Axis of evil (cosmology)

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The "axis of evil" is a name given to the apparent correlation between the plane of the Solar System and aspects of the cosmic microwave background (CMB). It gives the plane of the Solar System and hence the location of Earth a greater significance than might be expected by chance – a result which has been claimed to be evidence of a departure from the Copernican principle as assumed in the concordance model.


The cosmic microwave background (CMB) radiation signature presents a direct large-scale view of the universe that can be used to identify whether our position or movement has any particular significance. There has been much publicity about analysis of results from the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck mission that show both expected and unexpected anisotropies in the CMB.[1] The motion of the solar system, and the orientation of the plane of the ecliptic are aligned with features of the microwave sky, which on conventional thinking are caused by structure at the edge of the observable universe.[2][3] Specifically, with respect to the ecliptic plane the "top half" of the CMB is slightly cooler than the "bottom half"; furthermore, the quadrupole and octupole axes are only a few degrees apart, and these axes are aligned with the top/bottom divide.[4]

Lawrence Krauss is quoted as follows in a 2006 article:[5]

The new results are either telling us that all of science is wrong and we're the center of the universe, or maybe the data is simply incorrect, or maybe it's telling us there's something weird about the microwave background results and that maybe, maybe there's something wrong with our theories on the larger scales.


Some anomalies in the background radiation have been reported which are aligned with the plane of our solar system. These are unexplained by the Copernican principle and suggest that the solar system's alignment is special in relation to the background radiation of the universe.[6] Land and Magueijo in 2005 dubbed this alignment the "axis of evil" owing to the implications for current models of the cosmos,[7] although several later studies have shown systematic errors in the collection of those data and the way they have been processed.[8][9][10] Various studies of the CMB anisotropy data either confirm the Copernican principle,[11] model the alignments in a non-homogeneous universe still consistent with the principle,[12] or attempt to explain them as local phenomena.[13] Some of these alternate explanations were discussed by Copi et al., who claimed that data from the Planck satellite could shed significant light on whether the preferred direction and alignments were spurious.[14][15] Coincidence is a possible explanation. Chief scientist from WMAP, Charles L. Bennett suggested coincidence and human psychology were involved, "I do think there is a bit of a psychological effect, people want to find unusual things."[16]

Data from the Planck Telescope published in 2013 has since found stronger evidence for the anisotropy.[17] "For a long time, part of the community was hoping that this would go away, but it hasn't", says Dominik Schwarz of the University of Bielefeld in Germany.[18]

In 2015, there was no consensus on the nature of this and other observed anomalies[19] and their statistical significance is unclear. For example, a study that includes the Planck mission results shows how masking techniques could introduce errors that when taken into account can render several anomalies, including the axis of evil, not statistically significant.[20] A 2016 study compared isotropic and anisotropic cosmological models against WMAP and Planck data and found no evidence for anisotropy.[21]

See also[edit]


