Editing Sunlight (section)

{{Short description|Light emitted by the Sun}}
{{other uses}}
{{Redirect|Sunshine}}
[[File:STS-134 EVA4 view to the Russian Orbital Segment.jpg|thumb|right|The Sun, as seen from low Earth orbit overlooking the [[International Space Station]]. This sunlight is not filtered by the lower atmosphere, which blocks much of the solar spectrum.]]
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 | image1    = Spring Lake, New Jersey Beach at Sunrise.jpg|
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 | caption2  = Sunlight shining upon two different sides of the [[U.S. state]] of [[New Jersey]]. [[Sunrise]] on the [[Jersey Shore]] at [[Spring Lake, New Jersey|Spring Lake]], [[Monmouth County, New Jersey|Monmouth County]] (above), and [[sunset]] on the Shore at [[Sunset Beach (New Jersey)|Sunset Beach]], [[Cape May County, New Jersey|Cape May County]] (below). Both are filtered through high [[stratus clouds]].
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[[File:Apollo 7 Florida.jpg|thumb|right|Sunrise over the [[Gulf of Mexico]] and [[Florida]]. Taken on 20 October 1968 from [[Apollo 7]].]]

'''Sunlight''' is the portion of the [[electromagnetic radiation]] which is emitted by the [[Sun]] (i.e. solar radiation) and received by the [[Earth]], in particular the [[visible spectrum|visible]] light perceptible to the [[human eye]] as well as invisible [[infrared]] (typically perceived by humans as warmth) and [[ultraviolet]] (which can have physiological effects such as [[sunburn]]) lights. However, according to the [[American Meteorological Society]], there are "conflicting conventions as to whether all three [...] are referred to as light, or whether that term should only be applied to the visible portion of the spectrum."<ref>{{cite web |title=Sunlight |website=Glossary of Meteorology |publisher=Anerican Meteorological Society |access-date=2025-03-23 |url=https://glossary.ametsoc.org/wiki/Sunlight#:~:text=Light%20from%20the%20sun%3B,greater%20than%20about%200.7%20%CE%BCm.}}</ref> Upon reaching the Earth, sunlight is [[light scattering by particles|scattered]] and [[attenuation|filtered]] through the [[atmosphere of Earth|Earth's atmosphere]] as [[daylight]] when the Sun is above the [[horizon]]. When direct [[solar radiation]] is not blocked by [[cloud]]s, it is experienced as '''sunshine''', a combination of bright [[light]] and [[radiant heat]] (atmospheric). When [[cloud cover|blocked by clouds]] or [[diffuse reflection|reflected off other objects]], sunlight is [[diffuser (optics)|diffused]]. Sources estimate a global average of between 164 watts to 340 watts<ref>{{cite web|access-date=2022-01-27|title=Climate and Earth's Energy Budget|url=https://earthobservatory.nasa.gov/features/EnergyBalance/page2.php|date=14 January 2009|website=earthobservatory.nasa.gov}}</ref> per square meter over a 24-hour day;<ref>{{cite web | url=http://zebu.uoregon.edu/disted/ph162/l4.html | title=Basics of Solar Energy | access-date=2016-12-06 | url-status=live | archive-url=https://web.archive.org/web/20161128021408/http://zebu.uoregon.edu/disted/ph162/l4.html | archive-date=2016-11-28 }}</ref> this figure is estimated by NASA to be about a quarter of Earth's average [[total solar irradiance]].

The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for [[vitamin D3|vitamin D<sub>3</sub>]] synthesis and a [[mutagen]].

Sunlight takes about 8.3&nbsp;minutes to reach Earth from the surface of the Sun.<ref>{{cite book |title=An Introduction to the Sun and Stars |edition=illustrated |first1=S. Jocelyn |last1=Bell Burnell |publisher=Cambridge University Press |year=2004 |isbn=9780521546225 |page=56 |url=https://books.google.com/books?id=lb5owLGIQGsC}} [https://books.google.com/books?id=lb5owLGIQGsC&pg=PA56 Extract of page 56]</ref> A photon starting at the center of the Sun and changing direction every time it encounters a [[charged particle]] would take between 10,000 and 170,000 years to get to the surface.<ref>{{cite web |url= http://sunearthday.nasa.gov/2007/locations/ttt_sunlight.php |title= The 8-minute travel time to Earth by sunlight hides a thousand-year journey that actually began in the core |publisher= [[NASA]] |website= SunEarthDay.NASA.gov |access-date= 2012-02-12 |url-status= dead |archive-url= https://web.archive.org/web/20120122162340/http://sunearthday.nasa.gov/2007/locations/ttt_sunlight.php |archive-date= 2012-01-22 }}</ref>

Sunlight is a key factor in [[photosynthesis]], the process used by plants and other [[autotroph]]ic organisms to convert [[light energy]], normally from the Sun, into [[chemical energy]] that can be used to synthesize carbohydrates and fuel the organisms' activities.

''[[Daylighting (architecture)|Daylighting]]'' is the natural lighting of interior spaces by admitting sunlight.
''[[Solar irradiance]]'' is the rate of solar energy received by a unit area from sunlight.