I just saw a great five-minute video called Is Pluto A Planet? that explains how the word “planet” has evolved over time. What I found fascinating is that kids in the early 1800s learned the 11 planets:
Like most people reading this blog who learned about planets after the 1930 discovery of Pluto, I learned that there are nine planets.
In an astronomy class in seventh grade, I even learned a mnemonic that I still remember today, thanks to Mr. Huntley — a teacher who wrote notes on the board and had us copy them during class time. He also kept us entertained by teaching us how to rip phone books in half by breaking the spine first.
The mnemonic we learned was “Mother Very Easily Makes A Jelly Sandwich Using No Peanutbutter” The “A” stood for the asteroid belt between Mars and Jupiter. I had no idea what the asteroid belt really was — but I got 100% on all of Mr. Huntley’s tests, and isn’t that what matters?
Not until I just saw the 5-minute Pluto video did I realize that the first four objects discovered in the asteroid belt were initially considered planets (from 1807-1845) until astronomers re-classified planets in the solar system in light of new discoveries. That explains the drop from 11 planets back to seven (Neptune and Pluto were discovered in 1846 and 1930, respectively).
It’s interesting also — and the video points this out — that early people thought the sun and moon and other objects in the sky revolved around the Earth, so the Earth itself could not be a planet because it was the center of everything.
I’m glad that I learned (and still remember) Mr. Huntley’s mnemonic, but I’m sad that we wasted so much time in 7th grade copying notes off of the board when we could have discussed the history of the planets, and how our conception of the universe has evolved over time and continues to evolve in light of new discoveries.
By teaching students to memorize unexamined “facts,” we rob them of the joy of discovery and we take from them the opportunity to figure out things for themselves.
I’m still uneasy when I see books that discuss the “eight planets” (when I was a kid, there were nine nine nine!) But I’m heartened to learn that there are also books out there that question our view of the solar system.
I’m excited for students at Triangle Learning Community middle school to confront different perspectives. Are there eight planets? Or maybe 11?
so that they will want to explore the ambiguity of the solar system.
Here’s a still from the video that makes a nice distinction between “terrestrial planets” and “gas giants” (Pluto is in the Kuiper Belt):
At TLC, we won’t copy any “facts” off the board — we’ll read information from a variety of sources and spend our time making real projects that work to sort through the delicious ambiguities.
We can play with mnemonics as a starting point — but mnemonics should just be a starting point. The real work comes from digging deep and exploring the complexities of the universe.
Addition: Today’s Transit of Venus event is a great hook for students to explore the universe. Click the link for a nice 4-minute video from NASA.