Probing for Understanding

“Be very, very careful what you put into that head, because you will never, ever get it out.” – Attributed to Cardinal Thomas Wolsey (1473-1530)

As with most quotes, the one above is surely taken out of context. Educators like it because it speaks to them of the importance of conveying accurate content to learners during a course of instruction, lest erroneous prior conceptions get reinforced, or new ones formed. The short film A Private Universe debuted in 1987, and immediately became an important resource to help educators understand the importance of learner engagement in hands-on activities to forestall, and correct, misconceptions they hold related to natural, particularly astronomical, phenomena. The film starts with the now-famous scene at a Harvard University commencement where new graduates and faculty members are asked to explain their understanding of the reasons for the seasons, and the causes of the phases of the Moon. A Private Universe showed how even the most highly educated can have enduring misconceptions, and how traditional science instruction does little to replace them.

Educators at every level have a pretty good idea of what prior conceptions learners bring with them, important knowledge when designing educational experiences.   In a formal classroom environment, the educator has the added benefit of having more time to probe learners’ ideas, and using what they glean to make adjustments to their instructional plan. One of the easiest strategies in the classroom involves the use of a “formative assessment probe,” where learners are presented with a description of a phenomenon, and a set of responses from which they have to select the one they agree with the most. Learners are also asked to provide a reasoned explanation for why they agree with their selected response.

Probes such as these are useful when working with both pre- and in-service teachers during a professional development workshop. Not only do they serve to engage the teachers in educational best practices, it also allows us to have a better understanding of the misconceptions they have about astronomical concepts and phenomena. During a recent visit to a science methods class for pre-service teachers in an elementary credential program, the following probe was used:

crescent moon probe copy

This probe is found in: Uncovering Student Ideas in Astronomy, by Page Keeley and Cary Sneider. 2012. NSTA Press. Arlington, Virginia

Much as the Harvard graduates had misconceptions about the causes of the phases of the Moon, many of the prospective teachers in the class had their own. This particular probe was selected to discover their mental model of how much of the Moon is lit at any time, and what it would look like if we are unable to see the fully lit side from Earth. Elementary teachers, let alone prospective elementary teachers, seldom have an extensive background in science, so it was not surprising to discover most of the students had uncertainty about how much of the Moon is lit at any time. A couple of the students had the misconception the dark part of the Moon was because of the Moon passing into Earth’s shadow. One student asked why we could not see stars through the transparent darkened portion of the Moon.

Following the probe, students were given white polystyrene balls, with only a single light bulb for illumination, and were asked to test their ideas. They were able to model how much of their “moon” was illuminated at any time, and to observe how it would look at different positions as the ball orbited their heads.

The results were amazing! Combining the formative assessment probe to determine the learners’ current mental models, with a modeling activity produced a significant conceptual shift to eventually provide fertile ground for an accurate understanding of phenomena to include phases of the Moon, and solar and lunar eclipses. When asked if their understanding depended on the hands-on modeling experience, the response was a unanimous YES! And, they became more likely to affect a change in student understanding once they have classrooms of their own.

At the end of the sessions, these university students reflected on their experience:

I used to think… the moon just turned dark; but now I know… that it is it’s own shadow.

I used to think… the shadow on the moon was the earth; but now I know… it’s the moon’s own shadow.

I used to think… that the part showing on the moon was the only part lit by the sun; but now I know… that half is always lit and it’s all about perspective.


The Astroteacher and Page Keeley are co-presenting at the 2016 NSTA conference [] in Nashville (March 31–April 3) and will focus on the use of probes to support eclipse modeling activities.

This post originally appeared in the Education Matters column of the winter 2016 issue of Mercury Magazine, published by the Astronomical Society of the Pacific.

This entry was posted in Astronomy, Education Matters, Science Education. Bookmark the permalink.

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