Chasing an elusive particle

When one year ends and another begins, that is an occasion to take stock of a field in order to see where we are and which way are we headed. In mid-December last year, I attended an international conference on gravitation and cosmology held in the pleasant surroundings of Mobor beach, Goa. It is perhaps a testimony to the interesting subject that the conference rooms were well filled despite the lure of the beach.

As a matter of fact, the conference was part of a series in which one conference is held every four years, the series having started in 1987 in Goa. Thus, for many of us who had attended the first conference, this was a nostalgic occasion. We could recall the warmth of Goan welcome and such highlights as the boat trip on the river, courtesy the chief minister, the gastronomic heights attained by Goan food and the pleasant weather. But to me the academic interest lay in seeing how the subject had advanced over the past 24 years, and how the present conference was opening out new vistas for the subject.
A major source of interest, of course, lay in what the CERN experiment on the Large Hadron Collider (LHC) had produced. The hope was that the ultra-energetic collisions of particles would produce the much sought after Higgs Boson, popularly known as the God’s particle. For, theory suggests that this particle provides the mechanism for generating masses of basic particles. Since mass is a fundamental property of a particle, it is argued that the Higgs Boson is God’s means for achieving this. So far God has not obliged and clear-cut evidence of the
God particle remains
elusive.
It is frequently claimed that the LHC replicates the Big Bang — the explosive conditions at the time of the creation of the universe. I wish the scientists had avoided the unnecessary hype. To put the conditions in proper perspective, the energy generated per particle in the LHC is around a thousand-billionth part of the energy per particle produced in the era of inflation, that is, very rapid expansion of the early universe. So to claim that you have simulated the Big Bang is like a schoolboy claiming after winning a high jump medal that he is close to jumping on to the moon.
The cosmologists were on stage claiming how accurately they are able to describe the very early universe. Indeed technology has come to the assistance of the cosmologist as much as it has helped the particle physicist. So many astronomical measurements can now be performed reliably accurately, measurements that would not have been possible a decade or two ago. However, these measurements need a model of the universe to explain and the model starts with several speculative assumptions. For example, the astronomer is told that only four per cent of all matter in the universe is visible to him with the best of the telescopes at his disposal. What about the remaining 96 per cent? That is made of dark matter and dark energy, neither of which can be proved to exist by any laboratory or astronomical means. Although very persuasive but indirect reasons are advanced by the Big Bang cosmologists for believing that the universe does have the above dark matter-dark energy domination, an objective look at the present scenario reminds one of the Hans Anderson story, The Emperor’s New Clothes.
The Goa meeting was also dominated by the major efforts under way for Indian participation in the worldwide gravitational radiation detection programme. Like the light rays and their other versions like radio waves, infrared, X-rays etc., the astronomer is trying to add gravitational waves to his observing repertoire. The trouble is that they are too feeble to be readily seen — one may compare the attempt with the observing of candle light located as far away as the sun! Still, high technology does hold out the hope of observing these waves emerging in special circumstances.
There has been an indirect method of demonstrating that waves causing such feeble effects do, in fact, exist. In 1979, monitoring of two stars going round each other showed that the orbital period of the binary system was decreasing steadily. The general theory of relativity suggests that such a binary system radiates gravitational waves thereby losing energy. And the loss of energy results in the shrinking of the binary orbit, thereby resulting in the decrease of the period. In this particular case the result so calculated agreed exactly with the observed rate of decrease. While such indirect confirmation adds to our belief in the validity of the relativity theory, a direct demonstration of the existence of gravitational waves will be hailed as a major discovery.
Both these examples are the consequences of a major revolution that took place in the first two decades of the 20th century. The theory of relativity and the quantum theory both added extra perspective to classical physics, thus raising hopes that the goal of understanding the universe in the large and the tiniest of structure in the small was nigh. The 20th century was therefore seen as the century of physics and distinguished scientists declared their expectation that the end of physics was imminent. Now, nearly a century later, the expected revolution in understanding the universe has not yet occurred. Perhaps we are realising the truth of the cautionary remark of the controversial but highly perceptive cosmologist Fred Hoyle. The remark, made in 1970 when several cosmologists were declaring that with their findings the universe was more or less understood, runs like this: “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 this 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.”

The writer, a renowned astrophysicist, is professor emeritus at Inter-University Centre for Astronomy and Astrophysics, Pune University Campus