Is Bart setting up as a sun dial? Diagonally speaking this is a long shot, as we know from Bart's past estrangement. His shadow may caste him off rather than the reverse. Readers might remember the pickled beet episode where Bart's shadow left and how eventually Bart coaxed it back with by wearing a large strawberry on his head. Since then Bart has thought of his shadow as a form on endarklement, having had next to no success with enlightenment.
Bart claims his disappearance ( see Cloud Storage - The Plain Facts of Going, Going, Gone )was a result of him losing track of time while he was reading The Lord of The Rings -and now refers to his tractor as Shadow Facts. Mavis says no, no, no he just watched the movie, and this is a Facts Pas. Bart is perplexed.
CONVERSATION