's new book traces a significant and surprising notion through the work of Johannes Kepler: in order to account for real physical motions, one has to investigate artificially produced shadows and reflections. Measuring Shadows: Kepler's Optics of Invisibility
(The Pennsylvania State University Press, 2016) beautifully places Kepler's optics into conversation with the art and literature of the period. It looks carefully at the crucial ways that changing notions of visibility set Kepler's optics up as the cornerstone to his radical Copernican astronomy as Kepler made three moves that helped him bridge the visual gap between the heavens and its observers: (1) He defined light as a mathematical body, (2) He showed how instruments of observation could be manipulated mathematically to achieve exact representation of distant and almost invisible heavenly occurrences, and (3) He helped develop a new language for scientific observation by reformulating the relationship of mathematics to phenomena. In the course of his elegant analysis of how and why this all played out, Chen-Morris also guides readers through the relationships between Kepler's ideas, Shakespeare's writings, Renaissance painting, and more. Its a fascinating book.