A Star Has Faded: Remembering the Astrophysicist Jayant Vishnu Narlikar

The Wire

22-05-2025

The world lost Jayant Vishnu Narlikar, the astrophysicist, on May 20. In the course of his working career, Narlikar not only won for India a place in the pantheon of modern cosmology, but he showed the world how to stay true to the spirit of science.
Narlikar, with Fred Hoyle, espoused the 'steady state' theory of the evolution of the universe, which has been overtaken by the theory of the 'Big Bang.' However, all the question are by no means answered, and the work of Hoyle and Narlikar stays important, with the possibility that it may nose into relevance!
What follows is a short review of how our understanding has evolved.
Over centuries of contemplation through nights undisturbed by city lights, the ancients saw people, animals and gods in the heavens and wove theories and fables around them, as the first cosmologies. Traditional systems traced the movement of the sun and stars as circles around the earth and the paths of the planets as circles within circles. The method was quite accurate in predicting the position of planets and seasons and there was little reason, astronomical or philosophical, to doubt the model.
It was after the discovery of the telescope and Newton's laws of gravitation and motion, that the nature of the fainter, 'stellar' heavens was analysed. The bulk of stars were found to lie along a bright belt in the sky, called the Milky Way. This, we now understand, is because the earth is on the outside of a disk-shaped collection of stars, or galaxy. When we look along the plane of the disk, we see the vast number of stars that belong to the galaxy.
We know that the Milky Way is a galaxy because we can measure the distance to a star and this multitude of stars are found to lie together, while other stars are many times more distant. Distant stars are found to consist of groups of stars, or galaxies, and groups of galaxies, in their own right. The scale of distance was in millions of light years, or the distance light travels in millions of years. The farthest stars are over 10 billion light years away and this serves as an estimate of the age of the universe itself.
The last century was rich in theorising about the dynamics of this vast universe – the processes, the extent, and the question of whether the universe was changeless or turbulent. And much was discovered about the birth and death of stars, the nuclear fires that warmed them, supernovae, neutron stars and black holes. And the American astronomer, Edwin Hubble showed that all distant stars were receding, and the speed of recession was greater for stars that were further away – which implies an expanding universe!
The Milky Way. Photo: NASA.
The early 20th century saw two revolutions in scientific thought. These were the quantum theory and the theory of relativity. The quantum theory is the new way of thinking about matter at very small dimensions, like in atoms and atomic nuclei. At this minute scale, our everyday experience of 'smooth' changes gives way to changes in 'packets' or 'steps'. Even the conservation of energy does not hold for short durations and nature behaves more 'statistically' than according to rules.
The theory of relativity started from a discovery about the speed of light. Our usual experience is that if we are in a car that is moving at 100 kilometres per hour and we throw a stone backwards at 60 kmph, the stone will strike the ground at 100-60 = 40 kmph. But if a beam of light were shone from a speeding meteor, this speed would be the same both when measured by the meteor as well as on the ground!
Einstein solved the mystery with a new way of calculating speeds, which gave the correct, though unfamiliar results when things were moving at speeds near the speed of light, and stayed valid at ordinary speeds. And a consequence was that energy and mass are equivalent, by the famous E = mc² relation.
Einstein continued, to take into account the effect of gravity as well. As an isolated observer cannot distinguish acceleration from the effect of gravity, Einstein considered that gravity and acceleration were the same thing. With this basis, he rewrote the equations of motion, with the special way of treating space and time, and with the equivalence of mass and energy. In this representation, the presence of a mass got translated into a curve in the four-dimensional space-time, which then affected the motion of bodies just like gravity does!
Einstein then applied his new equations to the dynamics of the universe. One simplification was that stars and galaxies were not considered individually, but only 'on the average', as if the total mass of the universe were evenly spread, without 'lumpiness'. And the other, that the universe was essentially static, which is to say, not evolving or changing in any basic way.
But the approach did not lead to solutions that made good sense. An implication of the solutions was that the universe should contain a form of matter that had a quality that was the opposite of gravity – it repelled, with the force of repulsion increasing with distance! Einstein was forced to introduce an additional factor to remedy this. The Russian, Alexander Friedmann, suggested that these problems arose because of thinking the universe was static. If this condition were removed, the theory seemed to behave itself! The start of the theories of the expanding universe.
The image of an expanding universe implies that in the past the universe was smaller and at some time it must have been of zero dimension. In the 1940s, George Gamov proposed that the universe may have set out as a primeval atom that suddenly exploded, with tremendous density and heat, and become the origin of all matter and space. As this entity expanded, with particles and energy moving outwards, it would pass through stages of being just photons, then free electrons and then, neutral hydrogen atoms. And thus, over millions of years, the hydrogen would spread out into space, form collections as clouds that collapse into stars, then galaxies, and so on.
The Big Bang and expansion of the universe. Photo: NASA.
The theory has now been greatly refined and has passed many tests and can account for many things about the universe. But at the time, it sounded so fantastic, that the astrophysicist, Sir Fred Hoyle mockingly dubbed the theory the 'Big Bang', a name that has stuck.
