Steady-state model

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In the Big Bang, the expanding Universe causes matter to dilute over time, while in the Steady-State Theory, continued matter creation ensures that the density remains constant over time. Big Bang and Steady-State Theory.png
In the Big Bang , the expanding Universe causes matter to dilute over time, while in the Steady-State Theory, continued matter creation ensures that the density remains constant over time.

In cosmology, the steady-state model or steady state theory is an alternative to the Big Bang theory. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous creation of matter, thus adhering to the perfect cosmological principle, a principle that says that the observable universe is always the same at any time and any place.

Contents

From the 1940s to the 1960s, the astrophysical community was divided between supporters of the Big Bang theory and supporters of the steady-state theory. The steady-state model is now rejected by most cosmologists, astrophysicists, and astronomers. The observational evidence points to a hot Big Bang cosmology with a finite age of the universe, which the steady-state model does not predict. [1] [2]

History

In the 13th century, Siger of Brabant authored the thesis The Eternity of the World, which argued that there was no first man, and no first specimen of any particular: the physical universe is thus without any first beginning, and therefore eternal. Siger's views were condemned by the pope in 1277.

Cosmological expansion was originally seen through observations by Edwin Hubble. Theoretical calculations also showed that the static universe, as modeled by Albert Einstein (1917), was unstable. The modern Big Bang theory, first advanced by Father Georges Lemaître, is one in which the universe has a finite age and has evolved over time through cooling, expansion, and the formation of structures through gravitational collapse.

On the other hand, the steady-state model says while the universe is expanding, it nevertheless does not change its appearance over time (the perfect cosmological principle). E.g., the universe has no beginning and no end. This required that matter be continually created in order to keep the universe's density from decreasing. Influential papers on the topic of a steady-state cosmology were published by Hermann Bondi, Thomas Gold, and Fred Hoyle in 1948. [3] [4] Similar models had been proposed earlier by William Duncan MacMillan, among others. [5]

It is now known that Albert Einstein considered a steady-state model of the expanding universe, as indicated in a 1931 manuscript, many years before Hoyle, Bondi and Gold. However, Einstein abandoned the idea. [6]

Observational tests

Counts of radio sources

Problems with the steady-state model began to emerge in the 1950s and 60s – observations supported the idea that the universe was in fact changing. Bright radio sources (quasars and radio galaxies) were found only at large distances (therefore could have existed only in the distant past due to the effects of the speed of light on astronomy), not in closer galaxies. Whereas the Big Bang theory predicted as much, the steady-state model predicted that such objects would be found throughout the universe, including close to our own galaxy. By 1961, statistical tests based on radio-source surveys [7] had ruled out the steady-state model in the minds of most cosmologists, although some proponents of the steady state insisted that the radio data were suspect.[ citation needed ]

X-ray background

Gold and Hoyle (1959) [8] considered that matter that is newly created exists in a region that is denser than the average density of the universe. This matter then may radiate and cool faster than the surrounding regions, resulting in a pressure gradient. This gradient would push matter into an over-dense region and result in a thermal instability and emit a large amount of plasma. However, Gould and Burbidge (1963) [9] realized that the thermal bremsstrahlung radiation emitted by such a plasma would exceed the amount of observed X-rays. Therefore, in the steady-state cosmological model, thermal instability does not appear to be important in the formation of galaxy-sized masses. [10]

Cosmic microwave background

For most cosmologists, the refutation of the steady-state model came with the discovery of the cosmic microwave background radiation in 1964, which was predicted by the Big Bang theory. The steady-state model explained microwave background radiation as the result of light from ancient stars that has been scattered by galactic dust. However, the cosmic microwave background level is very even in all directions, making it difficult to explain how it could be generated by numerous point sources, and the microwave background radiation shows no evidence of characteristics such as polarization that are normally associated with scattering. Furthermore, its spectrum is so close to that of an ideal black body that it could hardly be formed by the superposition of contributions from a multitude of dust clumps at different temperatures as well as at different redshifts. Steven Weinberg wrote in 1972: "The steady state model does not appear to agree with the observed dL versus z relation or with source counts ... In a sense, this disagreement is a credit to the model; alone among all cosmologies, the steady state model makes such definite predictions that it can be disproved even with the limited observational evidence at our disposal. The steady state model is so attractive that many of its adherents still retain hope that the evidence against it will eventually disappear as observations improve. However, if the cosmic microwave radiation ... is really black-body radiation, it will be difficult to doubt that the universe has evolved from a hotter denser early stage." [11]

