Day
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A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours. As a day passes at a given location it experiences morning, noon, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.
Decimal clock face, made in around the start of the 19th century
Night in art
Image: Midtown Manhattan from Weehawken September 2021 panorama 1
Image: Midtown Manhattan from Weehawken September 2021 panorama 2
Lunar phase
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A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.
A full moon sets behind San Gorgonio Mountain in California on a midsummer's morning.
The phases of the Moon as viewed looking southward from the Northern Hemisphere. Each phase would be rotated 180° if seen looking northward from the Southern Hemisphere. The upper part of the diagram is not to scale, as the Moon, the Earth, and the Moon's orbit are all much smaller relative to the Earth's orbit than shown here.
An overexposed photograph of a crescent Moon reveals earthshine and stars.
A crescent Moon over Kingman, Arizona