To investigate the most basic and encompassing principles of Newtonian gravity, we sought general agreement
among astronomy instructors, textbook coverage, and gravity experts. A review of seven textbooks indicates that
gravity is generally presented starting with the historical progression, which closely parallels the progression of
student conceptions about gravity (Kavanagh and Sneider 2007a and 2007b). Most textbooks then discuss the
implications of falling, orbiting, and Newton’s Laws in terms of planet formation, launching rockets, and tides.
At this stage in the research, “a complete understanding of gravity for college introductory astronomy students”
will be generally defined as “accurate knowledge and application of the basic underlying concepts associated
with the Newtonian force of gravity.”