he would appear to take an infinite amount of time to cross that horizon and enter the hole. However, relativity is secondary to my main point, that some kind of nervous system is inescapable, and therefore so is the central role of experience. Science may not care, in objective terms, if Joe Namath felt time slow down; the timekeeper’s watch says it didn’t. It’s up to me, then, to show how subjectivity is actually reliable. In India’s spiritual tradition the zero state of consciousness is referred to as samadhi, where the mind enters pure consciousness. This state is an experience of an eternal timeless now. Here time does not exist as a measurable event. Only after pure consciousness splits into subject and object do we experience the flow of time.
Once again the findings of great sages mesh with quantum reality. (I apologize for giving the impression that all sages are either Indian or ancient. They cover the span of time, East and West. I give special weight to the ancients only because their spiritual observations have passed the test of time—whatever time turns out to be!) The underlying state of the universe is timeless. Before the first nanosecond of the Big Bang, there was only the potential for time in a dimension of all possibilities, after which quantum objects (e.g., energy, spin, charge, gravity) emerged. A potential doesn’t have a life span. It encompasses past, present, and future. The ground state of physics turns out to resemble the zero state of samadhi. Once these timeless possibilities begin to collapse into space-time events, our connection to eternity seems lost. That is an illusion, though, fostered by our dependence on clock time. You have always been eternal; you still are.
There is certainly a huge objection to the claim that we can experience eternity. How can the human mind think about the timeless when thoughts take time? Everything human takes time, from being born to lying on one’s deathbed. But the great sages noticed that the movement of thought is critical to time. If thoughts stop moving, so does time. We’ve all had a hint of this. When you say, “Sorry, I blanked out for a second,” you weren’t participating in time: the clock stopped. The Buddha took a more radical stance. He (and many other spiritual teachers) declared that when the mind stops, everything comes to a halt. It’s not just time that is the movement of thought—the whole universe is the movement of thought.
Take this insight seriously and you wind up with an earthshaking idea: the state of precreation thinks itself into becoming the universe. Infinity transforms itself into the finite. Using whatever vocabulary you prefer, a silent mind (belonging to God, Brahman, nirvana, the absolute) creates physical reality through a thought, because without a vibration or frequency, time cannot begin. The same is true of space. Without some kind of vibration, there is no Big Bang, no expanding universe.
Vibrations emerge from a silent, motionless source. Then, as time enters creation, it is adapted to whatever nervous system uses it, including our own. Snails, for example, have a neural network that experiences time in wide intervals, as long as five seconds, as if a snail is seeing the world in a series of snapshots taken five seconds apart. If you reach down and snatch a lettuce leaf away from a snail fast enough, the hungry creature will experience the leaf vanishing into thin air. A snail can’t make time speed up, but we humans have a special capacity: we can experience time at different speeds. Many versions of time are available to us, not just steady forward motion measured by the clock. We see the past repeat itself; we observe the cycle of life; we can take our imagination forward or backward; we feel time hang heavy, speed up, and even stop.
Medical doctors worry about “time sickness,” a generic term for disorders resulting from the speed of modern life. Too much speed leads to stress, which in turn leads to the higher levels of stress hormones connected to many lifestyle disorders, like heart attacks and hypertension. Time literally runs out for a certain percentage of the newly widowed, or the chronically lonely, for whom time is such a burden that they run the risk of premature death. That’s why it is so important not to merely describe time, as science does, but to understand it.
Changing your sense of self can give you more time, and improve its quality. A lot of research has been done on telomerase, a specific protein that seems to help cells live longer. The underlying theory is that telomerase keeps genes from unraveling and undergoing damaging mutations, so increased levels of telomerase may have a beneficial effect. Studies have shown that telomerase increases with positive lifestyle changes, and more than that, a person’s sense of well-being—particularly the positive psychological changes brought about by meditation—promotes telomerase activity. (A coauthor of this study from 2010 was Dr. Elizabeth Blackburn, professor at the University of California, San Francisco, who shared the Nobel Prize in Medicine for the discovery of telomerase.) Just as we can alter the way we metabolize food, we have control over how we metabolize all experiences, even one as abstract as time.
It boils down to this: Human beings stand on the cusp between time and the timeless. We are a lamp at the door, to use an ancient Vedic image. At any moment we can look into the manifest or the unmanifest, the visible or the invisible, the world of time or the infinite expanse of eternity. Once we escape the mind-made trap science has unwittingly laid, we find ourselves granted enormous freedom and power, but this mastery over Nature is not an endorsement of the use of blunt force. Instead of coercing the physical world to do our bidding, we can use consciousness to achieve anything at all. Once our minds can travel back to the source, we recognize ourselves as part of the creative process that gives rise to space, time, and the physical universe. Here is the true power of now.