Why did Aristotle believe heavy objects naturally move toward the center of Earth?

In the Aristotelian worldview, the universe was organized into an ordered cosmos where every element possessed a "natural place" and an innate tendency to move toward that location.1

Aristotle believed that terrestrial matter was composed of four fundamental elements: earth, water, air, and fire. Within this framework, he argued that heavy objects—specifically those composed of earth—possess a natural tendency to move toward the center of the universe, which he identified as the center of the Earth. This downward movement was considered a "natural motion," as opposed to "violent" or unnatural motion, which required an external cause.123

Conversely, lighter elements like fire had a natural tendency to move upward, away from the center. This system relied on the philosophical assumption that each element inherently seeks its proper stratum within the cosmos, a concept that remained a dominant explanation for terrestrial motion until it was eventually superseded by the development of modern gravitational theory.123