  1. ^ Challinor, Anthony (2012). "CMB anisotropy science: A review". Proceedings of the International Astronomical Union. 8: 42–52. arXiv:1210.6008. Bibcode:2013IAUS..288...42C. doi:10.1017/S1743921312016663. S2CID 41756934.
  2. ^ "Does the motion of the solar system affect the microwave sky?". CERN Courier. 2004-11-24. Retrieved 2023-09-12.
  3. ^ Copi, C. J.; Huterer, D.; Schwarz, D. J.; Starkman, G. D. (2006-03-21). "On the large-angle anomalies of the microwave sky". Monthly Notices of the Royal Astronomical Society. 367 (1): 79–102. arXiv:astro-ph/0508047. Bibcode:2006MNRAS.367...79C. doi:10.1111/j.1365-2966.2005.09980.x. ISSN 0035-8711. S2CID 6184966.
  4. ^ Sutter, Paul (2017-07-29). "The (Cosmological) Axis of Evil".
  5. ^ "The Energy of Empty Space That Isn't Zero". 2006-05-07. Retrieved 2018-08-05.
  6. ^ Mariano, Antonio; Perivolaropoulos, Leandros (2013). "CMB maximum temperature asymmetry axis: Alignment with other cosmic asymmetries". Physical Review D. 87 (4): 043511. arXiv:1211.5915. Bibcode:2013PhRvD..87d3511M. doi:10.1103/PhysRevD.87.043511. ISSN 1550-7998. S2CID 119258571.
  7. ^ Land, Kate; João Magueijo, João (2005). "Examination of Evidence for a Preferred Axis in the Cosmic Radiation Anisotropy". Physical Review Letters. 95 (7): 071301. arXiv:astro-ph/0502237. Bibcode:2005PhRvL..95g1301L. doi:10.1103/PhysRevLett.95.071301. PMID 16196772. S2CID 119473590.
  8. ^ Liu, Hao; Li, Ti-Pei (2009). "Improved CMB Map from WMAP Data". arXiv:0907.2731v3 [astro-ph].
  9. ^ Sawangwit, Utane; Shanks, Tom (2010). "Lambda-CDM and the WMAP Power Spectrum Beam Profile Sensitivity". arXiv:1006.1270v1 [astro-ph].
  10. ^ Liu, Hao; et al. (2010). "Diagnosing Timing Error in WMAP Data". Monthly Notices of the Royal Astronomical Society. 413 (1): L96–L100. arXiv:1009.2701. Bibcode:2011MNRAS.413L..96L. doi:10.1111/j.1745-3933.2011.01041.x. S2CID 118739762.
  11. ^ Zhang, Pengjie; Stebbins, Albert (2011). "Confirmation of the Copernican Principle at Gpc Radial Scale and above from the Kinetic Sunyaev-Zel'dovich Effect Power Spectrum". Physical Review Letters. 107 (4): 041301. arXiv:1009.3967. Bibcode:2011PhRvL.107d1301Z. doi:10.1103/PhysRevLett.107.041301. ISSN 0031-9007. PMID 21866989. S2CID 17627683.
  12. ^ Buckley, Robert G.; Schlegel, Eric M. (2013). "CMB dipoles and other low-order multipoles in the quasispherical Szekeres model". Physical Review D. 87 (2): 023524. arXiv:1907.08684. Bibcode:2013PhRvD..87b3524B. doi:10.1103/PhysRevD.87.023524. ISSN 1550-7998. S2CID 124552647.
  13. ^ Hansen, M.; Kim, J.; Frejsel, A. M.; Ramazanov, S.; Naselsky, P.; Zhao, W.; Burigana, C. (2012). "Can residuals of the solar system foreground explain low multipole anomalies of the CMB?". Journal of Cosmology and Astroparticle Physics. 2012 (10): 059. arXiv:1206.6981. Bibcode:2012JCAP...10..059H. doi:10.1088/1475-7516/2012/10/059. ISSN 1475-7516. S2CID 118396636.
  14. ^ Copi, Craig J.; Huterer, Dragan; Schwarz, Dominik J.; Starkman, Glenn D. (2010). "Large-angle anomalies in the CMB". Advances in Astronomy. 2010: 847541. arXiv:1004.5602. Bibcode:2010AdAst2010E..92C. doi:10.1155/2010/847541. ISSN 1687-7969. S2CID 13823900.
  15. ^ Copi, Craig J.; Huterer, Dragan; Schwarz, Dominik J.; Starkman, Glenn D. (2007-01-08). "The Uncorrelated Universe: Statistical Anisotropy and the Vanishing Angular Correlation Function in WMAP Years 1-3". Physical Review D. 75 (2): 023507. arXiv:astro-ph/0605135. Bibcode:2007PhRvD..75b3507C. doi:10.1103/PhysRevD.75.023507. ISSN 1550-7998. S2CID 15702227.
  16. ^ "Found: Hawking's initials written into the universe". New Scientist. 2010-02-07.
  17. ^ Planck Collaboration (2013). "Planck 2013 results. XXIII. Isotropy and statistics of the CMB". Astronomy & Astrophysics. 571 (27): A23. arXiv:1303.5083. Bibcode:2014A&A...571A..23P. doi:10.1051/0004-6361/201321534. S2CID 13037411.
  18. ^ Michael Brooks (Apr 30, 2016). "That's odd: Axis of evil stretches across the cosmos". New Scientist.
  19. ^ Santos, L.; Cabella, P.; Villela, T.; Zhao, W. (2015-10-05). "Influence of Planck foreground masks in the large angular scale quadrant CMB asymmetry". Astronomy & Astrophysics. 584: A115. arXiv:1510.01009. Bibcode:2015A&A...584A.115S. doi:10.1051/0004-6361/201526713. ISSN 0004-6361. S2CID 119028545.
  20. ^ Rassat, A.; Starck, J.-L.; Paykari, P.; Sureau, F.; Bobin, J. (2014-08-04). "Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking". Journal of Cosmology and Astroparticle Physics. 2014 (8): 006. arXiv:1405.1844. Bibcode:2014JCAP...08..006R. doi:10.1088/1475-7516/2014/08/006. ISSN 1475-7516. S2CID 119095714.
  21. ^ Saadeh, Daniela; Feeney, Stephen M.; Pontzen, Andrew; Peiris, Hiranya V.; McEwen, Jason D. (2016-09-21). "How isotropic is the Universe?". Physical Review Letters. 117 (13): 131302. arXiv:1605.07178. Bibcode:2016PhRvL.117m1302S. doi:10.1103/PhysRevLett.117.131302. ISSN 0031-9007. PMID 27715088. S2CID 453412.