Since this discovery, the Big Bang theory has been considered to provide the best explanation of the origin of the universe. In most astrophysical publications, the Big Bang is implicitly accepted and is used as the basis of more complete theories.[ citation needed ]

Violations of the cosmological principle

One of the fundamental assumptions of the steady-state model is the cosmological principle, which follows from the perfect cosmological principle and which states that our observational location in the universe is not unusual or special; on a large-enough scale, the universe looks the same in all directions (isotropy) and from every location (homogeneity). [12] However, recent findings suggest that violations of the cosmological principle, especially of isotropy, exist, with some authors suggesting that the cosmological principle is now obsolete. [13] [14] [15] [16]

Violations of isotropy

Evidence from galaxy clusters, [17] [18] quasars, [19] and type Ia supernovae [20] suggest that isotropy is violated on large scales.

Data from the Planck Mission shows hemispheric bias in the cosmic microwave background (CMB) in two respects: one with respect to average temperature (i.e. temperature fluctuations), the second with respect to larger variations in the degree of perturbations (i.e. densities). The European Space Agency (the governing body of the Planck Mission) has concluded that these anisotropies in the CMB are, in fact, statistically significant and can no longer be ignored. [21]

Already in 1967, Dennis Sciama predicted that the CMB has a significant dipole anisotropy. [22] [23] In recent years the CMB dipole has been tested and current results suggest our motion with respect to distant radio galaxies [24] and quasars [25] differs from our motion with respect to the CMB. The same conclusion has been reached in recent studies of the Hubble diagram of Type Ia supernovae [26] and quasars. [27] This contradicts the cosmological principle.

The CMB dipole is hinted at through a number of other observations. First, even within the CMB, there are curious directional alignments [28] and an anomalous parity asymmetry [29] that may have an origin in the CMB dipole. [30] Separately, the CMB dipole direction has emerged as a preferred direction in studies of alignments in quasar polarizations, [31] scaling relations in galaxy clusters, [32] [33] strong lensing time delay, [14] Type Ia supernovae, [34] and quasars & gamma-ray bursts as standard candles. [35] The fact that all these independent observables, based on different physics, are tracking the CMB dipole direction suggests that the Universe is anisotropic in the direction of the CMB dipole.[ citation needed ]

Nevertheless, some authors have stated that the universe around Earth is isotropic at high significance by studies of the cosmic microwave background temperature maps. [36]

Violations of homogeneity

Many large-scale structures have been discovered, and some authors have reported some of the structures to be in conflict with the homogeneity condition required for the cosmological principle, including

Other authors claim that the existence of large-scale structures does not necessarily violate the cosmological principle. [40] [13]

Quasi-steady state

Quasi-steady-state cosmology (QSS) was proposed in 1993 by Fred Hoyle, Geoffrey Burbidge, and Jayant V. Narlikar as a new incarnation of the steady-state ideas meant to explain additional features unaccounted for in the initial proposal. The model suggests pockets of creation occurring over time within the universe, sometimes referred to as minibangs,mini-creation events, or little bangs. [41] After the observation of an accelerating universe, further modifications of the model were made. [42] The Planck particle is a hypothetical black hole whose Schwarzschild radius is approximately the same as its Compton wavelength; the evaporation of such a particle has been evoked as the source of light elements in an expanding steady-state universe. [43]

Astrophysicist and cosmologist Ned Wright has pointed out flaws in the model. [44] These first comments were soon rebutted by the proponents. [45] Wright and other mainstream cosmologists reviewing QSS have pointed out new flaws and discrepancies with observations left unexplained by proponents. [46]

