The Hoyle–Narlikar theory of gravity is a Machian and conformal theory of gravity proposed by

Fred Hoyle Sir Fred Hoyle FRS (24 June 1915 – 20 August 2001) was an English astronomer who formulated the theory of stellar nucleosynthesis and was one of the authors of the influential B2FH paper. He also held controversial stances on other sci ...

and

Jayant Narlikar Jayant Vishnu Narlikar (born 19 July 1938) is an Indian astrophysicist and emeritus professor at the Inter-University Centre for Astronomy and Astrophysics (IUCAA). He developed with Sir Fred Hoyle the conformal gravity theory, known as Hoyl ...

that originally fits into the quasi

steady state model In cosmology, the steady-state model, or steady state theory is an alternative to the Big Bang theory of evolution of the universe. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous ...

of the universe.

Description

The

gravitational constant The gravitational constant (also known as the universal gravitational constant, the Newtonian constant of gravitation, or the Cavendish gravitational constant), denoted by the capital letter , is an empirical physical constant involved in ...

''G'' is arbitrary and is determined by the mean density of matter in the universe. The theory was inspired by the

Wheeler–Feynman absorber theory The Wheeler–Feynman absorber theory (also called the Wheeler–Feynman time-symmetric theory), named after its originators, the physicists Richard Feynman and John Archibald Wheeler, is an interpretation of electrodynamics derived from the assu ...

for

electrodynamics In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

. When Feynman, as a graduate student, lectured on the Wheeler–Feynman absorber theory in the weekly physics seminar at

Princeton Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the ni ...

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

was in the audience and stated at question time that he was trying to achieve the same thing for gravity.

Incompatibility

Stephen Hawking showed in 1965 that the theory is incompatible with an expanding universe, because the Wheeler–Feynman advanced solution would diverge. However, at that time the

accelerating expansion of the universe Observations show that the expansion of the universe is accelerating, such that the velocity at which a distant galaxy recedes from the observer is continuously increasing with time. The accelerated expansion of the universe was discovered duri ...

was not known, which resolves the divergence issue because of the cosmic event horizon.

Comparison with Einstein's General Relativity

The Hoyle–Narlikar theory reduces to Einstein's

general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...

in the limit of a smooth fluid model of particle distribution constant in time and space. Hoyle–Narlikar's theory is consistent with some cosmological tests.

Hypothesis

Unlike the

standard cosmological model The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) associated with ...

, the quasi steady state hypothesis implies the universe is eternal. According to Narlikar, multiple ''mini bangs'' would occur at the center of quasars, with various creation fields (or C-field) continuously generating matter out of empty space due to local concentration of

negative energy Negative energy is a concept used in physics to explain the nature of certain fields, including the gravitational field and various quantum field effects. Gravitational potential energy Gravitational potential energy can be defined as being n ...

that would also prevent violation of

conservation law In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves over time. Exact conservation laws include conservation of energy, conservation of linear momentum, c ...

s, in order to keep the mass density constant as the universe expands. The low-temperature

cosmic background radiation Cosmic background radiation is electromagnetic radiation from the Big Bang. The origin of this radiation depends on the region of the spectrum that is observed. One component is the cosmic microwave background. This component is redshifted p ...

would not originate from the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

but from metallic dust made from

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

e, radiating the energy of stars.

Challenge

However, the quasi steady-state hypothesis is challenged by observation as it does not fit into

WMAP The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic mic ...

data.

Notes

Bibliography

* * * * {{DEFAULTSORT:Hoyle-Narlikar theory of gravity General relativity Physical cosmology Theoretical physics Theories of gravity