Editing Lunar node (section)

===Inclination extremes===
Every 18.6 years, the angle between the Moon's orbit and Earth's [[equator]] reaches a maximum of 28°36′, the sum of Earth's [[Axial tilt|equatorial tilt]] (23°27′) and the Moon's [[orbital inclination]] (5°09′) to the [[ecliptic]]. This is called ''major [[lunar standstill]]''. Around this time, the Moon's [[declination]] will vary from −28°36′ to +28°36′. Conversely, 9.3 years later, the angle between the Moon's orbit and Earth's equator reaches its minimum of 18°20′. This is called a ''minor lunar standstill''. The last lunar standstill was a minor standstill in October 2015. At that time the descending node was lined up with the equinox (the point in the sky having [[right ascension]] zero and [[declination]] zero). The nodes are moving west by about 19° per year. The Sun crosses a given node about 20 days earlier each year.

When the inclination of the Moon's orbit to the Earth's equator is at its minimum of 18°20′, the centre of the Moon's disk will be above the [[horizon]] every day from latitudes less than 70°43' (90° − 18°20' – 57' parallax) north or south. When the inclination is at its maximum of 28°36', the centre of the Moon's disk will be above the horizon every day only from latitudes less than 60°27' (90° − 28°36' – 57' parallax) north or south.

At [[Polar regions of Earth|higher latitudes]], there will be a period of at least one day each month when the Moon does not rise, but there will also be a period of at least one day each month when the Moon does not set. This is similar to the [[Season|seasonal]] behaviour of the Sun, but with a period of 27.2 days instead of 365 days. Note that a point on the Moon can actually be visible when it is about 34 [[Minute and second of arc|arc minutes]] below the horizon, due to [[atmospheric refraction]].

Because of the inclination of the Moon's orbit with respect to the Earth's equator, the Moon is above the horizon at the [[North Pole|North]] and [[South Pole]] for almost two weeks every month, even though the Sun is below the horizon for six months at a time. The period from moonrise to moonrise at the poles is a [[tropical month]], about 27.3 days, quite close to the sidereal period. When the Sun is the furthest below the horizon ([[Winter Solstice|winter solstice]]), the Moon will be full when it is at its highest point. When the Moon is in [[Gemini (constellation)|Gemini]] it will be above the horizon at the North Pole, and when it is in [[Sagittarius (constellation)|Sagittarius]] it will be up at the South Pole.

The Moon's light is used by [[zooplankton]] in the Arctic when the Sun is below the horizon for months and must have been helpful to the animals that lived in Arctic and Antarctic regions when the climate was warmer.