Night
Night or night-time is the period in which the
sun is below the
horizon. The opposite of night is
day .
Encyclopedia
Night or
night-time is the period in which the
sun is below the
horizon. The opposite of night is
day .
Duration and geography
Nights are shorter than days on average due to two factors. One, the sun is not a point, but has an apparent size of about 32 minutes of arc. Two, the
atmosphere refracts
sunlight so that some of it reaches the ground when the sun is below the
horizon by about 34 minutes of arc. The combination of these two factors means that light reaches the ground when the centre of the sun is below the horizon by about 50 minutes of arc.
Without these effects, day and night would be the same length at the
autumnal and
vernal 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 closer to the poles. The summer and
winter solstices mark the shortest night and the longest night, respectively.
The closer a location is to the
North or
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 locations near the poles than in locations between the
Tropic of Cancer and the
Tropic of Capricorn. In the
Northern Hemisphere,
Denmark has shorter nights in June than
India has. In the
Southern Hemisphere,
Antarctica has longer nights in June than
Chile has. The Northern and Southern Hemispheres of the world experience the same patterns of night length at the same
latitudes, but the cycles are 6 months apart so that one hemisphere experiences long nights while the other is experiencing short nights .
Near the two poles, extreme variations in daylight hours result in a continuous day for a portion of the summer, followed by continuous night during the depths of winter.
Social aspects
Throughout history, night has primarily been a time of resting and
sleep for humans, since little work or labor can be done in the dark. On the other hand, exciting clandestine activities such as romance and crime flourish.
As artificial
lighting has improved, night-time activity has increased and become a significant part of the economy in most places.
Even without artificial light,
moonlight sometimes makes it possible to travel or work outdoors at night.
Night is often associated with danger and evil, because bandits and dangerous animals can be concealed by darkness. The belief in magic often includes the idea that magic and magicians are more powerful at night. Similarly, mythical and folkloric creatures as
vampires, and
werewolves are thought to be more active at night.
Ghosts are believed to wander around almost exclusively during night-time. In almost all cultures, there exist stories and legends warning of the dangers of night-time.
See also
