Classical planet

A classical planet is an astronomical object that you can see without special tools. It moves against the stars, which is why ancient people called them "wandering stars." There are seven classical planets, listed from brightest to dimmest: the Sun, the Moon, Venus, Jupiter, Mercury, Mars, and Saturn.

Ancient Greek astronomers, like Geminus and Ptolemy, were the first to write about these wandering lights during classical antiquity. They named them "planets," meaning "wanderers" in Greek, because they moved compared to the fixed stars. This helped people learn about the night sky and start the science of astronomy.

When the telescope was invented, scientists found many more objects in space. Today, only five of the original seven classical planets are still called planets. The Sun and the Moon are not planets. But Mercury, Venus, Mars, Jupiter, and Saturn are still part of our solar system, along with Earth, Uranus, and Neptune.

History

Babylonian

Main article: Babylonian astronomy

The ancient Babylonians saw seven planets moving in the sky. They named them in this order: the Moon, called Sin; the Sun, called Shamash; Jupiter, called Merodach; Venus, called Ishtar; Saturn, called Ninip; Mercury, called Nebo; and Mars, called Nergal.

Mandaean

Main article: Mandaean cosmology

In Mandaeism, the seven classical planets connect to old Babylonian beliefs. They are sometimes linked to a darker force led by Ruha, a queen figure. Each planet is thought to travel in a special ship. Pictures of these ships appear in Mandaean religious texts like the Scroll of Abatur. The planet names come from ancient languages like Akkadian and Sumerian.

Symbols

Main articles: Astrological symbols and Planet symbols

The symbols for the classical planets are very old. People used them in horoscopes and astrology. Early symbols include a circle with a ray for the Sun and a crescent for the Moon. Later, symbols for Mercury, Venus, Jupiter, and Saturn were created. These symbols often came from tools or objects linked to their stories. For example, Mercury used a caduceus, and Jupiter used a staff. These symbols have changed over time. The modern Sun symbol, a circle with a dot, first appeared during the Renaissance.

Planetary hours

Main articles: Planetary hours and Names of the days of the week

In old times, people thought the Ptolemaic system put the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn in a special order around the Earth. They split each day into seven parts, and each part was linked to one of these planets.

This idea helped name the days of the week. In many languages, the days are named after these planets. In English, some days come from old Norse gods, like Wednesday for Odin (who is like Mercury) and Thursday for Thor (who is like Jupiter).

Alchemy

Further information: Astronomical symbols and Alchemical symbol

In alchemy, each classical planet was linked to one of the seven metals known to ancient people. Alchemists used special symbols for both the planets and their matching metals. They believed that other metals were variations of these seven important ones.

Alchemy was often connected with astrology around the world. Both were used together in the search for hidden knowledge, also called the occult. The seven planets known to ancients were each thought to "rule" a certain metal:

• The Sun rules Gold
• The Moon rules Silver
• Mercury rules Mercury (also called quicksilver)
• Venus rules Copper
• Mars rules Iron
• Jupiter rules Tin
• Saturn rules Lead

Contemporary astrology

Main article: Planets in astrology

See also: Astrological sign § Dignity and detriment, exaltation and fall

Many cultures have used bright objects in the sky to tell stories and make predictions. In Western astrology, these bright objects are called planets. People use them to learn about personalities and life events.

In Indian astronomy and astrology, these bright objects are also important. They know the same seven visible "planets," including the Sun and Moon, plus two that cannot be seen.

Chinese astronomy and astrology use these bright objects too. Chinese astrology became very popular during the Han dynasty.

Naked-eye planets

Main article: Planetae

Some planets are easier to see at night than others. Venus is very bright and easy to spot, especially when the sun has just set. Mercury is harder to see because it stays close to the Sun. Mars looks brightest when it is far from the Sun in the sky. Jupiter and Saturn are large planets, but because they are far from the Sun, they do not shine as brightly. However, Jupiter often appears as one of the brightest objects in the night sky after Venus. Saturn’s rings can make it look brighter, but you need a telescope to see the rings.