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The classical planets commonly refer to the seven heavenly bodies in our solar system observable by the naked eye and known since prehistoric times. They include the Sun, the Moon, and the five closest planets to Earth: Mercury, Venus, Mars, Jupiter, and Saturn. Because their existence was known by many cultures all throughout the world since before recorded history, no discoverer is credited for them. The planets were typically named after the gods of their culture. Most Western cultures refer to them by their Latin names, in honor of the Roman pantheon, and probably led to the naming of the seven day week. Wikipedia does not have an article with this exact name. ... In astronomy, the Naked eye planets are Mercury, Venus, Mars, Jupiter, and Saturn. ... The solar system comprises the Earths Sun and the retinue of celestial objects gravitationally bound to it. ... The Sun is the star at the center of Earths solar system. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ... Note: This article contains special characters. ... Adjective Venusian or (rarely) Cytherean (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... For the Roman god, see Mars (mythology). ... Adjective Jovian Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Note: This article contains special characters. ... In English the days of the week are: Sunday Monday Tuesday Wednesday Thursday Friday Saturday Saturday and Sunday are commonly called the weekend and are days of rest and recreation in most western cultures. ...

History

In antiquity, the common perception of the universe was a geocentric one in which all heavenly objects revolved around the Earth. To an observer on Earth, stars appear to rotate around the night sky, but are always fixed relative to the other stars. These patterns of stars were charted as constellations by ancient peoples around the world. The observers noted, however, that a few of these heavenly objects, including the Sun and the Moon, appeared to rotate around the Earth at distinct periods and free of the other stars. These unfixed objects were called planets, from the Greek πλανήτης, planētēs, meaning "wanderer". The geocentric model (in Greek: geo = earth and centron = centre) of the universe is a paradigm which places the Earth at its center. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ...

In early Greek astronomy, the sizes and distances of the planets were not known, so they were inferred from observations of each planet's brightness and orbital period. Varying cultures produced different orderings for the planets.

One of the most exciting archaeological findings related to ancient Greece is the Antikythera mechanism, which is thought to be a device for calculating the motions of all celestial bodies known at that time, i.e. the classical planets. Ancient Greece is the period in Greek history spanning much of the Mediterranean and Black Sea basins and lasting for close to a millennium, until the rise of Christianity. ... The Antikythera mechanism is an ancient analog computer (as opposed to digital computer) designed to calculate astronomical positions. ...

Days of the Week

The Ptolemaic system placed the planets in order closest to Earth to furthest as the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. In addition, the day was divided into 7 hour intervals, each ruled by one of the classical planets. The first hour of each day would be named after the ruling planet, giving rise to the names and order of the Roman seven day week. Modern Latin based cultures, in general, directly inherited the days of the week from the Roman names which were themselves named after the classical planets (eg. Spanish Miercoles = Mercury, French Mardi = Mars). The modern English days of the week were inherited from gods of the old Germanic Norse culture (eg. Thursday = Thor). It can be correlated that the Norse gods could be attributed to each of the Roman planets and their gods, probably due to Roman influence rather than coincidentally by the naming of the planets. Mediaeval drawing of the Ptolemaic system. ... In English the days of the week are: Sunday Monday Tuesday Wednesday Thursday Friday Saturday Saturday and Sunday are commonly called the weekend and are days of rest and recreation in most western cultures. ...

The Planets

• The Sun was known for its obvious importance in providing life. It also served as literal universal constant in the passage of night and day. Many ancient cultures were able to accurately create calendars from charting the Sun thus predicting the regional seasons and solar events.

• The Moon and its phases were also charted by most cultures giving rise to lunar calendars. The lunar cycles were used to divide the solar/seasonal year called months.

• Mercury was known to have the quickest period probably leading it to be named for a Roman god associated with haste.

• Venus was identified as being the brightest object in the night sky after the Moon.

• Mars, now commonly known as "The Red Planet" is often associated with war due to its association to the Roman god. It is unknown, however, whether it was named after Mars due to its red color (as the color is very difficult to discern even with modern home telescopes), or if this was a matter of coincidence (Red was commonly associated by Romans for war and victory though this color connection to Mars may stem from the naming of the planet first.)

• Jupiter, now known as the largest planet in the solar system. Again, whether the Romans knew this or not is unknown, but this is a likely possibility as Jupiter does appear to outshine most of the other planets, yet has the second longest period. In other words, it appears large for its perceived distance. If they knew it was the largest planet, it is reasonable to assume they would name it after their ruler of the heavens.

• Saturn, now popularly known for its rings and being the second large planet, though whether the Romans knew this or not is debatable (the rings being difficult to discern even with modern house telescopes). The Roman naming was probably based on their (correct) assumption that Saturn was the furthest of the classical planets due to the length of its orbital period. The brightness being slightly less than Jupiter though brighter than most of the other planets. The Romans may have wisely named it for the Titan that was formerly deposed by the now greater Jupiter.

The Sun is the star at the center of Earths solar system. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ... In Egyptian mythology, Month is an alternate spelling for Menthu. ... Note: This article contains special characters. ... Adjective Venusian or (rarely) Cytherean (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... For the Roman god, see Mars (mythology). ... Adjective Jovian Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Note: This article contains special characters. ...

See also

• Naked Eye Planets
• Antikythera mechanism

The Antikythera mechanism is an ancient analog computer (as opposed to digital computer) designed to calculate astronomical positions. ...

External Links

• Chronology of Discoveries in the Solar System