In Inquiry, we have two not-yet satisfying theories to explain the moon phases:
Shadow-Theory: The first is that the earth can act as an obstacle for the paths of light from the earth, thereby being capable of casting a shadow on the moon. As the moon passes behind the earth, it can move into the shadow either fully or partially, creating moon’s phases. This idea clearly places the new moon as occurring when the moon is on the far side of the earth.
Cupping-Theory: The second is that the rays from the sun can only “cup” half the moon–the side facing the sun. When the moon is between the moon and the earth, you are staring at the uncupped side which is dark. You don’t see the moon because the lit side is facing the wrong way for you to see it.
- One problem this group is facing is that they *want* the full moon to be when the moon is opposite the sun, but they can’t figure out how the light rays get to the moon. That is, we know we’ve seen a full moon at night, but we can’t figure out how the light gets there, when the moon is tucked behind the earth. Here are possibilities we came up with:
- Maybe light scatters off the atmosphere of the earth, like the way we’ve seen light scatter off tissue paper.
- Maybe light “turns” and bends around the earth–the way we’ve seen happen with glass.
- Maybe light is getting to the moon from other objects besides the sun–star, planets, redirected sunlight off of asteroids.
- Maybe the sun is so big that there can still be straight paths that get to the moon, even when it’s behind the earth. Maybe the problem is we aren’t drawing things to scale.
- Maybe the moon orbits around the earth north-south, not east-west, so it’s never behind the earth.
Love those ideas.
Anyway, there was lots of movement in class towards the cupping theory (which by the way it’s called cupping because the student was trying to show which side of tennis ball was lit by cupping their hands around one half of the ball). I acknowledge what made sense about the idea, while really selling the problems we had identified. Another problem also came up, in which, a student said that the new moon explanation doesn’t really make sense, because it seems like that would be more of an eclipse, when the moon passes directly over the sun.
The idea about the how exactly the moon orbits around the earth has lead to some other ideas as well.
One group claims that the moon orbits the earth in the opposite directions that the earth spins. This group has some ideas for why this makes sense to them, and I’m not sure yet, but I think it has to do with thinking about what an app on their phone is showing them.
One group claims that the moon orbits the earth in same direction that the earth spins. This group claims that this can explain why the moon appears to rise later and later each day.
Other have floated the idea that the moon might changes its orbit, or that it’s orbit might not be perfectly with equator, or perfectly north-south, maybe it’s at an angle.
What about Moon Spin?
Another group worked during the day to develop the claim that the moon doesn’t spin. I pressed them to collect evidence for it, and they are working diligently to exam all the photos we’ve collected over the semester to prove that the same side of the moon is always facing toward the earth. Curious to see where they have gotten.
Thoughts about Directions for Tomorrow:
Push groups to seeing if by using props, if we can model all the moon phases by either casting shadows or by creating different moon cuppings. Then, bringing the challenge to representing those 3D models in 2D diagrams. Basically, right now our theories only discuss new and full moon, and I want to push the span of those theories to see how and if they can explain other phases.
Getting our orbit ideas well-developed enough so that they can be linked to observations. One group has done this–linking their model to moon rise times. But we need to do same thing with north-south orbits–what would we see differently in the earth was passing more northward or southward.
Scale! I’m stuck on whether we should try stick to things we can figure out from direct observations. OR, letting them first think about and look up the distance information… and then beginning modeling those scales. Going out to the football field with props, figuring out to diagram things to scale, and what implications that can have on whether light can get to the moon when it’s behind the earth.
I need an opportunity to problematize what N,E,S,W means, and how to relate that to maps, globes, our earthly perspective. That’s always a trouble.
Groups, of course, are interested in other questions
- How is moon seen differently in different parts of the world?
- Why does moon sometimes appear BIG, sometimes appear different colors?
- Where did the moon come from? How would life on earth be different without the moon?
- What’s the relationship between moon and the tides?
- Is their a relationship between moon and the seasons?
- Why does the moon appear to “turn” throughout the day?
Oh! Last idea that is really cool. The group that is focused on the claim that the earth rotates the same way the moon orbits the earth is using a cool clock analogy. They are claiming the moon only orbits a little bit each day. They are saying how when you look at a clock, you can see the second hand moving, and that’s like the earth moving–you can tell the earth is moving by watching the moon/sun. It’s harder to tell the minute hand is moving because it doesn’t move very far, you sort of have to wait a minute, and you can tell it’s moved. They think the moon is like this, it’s moving so slowly, that you can’t tell in a given day that it’s moved, but if you wait a day, you can tell it’s moved. They have this diagram labelled, “moon clock” that I haven’t yet had a chance to learn about, but I’m intrigued.