Night or nighttime (sp. night-time or night time) is the period of time between the sunsetШУУД ҮЗЭХ and
Night or nighttime (sp. night-time or night time) is the period of time between the sunset and the sunrise when the Sun is below the horizon. This occurs after dusk. The opposite of night is day[citation needed] (or "daytime" to distinguish it from "day" as used for a 24-hour period). The start and end points of time of a night vary based on factors such as season, latitude, longitude and timezone. At any given time, one side of the planet Earth is bathed in light from the Sun (the daytime) and the other side of the Earth is in the shadow caused by the Earth blocking the light of the sun. This shadow is what we call the darkness of night. Natural illumination is still provided by a combination of moonlight, planetary light, starlight, diffuse zodiacal light, gegenschein, and airglow. In some circumstances, bioluminescence, aurorae, and lightning can provide some illumination. The glow provided by artificial illumination is sometimes referred to as light pollution because it can interfere with observational astronomy and ecosystems. Nights are shorter than days on average due to two factors. Firstly, the sun is not a point, but has an apparent size of about 32 arc minutes. Secondly, the atmosphere refracts sunlight so that some of it reaches the ground when the sun is below the horizon by about 34 arc minutes. The combination of these two factors means that light reaches the ground when the center of the sun is below the horizon by about 50 arc minutes. Without these effects, day and night would be the same length at the autumnal (autumn/fall) and vernal (spring) equinoxes, the moments when the sun passes over the equator. In reality, around the equinoxes the day is almost 14 minutes longer than the night at the equator, and even more towards the poles. The summer and winter solstices mark the shortest and the longest night, respectively. The closer a location is to either the North Pole or the South Pole, the larger the range of variation in the night's length. Although equinoxes occur with a day and night close to equal length, before and after an equinox the ratio of night to day changes more rapidly in high latitude locations than in low latitude locations. In the Northern Hemisphere, Denmark
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