synodic

Click image for description Venus, the second planet from the Sun, is named after the Roman goddess Venus. A terrestrial planet, it is sometimes called Earth's "sister planet", as the two are very similar in size and bulk composition. Although all planets' orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 1%. As Venus is closer to the Sun than the Earth, it always appears in roughly the same direction from Earth as the Sun (the greatest e ...

Including:

• Venus - Physical characteristics
• Venus - Atmosphere
• Venus - Surface features
• Venus - Venus' moon
• Venus - Aspects
• Venus - Observations and explorations of Venus
• Venus - Lowest distances to earth
• Venus - Cultural references

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The term Blue Moon has at least three different meanings, which are described below. One is a common phrase for a rare event, that really has little to do with the moon itself. Another is a description of the apparent color of the moon, which is frequently yellowish and rarely bluish. Full moons are given names in folklore, and two definitions of blue moon are a name for a rare full moon that does not have a folk name. One modern blue moon definition is for a second, extra full moon that occurs in a calendar month. The o ...

Including:

• Blue moon - Earliest use in English
• Blue moon - Visibly blue moons
• Blue moon - Farmer's Almanac Blue Moons
• Blue moon - Calendar blue moons
• Blue moon - Time Zone Problems
• Blue moon - Calendar vs. Farmers' Almanac: 2004 – 2010

Read more here: » Blue moon: Encyclopedia - Blue moon

Analemma is a term in astronomy used to describe the plot of the positions of the Sun on the celestial sphere at the same time of day (at approximately 24 hour intervals) and from the same location on Earth on successive days through the calendar year. This appears as a figure eight. If the course of the Earth around the sun were a precise circle and if the Earth's polar axis stood perpendicular to the plane of its orbit, the Sun would always appear at the same point in the sky at the same time of day throughout the year and the anale ...

Including:

• Analemma - Explanation
• Analemma - Analemma on other planets

Read more here: » Analemma: Encyclopedia - Analemma

Deimos is probably an asteroid that was perturbed by Jupiter into an orbit that allowed it to be captured by Mars, though this hypothesis is still in some dispute. Like most bodies of its size, Deimos is highly nonspherical with dimensions of 15×12×10 km. Deimos is composed of carbon-rich rock, much like C-type (carbonaceous chondrite) asteroids, and ice. It is cratered, but the surface is noticeably smoother than that of Phobos, caused by the partial filling of craters with regolith. The two largest craters, Swift a ...

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Deimos moon, Deimos moon - Discovery, Deimos moon - Characteristics, Deimos moon - Deimos in fiction

Read more here: » Deimos moon: Encyclopedia II - Deimos moon - Characteristics

Phobos was discovered by American astronomer Asaph Hall on August 18, 1877 at the US Naval Observatory in Washington, D.C at about 09:14 GMT (contemporary sources, using the pre-1925 astronomical convention that began the day at noon, give the time of discovery as August 17 16:06 Washington mean time). [1]. Asaph Hall also discovered Deimos, Mars' other moon. The notebook of the discovery of Phobos by Asaph Hall is as follows: "I repeated the examination in the early part of the night of [August] 11th, and again found ...

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Phobos moon, Phobos moon - Discovery, Phobos moon - Orbital characteristics, Phobos moon - Physical characteristics, Phobos moon - Origin, Phobos moon - Hollow Phobos claims, Phobos moon - Jonathan Swift's 'prediction', Phobos moon - Phobos in fiction

Read more here: » Phobos moon: Encyclopedia II - Phobos moon - Discovery

Hipparchus astronomer - Motion of the Moon. Hipparchus also studied the motion of the Moon and confirmed the accurate values for some periods of its motion that Chaldean astronomers had obtained before him. The traditional value (from Babylonian System B) for the mean synodic month is 29 days;31,50,8,20 (sexagesimal) = 29.5305941... d. Expressed as 29 days + 12 hours + 793/1080 hours this value has been used later in the Hebrew calendar (possibly from Babylonian sources). The Chaldeans also kn ...

