Final answer:
Observing the gravitational interaction between a planet and its moon provides critical data that can be used to calculate the planet's mass. This involves complex calculations of the gravitational forces at play, which are possible with the aid of computers used by astronomers.
Step-by-step explanation:
Observing the effect of gravity between a planet and its moon allows us to determine the planet's mass. When studying celestial bodies, astronomers consider the gravitational forces that all planets exert on one another, which can cause slight variations in their orbits. Calculations of these complex gravitational interactions often require the use of large computers available at research institutions.
By using Newton's formulation of gravity and considering the mutual gravitational effects between celestial bodies, astronomers can calculate the masses of astronomical objects. For example, the observation of the orbit of a moon around a planet can provide data to calculate the planet's mass by analyzing the perturbations in the moon's orbit due to the planet's gravity.
Furthermore, historical insights, like those of Newton, suggest that gravity is not just an Earth-bound phenomenon, but a universal force of attraction, which keeps the planets and their moons in orbit. This understanding is crucial for predicting celestial motions and for space missions that use gravity-assisted flybys. The gravitational interactions play a key role in the history and evolution of our planetary system, as observed in the preserved impact history on the Moon.