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Apart from the presence of ice-containing clouds in the right position in the sky, the halo requires that the light source (Sun or Moon) be very high in the sky, at an elevation of 58° or greater. This means that the solar variety of the halo is impossible to see at locations north of 55°N or south of 55°S.
Using a single crystal, one needs to realize all possible 3D orientations of the crystal. This has recently been achieved by two approaches. The first one using pneumatics and a sophisticated rigging, [29] and a second one using an Arduino-based random walk machine which stochastically reorients a crystal embedded in a transparent thin-walled ...
Because astronomical objects are at such remote distances, casual observation of the sky offers no information on their actual distances. All celestial objects seem equally far away, as if fixed onto the inside of a sphere with a large but unknown radius, [1] which appears to rotate westward overhead; meanwhile, Earth underfoot seems to remain still.
A circumzenithal arc in Salem, Massachusetts, Oct 27, 2012. Also visible are a supralateral arc, Parry arc (upper suncave), and upper tangent arc. From top to bottom: a circumzenithal arc on top of a 46° halo, on top of a Parry arc, on top of a tangent arc, on top of a 22° halo, on top of the actual sun.
Its appearance as a vertical line is an optical illusion, resulting from the collective reflection off the ice crystals; but only those that are in the common vertical plane, direct the light rays towards the observer (See drawing). This is similar to viewing a light source on a body of water.
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. [7] In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre.
Sky-gazers can look forward to catching glimpses of four bright planets at the same time in the night sky. Venus and Saturn will appear in the southwest, Jupiter will gleam overhead, and Mars will ...
Diagram showing the relationship between the zenith, the nadir, and different types of horizon. The zenith (UK: / ˈ z ɛ n ɪ θ /, US: / ˈ z iː n ɪ θ /) [1] [2] is the imaginary point on the celestial sphere directly "above" a particular location.