The article tells about what night is, why it comes, what its duration depends on and on which planets it does not exist at all.
Ancient times
Night is one of the phenomena due to which life was born on our planet. After all, if you look at other celestial bodies of our system, that is, those on which the day does not change at all. The same Mercury, for example. Because of this, one side of it is hot, and the other is covered with eternal darkness. Naturally, there can be no atmosphere and other living conditions there.
The fear of darkness has been sitting in a person since prehistoric times, it was then that a lot depended on such a thing as the time of day. The night was not just an indicator of another day lived, it carried a lot of dangers - predators went hunting, in the dark you could not see the enemy or a trap ... Despite the fact that the cities are now well lit at night, the fear of the dark probably never will not leave a person. So what is night?
Definition
Night is a period of time during which for a particular point on the surface of our planet (or other celestial body) the central luminary is below the horizon line and, accordingly, does not illuminate it.
The length of the night varies and depends on many factors, such as latitude, the inclination of the planet’s axis with respect to the orbit, the time of year, and distance from the Sun. Due to the fact that the inclination of the axis of the planets, including the Earth, varies with respect to the planes of their orbits, the duration of the night period depends on the time of year.
polar night
Analyzing the question of what night is, one cannot but mention the polar one. It differs from the usual one in that in latitudes higher than polar, depending on the season, it may not occur at all or, on the contrary, may last up to six months.
In the astronomical concept, night comes at a time when the Sun is 18 degrees below the horizon.
Stars
Despite the familiarity of such a phenomenon as darkness at night, it is not inherent in all planets. For example, in the center of our galaxy, because of the huge cluster of stars, the night does not come even after the setting of some local sun. Rather, the stars shine so brightly that this time of day is not much different from day to day. So now we know what night is.
Ethics
According to the accepted rules of etiquette, the night comes at 11 pm, regardless of latitude or season. And after this time, it is considered uncultured to bother people with calls or something else.
What is a day? Morning afternoon Evening Night
Day is called time, which is approximately equal to the period of revolution of our planet around its axis. It is divided into 24 hours and consists of morning, afternoon, evening and night.
Mythology
Due to fear of the dark, people at all times attached this time of day to a mystical meaning. Even today, when the darkness in most countries does not threaten the attack of predators or someone else, urban legends are born or ancient from person to person, for example, about vampires or other creatures that can not stand sunlight.