I had them memorized by Orbital position and could arrange them by size around the same time I actually could recite the whole alphabet… well, I have to admit to being a tad slow on memorizing the “whole” alphabet. I kept getting tripped up somewhere between “i” and “p”.
Hey! No Jokes! I wasn’t actually making a joke there! I actually did have problems keeping track of the letters somewhere between those two letters! Perhaps it was one of the earlier signs of a learning disorder?
I could even arrange them by size though perhaps it would be hard to place Pluto. I guess Pluto always has been hard to place.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury, Pluto
‘Tis not that simple now. Besides the fact that there were Trans-Plutonian bodies of significant size discovered, and besides the fact that Pluto swang closer to the Sun than Neptune for a while on its eccentric inclined orbit, and besides the fact that a few larger asteroids were for a short while considered to be planets until their true mass was discovered — now we have over a thousand extra-solar planets to contend with.
At one time we also knew of cold “Gas Giants” like Jupiter, Saturn, Uranus, and Neptune; small rocky round bodies like Mercury, Mars, the Moon, and possibly some of the other round bodies of the Solar System; larger rocky round bodies with atmospheres like Earth and Venus; and small rocky bits like asteroids, meteors, and bits of dust. Not to mention the icy balls of comets and free floating dust. I included Mars with the small rocky round bodies even though we knew it had an atmosphere because of it’s well cratered surface — otherwise it could go in the grouping with Earth and Venus.
I wrote that paragraph looking through the eyes of someone from just before the Pioneer and Voyager probes past Jupiter and Saturn which showed us close-up views of their moons and introduced us to ice ball moons and how there were more sorts of celestial bodies than we thought.
That was an understatement because the menagerie of spheres attending the four gas giants introduced us to so many different sorts of bodies. Some had their own volcanism. One has an atmosphere with lakes and rivers… of hydrocarbon products, but looking so much like lakes, rivers, bays and features like on Earth as to seem like looking at home.
The exo-planets seem like they are introducing an even larger menagerie…
But the word “planet”, the word “moon”, the words “dwarf planet” all have their meanings. As do “celestial body” “exoplanet” “rogue planet” “natural satellite” “asteroid” “planetoid” “meteor” “micro-meteor” “space dust” “dust” “gas” not to mention “comets” all sorts of nebula and some other stuff.
I must admit not to agreeing with some of the distinctions officially made. Perhaps they were right in excluding Pluto from the planets, but I think that it is for the wrong reasons. Actually I think that location is a wrong reason for deciding if a body is a planet or not and I do not know that whether a clear orbit should determine it either.
Mars in orbit around the Sun, or if it were in orbit around a gas giant orbiting at the same distance from the Sun that Mars does would still be Mars. If Pluto were moved into a clear orbit between Uranus and Neptune would still be Pluto even though now it would now be considered to have “cleared its orbit”. Jupiter slung out of it’s orbit into interstellar space and now a “rogue planet” would still be Jupiter… although it’s wind patterns would undoubtedly be different without the addition of energy from the Sun. Jupiter also creates some of it’s own energy.
Would a planet that was much like the Earth, but frozen and sailing between the stars dark and nearly invisible, captured by the Sun and pulled into an orbit somewhere between Mars and Jupiter go from not being a planet to being a planet?
I think that bodies are planets or aren’t planets based on what they are not where they are. There might be different types of planets, just as there are different types of stars. There might be problems with a dividing line between stars and planets and between planets and planetoid… perhaps between planetoid and meteoroids or meteoroids and dust… But… location would not be part of the definition. There would be terrestrial planets and they might be divided by a few groups and gas giants might be divided into a couple of groups too. There might be different sorts of ice planets if they are not considered terrestrial or terrestrial might be divided to include rocky, ice, metal… etc.
There is so much to write about the different sorts and I believe over a thousand planets or planet candidates now.
I think things require some rethinking and the International Astronomical Union (IAU) was a bit short-sited despite the telescopes they have connections with.