The work described here advances the literature by presenting a fine grained description of a set of
learning trajectories on apparent celestial motion developed from students’ ideas across various ages and then
tested against an instructional intervention that could eventually lead to a full learning progression on
celestial motion. The results demonstrate that traditional instruction and observations of the world are not
sufficient to help students move beyond an intermediate level of understanding, even by adulthood, in this
concept area; targeted instruction is necessary. More importantly, we demonstrate how focused instruction
can move students to develop more sophisticated understandings of these topics.