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The nearest known planet to the Sun, at a mean distance of 35,983,100 miles (0.387 AU), is Mercury, the smallest and fastest planet, orbiting the Sun in 87.9686 days (0.241 of an Earth year) at a speed of 197,030 mph. It is only one-third the size of Earth but its high mean density is almost equal to that of the Earth. It is thought that this is because Mercury was originally 30% larger than it is today. Its iron flowed inwards to form a dense core, similar to that of Earth's. However, early in Solar System history it is thought another planetesimal hit the proto-Mercury at high speed, when it was beyond the orbit of Mars, ripping off its rocky outer layers to leave only a thin rocky layer on a large iron core, and propelling it towards the Sun.
In November 1991 it was announced at the American Astronomical Society that the North Pole of Mercury is thought to be made of ice. It is -235F there, but 800F elsewhere, a surprising 1000 variance in a planet only 3,000 miles wide. Ice is also expected to be present at its South Polar crater.
Viewed from Earth it can never appear more than 27 45' from the Sun so it is always in the same zodiac sign as the Sun or one adjacent to it. As its orbit is highly eccentric its maximum elongation east or west of the Sun can be as little as 18. Unusually, the perihelion point of Mercury changes with each orbit, advancing along its orbit at a rate of about 9 arcminutes and 26 arcseconds each century. The gravitational interactions that cause this could not be entirely accounted for in the nineteenth century, causing Urbain Jean Joseph Le Verrier to believe that another planet lay between the Sun and Mercury.
Mariner 10 took 18 photographs of Mercury's surface on 29 March 1974 and these revealed a cratered surface to the planet, providing evidence of heavy bombardment early in its history - 4.6 thousand million years ago - followed by volcanism. It is the hottest and coldest planet ranging between 90 and 600 K from night to day, due to its slow rotation period.
Mercury travels 1490 per annum and rotates exactly three times during each two orbits of the Sun. In the 58.65 Earth days it takes Mercury to turn, it will have moved two-thirds of the way around the Sun. If you were on its surface, the daily drift of the Sun would be almost equalled by a drift in the opposition direction caused by the planet's yearly motion, so that Mercury's day, noon to noon, is 176 days long - twice as long as its year. Therefore there can be no permanent daylight or permanent darkness, and no twilight region on the planet. It was thought until 1965, when radio wave bounce tests proved otherwise, that it always showed the same face to the Sun, while the other side remained in perpetual shadow. This contradicted the current theories as to the formation of the Solar System, which relied on its having a "fixed" orbit, and remains an enigma.


Mercury's sigil () combines the forms of the crescent of the Moon, circle of spirit and cross of matter, and represents its ability to bring things together and unify, using its active intelligence. It is also a pictograph of the caduceus, the baton signifying the power of wisdom which the god Mercury is often depicted carrying.
Mythologically, Mercury was Hermes, son of Maia and Jupiter, the winged messenger of the Greek gods, regarded as the god of eloquence, cunning, invention, roads and commerce. It was Hermes who led individuals to the depths of Hell, employing trickery to this end, since most would not freely follow. Busts of Hermes affixed to pillars were set up as boundary markers at street corners and so forth. The Romans personified him as Mercury the Trickster, god of science and commerce, patron of travellers, rogues, vagabonds and thieves. He ruled communication, logic, thinking and memory, and embodied all the forces of contradiction. As Trickster it is appropriate that astronomers were deceived by both the orbit and the rotation of Mercury for so long, and were then so reluctant to accept the new evidence, which overturned Newton's theories. Symbolically, the light and shadow duality of Mercury represent the conscious and unconscious in man, since Mercury symbolises mentality. 
The equivalent Egyptian god is Thoth, called Hermes Trismegistus (the Thrice Greatest Hermes) by the Neoplatonists, acting as the servant and scribe of Ra, a sun god. He made the Calendar and his control over hieroglyphics and divine words enhanced his magical powers. He was the founder of the Hermetic Art or Philosophy of Alchemy, the transmutations of base metal into gold. The Hindu equivalents are Hanuman, the monkey god, and Saram, who watches over the golden flock of stars and solar rays. Since Mercury is the god of wisdom he is also associated with the Buddha. Woden (or Odin), the Norse god, is another derivation of the word and concept of the Buddha and so is a further aspect of Mercury.
The fourth day of the week, over which Mercury has rulership, was Mercury dies in Latin, Mercredi in French. This translates directly as Wednesday, Woden being the Teutonic or Norse principal god, who granted heroism and victory and decided man's fate, and was the god of spiritual life.
Caesar commented that the Celts worshipped Mercury, a chieftain-type god, inventor of all the arts, presiding deity of commerce, and guardian of travellers, more than any of their other gods (followed by Apollo, Mars, Jupiter and Minerva).