See also

Notes and citations

  1. ↑ "Steady State theory". BBC. Retrieved January 11, 2015. [T]he Steady State theorists' ideas are largely discredited today...
  2. ↑ Kragh, Helge (1999). Cosmology and Controversy: The Historical Development of Two Theories of the Universe. Princeton University Press. ISBN   978-0-691-02623-7.
  3. ↑ Bondi, Hermann; Gold, Thomas (1948). "The Steady-State Theory of the Expanding Universe". Monthly Notices of the Royal Astronomical Society. 108 (3): 252. Bibcode:1948MNRAS.108..252B. doi: 10.1093/mnras/108.3.252 .
  4. ↑ Hoyle, Fred (1948). "A New Model for the Expanding Universe". Monthly Notices of the Royal Astronomical Society. 108 (5): 372. Bibcode:1948MNRAS.108..372H. doi: 10.1093/mnras/108.5.372 .
  5. ↑ Kragh, Helge (2019). "Steady-State theory and the cosmological controversy". In Kragh, Helge (ed.). The Oxford handbook of the history of modern cosmology. pp. 161–205. doi:10.1093/oxfordhb/9780198817666.013.5. ISBN   978-0-19-881766-6. the Chicago astronomer William MacMillan not only assumed that stars and galaxies were distributed uniformly throughout infinite space, he also denied 'that the universe as a whole has ever been or ever will be essentially different from what it is today.'
  6. ↑ Castelvecchi, Davide (2014). "Einstein's lost theory uncovered". Nature. 506 (7489): 418–419. Bibcode:2014Natur.506..418C. doi: 10.1038/506418a . PMID   24572403.
  7. ↑ Ryle and Clarke, "An examination of the steady-state model in the light of some recent observations of radio sources," MNRAW 122 (1961) 349
  8. ↑ Gold, T.; Hoyle, F. (1 January 1959). "Cosmic rays and radio waves as manifestations of a hot universe". 9: 583. Bibcode:1959IAUS....9..583G.{{cite journal}}: Cite journal requires |journal= (help)
  9. ↑ Gould, R. J.; Burbidge, G. R. (1 November 1963). "X-Rays from the Galactic Center, External Galaxies, and the Intergalactic Medium". The Astrophysical Journal. 138: 969. Bibcode:1963ApJ...138..969G. doi:10.1086/147698. ISSN   0004-637X.
  10. ↑ Peebles, P. J. E. (2022). Cosmology's century: an inside history of our modern understanding of the universe. Princeton Oxford: Princeton University Press. ISBN   9780691196022.
  11. ↑ Weinberg, Steven (1972). Gravitation and Cosmology . John Whitney & Sons. pp.  463–464. ISBN   978-0-471-92567-5.
  12. ↑ Andrew Liddle. An Introduction to Modern Cosmology (2nd ed.). London: Wiley, 2003.
  13. 1 2 Elcio Abdalla; Guillermo Franco Abellán; et al. (11 Mar 2022), "Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies", Journal of High Energy Astrophysics, 34: 49, arXiv: 2203.06142v1 , Bibcode:2022JHEAp..34...49A, doi:10.1016/j.jheap.2022.04.002, S2CID   247411131
  14. 1 2 Krishnan, Chethan; Mohayaee, Roya; Colgáin, Eoin Ó; Sheikh-Jabbari, M. M.; Yin, Lu (16 September 2021). "Does Hubble Tension Signal a Breakdown in FLRW Cosmology?". Classical and Quantum Gravity. 38 (18): 184001. arXiv: 2105.09790 . Bibcode:2021CQGra..38r4001K. doi:10.1088/1361-6382/ac1a81. ISSN   0264-9381. S2CID   234790314.
  15. ↑ Asta Heinesen; Hayley J. Macpherson (15 July 2021). "Luminosity distance and anisotropic sky-sampling at low redshifts: A numerical relativity study". Physical Review D. 104 (2): 023525. arXiv: 2103.11918 . Bibcode:2021PhRvD.104b3525M. doi:10.1103/PhysRevD.104.023525. S2CID   232307363 . Retrieved 25 March 2022.
  16. ↑ Jacques Colin; Roya Mohayaee; Mohamed Rameez; Subir Sarkar (20 November 2019). "Evidence for anisotropy of cosmic acceleration". Astronomy and Astrophysics. 631: L13. arXiv: 1808.04597 . Bibcode:2019A&A...631L..13C. doi:10.1051/0004-6361/201936373. S2CID   208175643 . Retrieved 25 March 2022.
  17. ↑ Lee Billings (April 15, 2020). "Do We Live in a Lopsided Universe?". Scientific American . Retrieved March 24, 2022.
  18. ↑ Migkas, K.; Schellenberger, G.; Reiprich, T. H.; Pacaud, F.; Ramos-Ceja, M. E.; Lovisari, L. (8 April 2020). "Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX-T scaling relation". Astronomy & Astrophysics. 636 (April 2020): 42. arXiv: 2004.03305 . Bibcode:2020A&A...636A..15M. doi:10.1051/0004-6361/201936602. S2CID   215238834 . Retrieved 24 March 2022.
