Naming the planets, a story stranger than the Sopranos

“Where do all these names come from, like Neptune, Pluto and Charon?”

Most of the planets and moons are named after ancient Greek and Roman gods and goddesses. Pluto was the king of the underworld or Hell and Charon was, and perhaps still is, the boatman who ferried dead bodies across the river Styx in Greek mythology to bring them into the underworld.

“I thought you said Pluto was discovered in 1930, so why was it named after a 2,500 year old Greek god?”

The Greek hell was cold and dark, rather than hot and that pretty well describes this part of the solar system. The other reason is that he was one of the last of the Titans not to have a planet named after him, so it seemed only fair. Charon was only discovered in 1978, but astronomers like to keep the traditions going.

“Who were the Titans?”

The Titans were a family of ancient Greek and Roman gods and outer five planets are named after them, Pluto, Neptune, Uranus, Saturn and Jupiter. The family squabbles of the Titans would stretch the belief of the most hardened soap opera fan. In the ancient myths Uranus was the father of this clan. Worried about what the rest of his family were plotting, he hid his children in a cave. His wife, guided by her maternal instincts, let the youngest, Saturn, free who of course immediately attacked his dad Uranus. He then promptly claimed the throne and married his sister. Knowing what children of gods can do he decided to swallow his newborn children rather than take any risks. Saturn’s wife, like her mother decided to protect the youngest. This spared child was called Zeus by the Greeks and Jupiter by the Romans. He bided his time, grew big and strong and returned as leader of the Olympians to take his father on. So he came back, killed Saturn his father and cut his brothers Neptune and Pluto from their father's body where they had been ever since being swallowed shortly after birth. Jupiter gave his brothers jobs to keep them busy. Neptune got the sea and Pluto got the not so great job of governor of hell. After this they all lived happily ever after until Christianity came along.

“Wow, mixed up family. What about the rest of the planets are they part of this story?”

The family saga of the outer planets is maintained even here. Mars, Venus and Mercury are all children of Jupiter in the myths. That just leaves Earth which was where the Romans and Greeks lived so couldn't really be named after a god.

“So they must have known these planets existed back in the times of the ancient Greeks and Romans?”

They knew the planets that you can see by looking up in the sky were different from stars but they had no idea they were solid round planets out in space.

“How did they know they were different?”

They could tell they were different because they moved across the sky whereas all the other stars stayed in fixed patterns. This is where the word planet comes from. The greeks called them planetai which means wanderers. They also learnt that these planets didn't wander anywhere but in definite patterns within a belt of stars called the Zodiac.

“The thing that astrologers go on about?”

The very same. Astrology is bunkum and the ancient Greek view of how the planets moved was pretty odd too even if it did provide an explanation for how these wandering planets could move among the stars. The Greek universe was centred on the Earth and had everything else revolving around it in perfect circles. Aristotle set this particular ball rolling with 55 spheres made from a perfect transparent substance that moved all the planets around. A bit later another Greek astronomer-philosopher, Ptolemy, fine tuned this clockwork universe and his ideas were considered to be the way the universe was for well over a thousand years. Ptolemy placed the Earth at the centre of the universe. But I'm being a bit unfair on the early Greeks, not all of them got it wrong.

“It doesn’t sound like they got much right to me.”

At around the same time as Aristotle, Aristarchus suggested that the sun was at the centre of the universe, but like the better theories of light around at the time, this was largely ignored and later swept carefully under the scholastic carpets of European monasteries. This was at a time when men were either killing each other or copying out pages from of ancient books over and over again back in the dark ages. Then came the renaissance in the 1500’s and some very clever people who were not afraid to stick their necks out a bit, even at the risk of getting them cut off.

“What was wrong with thinking the earth moved around the sun?”

Nothing at all, apart from the curious fact that the Christian Church at the time was supporting the theories developed by an ancient pagan civilisation. Perhaps this was because this theory gave the most important position in the universe to the Earth and since the church was on Earth that seemed appropriate to the leaders of the Church at the time.


“Since the bible says God made the universe, shouldn't heaven be at the centre?”

People have been burned at the stake for less heretical suggestions. Remember what happened to Anaxagoras after he suggested his hot rock idea for the Sun back at the start of this journey.