In astrology, Mercury represents our intellectual faculties, curiosity and ability to communicate with others, preceding relationship. It "signifieth subtill men, ingenious, inconstant: rymers, poets, advocates, orators, phylosophers, arithmeticians, and busie fellowes." Mercury has the ability to sort and index all the information ingested by the Moon, reasoning, storing, solving, interpreting, deducing, assimilating from experiences; it does not add profundity, however, or apply the knowledge it has processed. It has a left-brain function, but uniquely embodies both masculine and feminine principles, being both positive and negative; alchemists regarded Mercury with great importance as a compound of opposites. Its hermaphrodite nature is connected with its association with twilight, as it hovers between night and day, not quite belonging to either. When Mercury is at Inferior Conjunction its magnetic field causes the stream of electrified particles sent out from the Sun to deviate; these particles have an influence on the human nervous system.
Some astrologers differentiate between Mercury's night rulership of Gemini and its day rulership of Virgo, assigning Hermes to Gemini and Thoth (Hermes Trismegistus) to Virgo. In the Greek pantheon Mercury, the god of communication and healing, ruled Cancer. In esoteric astrology Mercury rules Aries. It is also an index of mentality, especially with short-term reactions, details, memory and day-to-day problems, and of how nervous energies will flow and manifest, acting as a gateway to understanding. Traditionally exalted in Virgo it is now regarded as being exalted in Aquarius.
The only major aspect that Mercury can make with the Sun, due to its proximity, is a conjunction, and this will occur twice in each cycle, once when Mercury passes the Sun on its near side (an inferior conjunction), and once on its far side (a superior conjunction). At this time it is invisible from Earth, and at its maximum distance from it (apogee). An inferior conjunction can easily be recognised in a chart because Mercury will be retrograde, as it overtakes Earth at its perigee (closest approach). From here Mercury moves into its "oriental retrograde state", becoming direct following its station. After its superior conjunction it moves into its "occidental direct state", becoming retrograde after its next station.
The varying angles at which Mercury is seen during its orbit produce phases, though these are difficult to observe. Half-phases occur at maximum elongation, with crescent and gibbous phases between its conjunctions and maximum elongations. Mercury can form conjunctions and sextiles with Venus, the other "inferior" planet. Mercury and Venus are only seen close to the horizon as the sun is rising or setting, but they need to be about 10 clear of the Sun to be visible to the naked eye.
A superior conjunction occurs every 115.9 days, allowing for the movement of Earth. On average it is direct for 94 days, and retrograde for 22 days. At the end of each cycle it will have moved roughly one-third of the way round the Zodiac. In 46 years it will be back at the same zodiacal position, give or take a couple of degrees, having plotted a series of grand trines moving successively through the elemental triplicities.
At the time of superior conjunction it is invisible in the Sun's glare, but as it moves away on its occidental direct course it becomes visible at around sunset. As it waxes, it appears higher in the sky, and remains in view for a longer time each day, up to 1 hours after sunset. As it approaches its first station it appears to slow down in its motion along the ecliptic, and the Sun appears to catch it up. After turning retrograde it mirrors its previous behaviour, speeding up and appearing more briefly, until its disappears at inferior conjunction. It next emerges after sunrise, on the other side of Sun, remaining visible until drowned by daylight, rising earlier and remaining visible for longer until reaching maximum elongation and turning direct. At this time it can be seen for up to 1 hours before sunrise.
These two types of conjunction symbolically suggest an opportunity to view both sides of an issue objectively. Mercury's fast orbit and slow rotation define its need to process vast amounts of sometimes-repetitive information rapidly prior to slowly forming a committed decision. The closer Mercury is to the Sun, the better the individual is able to communicate in a reciprocal way, but those with the two conjunct may be more involved in expressing their will than in obtaining feedback.



