Essential idea: Electric charges and masses each influence the space around them and that influence can be represented through the concept of fields.
Nature of science: Paradigm shift: The move from direct, observable actions being responsible for influence on an object to acceptance of a field's “action at a distance” required a paradigm shift in the world of science.
Understandings: Gravitational fields; Field lines
Applications and skills: Representing sources of mass, lines of gravitational force, and field patterns using an appropriate symbolism
Guidance: Gravitational fields are restricted to the radial fields around point or spherical masses and the (assumed) uniform field close to the surface of massive celestial bodies and planetary bodies
Utilization: Knowledge of vector analysis is useful for this sub-topic