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Most students meet cosmology as a settled story: the universe began in a Big Bang and has been expanding ever since. Jayant Narlikar spent much of his career arguing for an alternative, and at the same time built one of India's most important science institutions. You do not have to agree with his cosmology to learn from how he worked. This post covers his life and ideas from authoritative sources, a calculation of the Hubble time you can do with Class 11 units, and what students can take from him.
Who was Jayant Narlikar?
According to the Nature India obituary, Narlikar was born on 19 July 1938 in Kolhapur, Maharashtra. His father, Vishnu Vasudev Narlikar, was a noted mathematician. After his early education at Banaras Hindu University he went to the University of Cambridge for a PhD under the astronomer Fred Hoyle. He returned to India in 1972 to join the Tata Institute of Fundamental Research, where he built a group of young theorists who went on to lead fields from gravitational waves to observational astronomy.
The IUCAA tribute page records that he died peacefully in his sleep at his home in Pune on 20 May 2025. His honours, the obituary notes, included the Padma Bhushan in 1965, the Padma Vibhushan in 2004 and the UNESCO Kalinga Prize for popularising science in 1996. His wife, the mathematician Mangala Narlikar, is the subject of our post on her work in mathematics teaching.
What was the Hoyle-Narlikar theory?
In 1964 Hoyle and Narlikar published A new theory of gravitation in the Proceedings of the Royal Society. The abstract says the theory gives the same results as Einstein's for everyday, large-scale phenomena, so it passes the classical tests of general relativity, but differs in its implications for the universe as a whole. In their theory the sign of the gravitational constant is fixed rather than chosen, and its size follows from the average density of matter. They put it memorably: this would let a cosmologist "know how hard he will hit the ground if he is unfortunate enough to fall over a cliff." The theory also says there can be no empty universe, and the smallest possible universe contains two particles.
The Nature India obituary describes it as an early attempt to treat gravity as action at a distance, rooted in Mach's principle: the idea that a body's inertia depends on all the other matter in the universe.
Why did he question the Big Bang?
Hoyle and Narlikar felt the Big Bang model was mathematically unsatisfactory because of its singularity, a starting point where quantities such as density become infinite. The obituary quotes a line he often used: "Division by zero is not allowed." They championed the steady-state model, in which the universe has no beginning and new matter keeps appearing as space expands, and later developed the quasi-steady-state cosmology.
Most cosmologists today accept the Big Bang model, and the obituary is clear that Narlikar's alternative remained outside the mainstream. Our post on George Gamow and the Big Bang explains the evidence that persuaded them. What made Narlikar valuable was that he kept testing the standard view instead of simply accepting it.
A worked example: the Hubble time
Both pictures start from the same observation: galaxies recede with speed proportional to distance, v = H₀d. The quantity 1/H₀, called the Hubble time, sets the time scale of the expansion.
Take H₀ = 70 km/s per megaparsec, a round value often used in textbooks, and 1 megaparsec = 3.086 × 10^19 km.
Convert H₀ to s⁻¹. H₀ = 70 km/s ÷ 3.086 × 10^19 km = 2.27 × 10^−18 s⁻¹.
Invert. 1/H₀ = 1 / 2.27 × 10^−18 = 4.41 × 10^17 s.
Convert to years. One year is about 3.156 × 10^7 s, so 1/H₀ = 4.41 × 10^17 / 3.156 × 10^7 ≈ 1.4 × 10^10 years, about 14 billion years.
In the Big Bang model this is close to the age of the universe. In a steady-state universe, where H₀ never changes, 1/H₀ is the time in which distances grow by a factor of e (about 2.7), and the universe itself has no age. The same number means different things in different models.
Common mistakes: forgetting to convert megaparsecs to kilometres, which leaves you with mixed units, and confusing a megaparsec with a million light-years. A parsec is about 3.26 light-years. Our post on Edwin Hubble has the history of the measurement.
Why does IUCAA matter?
In 1988, the obituary says, Narlikar founded the Inter-University Centre for Astronomy and Astrophysics in Pune, starting in a cramped apartment. Telescopes are expensive and observing time scarce, so IUCAA was designed to let scholars from universities across India share facilities and research time. The IUCAA tribute calls it a "role model" institute for growing astronomy groups at Indian universities. He also wrote popular science and science fiction, and was an outspoken critic of astrology and pseudoscience.
What can a student take from Narlikar's way of working?
Ask what would prove an idea wrong. He questioned the Big Bang on mathematical grounds. When you learn a law, ask what observation would contradict it.
Keep units honest. Cosmology is unit conversion on a grand scale. Write units at every step, as in the example.
Explain for others. He wrote for children and the public. Explaining a chapter to a younger sibling shows you what you do not yet understand.
Build for others. IUCAA shared resources. Share notes and solutions in your study group.
If cosmological ideas are hard to picture, the Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing, so you can go through redshift, Hubble's law and gravitation one idea at a time.
Try it now: repeat the Hubble-time calculation with H₀ = 67 km/s per megaparsec and see how the answer changes.