Idiosyncrasies in Mercury's orbit led astronomers to believe that there was another hidden planet close to the sun. Le Verrier made his proposition in 1859, asserting that if a planet was not the cause, then it was a collection, or second belt, of asteroids. An amateur astronomer named Edmond Modeste Lescarbault wrote to Le Verrier the same year claiming to have observed the planet, a round spot, in transit, silhouetted against the Sun, on 26 March 1859. Le Verrier determined that this planet should be called Vulcan, after the Roman god of fire, because of its proximity to the Sun (Its average orbital radius would be 0.1427 AU). He calculated that it had an orbital period of 19 days 7 hours, making it impossible to observe except when in transit, or during an eclipse. He delivered these findings, believing Vulcan to be the largest of a new asteroid group, at the Paris Acad-mie des Sciences on 2 January 1860.
Although his theories were widely accepted at the time, doubts were expressed when neither the new planet nor any of its group could be observed during a total eclipse in Spain that fortuitously occurred in July 1860. Le Verrier became obsessed with observing Vulcan until in 1870 his entire staff at the Paris Observatory resigned in protest. He died in 1877, thus avoiding Vulcan's failure to appear during the total solar eclipse of 1878. For most astronomers this was the final nail in Vulcan's coffin: it did not exist.
Einstein realised on 18 November 1915 that his theory of relativity could explain how Mercury's perihelion anomalies were instead caused, revealing a breakdown in Newton's Laws of Gravity. The gravitational field of the Sun, into which Mercury delved quite deeply, was found to be the cause. Einstein was so moved by this realisation that he had palpitations of the heart, and later remarked, "For a few days I was beside myself with joyous excitement". Typically, Mercury had broken the rules again.
Some Esoteric astrologers still believe that Vulcan exists within the orbit of Mercury. There is no astronomical evidence to support this hypothesis, and Vulcan only has symbolic relevance today. Notwithstanding this, an ephemeris of Vulcan does exist, although its position is usually placed within 3 of Mercury and on the side closest to the Sun, or "rectified" from the placings of other planets in the chart.
Sightings thought to have been of Vulcan could have been of a comet or Earth-crossing asteroid, such as Icarus. Since Vulcan's orbit is supposedly within 7 of the Sun, its position corresponds to that of the other focal point of Mercury's elliptical orbit (the first being the Sun), Mercury's so-called Dark Sun, a point in space that could also have astrological significance.
Vulcan is the Latin name for Hephaestus, the divine smith and artisan, who was given to Venus (Aphrodite) as a husband by Jupiter (Zeus) and Juno (Hera). Ugly and lame, Vulcan, or Mulciber (the softener) was so sickly at birth that his mother Juno threw him from the heights of Olympus. Luckily, he fell into the sea where the sea goddess Thetis took charge of him, and helped him set up his first smithy. When Juno saw Thetis wearing a beautiful brooch, which he had made for her, she discovered his destiny and restored him to Olympus, where in his smithy with the Cyclops under Mount Etna and in workshops beneath other volcanoes he forged thunderbolts for Jupiter. In a later quarrel with Jupiter, he was again hurled out and spent a whole day in fall, breaking both legs and becoming permanently lame. His work was of matchless skill, including his own golden leg-supports, and a set of mechanical women entrusted with smithying tasks of great complexity. It was Vulcan who created Pandora, the clay woman commissioned by Jupiter. Because of Venus's affairs with Mars and others, he became special patron of cuckolds.



In the intuitional astrology of Alice Bailey, Vulcan is one of the sacred planets, connected especially with the First Ray. It also symbolises, in esoteric astrology, a planetary state that represents the future embodiment of Earth, when humanity has reached its highest spiritual consciousness. The Vulcanian element in man is the stuff of which we are made, but which eludes analysis. Vulcan puts us all in the furnace, and by burning away the dross, reveals the essence of our being. Vulcan is the esoteric ruler of Taurus. According to Manilius and the Romans, Vulcan, god of fire and metals, was the Greek pantheon ruler of Libra.

Last updated 26 April 2004