Editing Sunset (section)

{{Short description|Daily falling of the Sun below the horizon}}
{{other uses}}
{{Distinguish|Dusk}}
[[File:Anatomy of a Sunset-2.jpg|thumb|upright=1.35|Actual sunset: Two minutes before the Sun disappears below the horizon.]]

'''Sunset''' (or '''sundown''') is the disappearance of the [[Sun]] at the end of the [[Sun path]], below the [[horizon]] of the [[Earth]] (or any other [[astronomical object]] in the [[Solar System]]) due to its [[Earth's rotation|rotation]]. As viewed from everywhere on Earth, it is a phenomenon that happens approximately once every 24 hours, except in areas close to the [[Geographical pole|poles]]. The [[equinox]] Sun sets due west at the moment of both the spring and autumn equinoxes. As viewed from the [[Northern Hemisphere]], the Sun sets to the northwest (or not at all) in the spring and summer, and to the southwest in the autumn and winter; these seasons are reversed for the [[Southern Hemisphere]].

The sunset is defined in [[astronomy]] the moment the upper limb of the Sun disappears below the horizon.<ref>{{Citation|last=Ridpath|first=Ian|title=sunset|date=2012-01-01|url=https://www.oxfordreference.com/view/10.1093/acref/9780199609055.001.0001/acref-9780199609055-e-3625|work=A Dictionary of Astronomy|publisher=Oxford University Press|language=en|doi=10.1093/acref/9780199609055.001.0001|isbn=978-0-19-960905-5|access-date=2021-10-05|url-access=subscription}}</ref> Near the horizon, [[atmospheric refraction]] causes [[sunlight]] rays to be distorted to such an extent that geometrically the solar disk is already about one diameter below the horizon when a sunset is observed.
[[File:Cape may.jpg|thumb|left|upright=1.35|Sunset over the [[Delaware Bay]] at [[Sunset Beach, New Jersey|Sunset Beach]], [[New Jersey]], U.S., seen through [[cirrus cloud]]s]]Sunset is distinct from [[twilight]], which is divided into three stages. The first one is ''[[Twilight#Civil_twilight|civil twilight]]'', which begins once the Sun has disappeared below the horizon, and continues until it descends to 6 degrees below the horizon. The early to intermediate stages of twilight coincide with ''[[Dusk|predusk]]''. The second phase is ''[[Twilight#Nautical_twilight|nautical twilight]]'', between 6 and 12 degrees below the horizon. The third phase is ''[[Twilight#Astronomical_twilight|astronomical twilight]]'', which is the period when the Sun is between 12 and 18 degrees below the horizon.<ref name="USNO">{{cite web|url=http://aa.usno.navy.mil/faq/docs/RST_defs.php|title=Definitions from the US Astronomical Applications Dept (USNO)|access-date=2016-06-17|archive-date=2015-08-14|archive-url=https://web.archive.org/web/20150814180458/http://aa.usno.navy.mil/faq/docs/RST_defs.php|url-status=dead}}</ref> ''[[Dusk]]'' is at the very end of astronomical twilight, and is the darkest moment of twilight just before [[night]].<ref>{{cite web |title=Full definition of Dusk |url=https://www.merriam-webster.com/dictionary/dusk}}</ref> Finally, night occurs when the Sun reaches 18 degrees below the horizon and no longer illuminates the sky.<ref>{{Cite web|date=2020-12-03|title=Sunset vs Dusk [What Is The Difference Between The Two?]|url=https://www.astronomyscope.com/sunset-vs-dusk/|access-date=2021-10-03|website=Astronomy Scope|language=en-us}}</ref>

Locations further north than the [[Arctic Circle]] and further south than the [[Antarctic Circle]] experience no full sunset or [[sunrise]] on at least one day of the year, when the [[polar day]] or the [[polar night]] persists continuously for 24 hours. At latitudes greater than within half a degree of either pole, the sun cannot rise or set on the same date on any day of the year, since the sun's angular elevation between solar noon and midnight is less than one degree.