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Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight,
Daylight Chart
shows sunrise and sunset times in a chart, for any location in the world
Length of Day and Twilight – Deriving the formulas to calculate the length of day
{{Authority control Atmospheric optical phenomena Light Parts of a day Visibility
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. It is also called sky radiation, the determinative process for cha ...
, and (often) both of these reflected by Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by astronomical objects is generally not considered daylight. Therefore, daylight excludes moonlight, despite it being reflected indirect sunlight.
Definition
Daylight is present at a particular location, to some degree, whenever theSun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
is above the local horizon. (This is true for slightly more than 50% of the Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
at any given time. For an explanation of why it is not exactly half, see here
Here is an adverb that means "in, on, or at this place". It may also refer to:
Software
* Here Technologies, a mapping company
* Here WeGo (formerly Here Maps), a mobile app and map website by Here Technologies, Here
Television
* Here TV (form ...
). However, the outdoor illuminance
In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate w ...
can vary from 120,000 lux for direct sunlight at noon
Noon (or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 noon), 12 p.m. (for post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 ( military time).
Sola ...
, which may cause eye pain, to less than 5 lux for thick storm cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
s with the Sun at the horizon (even <1 lux for the most extreme case), which may make shadows from distant street lights visible. It may be darker under unusual circumstances like a solar eclipse or very high levels of atmospheric particulates
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The t ...
, which include smoke (see New England's Dark Day
New England's Dark Day occurred on May 19, 1780, when an unusual darkening of the daytime sky was observed over the New England states and parts of Canada. The primary cause of the event is believed to have been a combination of smoke from forest ...
), dust, and volcanic ash.
Intensity in different conditions
For comparison, nighttime illuminance levels are: For a table of approximate daylight intensity in theSolar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
, see sunlight.
See also
References
External links
Daylight Chart
shows sunrise and sunset times in a chart, for any location in the world
Length of Day and Twilight – Deriving the formulas to calculate the length of day
{{Authority control Atmospheric optical phenomena Light Parts of a day Visibility