Shen is also known for his cosmological hypotheses in explaining the variations of planetary motions, including retrogradation. His colleague Wei Pu realized that the old calculation technique for the mean Sun was inaccurate compared to the apparent Sun, since the latter was ahead of it in the accelerated phase of motion, and behind it in the retarded phase. Shen's hypotheses were similar to the concept of the epicycle in the Greco-Roman tradition, only Shen compared the side-section of orbital paths of planets and variations of planetary speeds to points in the tips of a willow leaf. In a similar rudimentary physical analogy of celestial motions, as John B. Henderson describes it, Shen likened the relationship of the Moon's path to the ecliptic, the path of the Sun, "to the figure of a rope coiled about a tree."