Editing Axial tilt (section)

== Standards ==
There are two standard methods of specifying a planet's tilt.  One way is based on the planet's ''north pole'', defined in relation to the direction of Earth's north pole, and the other way is based on the planet's ''positive pole'', defined by the [[Axis–angle representation|right-hand rule]]:

* The [[International Astronomical Union]] (IAU) defines the ''north pole'' of a planet as that which lies on Earth's north side of the [[invariable plane]] of the [[Solar System]];<ref>''Explanatory Supplement 1992'', p. 384</ref> under this system, [[Venus]] is tilted 3° and rotates [[retrograde motion|retrograde]], opposite that of most of the other planets.<ref name="CorreiaVenusI">{{cite journal
 |author1=Correia, Alexandre C. M.
 |author2=Laskar, Jacques
 |author3=de Surgy, Olivier Néron
 |title=Long-term evolution of the spin of Venus I. theory
 |journal=Icarus |volume=163 |issue=1 |pages=1–23
 |date=May 2003
 |url=http://www.imcce.fr/Equipes/ASD/preprints/prep.2002/venus1.2002.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.imcce.fr/Equipes/ASD/preprints/prep.2002/venus1.2002.pdf |archive-date=9 October 2022 |url-status=live
 |doi=10.1016/S0019-1035(03)00042-3
 |bibcode=2003Icar..163....1C
}}</ref><ref>{{cite journal
 |author1=Correia, A. C. M.
 |author2=Laskar, J.
 |date=2003
 |title=Long-term evolution of the spin of Venus: II. numerical simulations
 |journal=Icarus
 |volume=163 |issue=1 |pages=24–45
 |url=http://www.imcce.fr/Equipes/ASD/preprints/prep.2002/venus2.2002.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.imcce.fr/Equipes/ASD/preprints/prep.2002/venus2.2002.pdf |archive-date=9 October 2022 |url-status=live
 |doi=10.1016/S0019-1035(03)00043-5
 |bibcode=2003Icar..163...24C
}}</ref>
* The IAU also uses the right-hand rule to define a ''positive pole''<ref>{{cite journal|title=Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006|journal=Celestial Mechanics and Dynamical Astronomy|volume=98|issue=3|pages=155–180|doi=10.1007/s10569-007-9072-y|year=2007|last1=Seidelmann|first1=P. Kenneth|last2=Archinal|first2=B. A.|last3=a'Hearn|first3=M. F.|last4=Conrad|first4=A.|last5=Consolmagno|first5=G. J.|last6=Hestroffer|first6=D.|last7=Hilton|first7=J. L.|last8=Krasinsky|first8=G. A.|last9=Neumann|first9=G.|last10=Oberst|first10=J.|last11=Stooke|first11=P.|last12=Tedesco|first12=E. F.|last13=Tholen|first13=D. J.|last14=Thomas|first14=P. C.|last15=Williams|first15=I. P.|bibcode=2007CeMDA..98..155S|doi-access=free}}</ref> for the purpose of determining orientation. Using this convention, Venus is tilted 177° ("upside down") and rotates prograde.