Editing Orbital inclination (section)

==Observations and theories==
Most planetary orbits in the Solar System have relatively small inclinations, both in relation to each other and to the Sun's equator:

{{solar system inclinations}}

On the other hand, the [[dwarf planet]]s [[Pluto]] and [[Eris (dwarf planet)|Eris]] have inclinations to the ecliptic of 17° and 44° respectively, and the large [[asteroid]] [[2 Pallas|Pallas]] is inclined at 34°.

In 1966, [[Peter Goldreich]] published a classic paper on the evolution of [[Orbit of the Moon|the Moon's orbit]] and on the orbits of other moons in the Solar System.<ref>{{cite journal|last1=Peter Goldreich|title=History of the Lunar Orbit|journal=[[Reviews of Geophysics]]|volume=4|issue=4|pages=411–439|date=Nov 1966|doi=10.1029/RG004i004p00411|bibcode=1966RvGSP...4..411G}} Termed "classic" by {{cite journal|last1=[[Jihad Touma]] & [[Jack Wisdom]]|title=Evolution of the Earth-Moon system|journal=[[The Astronomical Journal]]|volume=108|pages=1943|date=Nov 1994|doi=10.1086/117209|bibcode=1994AJ....108.1943T|doi-access=free}}</ref> He showed that, for each planet, there is a distance such that moons closer to the planet than that distance maintain an almost constant orbital inclination with respect to the planet's equator (with an [[Nodal precession|orbital precession]] mostly due to the tidal influence of the planet), whereas moons farther away maintain an almost constant orbital inclination with respect to the [[ecliptic]] (with precession due mostly to the tidal influence of the sun). The moons in the first category, with the exception of [[Neptune]]'s moon [[Triton (moon)|Triton]], orbit near the equatorial plane. He concluded that these moons formed from equatorial [[accretion disk]]s. But he found that the Moon, although it was once inside the critical distance from the Earth, never had an equatorial orbit as would be expected from various [[Origin of the Moon|scenarios for its origin]]. This is called the lunar inclination problem, to which various solutions have since been proposed.<ref>{{cite journal|last1=Kaveh Pahlevan & Alessandro Morbidelli|title=Collisionless encounters and the origin of the lunar inclination|journal=Nature|volume=527|issue=7579|pages=492–494|date=26 November 2015|doi=10.1038/nature16137|arxiv=1603.06515|bibcode=2015Natur.527..492P|pmid=26607544|s2cid=4456736}}</ref>