Night (also described as night time, unconventionally spelled as "nite") is the period of

ambient Ambient or Ambiance or Ambience may refer to: Music and sound * Ambience (sound recording), also known as atmospheres or backgrounds * Ambient music, a genre of music that puts an emphasis on tone and atmosphere * ''Ambient'' (album), by Moby * ...

darkness Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown. Human vision is unable to distinguish colors in conditions of very low ...

from

sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spr ...

sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology ...

during each 24-hour day, when 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 rad ...

is below the horizon. The exact

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, t ...

when night begins and ends depends on the location and varies throughout the year, based on factors such as

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and po ...

and

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

. The word can be used in a different sense as the time between bedtime and

morning Morning is the period from sunrise to noon. There are no exact times for when morning begins (also true of evening and night) because it can vary according to one's lifestyle and the hours of daylight at each time of year. However, morning stric ...

. In common communication, the word ''night'' is used as a farewell ("good night", sometimes shortened to "night"), mainly when someone is going to sleep or leaving. Astronomical night is the period between astronomical

dusk Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall.''The Random House College Dictionary'', "dusk". At predusk, during early to intermediate stages of twilight, enou ...

and astronomical

dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's ho ...

when the Sun is between 18 and 90 degrees below the horizon and does not illuminate the sky. As seen from

s between about 48.56° and 65.73° north or south of the

Equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...

, complete darkness does not occur around the summer solstice because, although the Sun sets, it is never more than 18° below the horizon at lower

culmination In observational astronomy, culmination is the passage of a celestial object (such as the Sun, the Moon, a planet, a star, constellation or a deep-sky object) across the observer's local meridian. These events were also known as meridian tran ...

, −90° Sun angles occur at the

Tropic of Cancer The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted tow ...

on the

December solstice The December solstice, also known as the southern solstice, is the solstice that occurs each December – typically on 21 December, but may vary by one day in either direction according to the Gregorian calendar. In the Northern Hemisphere, the ...

and

Tropic of Capricorn The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reach ...

on the

June solstice The June solstice is the solstice on Earth that occurs annually between 20 and 22 June according to the Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pop ...

, and at the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...

equinoxes A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and se ...

. And as seen from latitudes greater than 72° north or south of the equator, complete darkness does not occur both

because, although the Sun sets, it is never more than 18° below the horizon. The opposite of night is

day A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two s ...

(or "

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 he ...

", to distinguish it from "day" referring to a 24-hour period).

Twilight Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this ...

is the period of night after sunset or before sunrise when the Sun still illuminates the sky when it is below the horizon. At any given time, one side of

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 surf ...

is bathed in sunlight (the daytime), while the other side is in

caused by Earth blocking the sunlight. The central part of the shadow is called the

umbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast. ...

, where the night is darkest. Natural illumination at night is still provided by a combination of

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 ...

, planetary light,

starlight Starlight is the light emitted by stars. It typically refers to visible electromagnetic radiation from stars other than the Sun, observable from Earth at night, although a component of starlight is observable from Earth during daytime. Sunl ...

zodiacal light The zodiacal light (also called false dawn when seen before sunrise) is a faint glow of diffuse sunlight scattered by interplanetary dust. Brighter around the Sun, it appears in a particularly dark night sky to extend from the Sun's directio ...

gegenschein Gegenschein (; ; ) or counterglow is a faintly bright spot in the night sky centered at the antisolar point. The backscatter of sunlight by interplanetary dust causes this optical phenomenon. Explanation Like zodiacal light, gegenschein is s ...

, and

airglow Airglow (also called nightglow) is a faint emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffu ...

. In some circumstances,

aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...

, and

bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some ...

can provide some illumination. The

glow Glow or GLOW may refer to: In science and technology In computing and telecommunications * Glow (JavaScript library), an open-source JavaScript library created by the BBC * Glow (Scottish Schools National Intranet), a telecommunications project i ...

provided by artificial lighting is sometimes referred to as

light pollution Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day or night. Light po ...

because it can interfere with

observational astronomy Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical ...

and

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

Duration and geography

On Earth, an average night is shorter than

due to two factors. Firstly, the

's apparent disk is not a point, but has an

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a