Context: 

Eminent Indian astrophysicist and founder of Hoyle–Narlikar Theory of Gravity passed away in Pune at the age of 87.

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• He was a science communicator and a Padma Vibhushan awardee. 
• 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.
• He was the Founder-Director of the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune.

Hoyle–Narlikar Theory of Gravity

• The theory suggests that the mass of an object is influenced by interactions with all other matter in the universe. 
• It is an alternative to Einstein's General Relativity that proposes the universe is in a steady state and continuously expanding. 
• This theory also incorporates the concept of a "creation field" that continuously generates new matter in the universe, particularly hydrogen atoms, to maintain a constant density as the universe expands. 
• The Hoyle–Narlikar theory of gravity is rooted in Mach’s Principle, which posits that:
• The mass of every object is influenced by its interaction with every other object in the universe.
• Albert Einstein was inspired by Mach’s Principle but could not fully incorporate it into his theory of general relativity.
• Hoyle and Narlikar went further by:
• Literally integrating Mach’s Principle into their theory.
• Proposing that inertia (resistance to change in motion) arises from the collective gravitational interaction with all matter in the universe.

Concept of the C-Field

• Hoyle–Narlikar theory introduces the concept of a "Creation Field" (C-field):
• A hypothetical negative-energy field.
• Responsible for the continuous creation of matter.
• This was proposed to support the Steady-State Theory of the universe:
• The universe has no beginning and will exist forever.
• In contrast to Big Bang cosmology, which states:
• The universe began ~13 billion years ago and has been expanding since.
• When the C-field becomes strong enough at a point in space:
• A new hydrogen atom appears, supporting the idea of a constantly regenerating universe.