Why are the planets named after the Roman gods and not the Greek gods?

In Greek, the planets still have the names of the corresponding Greek gods (Poseidon, Aphrodite, etc.). But medieval science was dominated by speakers of Latin, and the English and Romance languages use the Roman names of the planets.

The main visible planets Mercury Venus Mars Jupiter and Saturn were named after Roman gods due to the influence of Latin and Roman culture on our society. Uranus on the other hand was not named after a Roman god but the name is the Latinized version of the Greek god of the sky, Ouranos.

Our astronomy comes from Babylonian culture, through the Greek language. The root of the names does come from Greek mythology.

Rome was founded by exiled Greek soldiers who brought their culture (and myths) with them, but adopted the local god names - and adapted them to their own mythology.

Thus, the Latin god Iuppiter (a relatively minor god) became associated with Zeus (the head god under the Greek). And the planet known as Zeus to the Greeks, became known as "Iuppiter" to the Latin-speaking people in Rome.

Fast forward a dozen centuries.

In the Middle Ages, scientists from different countries started to write to each other, to tell of their discoveries and of their need for more information. The correspondence was being done through the Church, therefore Latin became the international language of science.

Therefore, astronomers used the Latin names of the planets, thus making it look AS IF the planets had been named after Latin gods.

But the discovery of the next planet, beyond Chronos (Saturnus), and its naming process, made it clear that the mythology behind the names is Greek:

In order, the outer planets (beyond Earth) are:

Mars (the Latin version of the Greek war god Ares)

Jupiter (in Greek mythology, Zeus is the father of Ares)

Saturn (Chronos is the father of Zeus)

Thus, for the next planet, they got the name of the father of Chronos, who was Ouranos.

The name is clearly from Greek mythology, even though the spelling was Latinized to Uranus.

Ouranos had no father (in Greek mythology). The next planet outward then had to use another ploy. In a telescope, its color is clearly aquamarine (between blue and green) just like sea water. Poseidon was the Greek god of the sea, and his Latinized version was Neptune (he was the god of horses, before the exiled Greek soldiers aligned him with Poseidon).

If the planets had been named after Roman gods (before the Greek modification), then Neptune would not have made any sense. However, if you accept that the names are derived from Greek mythology, then "translated" to the equivalent Latin name, then both Uranus (Ouranos) and Neptune (Poseidon) make sense.

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It is only "recently" that Latin has stopped being the international language of science. Many other languages have retained the Latin roots for their own names (for example, Soleil, Terre, Lune, in French). In other languages, some of the names reverted to earlier uses, for example the Russian Солнце (pronounced Soln'tse) from a word meaning "bright", and the English "Earth" from an old nordic word "Erd" meaning "home, the place where we grow food".

original Greek and Latin names:

Helios = Sol = Sun (we will have adjectives like heliocentric and solar)

Selene = Luna = Moon (selenography, lunar)

Gea (or Gaia) = Terra = Earth (all the roots geo- as in geography; terrestrial)

Hermes = Mercurius

Aphrodite = Venus (planet sometimes called Lucifer by Romans)

Ares = Mars (link to war = red, color of blood)

Zeus = Iuppiter = Jupiter

Chronos = Saturnus

You DO realize that the names are different in every language?

Because Rome was more powerful... So had more influence.

Because Italy has better food. :}