page_title: Night
section_title: On other celestial bodies
hierarchical_section_title: Night / On other celestial bodies
caption_attribution_description: English: A waning moon. 日本語: 下弦の月。
context_page_description: Night or nighttime is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends on the location and varies throughout the year. When night is considered as a period that which follows evening, it is usually considered to start around 8 pm and to last to about 4 am. Night ends with coming of morning at sunrise.
  The word can be used in a different sense as the time between bedtime and morning. In common communication, the word night is used as a farewell and sometimes shortened to "night", mainly when someone is going to sleep or leaving. Good night!" Unlike "good morning", "good afternoon", and "good evening", "good night" is not used as a greeting.
  Complete darkness or astronomical night is the period between astronomical dusk and astronomical dawn when the Sun is between 18 and 90 degrees below the horizon and does not illuminate the sky.
context_section_description: The phenomenon of day and night is due to the rotation of a celestial body about its axis, creating an illusion of the sun rising and setting. Different bodies spin at very different rates, however. Some may spin much faster than Earth, while others spin extremely slowly, leading to very long days and nights. The planet Venus rotates once every 224.7 days – by far the slowest rotation period of any of the major planets. In contrast, the gas giant Jupiter's sidereal day is only 9 hours and 56 minutes. However, it is not just the sidereal rotation period which determines the length of a planet's day-night cycle but the length of its orbital period as well - Venus has a rotation period of 224.7 days, but a day-night cycle just 116.75 days long due to its retrograde rotation and orbital motion around the Sun. Mercury has the longest day-night cycle as a result of its 3:2 resonance between its orbital period and rotation period - this resonance gives it a day-night cycle that is 176 days long. A planet may experience large temperature variations between day and night, such as Mercury, the planet closest to the sun. This is one consideration in terms of planetary habitability or the possibility of extraterrestrial life.
caption: Waning moon
exif: {}