Originally Posted by Robert Tulip

Yes, it is the sum of gravitational effects from the astronomical objects involved. However, this material suggests a more complex picture of gravitational effects, including harmonic effects, than is now understood. For example, Edward Lorenz's work on sensitive dependence on initial conditions can be applied to ecologies which evolve within pulsing gravitational cycles. The impact of gravitational cycles on complex living organisms is a gravitational effect, but this is mediated by a cumulatively adapted genetic response by the organism. Hence the gravitational mechanism is indirect, mediated through complex cyclic structures, rather than a direct immediate effect of momentary gravitational force.