Give meaning to our everyday lives
'The arrow of time': In our part of the world the rainy season gives way to the dry season
If the philosopher Heraclitus is right, time inexorably goes forward. What was will never be again. But does not time go in cycles sometimes? We have the seasons – summer giving way to spring and to autumn and winter in cycles year after year. In tropical countries instead of four seasons we have two, the rainy season and the dry season, the monsoon rains followed by the heat of April.
The life of certain animals too follows a predictable pattern. The butterfly lays its eggs which become caterpillars which in turn become a chrysalis and finally becomes a beautiful butterfly again. But the seasons are not exactly the same, it is a different summer and a different winter. The butterflies though alike are not the same butterflies that laid the eggs. They are of another generation.
The physicist Arthur Eddington coined the phrase‘ the arrow of time’. In his book The Nature of the Physical World, he connected “Time’s Arrow” to the second law of thermodynamics. Originally concerned with the performance of steam engines it states that heat can only flow from a hotter body to a cooler one, ice melts and monuments will crumble. The link between this law and time can be illustrated with a film of a child who enters a china shop and riots breaking the crockery. If the film ran in the right direction, we would see the child enter the shop, run up and down the aisles, knock into shelves and break the china. But if we were to see the child walk backwards out of the shop and broken crockery pieces gather themselves and go back on the shelves, we would know that the film is playing backwards.
Prior to the second law of thermodynamics, the laws by the two giants of physics Isaac Newton and Albert Einstein did not incorporate a direction for time. The laws worked just fine, backwards or forwards. Take the example of the earth rotating around the sun governed by Newtonian laws. If we were to make a film from outer space whether we ran the film forwards or backwards we would not know the difference. The earth would still go around the sun.
The second law of thermodynamics incorporates an important concept – a measure of disorder, called entropy. In layman’s terms, things in our lives if left to themselves would disintegrate and become disordered. Think of a house. Without regular maintenance, it will go to rack and ruin and if abandoned for sufficiently long, disappear and become a mound of earth. Though entropy is a complex event we experience it all the time. A hot cup of tea left without drinking will cool, a cube of ice outside a refrigerator will melt into a puddle of water.
Entropy affects other aspects of our lives as well. Our bodies age, we lose muscle mass, we start slowing down mentally as well as physically. It affects relationships too. After marriage, there is the honeymoon period where couples experience exhilarating heights of passion. But with the advent of children and stress of balancing work life with housework and economic pressures, romance fades and the relationship becomes dull routine – unless couples take active measures to infuse energy into the relationship.
Entropy applies to larger things than our day to day lives. It applies to the Universe as well. The Universe began 13.7 billion years ago in a big bang. Since then it is evolving, new stars and planets are born and old ones die. The Universe is also expanding, the stars and planets are rushing away from each other. In the beginning,the Primordial Era, the Universe was without any stars, a swirling mass of glowing hot matter. Now we are in the Stelliferous Era, the age of stars. Stars do not go on forever but have a finite life.
Our sun too will one day die – six billion years from now. Before it dies it will expand into a red giant consuming the Earth and reducing it to a charred mass and if we still exist, and unless we have developed interstellar travel, civilization too will die. But the birth and death of stars will not last forever. Four trillion years from now all stars will die and the cosmos will enter its final phase, the Degenerate Era. Once all the stars die only black dwarfs; dark, dense decaying balls of degenerate matter will remain. Eventually, they too will be gone and the Universe will become a sea of photons all at the same temperature, absolute zero. The Universe will be at rest and unchanging. The arrow of time will end and time will stand still forever.
Does this depress you? Don’t worry, it will not happen for a long long time, a 10100 years to be more precise, a very large number indeed. You might question, if the arrow of time drives everything towards chaos and disorder how do we account for evolution? How did all the wonderful life forms that inhabit our earth evolve from lowly single-celled organisms? Isn’t evolution a violation of the second law of thermodynamics? But there is no paradox here. Though decline is inexorable between the beginning and the end there is room for complexity, just as in the Universe there is a time of growth of the stars. As an analogy think of a cup of cappuccino. Once you stir, it becomes a uniformly brown liquid but before, the cream will form beautiful swirling patterns of white in the brown coffee.
What lessons for life can we draw from an abstract law in physics? We learn that time does move inexorably forward. The only time we have available to live is now. The past doesn’t exist. It’s just memories in the present. The future doesn’t exist either. It’s just thoughts in the present. The great poet Omar Khayyám was right when he said, “The Moving Finger writes; and, having writ, Moves on: nor all thy Piety nor Wit. Shall lure it back to cancel half a Line, Nor all thy Tears wash out a Word of it.”
Don’t waste your time regretting past mistakes or worrying about future problems yet to happen. But between the beginning and the end of time, in the interval between birth and death, we have a glorious opportunity to engage with life, live according to our values, build and grow, in our relationships, our work and enjoyment of life. Remember, to maintain what we build we have to expend energy and work on them otherwise they will crumble into dust. As yet we have no answer to the question what is the meaning of the Universe but while we wait, we can give meaning to our everyday lives and pass on our legacy to future generations. That will endure to the ends of time.