  19. ↑ Nathan J. Secrest; Sebastian von Hausegger; Mohamed Rameez; Roya Mohayaee; Subir Sarkar; Jacques Colin (February 25, 2021). "A Test of the Cosmological Principle with Quasars". The Astrophysical Journal Letters. 908 (2): L51. arXiv: 2009.14826 . Bibcode:2021ApJ...908L..51S. doi: 10.3847/2041-8213/abdd40 . S2CID   222066749.
  20. ↑ B. Javanmardi; C. Porciani; P. Kroupa; J. Pflamm-Altenburg (August 27, 2015). "Probing the Isotropy of Cosmic Acceleration Traced By Type Ia Supernovae". The Astrophysical Journal Letters. 810 (1): 47. arXiv: 1507.07560 . Bibcode:2015ApJ...810...47J. doi:10.1088/0004-637X/810/1/47. S2CID   54958680 . Retrieved March 24, 2022.
  21. ↑ "Simple but challenging: the Universe according to Planck". ESA Science & Technology . October 5, 2016 [March 21, 2013]. Retrieved October 29, 2016.
  22. ↑ Dennis Sciama (12 June 1967). "Peculiar Velocity of the Sun and the Cosmic Microwave Background". Physical Review Letters. 18 (24): 1065–1067. Bibcode:1967PhRvL..18.1065S. doi:10.1103/PhysRevLett.18.1065 . Retrieved 25 March 2022.
  23. ↑ G. F. R. Ellis; J. E. Baldwin (1 January 1984). "On the expected anisotropy of radio source counts". Monthly Notices of the Royal Astronomical Society. 206 (2): 377–381. doi: 10.1093/mnras/206.2.377 . Retrieved 25 March 2022.
  24. ↑ Siewert, Thilo M.; Schmidt-Rubart, Matthias; Schwarz, Dominik J. (2021). "Cosmic radio dipole: Estimators and frequency dependence". Astronomy & Astrophysics. 653: A9. arXiv: 2010.08366 . Bibcode:2021A&A...653A...9S. doi:10.1051/0004-6361/202039840. S2CID   223953708.
  25. ↑ Secrest, Nathan; von Hausegger, Sebastian; Rameez, Mohamed; Mohayaee, Roya; Sarkar, Subir; Colin, Jacques (25 February 2021). "A Test of the Cosmological Principle with Quasars". The Astrophysical Journal. 908 (2): L51. arXiv: 2009.14826 . Bibcode:2021ApJ...908L..51S. doi: 10.3847/2041-8213/abdd40 . ISSN   2041-8213. S2CID   222066749.
  26. ↑ Singal, Ashok K. (2022). "Peculiar motion of Solar system from the Hubble diagram of supernovae Ia and its implications for cosmology". Monthly Notices of the Royal Astronomical Society. 515 (4): 5969–5980. arXiv: 2106.11968 . doi:10.1093/mnras/stac1986.
  27. ↑ Singal, Ashok K. (2022). "Solar system peculiar motion from the Hubble diagram of quasars and testing the cosmological principle". Monthly Notices of the Royal Astronomical Society. 511 (2): 1819–1829. arXiv: 2107.09390 . doi:10.1093/mnras/stac144.
  28. ↑ de Oliveira-Costa, Angelica; Tegmark, Max; Zaldarriaga, Matias; Hamilton, Andrew (25 March 2004). "The significance of the largest scale CMB fluctuations in WMAP". Physical Review D. 69 (6): 063516. arXiv: astro-ph/0307282 . Bibcode:2004PhRvD..69f3516D. doi:10.1103/PhysRevD.69.063516. ISSN   1550-7998. S2CID   119463060.
  29. ↑ Land, Kate; Magueijo, Joao (28 November 2005). "Is the Universe odd?". Physical Review D. 72 (10): 101302. arXiv: astro-ph/0507289 . Bibcode:2005PhRvD..72j1302L. doi:10.1103/PhysRevD.72.101302. ISSN   1550-7998. S2CID   119333704.
  30. ↑ Kim, Jaiseung; Naselsky, Pavel (10 May 2010). "Anomalous parity asymmetry of the Wilkinson Microwave Anisotropy Probe power spectrum data at low multipoles". The Astrophysical Journal. 714 (2): L265–L267. arXiv: 1001.4613 . Bibcode:2010ApJ...714L.265K. doi:10.1088/2041-8205/714/2/L265. ISSN   2041-8205. S2CID   24389919.
  31. ↑ Hutsemekers, D.; Cabanac, R.; Lamy, H.; Sluse, D. (October 2005). "Mapping extreme-scale alignments of quasar polarization vectors". Astronomy & Astrophysics. 441 (3): 915–930. arXiv: astro-ph/0507274 . Bibcode:2005A&A...441..915H. doi:10.1051/0004-6361:20053337. ISSN   0004-6361. S2CID   14626666.
  32. ↑ Migkas, K.; Schellenberger, G.; Reiprich, T. H.; Pacaud, F.; Ramos-Ceja, M. E.; Lovisari, L. (April 2020). "Probing cosmic isotropy with a new X-ray galaxy cluster sample through the scaling relation". Astronomy & Astrophysics. 636: A15. arXiv: 2004.03305 . Bibcode:2020A&A...636A..15M. doi:10.1051/0004-6361/201936602. ISSN   0004-6361. S2CID   215238834.
