The article tells about what night is, why it comes, what determines its duration and on which planets it does not happen at all.
Ancient times
Night is one of the phenomena that gave rise to life on our planet. After all, if you look at other celestial bodies in our system, that is, those on which the change of day does not occur at all. The same Mercury, for example. Because of this, one side of it is red-hot, and the other is covered with eternal darkness. Naturally, there can be no atmosphere or other conditions for life there.
Fear of the dark has been in a person since prehistoric times, it was then that a lot depended on such a phenomenon as the time of day. The night was not just an indicator of another day lived, it carried a lot of dangers - predators went out to hunt, in the dark you could not see the enemy or a trap … Despite the fact that cities are now well lit at night, fear of the dark will probably never will not leave the person. So what is the night?
Definition
Night is a period of time during which, for a particular point on the surface of our planet (or another celestial body), the central luminary is below the horizon line and,respectively, does not illuminate it.
The duration of the night varies and depends on many factors, such as latitude, the inclination of the planet's axis in relation to the orbit, the time of year and distance from the Sun. Due to the fact that the tilt of the axis of the planets, including the Earth, varies in relation to the planes of their orbits, the duration of the night period depends on the season.
Polar night
Deciphering the question of what night is, one cannot fail to mention the polar one. It differs from the usual one in that in latitudes above the polar, depending on the season, it may not occur at all or, on the contrary, last up to six months.
In astronomical terms, night occurs when the Sun is 18 degrees below the horizon.
Stars
For all 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, due to a huge cluster of stars, night, even after the sunset of some local sun, still does not come. Or rather, the stars shine so brightly that this time of day is not much different from the day. So now we know what night is.
Ethics
According to accepted rules of etiquette, night falls at 11 pm, regardless of latitude or season. And after this time, it is considered uncivilized to disturb people with calls or otherwise.
What is a day? Morning, afternoon, evening, night
Days are called the time, which is approximately equal to the circulation periodour planet around its axis. It is divided into 24 hours and consists of morning, afternoon, evening and night.
Mythology
Because of the fear of the dark, people at all times attached a mystical meaning to this time of day. Even today, when darkness in most countries does not threaten to be attacked by predators or anyone else, urban legends are born or ancient ones are passed from person to person, for example, about vampires or other creatures that cannot stand sunlight.
