Daylight is the combination of all direct and indirect

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

during the

daytime Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemis ...

. This includes direct

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

landform A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, ...

s and buildings. Sunlight scattered or reflected by

astronomical object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...

s is generally not considered daylight. Therefore, daylight excludes

moonlight Moonlight consists of mostly sunlight (with little earthlight) reflected from the parts of the Moon's surface where the Sun's light strikes. Illumination The intensity of moonlight varies greatly depending on the lunar phase, but even the ful ...

, despite it being reflected indirect sunlight.

Definition

Daylight is present at a particular location, to some degree, whenever the

Sun 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 The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...

. (This is true for slightly more than 50% of the

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

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 Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

, 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 co ...

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 A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six month ...

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 ter ...

, 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 the

Solar System The Solar SystemCapitalization 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 S ...

, see

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

Definition

Intensity in different conditions

See also

References

External links