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Hipparchus astronomer, Hipparchus astronomer - Life and work, Hipparchus astronomer - Babylonian sources, Hipparchus astronomer - Geometry and trigonometry, Hipparchus astronomer - Lunar and solar theory, Hipparchus astronomer - Motion of the Moon, Hipparchus astronomer - Orbit of the Moon, Hipparchus astronomer - Apparent motion of the Sun, Hipparchus astronomer - Orbit of the Sun, Hipparchus astronomer - Calendar, Hipparchus astronomer - Distance parallax size of the Moon and Sun, Hipparchus astronomer - Eclipses, Hipparchus astronomer - Astronomical instruments and astrometry, Hipparchus astronomer - Geography, Hipparchus astronomer - Star catalogue, Hipparchus astronomer - Celestial bodies, Hipparchus astronomer - Celestial coordinate systems, Hipparchus astronomer - Brightness of stars, Hipparchus astronomer - Precession of the equinoxes 146 BC-130 BC, Hipparchus astronomer - Hipparchus and astrology, Hipparchus astronomer - Named after Hipparchus, Hipparchus astronomer - Literature

Read more here: » Hipparchus astronomer: Encyclopedia II - Hipparchus astronomer - Lunar and solar theory

The controversy whether or not ancient Macedonia should be considered a Hellenic state is addressed variously: based on ancient sources, and on linguistic evidence. Neither approach is conclusive, Herodotus seems to assert that the Macedonian aristocracy was of Achaean origin while Macedonian people were of Dorian stock. Linguistics seems to point inconclusively to either Macedonian as an archaic form of Greek, Macedonian as part of a Graeco-Macedonian subfamily of Indo-European, or Macedonian as an in ...

See also:

Macedon, Macedon - Early history, Macedon - Expansion, Macedon - Decline, Macedon - Calendar, Macedon - Language, Macedon - Hellenic controversy, Macedon - Herodotus, Macedon - Linguistics

Read more here: » Macedon: Encyclopedia II - Macedon - Hellenic controversy

In recent times, people have taken to calling a full moon a blue moon based on the Gregorian calendar. By this use of the term, a blue moon is the second of two full moons to occur in the same calendar month. This definition of blue moon originated from a mistake in an article in the 1946 Sky & Telescope magazine, which failed in an attempt to infer the earlier definition used in the original Farmer's Almanac (see above). It was helped to popularity when a Trivial Pursuit question used this as a source for one ...

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Blue moon, Blue moon - Earliest use in English, Blue moon - Visibly blue moons, Blue moon - Farmer's Almanac Blue Moons, Blue moon - Calendar blue moons, Blue moon - Time Zone Problems, Blue moon - Calendar vs. Farmers' Almanac: 2004 – 2010

Read more here: » Blue moon: Encyclopedia II - Blue moon - Calendar blue moons

Venus - Atmosphere. Venus has an atmosphere consisting mainly of carbon dioxide and a small amount of nitrogen, with a pressure at the surface about 90 times that of Earth (a pressure equivalent to a depth of 1 kilometer under Earth's oceans); its atmosphere is also roughly 90 times more massive than ours. This enormously CO2-rich atmosphere results in a strong greenhouse effect that raises the surface temperature more than 400 °C (750 °F) above what it would be otherwise, causing temperatu ...

See also:

Venus, Venus - Physical characteristics, Venus - Atmosphere, Venus - Surface features, Venus - Venus' moon, Venus - Aspects, Venus - Observations and explorations of Venus, Venus - Lowest distances to earth, Venus - Cultural references

Read more here: » Venus: Encyclopedia II - Venus - Physical characteristics

Due to the earth's tilt on its axis (23.45°) and its elliptical orbit around the sun, the relative location of the sun above the horizon is not constant from day to day when observed at the same time on each day. Depending on one's geographical latitude, this loop will be inclined at different angles. The vertical coordinate of a point corresponding to a date corresponds to the declination of the sun on that date, while the horizontal coordinate indicates whether the sun is "fast" or "slow" comp ...

