According to many modern scientists, space and time were created at a singular event, referred to as the “Big Bang.” As a result, the universe started to expand and new stars and planets came into being. Time itself, nonetheless, is a relative matter as it is not always absolute. For example, both location and movement have an effect on the flow and the “speed” of time. Someone who is at the bottom of the ocean and another who is floating in space will have different measurements of time.
Imaginary Time and the Possibility of Reversing Time Flow
Consequently, scientists have agreed on the idea of “imaginary” time. This concept is similar to motions in space, meaning that if one can go south or north, forward and backward, technically such movements should also be possible and even plausible in time. Then time could flow in either or both directions, forward and backward.
But the perception of time is only in one direction. People can remember the past, experience the present moment and do not know what will happen in the future. If the universe starts contracting then there should be the possibility of time flowing backward. That would mean that one would not remember the past, but only the future and one would die first, then reverse to one`s birth, such as the fictional (and curious) case of Benjamin Button.
This kind of thought seems counter-intuitive. Hawking explains that time is experienced in one direction for the following three reasons or arrows of time: the psychological arrow, the second law of thermodynamics and the cosmological arrow.
Memory, the Psychological Perception of Time and the Second Thermodynamic Law
The psychological arrow refers to the human perception of time. It is the subjective experience and is rooted in how the brain works. Although still comparatively little is known about the functioning of the brain, it can be compared to the processes of a computer. In order to remember, energy or heat is necessary to produce memory and it can only exist in a backward motion, in the form of remembering the past.
According to the second law of thermodynamics, disorder, or entropy, increases with time. This fact is congruent with personal experience of the world. A cup that falls on the floor will break into pieces. It takes little time to destroy or create disorder, but one needs to spend energy to (re-)create order. A cup will never, in one`s experience, return in its whole form on the table. Similarly, if one buys a new car, it will deteriorate over time, with rust or through continued use. A room that is left alone will increase its disorder - dust and dirt will accumulate over time - until one cleans it; in other words, it would never clean itself on its own! Thus, all things may start at an ordered state, yet have the continual tendency to increase in disorder over time.
The Cosmological Arrow of Time and the Contraction of the Universe
The final reason for the forward flow of time is the cosmological arrow. The universe is expanding and hence one experiences time flow, but should it not be the reverse during its contraction? Hawking claims that it is a fallacy to believe such a thing. The problem may lie in the fact that scientists are dealing with imaginary time, which is seen as absolute and not with relative time that is one's immediate experience of the world itself. It would seem more plausible and less far-fetched to consider time to continue to flow forward in agreement with the other two arrows than to presuppose a contradiction to such experiences of the world.
In conclusion, although time could theoretically flow in a backward motion, it is not plausible due to the psychological perception of time and the second law of thermodynamics. Such ideas, however, are interesting to consider, especially when considering concepts and remote possibilities, such as time travel.
Sources
Hawking, Stephen. A Brief History of Time. New York: Bantam Books, 1998.
Readers may also enjoy Scientific Determinism and Heisenberg's Uncertainty Principle, Hawking's Definition of Scientific Theories about the Universe, and Time is Money and How the Clock Came to Shape Western Capitalism.
Arash Farzaneh - Arash Farzaneh is a writer and a language professor. He has a Master's degree in French literature with a minor in Psychology. Since his ...
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