The Illusiveness Of Time

Salvador Dali’s painting, “The Persistence of Memory,” is a splendid illustration of a deep mystery — the concept we call time. This surreal painting shows ants devouring a clock and time melting into oblivion. Is time an illusion that melts away as depicted in the painting or a fundamental reality that weaves the fabric of the cosmos with space?

Throughout history, humans have been intrigued by the nature of time. Philosophers like Plato, who contemplated time as immortal, and Newton, who elevated time as eternal, might not accept the death of time. However, the last century witnessed the descent of time from immortal to mortal through Albert Einstein’s equations. Now, the descendants of Einstein are trying to annihilate time, which had been wounded in the revolution unleashed by the theory of relativity.

Theoretical physicist and cosmologist Carlo Rovelli points out: “We never really see time. We say we measure time with clocks, but we see only the hands of the clocks, not time itself. And the hands of a clock are a physical variable like any other. So in a sense we cheat, because what we really observe are physical variables as a function of other physical variables, but we represent that as if everything is evolving in time.”

In other words, the dynamics of the universe are not progressing as evolution in time — the currently held notion in science — but as a network of correlated variables. Time emerges as an effect of the actions of correlated variables. This is similar to saying that temperature results from the interaction of a large number of molecules. Similarly, time is the manifestation of the interaction of some variables, rather than a fundamental quality of the universe.

In classical physics, time is a river flowing simply in the forward direction. The observer or external forces like gravity have no impact on the flow of time. Everything we know surfaced, survived and departed during the course of this river, such as men and women, science and music, thoughts and feelings. Nothing could endure but time. Like an arrow shot by the Big Bang, time traveled (existed) for about 13.7 billion years along with its anomalous twin “space.”

The general theory of relativity demonstrated that clocks in a stronger gravitational field tick at a slower rate while the special theory of relativity argued that clocks moving at high speeds will appear to tick slower than non-moving ones. As a modern day example, atomic clocks on board GPS satellites move faster by about 45,900 nanoseconds (which is one-billionth of a second) a day because they are in a weaker gravitational field as they are at a higher altitude than atomic clocks on the earth’s surface. Similarly, GPS clocks run slower by about 7,200 nanoseconds a day, as predicted by special theory of relativity, owing to the fact that the satellites have orbital speeds of about 3.9 km/second in a frame centered on the Earth. To offset these time variations the satellite clocks are reset before launch to compensate for these predicted effects. This is the consequence of Einstein’s theory, something that was unimaginable for the scientific community when Einstein predicted it decades ago.

Even the time-span of our present day will change in a strong gravitational field. “If you feel there aren’t enough hours in a day, just wait,” says Max Tegmark, a cosmologist at the Massachusetts Institute of Technology. “In a few hundred million years, tidal friction will have slowed Earth’s rotation to make the day 25 hours long.”

If time is a dimension like space as suggested by the theory of relativity, it must be plausible to go back and forth in time as we do in other dimensions, such as up and down, left and right and forward and backward. Yet, in our universe the cosmological arrow of time is not known to reverse direction since the beginning of the universe.

Contrary to our expectations, however, the laws of physics do not discriminate between past, present and future. We are obsessed with time and time keeping and it follows us like a shadow all the time. Physics tells us that all moments exist equally, at once. It’s only our perception that distinguishes the present from the past or future. Or, as cosmologist Tegmark puts it, “If life were a movie, physical reality would be the entire DVD: Future and past frames exist just as much as the present one.”

Though back (past) and forth (future) time travel is permitted by the laws of physics, it is riddled with paradoxes. Among the most well known is the “twin paradox’ in which one twin travels at relativistic speeds (comparable to that of light) through the universe for many years leaving his twin brother behind on earth. When he returns he would have aged much less than his sibling. The theory of relativity dictates that in a fast moving frame of reference all clocks, and thus aging, would move slowly.

Another paradox offers an even grimmer outcome. What if you travel back in time and murder your grandfather? Some physicists suggested the laws of physics must always conspire to prevent travel into the past and thus the impossibility of such a paradox. However a few others believe that such actions simply cause space-time to branch off into a new parallel universe that doesn’t interfere with the current one.

Modern science is not the first to attempt to comprehend the illusive nature of time. Mythology likewise sought such answers too. For instance, in Devi Bhagwata Purana, Narada asks Vishnu about the meaning of Maya, to which Vishnu replies that it is the illusion generated as a consequence of our interaction with the physical world.