See also:

Analemma, Analemma - Explanation, Analemma - Analemma on other planets

Read more here: » Analemma: Encyclopedia II - Analemma - Explanation

Mars has only a thin atmosphere; however, it is extremely dusty and there is much light that is scattered about. The sky is thus rather bright during the daytime and stars are not visible. Extraterrestrial skies - The colour of the Martian sky. Generating accurate true-colour images from Mars' surface is surprisingly complicated [1]. To give but one aspect to consider, there is the Purkinje effect: the human eye's response to colour depends on the level of ambient light — red objects appear to darken fas ...

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Extraterrestrial skies, Extraterrestrial skies - Mercury, Extraterrestrial skies - The Sun from Mercury, Extraterrestrial skies - Other planets seen from Mercury, Extraterrestrial skies - Venus, Extraterrestrial skies - The Moon, Extraterrestrial skies - The Sun from the Moon, Extraterrestrial skies - The Earth from the Moon, Extraterrestrial skies - Eclipses from the Moon, Extraterrestrial skies - Mars, Extraterrestrial skies - The colour of the Martian sky, Extraterrestrial skies - The Sun from Mars, Extraterrestrial skies - Mars' moons as seen from Mars, Extraterrestrial skies - Earth from Mars, Extraterrestrial skies - The skies of Mars' moons, Extraterrestrial skies - Asteroids, Extraterrestrial skies - 87 Sylvia and its moons Romulus and Remus, Extraterrestrial skies - Jupiter, Extraterrestrial skies - Jupiter's moons as seen from Jupiter, Extraterrestrial skies - The skies of Jupiter's moons, Extraterrestrial skies - Saturn, Extraterrestrial skies - The skies of Saturn's moons, Extraterrestrial skies - Uranus, Extraterrestrial skies - Neptune, Extraterrestrial skies - The sky of Triton, Extraterrestrial skies - Pluto and Charon, Extraterrestrial skies - Comets, Extraterrestrial skies - Extrasolar planets

Read more here: » Extraterrestrial skies: Encyclopedia II - Extraterrestrial skies - Mars

The first Macedonian state emerged 8th or early 7th century BC under the Argead Dynasty, when the Macedonians are said to have migrated to the region from further west. Their first king is recorded as Perdiccas I. Around the time of Alexander I of Macedon, the Macedonians started to expand into Eordaia, Bottiaea, Pieria, Mygdonia, and Almopia. Near the modern city of Edessa, Perdiccas I (or, more likely, his son, Argaeus I) b ...

See also:

Macedon, Macedon - Early history, Macedon - Expansion, Macedon - Decline, Macedon - Calendar, Macedon - Language, Macedon - Hellenic controversy, Macedon - Herodotus, Macedon - Linguistics

Read more here: » Macedon: Encyclopedia II - Macedon - Early history

After that, in 135 BC, enthusiastic about a nova in the constellation of Scorpius, he measured with an equatorial armillary sphere ecliptical coordinates of about 1,000 stars (the exact number is not known) for his star catalogue. He also knew the work Phainomena (Phenomena). That poem, known as Phaenomena or Arateia, describes the constellations and the stars that form them. Hipparchus' commentary contains many measurements of stellar position and times for rising, culmination, and setting of the constella ...

See also:

Hipparchus astronomer, Hipparchus astronomer - Life and work, Hipparchus astronomer - Babylonian sources, Hipparchus astronomer - Geometry and trigonometry, Hipparchus astronomer - Lunar and solar theory, Hipparchus astronomer - Motion of the Moon, Hipparchus astronomer - Orbit of the Moon, Hipparchus astronomer - Apparent motion of the Sun, Hipparchus astronomer - Orbit of the Sun, Hipparchus astronomer - Calendar, Hipparchus astronomer - Distance parallax size of the Moon and Sun, Hipparchus astronomer - Eclipses, Hipparchus astronomer - Astronomical instruments and astrometry, Hipparchus astronomer - Geography, Hipparchus astronomer - Star catalogue, Hipparchus astronomer - Celestial bodies, Hipparchus astronomer - Celestial coordinate systems, Hipparchus astronomer - Brightness of stars, Hipparchus astronomer - Precession of the equinoxes 146 BC-130 BC, Hipparchus astronomer - Hipparchus and astrology, Hipparchus astronomer - Named after Hipparchus, Hipparchus astronomer - Literature

