Editing Cosmological principle (section)

=== Violations of homogeneity ===
The cosmological principle implies that at a sufficiently large scale, the universe is [[homogeneous]]. Based on [[N-body simulation]]s in a ΛCDM universe, Jaswant Yadav and his colleagues showed that the spatial distribution of galaxies is statistically homogeneous if averaged over scales of 260[[Parsec#Megaparsecs and gigaparsecs|/''h'' Mpc]] or more.<ref name="Yadav">{{cite journal |last1=Yadav |first1=Jaswant |last2=Bagla |first2=J. S. |last3=Khandai |first3=Nishikanta |date=25 February 2010 |title=Fractal dimension as a measure of the scale of homogeneity |journal=Monthly Notices of the Royal Astronomical Society |volume=405 |issue=3 |pages=2009–2015 |arxiv=1001.0617 |bibcode=2010MNRAS.405.2009Y |doi=10.1111/j.1365-2966.2010.16612.x |doi-access=free |s2cid=118603499}}</ref>

A number of observations have been reported to be in conflict with predictions of maximal structure sizes:
* The [[Clowes–Campusano LQG]], discovered in 1991, has a length of 580 Mpc, and is marginally larger than the consistent scale.
* The [[Sloan Great Wall]], discovered in 2003, has a length of 423 Mpc,<ref name=apj624_2_463>{{Cite journal | display-authors=1 | last1=Gott | first1=J. Richard III | last2=Jurić | first2=Mario | last3=Schlegel| first3=David | last4=Hoyle | first4=Fiona | last5=Vogeley | first5=Michael | last6=Tegmark | first6=Max | last7=Bahcall | first7=Neta |last8=Brinkmann | first8=Jon | title=A Map of the Universe | journal=The Astrophysical Journal | volume=624 | issue=2 | pages=463–484 |date=May 2005 | doi=10.1086/428890 | bibcode=2005ApJ...624..463G |arxiv = astro-ph/0310571| s2cid=9654355 }}</ref> which is just barely consistent with the cosmological principle.
* [[U1.11]], a [[large quasar group]] discovered in 2011, has a length of 780 Mpc, two times larger than the upper limit of the homogeneity scale.
* The [[Huge-LQG]], discovered in 2012, is three times longer and two times wider than is predicted to be possible by current models.
* In November 2013, a new structure 10 billion light years away measuring 2000–3000 Mpc (more than seven times that of the Sloan Great Wall) was discovered, the [[Hercules–Corona Borealis Great Wall]], putting further doubt on the validity of the cosmological principle.<ref>{{citation|arxiv=1311.1104|last1= Horvath|first1= I.|title= The largest structure of the Universe, defined by Gamma-Ray Bursts|last2=  Hakkila|first2= J.|last3=  Bagoly|first3= Z.|year= 2013}}</ref>
* In September 2020, a 4.9{{px2}}''σ'' conflict was found between the kinematic explanation of the CMB dipole and the measurement of the dipole in the angular distribution of a flux-limited, all-sky sample of 1.36 million quasars.<ref>{{Cite journal|last1=Secrest|first1=Nathan|last2=von Hausegger|first2=Sebastian|last3=Rameez|first3=Mohamed|last4=Mohayaee|first4=Roya|last5=Sarkar|first5=Subir|last6=Colin|first6=Jacques|date=2021-02-01|title=A Test of the Cosmological Principle with Quasars|journal=The Astrophysical Journal Letters|volume=908|issue=2|pages=L51|doi=10.3847/2041-8213/abdd40|arxiv=2009.14826|bibcode=2021ApJ...908L..51S|s2cid=222066749|issn=2041-8205 |doi-access=free }}</ref>
* In June 2021, the [[The Giant Arc|Giant Arc]] was discovered, a structure spanning approximately 1000 Mpc.<ref>{{Cite web|url=https://www.newscientist.com/article/2280076-line-of-galaxies-is-so-big-it-breaks-our-understanding-of-the-universe/|title = Line of galaxies is so big it breaks our understanding of the universe}}</ref> It is located 2820 Mpc away and consists of galaxies, galactic clusters, gas, and dust.
* In January 2024, the [[Big Ring]] was discovered. It is located 9.2 billion light years away from Earth and has a diameter of 1.3 billion light years, giving it an angular size of 15 full moons as seen from Earth.<ref>{{Cite web |title=A Big Cosmological Mystery |url=https://www.uclan.ac.uk/news/big-ring-in-the-sky |access-date=2024-01-15 |website=University of Central Lancashire |language=en}}</ref>

However, as pointed out by Seshadri Nadathur in 2013 using statistical properties,<ref name=Nadathur>{{cite journal|last=Nadathur|first=Seshadri|title=Seeing patterns in noise: gigaparsec-scale 'structures' that do not violate homogeneity|journal=Monthly Notices of the Royal Astronomical Society|date=2013|volume=434|issue=1|pages=398–406|doi=10.1093/mnras/stt1028|doi-access=free |arxiv=1306.1700|bibcode =2013MNRAS.434..398N|s2cid=119220579}}</ref> the existence of structures larger than the homogeneous scale (260[[Parsec#Megaparsecs and gigaparsecs|/''h'' Mpc]] by Yadav's estimation)<ref name=Yadav /> does not necessarily violate the cosmological principle in the ΛCDM model (see ''{{section link|Huge-LQG#Dispute}}'').<ref name="Labini">{{cite journal| vauthors = Sylos-Labini F, Tekhanovich D, Baryshev Y|title=Spatial density fluctuations and selection effects in galaxy redshift surveys|journal=Journal of Cosmology and Astroparticle Physics|date=2014|volume=7|number=13|page= 35|doi=10.1088/1475-7516/2014/07/035|arxiv=1406.5899|bibcode = 2014JCAP...07..035S|s2cid=118393719}}</ref>