The view is echoed in Buddhism. “From the Buddhist perspective, time is the experience of being present right now, in this very moment. We in the West, however, like to measure things. In this way, clock time gives us a sense of coherence and stability. But in terms of our inner lives, no time exists except for what is happening in the present moment,” says Joan Halifax, a Zen Buddhist and a distinguished scholar at the Library of Congress.

The subjective nature of time is implicit in human life, not just in cosmology or physics. Some events speed up time for us, while others make it crawl. “Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That’s relativity,” Einstein once explained.

Neuroscientists examining how the brain perceives time say that the sensation of the passage of time depends on how richly the memories are laid down. Tragic events are likely to be perceived as more recent than they really are or events that are not registered as strongly.

Many researchers believe that information and the mode of processing provide the sense of past and future. It is the “flow of information” rather than the “flow of time” that creates this impression — much like a system stores past information (memory) to be recollected and focuses attention on the most recent information.

Often, biologists refer to a biological clock based on which our cellular actions are carried out. So if we are completely insulated from our surroundings, the biological clock might function to generate the perception of time passing by.

But not everyone agrees. “Time has little impact on biology,” says Michael West, a gerontologist who teaches at the University of California, Berkeley. “From a gerontologist’s standpoint, biological time is not wear-and-tear, it’s a genetic program,” says West. “It’s sort of like a time bomb. The cells are programmed to last just long enough for us to bear children, and no longer.” The absence of clocks in our system do not guarantee an eternal life; we will fall apart anyway.

At another level we relate this illusive time to death. In Sanskrit, Kala means time and the Hindu mythology refers to Kala (Yama) as the personified god of death. It’s no surprise that time and death are synonyms in Puranas. The conversation between Nachiketas and Yama is the theme of Kathopanishad, one of the 108 Hindu scriptures of the Vedanta philosophy.

Nachiketas to Yama : “Some say that when man dies he continues to exist, others that he does not. Explain, and that shall be my third gift.”

Did time begin with space at the big bang? Our current models of the universe emphasize this supposition and it should end with space. The second law of thermodynamics, often called the “death warrant of universe,” asserts that the entropy (disorder) of the universe must increase and thus the cosmological arrow of time must always go forward. Thus cause precedes effect.

All physicists agree on the absence of universal time, because time is a matter of perspective. We can divide time periods in any unit from years to nanoseconds or even beyond. What is the smallest interval of time that can exist? Quantum theory says that it is Planck time, which is equal to 10^-43 seconds. Below that the meaning of time loses any physical meaning. So we have to say the universe came into existence when it was 10^-43 seconds old. What if reality unfolded even at a lower time interval? There are no answers at least for now.

On grander scales, time should not be larger than 13.7 billion years, the current age of the universe. Yet, we do not know if time had the same rate of flow in every phase or part of the universe. This is why some physicists argue that the veil of illusion attributable to time must be removed to learn the truth. Theoretical computations show that the expansion of the universe at an accelerated rate may also be the result of our false notion of time. They anticipate a subsequent revolution in physics would be a cosmos depicted without the constraint of time. But, what if the universe is itself an illusion followed by life?

Time is the most familiar experience we deal with yet we don’t know much about it. Black holes provide us a clue to what one can call the “end of time.” The intense gravitational force slows and ultimately freezes time. For an observer outside the black hole, a falling object would appear frozen in time.

“The black hole teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but,” wrote John Wheeler, the visionary physicist who coined the term “black hole.”

As one can imagine, the pursuit of the real nature of time or its illusion is profoundly complex. But that doesn’t impede modern scientists from trying to crack the code. The latest attempt is by Sean Carroll, a Caltech Physicist. His book, From Eternity to Here: The Quest for the Ultimate Theory of Time, released in January 2010, offers a lucid and fascinating discussion about the nature of time. He hypothesizes that our universe may be a relatively young member of a big family and that in several of our sibling universes time runs in the reverse direction. Some others, he argues, don’t experience time at all; once a universe cools off and reaches maximum entropy, there is no past or present.

In the section “Aranya Parva” in the Mahabharata, Yama disguised as Yaksha posed many questions to challenge Yudhistra.

Yaksha asked: “What is the greatest wonder in the world?”

Yudhishthira replied: “Every day, men see creatures depart to Yama’s abode and yet, those who remain seek to live forever. This verily is the greatest wonder.”

As Lee Smolin, a theoretical physicist, once commented: “So, what is time? Is it the greatest mystery? No, the greatest mystery must be that each of us is here, for some brief time, and that part of the participation that the universe allows us in its larger existence is to ask such questions. And to pass on, from schoolchild to schoolchild, the joy of wondering, of asking, and of telling each other what we know and what we don’t know.”