One of the problems with the theory, at the time, was that parameters then available put the age of the universe at two billion years. This was short of geological evidence on the earth, of four to five billion years, and some galaxies were over ten billion years old. The figure now computed is in better agreement, but in the 1940s, this was a serious snag.
Gamov had also proposed that the early universe, being intensely hot, would have emitted radiation. Any traces of this emission, in the form of uniform background radiation, would be evidence of that first, blazing fireball. But in the 1940s, no such radiation had been detected.
It was about then that Hoyle, with Herman Bondi and Thomas Gold, proposed an alternate theory. The theories till then had been based on a 'cosmological principle', that the universe was homogenous and the same in all directions. Hoyle went a step further, that the universe was also the same at all times , or in a steady state .
This is not to say that the there are no processes in the universe. Stars would still be born, collapse, synthesise the elements, explode as supernovae, crush into black holes… but the totality of the heavens would remain unchanged like a street scene is much the same through the afternoon, though hundreds come and go.
But what of the expansion of the universe, the receding of the farthest stars? Hoyle, Bondi and Gold said that this would be compensated by spontaneous 'creation' of matter everywhere in the universe. Like spontaneous creation of matter by gamma rays, and other phenomena that allow violations of conservation, in small quantities. As the universe has vast spaces of near vacuum, the required rate of production of matter is minute, only one atom of hydrogen per litre of space every billion years! And we have no experimental competence to measure anything so meagre as that!
The suggestion, in fact, is not far-fetched, if we consider the possible hypotheses: that all matter has always existed that all matter was created at some definite time, the moment of creation that matter is being continuously created.
The first possibility implies that in the infinite time, all free hydrogen in the universe would have formed stars and converted to the higher elements, which is not true. The second possibility is nothing but the big bang theory, which, at the time, had serious flaws. The third possibility, the steady state, was hence a reasonable alternative.
But the steady state theory relied not on observation or deduction but leaned on the 'perfect cosmological principle'. Was this not like the Ptolemaic reliance on the 'perfection' of the circle to justify a picture of the cosmos?
This was when Narlikar, a young research scholar at Cambridge got active and collaborated with Hoyle to develop a rigorous basis for the steady state theory.
Narlikar was born in Kohlapur, Maharashtra in 1938 and was educated at the Banaras Hindu University. He continued his studies in Mathematics and astronomy at Fitzwilliam House, Cambridge, to be selected as a research scholar by Fred Hoyle, in 1960.
During the early 1960s, Narlikar and Holye developed an efficient theory for the continuous creation of matter in the setting of Einstein's General Relativity Theory. Historically, what Newton's theory of gravitation did was to link two bodies 'at a distance', with no apparent connection between them. Einstein had replaced this 'action at a distance' or the idea of a 'field' with the force of gravity being due to the structure of space-time.
Hoyle and Narlikar now attempted a new theory of gravitation to support the creation hypothesis. Hoyle and Narlikar brought in an idea that mass and inertia of matter was not an intrinsic property but arose from interaction with distant bodies – the equation they developed relates the mass of any object with the total mass of the observable universe. The equation also implied the creation of new matter quite naturally, and not by the ad hoc insertion of new terms, like Hoyle had done earlier. The theory, in fact uses the energy of the universe's expansion itself to create the new matter!
Just about this time, however, researchers stumbled on a discovery – a uniform microwave radiation background in all space, the radiation that George Gamov had proposed! This was powerful ratification of the big bang theory, which so revived the big bang school that the steady state hypothesis began to sound like heresy! As other problems with the big bang theory had also been resolved, the rasion d'être of an alternate theory, read the steady state, now evaporated.
The steady state theory had also not made any specific assertion that could be established by experiment. Furthermore, the background microwave radiation had no explanation in the steady state theory. For all its intellectual validity, the steady state theory began to be, at best, of academic interest.
But Hoyle and Narlikar came out with a modified steady state theory, which permitted 'mini bangs' in localised 'bubbles' where the universe may expand and contract without creation. While the explanation has been viewed as 'contrived', Hoyle and Narlikar and Narlikar with others, have persisted with revisions and alternates, in keeping alive a line of research which cannot be abandoned just because some objections have been removed from a theory which still bristles with problems. This is all the more important in a field, where as one thinker said, we are like the fruit fly, who, based on a glimpse of humans during its brief hours of life, is trying to work out the nature of human genetics!
Cosmology is still not out of the woods, and when light begins to fall on the idea of dark matter, some of it may fall on the body of work of Narlikar and Hoyle.
Narlikar went on be elected Fellow of King's College and worked in the Institute of Theoretical Astrophysics at Cambridge. In 1972, he returned to India and managed the Theoretical Group for Astrophysics at the Tata Institute of Fundamental Research, Mumbai.
He became active in promoting the popularisation of science, authoring several books in English and Marathi, and was the founding Director of the Inter University Centre for Astronomy and Astrophysics, Pune, till 2003.
S. Ananthanarayanan has been writing columns for Indian newspapers on developments in science and technology for lay-person readers, and blogs at simplescience.in.