Read more here: » Hipparchus astronomer: Encyclopedia II - Hipparchus astronomer - Star catalogue

Hipparchus is credited with the invention or improvement of several astronomical instruments, which were used for a long time for naked-eye observations. According to Synesius of Ptolemais (4th century) he made the first astrolabion: this may have been an armillary sphere (which Ptolemy however says he constructed, in Almagest V.1); or the predecessor of the planar instrument called astrolabe (also mentioned by Theon of Alexandria). With an astrolabe Hipparchus was the first to be able to measure the geographical latitude and t ...

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Hipparchus astronomer, Hipparchus astronomer - Life and work, Hipparchus astronomer - Babylonian sources, Hipparchus astronomer - Geometry and trigonometry, Hipparchus astronomer - Lunar and solar theory, Hipparchus astronomer - Motion of the Moon, Hipparchus astronomer - Orbit of the Moon, Hipparchus astronomer - Apparent motion of the Sun, Hipparchus astronomer - Orbit of the Sun, Hipparchus astronomer - Calendar, Hipparchus astronomer - Distance parallax size of the Moon and Sun, Hipparchus astronomer - Eclipses, Hipparchus astronomer - Astronomical instruments and astrometry, Hipparchus astronomer - Geography, Hipparchus astronomer - Star catalogue, Hipparchus astronomer - Celestial bodies, Hipparchus astronomer - Celestial coordinate systems, Hipparchus astronomer - Brightness of stars, Hipparchus astronomer - Precession of the equinoxes 146 BC-130 BC, Hipparchus astronomer - Hipparchus and astrology, Hipparchus astronomer - Named after Hipparchus, Hipparchus astronomer - Literature

Read more here: » Hipparchus astronomer: Encyclopedia II - Hipparchus astronomer - Astronomical instruments and astrometry

Under Philip II, (359-336 BC), Macedon expanded into the territory of the Paionians, Thracians, and Illyrians. This brought into its orbit the Monastir (now Bitola) and Gevgelija districts of what is now the Republic of Macedonia. Macedon became more politically involved with the south-central city-states of Ancient Greece, but it also retained more archaic features like the palace-culture, first at Aegae (modern Vergina) then at Pella, resembling Mycenaean culture more than classic Hellenic city-states, and other archaic customs, like Philip's multiple wives in addition to his Epirote ...

See also:

Macedon, Macedon - Early history, Macedon - Expansion, Macedon - Decline, Macedon - Calendar, Macedon - Language, Macedon - Hellenic controversy, Macedon - Herodotus, Macedon - Linguistics

Read more here: » Macedon: Encyclopedia II - Macedon - Expansion

Hipparchus is perhaps most famous for having been the first to measure the precession of the equinoxes. There is some suggestion that the Babylonians may have known about precession, but it appears that Hipparchus was the first to really understand it and measure it. According to al-Battani, Chaldean astronomers had distinguished the tropical and sidereal year. He stated that they had, around 330 BC, an estimation for the length of the sidereal year to be SK = 365 days 6 hours 11 min (= 365.258 days) with an er ...

