Moon Phases
Teachers worldwide find Moon phases a particularly troublesome topic [1]. Normal teaching methods just aren’t enough to help learners move past their misconceptions.
The most common misconception is that Moon phases are caused by the Earth’s shadow[1]. This idea is easy to communicate and rarely challenged in everyday life. The Moon’s visibility - both in our cultures and our skies - means that learners are likely to have encountered and used this misconception many times over many years. Every occasion will have made it easier to recall and more strongly believed.
So, how do you remove such a well-embedded misconception? The simple answer is: you can’t.
The misconception is encoded in their brain, and there’s nothing you can do about that [3]. But what you can do is to try to help learners reduce how much they mentally call upon it. If they are able to construct an alternative (hopefully correct!) understanding, then it is possible to lower the relative status of the misconception, until it is eventually ignored [3].
To achieve this, you need to ‘co-activate’ the two conceptions, meaning you need to get the learner to think about both their misconception and the correct explanation alongside each other. Which is difficult because brains really don’t like holding two conflicting concepts at one time.
It turns out that teaching Moon Phases has a lot more in common with debunking conspiracy theories than it does with normal teaching. Luckily, debunking is a hot topic in psychology, which can offer us some practical advice.
Research suggests an approach structured as follows [2,4]:
State the correct conception
Acknowledge the misconception
Refute the misconception
Explain the correct conception
Practice using the correct conception
1. State the correct conception
The first thing they hear is more likely to stick, so don’t start with the misconception. Start by briefly stating the correct explanation. For example:
“Moon phases are created by the changing angle of the Sun. The Sun can only light half the Moon at one time, and it’s not always the half we are looking at.”
This means we should avoid asking people what they think causes Moon phases! Recalling and thinking about their misconceptions will only strengthen them.
2. Acknowledge the misconception
This step is tricky to get right. You don’t want to add yet another link of familiarity to the misconception (“I remember hearing this in the planetarium”). Tell them that you are going to say something that is not true, then state it as briefly as possible. Don’t explain it in detail, and don’t explain why people might believe it.
For example: “You might have heard other explanations for Moon Phases, but as soon as you start to think about these in more detail you will realise they can’t quite be right. One common Moon-myth is that the phases have something to do with the Earth’s shadow.”
3. Refute the misconception
Pull it apart and show them why it cannot be correct. Provide them with new information and evidence that does not fit with the incorrect model.
The planetarium could be used to:
Show the true scale and structure of the solar system.
Show how a lunar eclipse contrasts visually to normal phases.
Show images of Earth, Moon or other planets in space, and consider how they are lit.
Be careful to avoid explaining the misconception in detail, or having them think about it. Don’t ask them to use the full misconception to work something out - this process will only embed it more strongly in their minds. Focus on the positive, correct information that conflicts with it. For example:
“Let’s zoom in on Venus as if we had a telescope. Venus is closer to the Sun than we are, and it has no Moon. Can you see its crescent shape?”, or maybe “The Moon looks bright where it is lit by the Sun. Could the Earth block some of that light? Yes - and it’s called a lunar eclipse. Eclipses are very exciting and rare events; here are some photos of a lunar eclipse that I saw two years ago - doesn’t the Moon look strange.”
You need to make them realise that they have a gap in their knowledge. This will be uncomfortable for a lot of people but it’s a necessary step.
4. Explain the correct conception
Once you have created a knowledge gap, it’s important to fill this straight away. The learner’s discomfort makes them open to the possibility of relieving that feeling by accepting an alternative conception.
Now is the time to explain why we have phases! But this must be done in a way that they can properly understand. They need to really ‘get it’; it needs to make sense to them. Part of the problem with Moon Phases as a topic is that this step is really difficult! But if you don’t have time to do this step well, then your intervention is unlikely to succeed (and it may well just result in reinforcing the misconception).
Make sure you give them time to think. And avoid scale-distorted and/or simplified visual models that imply a lunar eclipse should occur every month. These will lead learners to recall and reinforce their misconception.
There are some difficult steps to understanding phases, including:
The land below my feet is not a fixed, everyday object (like the floor of my room), but rather part of a spherical astronomical object in space.
The Moon is much further from Earth than most pictures show it to be.
Imagining what an object will look like from a different viewpoint. (This can be very difficult for children even if they have a 3D model in front of them.)
You might consider providing teachers with a list of required prior knowledge, and/or offering pre-visit materials to help them cover these and other key concepts before their visit to the dome.
5. Practice using the correct conception
Once learners understand the ‘correct’ conception, they need to use it. The more they think about it (and the more useful they find it), the more the brain will value it over the misconception.
Constructing their own arguments about why the misconception is false is particularly helpful. But again, beware repeating the whole misconception! If you can pull it apart into elements then that is more helpful. This is like giving someone a vaccine that includes just one part of the virus to help their body learn how to fight it. For example:
“So here’s a morning sky: there’s the Quarter Moon, and there’s the Sun. The Sun is shining on the Moon to light it up. But this half of the Moon is dark. What if someone told you that this half is dark because something else in space was blocking the sunlight from reaching it? Can you see anything that could be doing that? Have a think. What would you say to that person - how would you explain why it’s dark on that side? Try your argument out on the person sat next to you and see if they think it would work.”
Finally, finish up by stating the correct answer one more time. Final words are sticky.
What next?
Where two conflicting conceptions are held, the brain actively inhibits use of the lower-status one [3]. The new conception will need to be recalled and used many times to raise its status enough to win out long term. It’s not uncommon for people to slide back to using an old misconception if the new conception is not continually elaborated upon and used and recalled [3].
This means that there is huge value in providing activities for learners to use after their visit to the planetarium. Especially if the activity is something they can do without support, on a repeated basis - for instance: “Every time you see the Moon, think where the Sun must be to be lighting it like that”.
Trying to effect conceptual change to banish a misconception from a learner’s thinking is a great but worthy task. It just takes time. Planetariums are a fantastic place to visualise memorable true-scale models that can help with this process.
References
1. Learning about Phases of the Moon and Eclipses: A Guide for Teachers and Curriculum Developers, Kavanagh, Astronomy Education Review 2005, Issue 1, Vol. 4 19-52.
2. How to Help Students Overcome Misconceptions, Taylor, The Learning Scientists Blog 2017, https://www.learningscientists.org/blog/2017/7/25-1 .
3. Inhibition and Conceptual Learning in Science: a Review of Studies, Mason & Zaccoletti, Educational Psychology Review 2021, 33, 181-212 .
4. Debunking: A Meta-Analysis of the Psychological Efficacy of Messages Countering Misinformation, Chan et al., Psychological Science 2017, Vol. 28(11) 1531-1546.
Further references available on request.
With thanks to Julia Plummer, Ken Brandt and Shannon Schmoll of the IPS Education Committee for comments.