Steady-state model

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This article is about the cosmological theory. For other uses, see Steady state (disambiguation).
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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.

In

perfect cosmological principle, a principle that says that the observable universe
is always the same at any time and any place.

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

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

See also: Source counts

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

Main articles:
Perfect cosmological principle

One of the fundamental assumptions of the steady-state model is 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,

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

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

  • The Clowes–Campusano LQG, discovered in 1991, which has a length of 580 Mpc
  • The Sloan Great Wall, discovered in 2003, which has a length of 423 Mpc,[37]
  • U1.11, a large quasar group discovered in 2011, which has a length of 780 Mpc
  • The Huge-LQG, discovered in 2012, which is three times longer than and twice as wide as is predicted possible according to ΛCDM
  • The Hercules–Corona Borealis Great Wall, discovered in November 2013, which has a length of 2000–3000 Mpc (more than seven times that of the SGW)[38]
  • The
    Giant Arc, discovered in June 2021, which has a length of 1000 Mpc[39]

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,

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. ISBN 978-0-691-02623-7
    .
  3. doi:10.1093/mnras/108.3.252
    .
  4. doi:10.1093/mnras/108.5.372
    .
  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. 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. Bibcode:1959IAUS....9..583G. {{cite journal}}: Cite journal requires |journal= (help
    )
  9. ISSN 0004-637X
    .
  10. ISBN 9780691196022
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  11. ISBN 978-0-471-92567-5
    .
  12. ^ Andrew Liddle. An Introduction to Modern Cosmology (2nd ed.). London: Wiley, 2003.
  13. ^
    S2CID 247411131
  14. ^
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  15. S2CID 232307363
    . Retrieved 25 March 2022.
  16. 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. S2CID 215238834
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  19. S2CID 222066749
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  20. S2CID 54958680
    . Retrieved March 24, 2022.
  21. ESA Science & Technology
    . October 5, 2016 [March 21, 2013]. Retrieved October 29, 2016.
  22. doi:10.1103/PhysRevLett.18.1065
    . Retrieved 25 March 2022.
  23. doi:10.1093/mnras/206.2.377
    . Retrieved 25 March 2022.
  24. S2CID 223953708
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  25. S2CID 222066749
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  26. doi:10.1093/mnras/stac1986
    .
  27. doi:10.1093/mnras/stac144
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  28. S2CID 119463060
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  29. S2CID 119333704
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  30. S2CID 24389919
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  31. S2CID 14626666
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  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.
    S2CID 215238834
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  33. S2CID 232352604
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  34. S2CID 235352881
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  35. S2CID 248713777
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  36. S2CID 453412
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  37. S2CID 9654355
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  38. arXiv:1311.1104 [astro-ph.CO
    ].
  39. ^ "Line of galaxies is so big it breaks our understanding of the universe".
  40. S2CID 119220579
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  41. ^ Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1993). "A quasi-steady state cosmological model with creation of matter".
    doi:10.1086/172761
    .
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994).     "Astrophysical deductions from the quasi-steady state cosmology".
    hdl:11007/1133
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    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994).     "Astrophysical deductions from the quasi-steady state: Erratum".
    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".
    Bibcode:1994A&A...289..729H
    .
    Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1995).     "The basic theory underlying the quasi-steady state cosmological model".
    S2CID 53449963
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  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.
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  43. S2CID 121245869
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  44. ^ Wright, E. L. (1994). "Comments on the Quasi-Steady-State Cosmology". Monthly Notices of the Royal Astronomical Society. 276 (4): 1421.
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  45. ^ Hoyle, F.; Burbidge, G.; Narlikar, J. V. (1994). "Note on a Comment by Edward L. Wright".
    arXiv:astro-ph/9412045
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  46. ^ Wright, E. L. (20 December 2010). "Errors in the Steady State and Quasi-SS Models".
    UCLA
    , Physics & Astronomy Department.

Further reading

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