S K Y   I N F O R M A T I O N

― ASTRONOMY FACT SHEETS ―

 

SO JUST WHAT IS THE NAME OF OUR PLANET?

 

We know our world as the Earth.  But is that its name? 

The other planets of our solar system are all named for mythological beings.  Venus is the Roman goddess of love and beauty; Mars, the Roman god of war; Jupiter the king of the Roman gods.  But the Earth—what is it named for?  Dirt?

            And what about the moon?  It, too, has fallen between the celestial cracks.  Other planets' satellites have been endowed with beautiful names from mythology:  Miranda, Titan, Ganymede, Charon.  But our moon is just, well, "the moon."

            The problem, when you get right down to it, is that our planet and its natural satellite do not have official names.  The explanation for this dates back many centuries.

            "During antiquity, people knew of five planets," explains E. N. Genovese, Professor Emeritus of Classics and Humanities at San Diego State University.  "In the fourth century BCE, they called Jupiter 'Zeus-Star,' Saturn 'Chronos-Star,' Venus 'Aphrodite-Star,' Mercury 'Hermes-Star,' and Mars 'Ares-Star.' 

            “The moon was given the name 'Selene' in Greek,” he continued.  “It's just a generic name for something that shines, as is the Latin 'Luna.'  Neither word has anything to do with divinities, but they were later applied to divinities of those bodies.  Then as mythology developed—because there were two names—people made a separation and lost touch with the original application of the name.

            "The same goes for 'Earth.'  The word is Germanic—the German word for Earth is Erde.  It's just a word for the ground or dirt, and it got extended to something larger.  Of course, when the word was first derived, people had no sense of the Earth being one of the planets.  Once that was established, the name got transferred rather quickly."

            This worked fine for many centuries.  Then, in March of 1781, musical composer and amateur astronomer William Herschel found a new planet among the stars of the constellation Gemini.  In an attempt to get England’s King George III on his side (and some money in his pocket for doing astronomy), Herschel suggested naming the new world Georgium Sidus—“George’s Star”—after the King.  Fortunately, saner minds prevailed, and it was eventually named “Uranus”—the Latinized form of “Ouranos”, the Greek god of the heavens.

            Strictly speaking, Uranus was the only Greek name among the Roman planetary names.  But since Uranus was the god of the heavens, it seemed appropriate for the first planet found in modern times.  Later, when large bodies were discovered in 1846 and 1930, scientists named them after the Roman gods Neptune and Pluto.

            Today, as astronomical discoveries mount at a record pace, astronomers spend large amounts of time devising names.  Charged with this task is the Working Group for Planetary System Nomenclatrure (WGPSN) of the International Astronomical Union (IAU).

            "We try to follow a consistent theme," says Merton Davies of the Rand Corporation, a former member of that group.  "For instance, the names of all except one of the original satellites of Uranus were taken from Shakespeare.  So when new satellites were discovered at Uranus, we selected names from Shakespeare.  At Neptune we use a theme of water gods."

            Has the IAU ever considered creating and approving a proper name for our planet and its natural satellite—something to replace the generic terms Earth and moon?  "I suspect not," says Davies.  "The main reason is that the names work.  They're within the literature, and they're useful in communication.  It would be a terrible chore to try to change them."

            Granted, there are more pressing problems facing us today.  But suppose we did want to name the Earth and the moon; what might we come up with?  Our first thought might be to call our planet Terra, from which such words as "terrestrial" have sprung.  After all, it seems most natural.  But it would not fit the scheme; Terra is not the name of a god.  More appropriate might be Tellus, the Roman goddess of the earth, protector and developer of the sown seed.  We, then, would be named Tellurians.

            The moon has been known by many names over the ages:  Artemis, Diana, Phoebe, Cynthia, and Selene.  Perhaps most fitting is Luna, Roman goddess of the moon and the months.  Future inhabitants of that world might then be known as Lunarians.

            At present, of course, it's all academic.  The Earth is the Earth and the moon is the moon.  And that suits some people just fine.  "To me, the most beautiful words are the simplest and the oldest," says Charles Harrington Elster, author of the book There Is No Cow In Moscow.  "They're the most flexible and the most useful.  The fixed names of the planets that came from classical mythology are quite lovely.  But you'll never change Earth and moon."

            Beautiful words, yes.  Proper names, no. 

            And while it's true that having no official name for our planet and its natural satellite may not seem important now, it may become necessary someday.  Imagine the confusion in trying to draw up treaties, diplomatic arrangements, and trade agreements with future human colonists of other worlds without having an official name for ours. 

            And just wait until our first encounter with an extraterrestrial being—one who has visited worlds throughout our galaxy.  I'd love to see the smirk on his little green face when we tell him our planet doesn't have a name. 

            Why should it?  It's the Earth!