Assertion: moon's orbit | /r/HasProperty | affected by two forces
Facets:
value: in practice
type: TEMPORAL
Source sentences:
text: The orbit of a moon or other satellite is affected by two forces: gravity, and the centripetal force.
text: However, in practice, orbits are affected or perturbed, by other forces than simple gravity from an assumed point source (see the next section), and thus the orbital elements change over time.