What does evection mean?
Definitions for evection
evec·tion
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Wiktionary
evectionnoun
Modification of the lunar orbit due to the gravitational effects of the Sun.
Wikipedia
Evection
In astronomy, evection (Latin for "carrying away") is the largest inequality produced by the action of the Sun in the monthly revolution of the Moon around the Earth. The evection, formerly called the moon's second anomaly, was approximately known in ancient times, and its discovery is attributed to Ptolemy. The current name itself dates much more recently, from the 17th century: it was coined by Bullialdus in connection with his own theory of the Moon's motion.Evection causes the Moon's ecliptic longitude to vary by approximately ± 1.274° (degrees), with a period of about 31.8 days. The evection in longitude is given by the expression + 4586.45 ″ sin ( 2 D − ℓ ) {\displaystyle +4586.45''\sin(2D-\ell )} , where D {\displaystyle D} is the mean angular distance of the Moon from the Sun (its elongation), and ℓ {\displaystyle \ell } is the mean angular distance of the Moon from its perigee (mean anomaly).It arises from an approximately six-monthly periodic variation of the eccentricity of the Moon's orbit and a libration of similar period in the position of the Moon's perigee, caused by the action of the Sun.The evection opposes the Moon's equation of the center at the new and full moons, and augments the equation of the center at the Moon's quarters. This can be seen from the combination of the principal term of the equation of the center with the evection: + 22639.55 ″ sin ( ℓ ) + 4586.45 ″ sin ( 2 D − ℓ ) . {\displaystyle +22639.55''\sin(\ell )+4586.45''\sin(2D-\ell ).} At new and full moons, D=0° or 180°, 2D is effectively zero in either case, and the combined expression reduces to + ( 22639.55 − 4586.45 ) ″ sin ( ℓ ) . {\displaystyle +(22639.55-4586.45)''\sin(\ell ).} At the quarters, D=90° or 270°, 2D is effectively 180° in either case, changing the sign of the expression for the evection, so that the combined expression then reduces to + ( 22639.55 + 4586.45 ) ″ sin ( ℓ ) {\displaystyle +(22639.55+4586.45)''\sin(\ell )} .
Webster Dictionary
Evection
the act of carrying up or away; exaltation
Evection
an inequality of the moon's motion is its orbit to the attraction of the sun, by which the equation of the center is diminished at the syzygies, and increased at the quadratures by about 1¡ 20'.
Evection
the libration of the moon
Etymology: [L. evectio a going up, fr. evehere to carry out; e out + vehere to carry: cf. F vection.]
Wikidata
Evection
Evection, in astronomy, is the largest inequality produced by the action of the Sun in the monthly revolution of the Moon around the Earth. The evection, formerly called the moon's second anomaly, was approximately known in ancient times, and its discovery is attributed to Ptolemy. Evection causes the Moon's ecliptic longitude to vary by approximately ± 1.274°, with a period of about 31.8 days. The evection in longitude is given by the expression, where is the elongation, i.e. mean angular distance of the Moon from the Sun, and is the moon's mean anomaly, i.e. mean angular distance of the moon from its perigee. It can be considered as arising from an approximately 6-monthly periodic variation of the eccentricity of the Moon's orbit and a libration of similar period in the position of the Moon's perigee, caused by the action of the Sun. The evection can be considered as opposing the Moon's equation of the center at the new and full moons, and augmenting the equation of the center at the Moon's quarters. This can be seen from the combination of the principal term of the equation of the center with the evection: .
Chambers 20th Century Dictionary
Evection
e-vek′shun, n. (astron.) a lunar inequality resulting from the combined effect of the irregularity of the motion of the perigee, and alternate increase and decrease of the eccentricity of the moon's orbit. [L. evection-em—e, out, vehĕre, vectum, to carry.]
Dictionary of Nautical Terms
evection
A term for the libration of the moon, or that apparent oscillatory inequality in her motion, caused by a change in the excentricity of her orbit, whereby her mean longitude is sometimes increased or diminished to the amount of 1° 20′, whereby we sometimes see a little further round one side than at others.
Anagrams for evection »
civetone
Numerology
Chaldean Numerology
The numerical value of evection in Chaldean Numerology is: 9
Pythagorean Numerology
The numerical value of evection in Pythagorean Numerology is: 3
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"evection." Definitions.net. STANDS4 LLC, 2024. Web. 18 Apr. 2024. <https://www.definitions.net/definition/evection>.
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