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Hipparchus astronomer, Hipparchus astronomer - Life and work, Hipparchus astronomer - Babylonian sources, Hipparchus astronomer - Geometry and trigonometry, Hipparchus astronomer - Lunar and solar theory, Hipparchus astronomer - Motion of the Moon, Hipparchus astronomer - Orbit of the Moon, Hipparchus astronomer - Apparent motion of the Sun, Hipparchus astronomer - Orbit of the Sun, Hipparchus astronomer - Calendar, Hipparchus astronomer - Distance parallax size of the Moon and Sun, Hipparchus astronomer - Eclipses, Hipparchus astronomer - Astronomical instruments and astrometry, Hipparchus astronomer - Geography, Hipparchus astronomer - Star catalogue, Hipparchus astronomer - Celestial bodies, Hipparchus astronomer - Celestial coordinate systems, Hipparchus astronomer - Brightness of stars, Hipparchus astronomer - Precession of the equinoxes 146 BC-130 BC, Hipparchus astronomer - Hipparchus and astrology, Hipparchus astronomer - Named after Hipparchus, Hipparchus astronomer - Literature

Read more here: » Hipparchus astronomer: Encyclopedia II - Hipparchus astronomer - Precession of the equinoxes 146 BC-130 BC

Phobos is a dark body that appears to be composed of C-type surface materials. It is similar to the C-type (blackish carbonaceous chondrite) asteroids that exist in the outer asteroid belt. Phobos's density is too low to be pure rock, however, and it is probably composed of a mixture of rock and ice. The Soviet spacecraft Phobos 2 detected a faint but steady outgassing from Phobos. Unfortunately Phobos 2 failed before it could determine the nature of the material, but it is most likely water. Recent images from Mars Global Surveyor indicates that Phobos is covered with a layer of fine dust about a m ...

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Phobos moon, Phobos moon - Discovery, Phobos moon - Orbital characteristics, Phobos moon - Physical characteristics, Phobos moon - Origin, Phobos moon - Hollow Phobos claims, Phobos moon - Jonathan Swift's 'prediction', Phobos moon - Phobos in fiction

Read more here: » Phobos moon: Encyclopedia II - Phobos moon - Physical characteristics

Venus has been observed several times within the past 4000 years by a number of people, including the Greeks. Venus - Lowest distances to earth. At inferior conjunction, Venus can get closer to earth than any other planet--little more than 100 times the Moon's average distance. On December 16th, 1850, Venus reached since 1800 the lowest distance to earth with a value of 0,264138541298281 AU = 39514827 kilometres. This will be the closest approach of Venus to earth until December 16th, 2101 when Venus will ...

See also:

Venus, Venus - Physical characteristics, Venus - Atmosphere, Venus - Surface features, Venus - Venus' moon, Venus - Aspects, Venus - Observations and explorations of Venus, Venus - Lowest distances to earth, Venus - Cultural references

Read more here: » Venus: Encyclopedia II - Venus - Observations and explorations of Venus

The first episode of the computer and video game Doom takes place in a UAC base on Phobos. Phobos also featured in Kim Stanley Robinson's Mars trilogy as having a base built by the first colonists to Mars. Later the moon is overtaken by multinational forces and is de-orbitted by the Martian rebels. ...

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Phobos moon, Phobos moon - Discovery, Phobos moon - Orbital characteristics, Phobos moon - Physical characteristics, Phobos moon - Origin, Phobos moon - Hollow Phobos claims, Phobos moon - Jonathan Swift's 'prediction', Phobos moon - Phobos in fiction

Read more here: » Phobos moon: Encyclopedia II - Phobos moon - Phobos in fiction

Around 1958, the distinguished Russian astrophysicist Iosif Samuilovich Shklovsky, studying the secular acceleration of Phobos' orbital motion, suggested a "thin sheet metal" structure for Phobos, a suggestion which led to speculations on Phobos' artificial origin. Shklovsky based his analysis on estimates of the upper martian atmosphere's density, and deduced that for the weak braking effect to be able to account for the secular acceleration, Phobos had to be very light —one calculation yielded a hollo ...

See also:

Phobos moon, Phobos moon - Discovery, Phobos moon - Orbital characteristics, Phobos moon - Physical characteristics, Phobos moon - Origin, Phobos moon - Hollow Phobos claims, Phobos moon - Jonathan Swift's 'prediction', Phobos moon - Phobos in fiction

Read more here: » Phobos moon: Encyclopedia II - Phobos moon - Hollow Phobos claims