We sought expert advice by interviewing five Physicists/Astrophysicists (see Note-2) and one Geological Scientist
(see Note-3) and asking for feedback from AstroLearnr listserv members, of which 11 responded (see Note-
4). Personal communication with other Physics and Astronomy experts was also crucial (see Note-5). All agree
that gravity is a foundational topic for astronomy and critical thinking in general. Discussions reveal that gravity
has many, many facets. Some of the most important aspects that were brought up include the following: