Final answer:
Newton's law of universal gravitation is relevant to the discovery of Earth's internal structure because the gravitational force between different parts of the Earth's interior affects the distribution of mass and helps shape its structure.
Step-by-step explanation:
Newton's law of universal gravitation is relevant to the discovery of Earth's internal structure because it helps explain the phenomenon of gravity, which is responsible for the distribution of mass within the planet. According to Newton's law, every object in the universe attracts every other object with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them. This means that the gravitational force between different parts of the Earth's interior affects the distribution of mass and helps shape its structure.