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Earthshine has a calculated maximum apparent magnitude of −3.69 as viewed from Earth. [3] This phenomenon is most visible from Earth at night (or astronomical twilight) a few days before or after the day of new moon, [5] when the lunar phase is a thin crescent. On these nights, the entire lunar disk is both directly and indirectly sunlit, and ...
Earth's rotational velocity also varies in a phenomenon known as length-of-day variation. [171] Earth's annual orbit is elliptical rather than circular, and its closest approach to the Sun is called perihelion. In modern times, Earth's perihelion occurs around 3 January, and its aphelion around 4 July.
According to an old Albanian custom, when an Albanian migrates to a foreign land, he takes with him a bag of earth of the "mother earth" (Alb. baltë mëmë-dheu), which in case the emigrant dies abroad, would be thrown on the grave, so that the earth would be light to the dead person.
The Earth phase, Terra phase, terrestrial phase, or phase of Earth, is the shape of the directly sunlit portion of Earth as viewed from the Moon (or elsewhere extraterrestrially). From the Moon, the Earth phases gradually and cyclically change over the period of a synodic month (about 29.53 days), as the orbital positions of the Moon around ...
Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arcseconds) per hundred years because of planetary perturbations.
Objects less than about twice the mass of Earth are expected to be rocky like Earth; beyond that, they become a mixture of volatiles and gas like Neptune. [54] The planet Gliese 581c , with a mass 5.5–10.4 times the mass of Earth, [ 55 ] attracted attention upon its discovery for potentially being in the habitable zone, [ 56 ] though later ...
The study of light, known as optics, is an important research area in modern physics. The main source of natural light on Earth is the Sun. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps.
The Day the Earth Smiled is a composite photograph taken by the NASA spacecraft Cassini on July 19, 2013. During an eclipse of the Sun , the spacecraft turned to image Saturn and most of its visible ring system , as well as Earth and the Moon as distant pale dots.