We learn from history that Alexander from Macedonia, while a small boy, had expressed concern that his father Phillip, ruler of Macedonia, was conquering new territories at such a rate that nothing would be left for him to conquer. The concern was justified, if Phillip had come close to conquering all the territory on the Earth.
As we know now, this was far from the case. Nevertheless, given the horizon that encompassed the dealings of the Greeks those days, Alexander’s perception of the extent of the world was necessarily incomplete. For example, the Americans did not feature in that perception.
Just as rulers who declared themselves conquerors of the world, without really knowing how big the world is, scientists also delude themselves from time to time by their belief that the end of their discipline is nigh.
The end here signifies that all questions in the field have been answered and the discipline providing the answers has nothing more to decide except minor issues. What is not realised in such cases is that a whole new type of questions are waiting round the corner which our scientists were unaware because they were not yet ready to ask them.
It is interesting to see how one delusion gives way to another.
The geocentric theory, for example, was finally demolished and replaced by the heliocentric theory. The Sun was endowed with the importance of being the centrepiece of the solar system. The laws of Kepler and Newton gave dynamical proof of how the solar system operates. The Sun’s importance led to the firm belief that it occupies the central position in our Milky Way galaxy.
Indeed, the map of the Milky Way made by William Herschel put the Sun at the Galactic Centre. This belief was firm right up to the early 20th century. Astronomers suggesting otherwise were ignored or shouted down. But eventually new, improved telescopes and new observations dislodged the Sun from that so-called privileged position, placing it at a distance of 30,000 light years.
Likewise, around this time, astronomers had to abandon another of their holy cows: the belief that our Milky Way represents the whole of the universe. It came as a shock to them that many nebulae — faint cloudlike structures that were believed to be small systems in the Milky Way — were in fact galaxies like it, situated far beyond the Milky Way. Thus the universe was not confined to the Milky Way but extended far beyond.
It is not just the astronomers who discovered that the universe is richer than they believed. Down to earth physicists also have passed through a false sense of comfort that their subject has delivered all that was asked for and is getting ready to be shut down. Such a feeling had developed towards the last two decades of the 19th century. Newton’s laws of mechanics and gravitation had explained all one needed to know about motions of planets and satellites.
In the electromagnetic theory, Coulomb, Ampere, Volta, Faraday and Maxwell unravelled the intricate yet symmetric interaction between electricity and magnetism. The result of Maxwell’s equations was the conclusion that electromagnetic disturbances travel as a wave with the speed of light.
Indeed, the remarkable conclusion was that light itself is an electromagnetic wave with different forms showing up as radio waves, microwaves, infrared, etc. This 19th century achievement was paralleled by progress in understanding how heat energy operates, what are heat engines and what are the rules covering conversion of heat to mechanical energy and vice versa.
All these achievements led to the impression that most of the problems relating to nature were now understood and solved. Maybe some minor problems remained to be sorted out. Which is why, towards the end of the 19th century, the feeling was developing that the end of physics was near.
Indeed, two major revolutions in physics in the beginning of the 20th century — the theory of relativity and quantum theory — shattered this complacency. They required a complete overhaul of physics and the new order took some time to establish. Physics had not ended but was beginning anew.
Ironically, the developments of particle physics and cosmology led in the 1980s to the anticipation that physics was nearing an end! Speculations on how physics behaves at very high energy seemed useful in understanding how the universe behaved shortly after its origin in a Big Bang and vice versa. Stephen Hawking in his inaugural lecture on appointment to the chair once occupied by Newton, expected that physics was about to end. Both particle physics and cosmology were expected to help understand each other.
Instead they raised more questions and speculations like dark matter and dark energy. The understanding of grand unification of fundamental forces seems as remote as it did in the 1980s. So physics has by no means ended!
Fred Hoyle, the iconoclast cosmologist and an agnostic about Big Bang had these words of caution: “I think it is very unlikely that a creature evolving on this planet, the human being, is likely to possess a brain that is fully capable of understanding physics in its totality. I think it is inherently improbable in the first place, but, even if it should be so, it is surely wildly improbable that this situation should just have been reached in the year 1970.”
Hoyle made this remark at the 1970 Vatican Conference on Cosmology, when several supporters of Big Bang were claiming that the subject was nearing completion. In fact, many assumptions made with an air of certainty about the universe in 1970 had to be replaced by new ones in recent years again, with the same degree of certainty.
The writer, a renowned astrophysicist, is professor emeritus at Inter-University Centre for Astronomy and Astrophysics, Pune University Campus