  33. ↑ Migkas, K.; Pacaud, F.; Schellenberger, G.; Erler, J.; Nguyen-Dang, N. T.; Reiprich, T. H.; Ramos-Ceja, M. E.; Lovisari, L. (May 2021). "Cosmological implications of the anisotropy of ten galaxy cluster scaling relations". Astronomy & Astrophysics. 649: A151. arXiv: 2103.13904 . Bibcode:2021A&A...649A.151M. doi:10.1051/0004-6361/202140296. ISSN   0004-6361. S2CID   232352604.
  34. ↑ Krishnan, Chethan; Mohayaee, Roya; Colgáin, Eoin Ó; Sheikh-Jabbari, M. M.; Yin, Lu (2022). "Hints of FLRW breakdown from supernovae". Physical Review D. 105 (6): 063514. arXiv: 2106.02532 . Bibcode:2022PhRvD.105f3514K. doi:10.1103/PhysRevD.105.063514. S2CID   235352881.
  35. ↑ Luongo, Orlando; Muccino, Marco; Colgáin, Eoin Ó; Sheikh-Jabbari, M. M.; Yin, Lu (2022). "Larger H0 values in the CMB dipole direction". Physical Review D. 105 (10): 103510. arXiv: 2108.13228 . Bibcode:2022PhRvD.105j3510L. doi:10.1103/PhysRevD.105.103510. S2CID   248713777.
  36. ↑ Saadeh D, Feeney SM, Pontzen A, Peiris HV, McEwen, JD (2016). "How Isotropic is the Universe?". Physical Review Letters. 117 (13): 131302. arXiv: 1605.07178 . Bibcode:2016PhRvL.117m1302S. doi:10.1103/PhysRevLett.117.131302. PMID   27715088. S2CID   453412.
  37. ↑ Gott, J. Richard III; et al. (May 2005). "A Map of the Universe". The Astrophysical Journal. 624 (2): 463–484. arXiv: astro-ph/0310571 . Bibcode:2005ApJ...624..463G. doi:10.1086/428890. S2CID   9654355.
  38. ↑ Horvath, I.; Hakkila, J.; Bagoly, Z. (2013). "The largest structure of the Universe, defined by Gamma-Ray Bursts". arXiv: 1311.1104 [astro-ph.CO].
  39. ↑ "Line of galaxies is so big it breaks our understanding of the universe".
  40. ↑ Nadathur, Seshadri (2013). "Seeing patterns in noise: gigaparsec-scale 'structures' that do not violate homogeneity". Monthly Notices of the Royal Astronomical Society. 434 (1): 398–406. arXiv: 1306.1700 . Bibcode:2013MNRAS.434..398N. doi:10.1093/mnras/stt1028. S2CID   119220579.
  41. ↑ Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1993). "A quasi-steady state cosmological model with creation of matter". The Astrophysical Journal . 410: 437–457. Bibcode:1993ApJ...410..437H. doi: 10.1086/172761 .
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994). "Astrophysical deductions from the quasi-steady state cosmology". Monthly Notices of the Royal Astronomical Society . 267 (4): 1007–1019. Bibcode:1994MNRAS.267.1007H. doi: 10.1093/mnras/267.4.1007 . hdl:11007/1133.
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994). "Astrophysical deductions from the quasi-steady state: Erratum". Monthly Notices of the Royal Astronomical Society . 269 (4): 1152. Bibcode:1994MNRAS.269.1152H. doi: 10.1093/mnras/269.4.1152 .
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994). "Further astrophysical quantities expected in a quasi-steady state Universe". Astronomy and Astrophysics . 289 (3): 729–739. Bibcode:1994A&A...289..729H.
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1995). "The basic theory underlying the quasi-steady state cosmological model". Proceedings of the Royal Society A . 448 (1933): 191. Bibcode:1995RSPSA.448..191H. doi:10.1098/rspa.1995.0012. S2CID   53449963.
  42. ↑ Narlikar, J. V.; Vishwakarma, R. G.; Burbidge, G. (2002). "Interpretations of the Accelerating Universe". Publications of the Astronomical Society of the Pacific. 114 (800): 1092–1096. arXiv: astro-ph/0205064 . Bibcode:2002PASP..114.1092N. doi:10.1086/342374. S2CID   15456774.
  43. ↑ Hoyle, F. (1993). "Light element synthesis in Planck fireballs". Astrophysics and Space Science. 198 (2): 177–193. doi:10.1007/BF00644753. S2CID   121245869.
  44. ↑ Wright, E. L. (1994). "Comments on the Quasi-Steady-State Cosmology". Monthly Notices of the Royal Astronomical Society. 276 (4): 1421. arXiv: astro-ph/9410070 . Bibcode:1995MNRAS.276.1421W. doi:10.1093/mnras/276.4.1421. S2CID   118904109.
  45. ↑ Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994). "Note on a Comment by Edward L. Wright". arXiv: astro-ph/9412045 .
  46. ↑ Wright, E. L. (20 December 2010). "Errors in the Steady State and Quasi-SS Models". UCLA, Physics & Astronomy Department.

