Time in lines and cycles
“I never think of the future – it comes soon enough”. Albert Einstein
It is certainly fair to suggest that the concept of time begins within the confines of personal human consciousness. The way that people interpret time is neither universal nor cast in stone, but rather the interplay between various factors including culture and religion. In general, time is viewed in one of two ways; simply put, it can be viewed in the form of a line or in the form of a circle.
Many things in nature occur in recurring cycles. Days, tides, seasons, and years are all cyclic in nature. They happen over and over again. Perhaps because we are surrounded by such patterns, most forms of life have come to adapt to and react in cyclic ways. Molting, hibernation and mating, for example, follow distinctive patterns that repeat in the natural world year after year. It stands to reason, then, that man's habitat and lifestyle would be affected by such naturally occurring cyclic patters too. Beyond that, it is possible to conceive of the idea that there are circular rhythms happening around us right now that are simply too grandiose to measure or even comprehend in one lifetime: re-creations of the entire universe, the persistence of earthquakes, continental shift, and even life and death itself.
The concept of time as a circle is an ancient one that has been incorporated into the mythology and religion of numerous cultures, from the Mayans and Aztecs to Hindus and Christians. Though different in description, each believes in some form of continuous time, either through life after death or rebirth. Others view the endless circle of time from the perspective of the universe as a whole. “Many cosmologists continue to believe that previous universes may have existed before the Big Bang and that other universes may yet rise out of the ashes of our own.” (Aveni). Whether concerned with human life cycles or the potential life expectancy of the world as we know it, the spinning and rotating of days and millennia have been noted by people of varying religious beliefs and cultural backgrounds since the beginning of time.
The linear nature of time can be summarized by the concept of the “arrow of time,” a phrase coined in the 1930’s. It turns out that there are many obstacles to overcome when studying the arrow of time, the first of which is to figure out why it exists to begin with. Why do people recognize a past separated from a present time, which is, in turn, separated from the future? So far philosophers and physicists have not established a definite reason. Basic scientific laws, with few exceptions, are not dependent on time, but could work just as easily “backwards” as they do in our present forward-looking paradigm. In spite of that, processes like a cup breaking or milk mixing with coffee have come to be known as irreversible processes, because as far as we can tell, they only go one way. Glasses don’t generally pick themselves up off the floor and put themselves back together, and coffee doesn’t separate itself into hot coffee and cold milk after the two have been mixed. Though there is only one arrow of time, there are many different ways to look at it. The cosmological arrow of time is the one most people think of when they think of irreversible processes.
The cosmological arrow of time is the one viewed when we ponder the question of whether or not time could reverse itself. This is not the same thing as time travel. If the cosmological arrow were to reverse, we would relive the past in reverse order, not go back to the beginning and simply live it over again through to the present. It is possible that if the arrow of time were going backwards for life on another planet somewhere, they would remember what we would consider to be the future and grow younger as time goes on. If the cosmological arrow of time reversed on earth, broken glasses would indeed pick themselves up off the floor and begin the process of self-reconstruction on a regular basis.
Another way to view the arrow of time is from the perspective of thermodynamics. The thermodynamic arrow of time deals with the second law of thermodynamics, originally discovered by German physicist Rudolf Clausius in the 19th century. His version of the law stated that, “in a closed system, entropy increases,” meaning that everything has a tendency to go from order to disorder. Glasses break, but they don’t go back together again. Time moves in only one direction. Entropy, then, is essentially a measure of the advent of disorder. Ludwig Boltzmann changed the law into a question of statistics in 1872 by saying that entropy does not always increase, but it is merely most likely to. Despite general acceptance, Boltzmann ran into trouble when confronted by the Poincare cycles – a modern-day, scientific version of circular time.
Henry Poincare’s theorem introduced the idea that the hypothetical coffee would in fact eventually split back into hot coffee and cold milk. Even though that would take a very, very long time, he argued that that does not change the fact that it would ultimately happen.
A Poincare cycle is the amount of time that it takes for an object to go back to the way it was before it started changing in the first place. How long would it take for coffee to re-split itself into its most basic components? These cycles essentially conclude that after enough time has passed, entropy stays the same. Because of Poincare, the thermodynamic law was once again changed to say that, “in a closed system, entropy is likely to increase for any period of time short compared to the Poincare period for that system.” Until the millions and millions of years necessary for the coffee to split up have passed and the cycle completes itself, it is going to remain un-split up, moving along, not in circular time, but in linear time.
Another way to view the arrow of time is from a primarily psychological perspective. This “mental line” can be related to the second law of thermodynamics quite easily. As time goes by, more stuff happens and we acquire more memories. The idea that the amount of memories we have increases as we head toward the future can be equated to the concept of ever increasing entropy; the cup cannot be put back together – we can not undo what has been done in our lifetime. The fact that the future is anticipated causes us to continually live our lives moving linearly forward.
Linear time places the recorded past behind us to be remembered while we move forward, toward the unknown and what is yet to come. This makes past events unchangeable in the mind’s eye, while entire lives are spent preparing to edit the future.
Those who cannot remember the past are condemned to repeat it.
The future ain’t what it used to be.
- Aveni, Anthony. Empires Of Time. NY: Basic Books, 1989.
- Hawking, Stephen. The Theory Of Everything. Beverly Hills, CA: Phoenix Books, 2005.
- Hawking, Stephen, and Leonard Mlodinow. A Briefer History of Time. NY: Random, 2005.