20-05-2025
Astrophysicist Jayant Narlikar passes away: What is the Hoyle–Narlikar theory of gravity?
Eminent Indian astrophysicist, science communicator, and Padma Vibhushan awardee Jayant Narlikar passed away in Pune on Tuesday (May 20) at the age of 87.
He was best known for propounding the Hoyle–Narlikar theory of gravity (also known as conformal gravity), which he developed with English astronomer and professor Fred Hoyle in 1964. The theory sought to improve on Albert Einstein's General Theory of Relativity, published in 1915.
Here is a look at the Hoyle–Narlikar theory of gravity.
Link to Mach's principle
At the heart of the Hoyle–Narlikar theory of gravity is the Mach's principle, which says that the mass of every object in the universe is affected by its interaction with every other object. Einstein was greatly inspired by the principle, but could not incorporate it into his theory.
Hoyle and Narlikar took Mach's principle more literally and claimed to have successfully included it in their theory. They said that the inertia of an object, that is the tendency to resist change in its state of motion, arises from its interaction with all other matter in the universe.
'As Hoyle and Narlikar see it, a universe with nothing in it is impossible. There must be at least two particles, each to give mass to the other. The masses, and therefore the gravity, of the sun and the earth are partly due to each other, partly to more distant objects such as the stars and galaxies,' according to a report in Time Magazine.
Concept of C-field
The Hoyle–Narlikar theory of gravity also proposed a 'creation field' (C-field), a hypothetical negative-energy field responsible for the continuous creation of matter. This helped explain the steady-state cosmology, which said that the universe had no beginning and will endure forever.
The steady-state concept of the universe is essentially an alternative to 'Big-Bang' cosmology, which proposed that the universe originated 13 billion years ago with an expansion and has been expanding ever since. Hoyle and Narlikar said that if the universe were this old and always expanding, we would not see anything in the sky.
'Hence, Dr Hoyle and other proponents of a steady‐state situation have proposed that hydrogen atoms are continually being created in space to fill the void resulting from such expansion. It is to account for this that Dr Hoyle has proposed the existence of an unseen force, or C-field. When this field becomes strong enough, at any point in space, a new hydrogen atom appears,' according to a report in The New York Times.
The Hoyle–Narlikar theory of gravity was not widely accepted, especially after the discovery of the cosmic microwave background (CMB) radiation in 1965. CMB — considered as an echo or shockwave of the Big Bang — is the cooled remnant of the first light that could travel freely throughout the universe.
However, the theory continues to draw attention for its attempt to integrate Mach's principle in cosmology.
