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When the Sun and Moon are at right angles, their
spherical astronomy
Spherical astronomy, or positional astronomy, is a branch of observational astronomy used to locate astronomical objects on the celestial sphere, as seen at a particular date, time, and location on Earth. It relies on the mathematical methods of ...
, quadrature is the configuration of a celestial object in which its elongation is a right angle
In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the ad ...
(90 degrees), i.e., the direction of the object as viewed from Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
is perpendicular
In geometry, two geometric objects are perpendicular if they intersect at right angles, i.e. at an angle of 90 degrees or π/2 radians. The condition of perpendicularity may be represented graphically using the '' perpendicular symbol'', � ...
to the position of the Sun
The position of the Sun in the sky is a function of both the time and the geographic coordinate system, geographic location of observation on Earth's surface. As Earth's orbit, Earth orbits the Sun over the course of a year, the Sun appears to mo ...
relative to Earth. It is applied especially to the position of a superior planet or the Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
at its first and last quarter phases. This is not to be confused with the Moon at dichotomy
A dichotomy () is a partition of a set, partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be
* jointly exhaustive: everything must belong to one part or the other, and
* mutually exclusive: nothi ...
(exactly half-lit) as viewed from Earth, which occurs at 89.85 degrees and 270.15 degrees.
As shown in the diagram, a planet (or other object) can be at the western quadrature (when it is to the west of the Sun when viewed from the Earth) or at the eastern quadrature (when it is to the east of the Sun when viewed from the Earth). Note that an inferior planet can never be at quadrature to the reference planet.
At quadrature, the shadow that a planet casts on its planetary rings
A ring system is a disc or torus orbiting an astronomical object that is composed of solid material such as dust, meteoroids, planetoids, moonlets, or stellar objects.
Ring systems are best known as planetary rings, common components of sate ...
or moons appears most offset from the planet (e.g., Saturn's rings); the dark side of a planet (e.g., Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
) is maximally visible.
When the Sun and Moon are at right angles, their tidal force
The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field, causing bodies to be pulled unevenly and as a result are being stretched towards the attraction. It is the ...
s counteract each other, and the tidal range
Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's prog ...
is smaller than average, resulting in '' neap tides''.
See also
*Astrological aspect
In astrology, an aspect is an angle that Planets in astrology, planets make to each other in the horoscope; as well as to the Ascendant, Midheaven, descendant (astrology), Descendant, Imum coeli, Lower Midheaven, and other points of astrological ...
References
;Attribution *{{1911, author=Anonymous, wstitle=Quadrature Astrological aspects Celestial mechanics Observational astronomy Orbits Spherical astronomy First quarter moon