0_Wizard
I love watching the sunset at night, it is the daily disappearance of the Sun below the horizon as a result of Earth's rotation.
Sunset or sundown is the daily disappearance of the Sun below the horizon as a result of Earth's rotation.
chosen_Sunset_0
Sunset
chosen_topic_0_Sunset
Sunset
Sunset or sundown is the daily disappearance of the Sun below the horizon as a result of Earth's rotation. The Sun will set exactly due west at the equator on the spring and fall equinoxes, each of which occurs only once a year. The time of sunset is defined in astronomy as the moment when the trailing edge of the Sun's disk disappears below the horizon. Near to the horizon, atmospheric refraction causes the ray path of light from the Sun to be distorted to such an extent that geometrically the Sun's disk is already about one diameter below the horizon when a sunset is observed. Sunset is distinct from twilight, which has three phases, the first being "civil" twilight, which begins once the Sun has disappeared below the horizon, and continues until it descends to 6 degrees below the horizon; the second phase is "nautical" twilight, between 6 and 12 degrees below the horizon; and the third is "astronomical" twilight, which is the period when the Sun is between 12 and 18 degrees below the horizon.
Archaeoastronomy
Archaeoastronomy (also spelled archeoastronomy) is the study of how people in the past "have understood the phenomena in the sky, how they used these phenomena and what role the sky played in their cultures". Clive Ruggles argues it is misleading to consider archaeoastronomy to be the study of ancient astronomy, as modern astronomy is a scientific discipline, while archaeoastronomy considers symbolically rich cultural interpretations of phenomena in the sky by other cultures. It is often twinned with "ethnoastronomy", the anthropological study of skywatching in contemporary societies. Archaeoastronomy is also closely associated with historical astronomy, the use of historical records of heavenly events to answer astronomical problems and the history of astronomy, which uses written records to evaluate past astronomical practice.
Extraterrestrial skies
In astronomy, an extraterrestrial sky is a view of outer space from the surface of a world other than Earth. The only extraterrestrial sky that has been directly observed and photographed by astronauts is that of the Moon. The skies of Titan, Mars, and Venus have been observed by space probes designed to land on the surface and transmit images back to Earth. Characteristics of extraterrestrial skies appear to vary substantially due to a number of factors. An extraterrestrial atmosphere, if present, has a large bearing on visible characteristics. The atmosphere's density and chemical composition can contribute to differences in colour, opacity (including haze) and the presence of clouds.
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometers, i.e. 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.
Twilight
Twilight on Earth is the illumination of the lower atmosphere when the Sun itself is not directly visible because it is below the horizon. Twilight is produced by sunlight scattering in the upper atmosphere, illuminating the lower atmosphere so that Earth's surface is neither completely lit nor completely dark. The word "twilight" is also used to denote the periods of time when this illumination occurs. The farther the Sun is below the horizon, the dimmer the twilight (other things such as atmospheric conditions being equal). When the Sun reaches 18 degrees below the horizon, the twilight's brightness is nearly zero, and evening twilight becomes nighttime.
Analemma
In astronomy, an analemma (; from Greek "analēmma" "support") is a diagram showing the variation of the position of the Sun in the sky over the course of a year, as viewed at a fixed time of day and from a fixed location on the Earth. The north–south component of the analemma is due to change of the Sun's declination caused by the tilt of the Earth's axis, and the east–west component is due to nonuniform rate of change of the Sun's right ascension, governed by combined effects of axial tilt and Earth's orbital eccentricity. The diagram has the form of a slender figure eight, and can often be found on globes of the Earth.
Orbit of the Moon
The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in about 27.323 days (a sidereal month) and one revolution relative to the Sun in about 29.530 days (a synodic month). Earth and the Moon orbit about their barycentre (common center of mass), which lies about from Earth's center (about of the radius of Earth). On average, the distance to the Moon is about from Earth's center, which corresponds to about 60 Earth radii. With a mean orbital velocity of , the Moon covers a distance approximately its diameter, or about half a degree on the celestial sphere, each hour.