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Redshift quantization, also referred to as redshift periodicity, redshift discretization, preferred redshifts and redshift-magnitude bands, is the hypothesis that the redshifts of cosmologically distant objects tend to cluster around multiples of some particular value.

<span class="mw-page-title-main">CMB cold spot</span> Region in space

The CMB Cold Spot or WMAP Cold Spot is a region of the sky seen in microwaves that has been found to be unusually large and cold relative to the expected properties of the cosmic microwave background radiation (CMBR). The "Cold Spot" is approximately 70 µK (0.00007 K) colder than the average CMB temperature, whereas the root mean square of typical temperature variations is only 18 µK. At some points, the "cold spot" is 140 µK colder than the average CMB temperature.

<span class="mw-page-title-main">Galaxy filament</span> Largest structures in the universe, made of galaxies

In cosmology, galaxy filaments are the largest known structures in the universe, consisting of walls of galactic superclusters. These massive, thread-like formations can commonly reach 50/h to 80/h Megaparsecs — with the largest found to date being the Hercules-Corona Borealis Great Wall at around 3 gigaparsecs (9.8 Gly) in length — and form the boundaries between voids. Due to the accelerating expansion of the universe, the individual clusters of gravitationally bound galaxies that make up galaxy filaments are moving away from each other at an accelerated rate; in the far future they will dissolve.

The Hoyle–Narlikar theory of gravity 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.

A large quasar group (LQG) is a collection of quasars that form what are thought to constitute the largest astronomical structures in the observable universe. LQGs are thought to be precursors to the sheets, walls and filaments of galaxies found in the relatively nearby universe.

<span class="mw-page-title-main">Huge-LQG</span> Possible astronomical structure

The Huge Large Quasar Group, is a possible structure or pseudo-structure of 73 quasars, referred to as a large quasar group, that measures about 4 billion light-years across. At its discovery, it was identified as the largest and the most massive known structure in the observable universe, though it has been superseded by the Hercules–Corona Borealis Great Wall at 10 billion light-years. There are also issues about its structure.

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