I was helping my 3rd grader with his science project. He had to make a poster about the Solar System. Instead of doing the 9 (Or 8, depending on who you ask) I had him do the 16th largest worlds and rank them by size. That way his class could see that just because some worlds were moons, doesn’t mean they are less interesting than planets.

It would also let them see that Ganymede and Titan are slightly bigger than Mercury and not much smaller than Mars. Tiny Pluto ranks number 16th, BTW.

We did all 16 worlds to scale.

We had trouble figuring out how many moon Jupiter, Saturn, Uranus and Neptune have. Depending on the source, we got different answers. So we ended up putting a question mark next to their number of moons, with a footnote that new moons are continuously being discovered around these worlds.

I also wondered if the teacher knew about the two new moons discovered around Pluto. We put Pluto has 3 moons. I hope she doesn't count that wrong.

I pulled out some of my old Astronomy books and was amazed at how much our knowledge has changed over the past 40 years.

One of my books, published in 1974, was still speculating that the dark patches on Mars may be plant life. They thought Uranus and Neptune were huge ice worlds.

A book published in 1985 was still using drawing for Uranus and Neptune because Voyager had yet to visit those worlds. And they were reporting Pluto as being bigger than what we know now.

Makes me wonder what will be outdated in my current Astronomy books in 20 or 40 years.