Beat the Seasons
Many popular misconceptions are born from misguided links to familiar, well-understood concepts. A good example is the misconception that summer is warmer because we are closer to the Sun. This misconception can be linked to past experiences of huddling closer to a heat source to catch more of its warmth. The misconception feels very natural and there is no immediately obvious evidence that might contradict it.
As discussed in previous columns, learners will interpret new information through the lens of their misunderstanding. They give more attention to evidence that agrees with their prior beliefs, and less to aspects that disagree. Unfortunately, they are likely to have encountered astronomy diagrams that have accidentally reinforced their mistaken beliefs.
It is especially important to consider the prior beliefs of your audience, and to be aware of the points at which you may be challenging these. Here are three mistaken models that your learners might be bringing into the dome:
What’s my Angle?
The solar system is often shown as if viewed from a tilted angle. This saves space on the page, but is an unexpected viewpoint for anyone expecting a map. Without clear explanation, it is no surprise that some people might expect the view to be a plan view, from ‘above’.
Consider Figure 1. If the first panel was interpreted as a plan view, the Earth would be different distances from the Sun at different times of year (as in panel 2). This would fit with the misconception that we are all closer in summer. (It would also mean we experienced two summers per orbit, but human brains automatically give less attention to things that do not fit with prior beliefs, so this may well be ignored.)
The planetarium’s ability to show planetary orbits from moving viewpoints is great for helping learners to commit an accurate 3D model to memory. Drawing attention to the orbit shape may help those who believe it to be more elliptical.
Rotating to a tilted viewpoint and mentioning that this is how orbits are often shown in books may help people align their prior experience with what they are seeing. (“Oh, my book isn’t wrong, it’s just showing it on a tilt”, rather than “She might say that but I know differently from my book”.)
Figure 1: Ambiguous diagrams can support misconceived ideas.
Elliptical over-exaggeration
The Earth’s orbit is, of course, not exactly circular. But explaining this to learners who have misconceptions about the seasons can cause confusion. This especially where diagrams exaggerate the ellipticity in order to show how the Sun is positioned at one focus of the orbit.
If the diagram in figure 2 was taken as showing true ellipticity, then this would fit with a ‘Summer is closer’ explanation for the seasons, showing just one summer and one winter each orbit. It still can’t be correct, as Northern summer coincides with Southern winter. Despite this, it is very likely to be accepted because it supports the prior misconception that the Sun is closer in summer.
Care should be taken whenever talking about the deviation of the Earth’s orbit from a circle for this reason, ensuring that this information is not being taken as evidence to support a misconceived seasons model.
Figure 2: Exaggerated scales can create mental models that reinforce misconceptions.
Lean In
Perhaps the learner knows that the Earth’s orbit is near-circular. They understand that when one of Earth has summer, the other has winter. And they know that seasons are caused by the ‘tilt’. Is this enough to banish the misconception that ‘summer is closer’? Not quite.
Recalling memories of standing near a bonfire, it’s not unreasonable to think of the summer hemisphere as leaning in towards the warmth, and the winter hemisphere as leaning away to cool off. Diagrams showing the Earth and Sun very close together could support this model.
Of course, it’s not possible to show the Sun and Earth in detail at true scale in the dome. They are so far apart! Presenters choose different ways to tackle this - usually either expanding the scale of both until they are visible, or having the Sun out of sight while looking at the Earth.
If you are going to change the scale of the Sun and/or Earth, I always recommend starting at true scale. Explain you are going to expand the objects, and then when you are finished, return them back to true scale again. Make a point of noticing how tiny they are in reality compared to the distances.
Figure 3: Using different scales for size and distance can encourage the learner to make misguided links to their own experiences.
The Reason for the Seasons
Seasons is a really tricky topic to teach even to someone without misconceptions, and it can’t be rushed. Take time to check at every step whether all the learners have mastered the understanding they will need to progress. Accept that it can’t be mastered during a single planetarium show; your task is to build on prior learning experiences and to give a firm foundation for future learning experiences.
Finally, remember that misconceptions can pop up in zombie form long after you thought they were gone; so keep checking! Encourage the learners to use their new, correct, models in as many different and useful ways as possible. This will boost the correct model’s status and make it more likely that this is called upon in future, rather than the misconception.