Hoyle–Narlikar theory of gravity

The Hoyle–Narlikar theory of gravity{{cite web |url=http://www.time.com/time/magazine/article/0,9171,898186,00.html |archive-url=https://web.archive.org/web/20111213230334/http://www.time.com/time/magazine/article/0,9171,898186,00.html |url-status=dead |archive-date=December 13, 2011 |title=Cosmology: Math Plus Mach Equals Far-Out Gravity |date=Jun 26, 1964 |publisher=Time |accessdate=7 August 2010}} is a Machian and conformal theory of gravity proposed by Fred Hoyle and Jayant Narlikar that originally fits into the quasi steady state model of the universe.{{cite journal |title=A New Theory of Gravitation |author1=F. Hoyle |author2=J. V. Narlikar |date=1964 |journal=Proceedings of the Royal Society A |doi=10.1098/rspa.1964.0227|bibcode = 1964RSPSA.282..191H |volume=282 |issue=1389 |pages=191–207 |s2cid=59402270 |url=http://ayuba.fr/mach_effect/hoyle-narlikar1964.pdf }}

The gravitational constant 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 for electrodynamics.{{cite journal |journal=Reviews of Modern Physics |volume=67 |issue=1 |pages=113–155 |doi= 10.1103/RevModPhys.67.113 |title=Cosmology and action-at-a-distance electrodynamics |author=Hoyle, Narlikar |date=1995|bibcode = 1995RvMP...67..113H |url=http://ayuba.fr/mach_effect/hoyle-narlikar1995.pdf }} When Richard Feynman, as a graduate student, lectured on the Wheeler–Feynman absorber theory in the weekly physics seminar at Princeton, Albert Einstein was in the audience and stated at question time that he was trying to achieve the same thing for gravity.{{cite book |last1=Feynman |first1=Richard P. |title=Surely You're Joking, Mr. Feynman! |date=1985 |publisher=W. W. Norton & Company |at=Part II, The Princeton years, pp. 91 et seq. | isbn=978-0393316049|title-link=Surely You're Joking, Mr. Feynman! }} Stephen Hawking showed in 1965 that the theory is incompatible with an expanding universe, because the Wheeler–Feynman advanced solution would diverge.{{cite journal | doi =10.1098/rspa.1965.0146 | last1=Hawking |first1=S. W. |date=20 July 1965 |volume=286 | issue=1406 |title=On the Hoyle–Narlikar Theory of Gravitation | journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | pages=313–319 |url=http://ayuba.fr/mach_effect/hawking1965.pdf |bibcode=1965RSPSA.286..313H | s2cid=122705280 }} However, at that time the accelerating expansion of the universe was not known, which resolves the divergence issue because of the cosmic event horizon.{{cite journal | doi =10.2514/6.2015-4082 | last1=Fearn |first1=H. | last2=Woodward | first2=J.F. | last3=van Rossum | first3=N. |date=23 July 2015 |title=New Theoretical Results for the Mach Effect Thruster | journal=AIAA Joint Propulsion Conference |url=https://arc.aiaa.org/doi/abs/10.2514/6.2015-4082 | url-access=subscription }}

The Hoyle–Narlikar theory reduces to Einstein's general relativity in the limit of a smooth fluid model of particle distribution constant in time and space.{{cite journal

| last = Rodal

| first = José

| title = A Machian wave effect in conformal, scalar--tensor gravitational theory

| journal = General Relativity and Gravitation

| volume = 51

| issue = 5

| pages = 64

| date = May 2019

| issn = 1572-9532

| doi = 10.1007/s10714-019-2547-9

| bibcode = 2019GReGr..51...64R

| s2cid = 182905618

}} Hoyle–Narlikar's theory is consistent with some cosmological tests.{{Cite journal |last1=Canuto |first1=V. M. |last2=Narlikar |first2=J. V. |title=Cosmological tests of the Hoyle-Narlikar conformal gravity |journal=The Astrophysical Journal |volume=236 |date=15 February 1980 |pages=6–23 |url=http://ayuba.fr/mach_effect/canuto1980.pdf |doi=10.1086/157714|bibcode=1980ApJ...236....6C }} Unlike the standard cosmological model, 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 that would also prevent violation of conservation laws, in order to keep the mass density constant as the universe expands.{{cite web

|author1=Vinodh Ilangovan

|author2=K. Manish Sharma

|author3=P. Chitra

|date=23 January 2010

|title=Jayant Narlikar's Cosmology

|website=NCBS news

|url=http://news.ncbs.res.in/archivednews/story/jayant-narlikars-cosmology

}}{{cite journal

|last1=Narlikar |first1=Jayant V.

|date=March 1974

|title=Mini-bangs in cosmology and astrophysics

|journal=Pramana

|volume=2

|issue=3

|pages=158–170

|url=http://repository.ias.ac.in/41206/1/35-Pub.pdf

|doi=10.1007/BF02847326

|bibcode=1974Prama...2..158N

|s2cid=123001024

}} The low-temperature cosmic background radiation would not originate from the Big Bang but from metallic dust made from supernovae, radiating the energy of stars.{{cite journal |title=Inhomogeneities in the Microwave Background Radiation interpreted within the framework of the Quasi-Steady State Cosmology |author1=J.V. Narlikar |author2=R.G. Vishwakarma |author3=Amir Hajian |author4=Tarun Souradeep |author5=G. Burbidge |author6=F. Hoyle |doi=10.1086/345928 |journal=Astrophysical Journal |volume=585 |issue=1 |pages=1–11 |year=2003 |arxiv=astro-ph/0211036|bibcode = 2003ApJ...585....1N |s2cid=15618626 }}{{cite journal |doi=10.1016/0375-9601(83)90927-1 |date=1983 |pages=75–76 |issue=2–3 |volume=99 |journal=Physics Letters A |title=Cosmic microwave background spectrum in the Hoyle–Narlikar cosmology |author1=J. V. Narlikar |author2=N. C. Rana |bibcode = 1983PhLA...99...75N |url=http://ayuba.fr/mach_effect/narlikar1983.pdf }} However, the quasi steady-state hypothesis is challenged by observation as it does not fit into WMAP data.{{cite web |url=http://www.astro.ucla.edu/~wright/stdystat.htm |title=Errors in the Steady State and Quasi-SS Models |author=Edward L. Wright |accessdate=7 August 2010}}