Editing Cosmological principle (section)

=== Violations of isotropy ===
The [[cosmic microwave background]] (CMB) is predicted by the ΛCDM model to be isotropic, that is to say that its intensity is about the same whichever direction we look at.<ref>{{Cite web | url=http://www.gizmag.com/universe-homogeneous-300-million-light-years/24149/ | title=Australian study backs major assumption of cosmology| date=17 September 2012}}</ref> Data from the [[Planck Mission]] shows hemispheric bias 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).<ref name="Planck">{{cite web | url=http://sci.esa.int/planck/51551-simple-but-challenging-the-universe-according-to-planck/ | title=Simple but challenging: the Universe according to Planck | work=[[ESA Science & Technology]] | orig-date=March 21, 2013 |date= October 5, 2016 | access-date=October 29, 2016}}</ref><ref>{{Cite journal |last1=Planck Collaboration |last2=Akrami |first2=Y. |last3=Ashdown |first3=M. |last4=Aumont |first4=J. |last5=Baccigalupi |first5=C. |last6=Ballardini |first6=M. |last7=Banday |first7=A. J. |last8=Barreiro |first8=R. B. |last9=Bartolo |first9=N. |last10=Basak |first10=S. |last11=Benabed |first11=K. |last12=Bersanelli |first12=M. |last13=Bielewicz |first13=P. |last14=Bock |first14=J. J. |last15=Bond |first15=J. R. |date=2020-09-01 |title=Planck 2018 results. VII. Isotropy and statistics of the CMB |url=https://ui.adsabs.harvard.edu/abs/2020A&A...641A...7P |journal=Astronomy and Astrophysics |volume=641 |pages=A7 |doi=10.1051/0004-6361/201935201 |arxiv=1906.02552 |bibcode=2020A&A...641A...7P |issn=0004-6361|hdl=10138/320318 |hdl-access=free }}</ref> The collaboration noted that these features are not strongly statistically inconsistent with isotropy.<ref>{{Cite journal |last1=Planck Collaboration |last2=Aghanim |first2=N. |last3=Akrami |first3=Y. |last4=Arroja |first4=F. |last5=Ashdown |first5=M. |last6=Aumont |first6=J. |last7=Baccigalupi |first7=C. |last8=Ballardini |first8=M. |last9=Banday |first9=A. J. |last10=Barreiro |first10=R. B. |last11=Bartolo |first11=N. |last12=Basak |first12=S. |last13=Battye |first13=R. |last14=Benabed |first14=K. |last15=Bernard |first15=J. -P. |date=2020-09-01 |title=Planck 2018 results. I. Overview and the cosmological legacy of Planck |url=https://ui.adsabs.harvard.edu/abs/2020A&A...641A...1P |journal=Astronomy and Astrophysics |volume=641 |pages=A1 |doi=10.1051/0004-6361/201833880 |arxiv=1807.06205 |bibcode=2020A&A...641A...1P |issn=0004-6361|hdl=10138/320876 |s2cid=119185252 |hdl-access=free }}</ref> Some authors say that the universe around Earth is isotropic at high significance by studies of the [[cosmic microwave background]] temperature maps.<ref name="Saadeh">{{cite journal| vauthors = Saadeh D, Feeney SM, Pontzen A, Peiris HV, McEwen, JD|title=How Isotropic is the Universe?|journal=Physical Review Letters|date=2016|volume=117|number=13|page= 131302 |doi=10.1103/PhysRevLett.117.131302|pmid=27715088|arxiv=1605.07178|bibcode = 2016PhRvL.117m1302S |s2cid=453412}}</ref> There are however claims of isotropy violations from [[galaxy cluster]]s,<ref name="Billings">{{cite web |author=Billings |first=Lee |date=April 15, 2020 |title=Do We Live in a Lopsided Universe? |url=https://www.scientificamerican.com/article/do-we-live-in-a-lopsided-universe1/ |access-date=March 24, 2022 |website=[[Scientific American]]}}</ref><ref name="Migkas et al">{{cite journal |author1=Migkas, K. |author2=Schellenberger, G. |author3=Reiprich, T. H. |author4=Pacaud, F. |author5=Ramos-Ceja, M. E. |author6=Lovisari, L. |date=8 April 2020 |title=Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX-T scaling relation |url=https://www.aanda.org/articles/aa/full_html/2020/04/aa36602-19/aa36602-19.html |journal=Astronomy & Astrophysics |volume=636 |issue=April 2020 |page=42 |arxiv=2004.03305 |bibcode=2020A&A...636A..15M |doi=10.1051/0004-6361/201936602 |s2cid=215238834 |access-date=24 March 2022}}</ref> [[quasar]]s,<ref>{{cite journal |last1=Secrest |first1=Nathan J. |last2=von Hausegger |first2=Sebastian |last3=Rameez |first3=Mohamed |last4=Mohayaee |first4=Roya |last5=Sarkar |first5=Subir |last6=Colin |first6=Jacques |date=February 25, 2021 |title=A Test of the Cosmological Principle with Quasars |journal=The Astrophysical Journal Letters |volume=908 |issue=2 |pages=L51 |arxiv=2009.14826 |bibcode=2021ApJ...908L..51S |doi=10.3847/2041-8213/abdd40 |s2cid=222066749 |doi-access=free }}</ref> and [[type Ia supernova]]e.<ref>{{cite journal |last1=Javanmardi |first1=B. |last2=Porciani |first2=C. |last3=Kroupa |first3=P. |last4=Pflamm-Altenburg |first4=J. |date=August 27, 2015 |title=Probing the Isotropy of Cosmic Acceleration Traced By Type Ia Supernovae |url=https://iopscience.iop.org/article/10.1088/0004-637X/810/1/47 |journal=The Astrophysical Journal Letters |volume=810 |issue=1 |page=47 |arxiv=1507.07560 |bibcode=2015ApJ...810...47J |doi=10.1088/0004-637X/810/1/47 |s2cid=54958680 |access-date=March 24, 2022}}</ref>