How did Democritus explain change through atoms and empty space?

Democritus explained change by positing that the universe consists of two fundamental realities: eternal, indivisible atoms and the void (empty space).12

He argued that qualitative changes—such as an object appearing to change color, taste, or state—are not fundamental transformations of matter. Instead, they are merely apparent changes caused by the rearrangement, position, or combination of atoms within the void. Because atoms are intrinsically immutable, nothing truly comes into being or perishes; rather, the compounds formed by these atoms increase or decrease, creating the phenomena of birth and death.12

The void is essential to this system because it provides the necessary space for atoms to move, collide, and rearrange. Democritus maintained that atoms differ only in quantitative properties—specifically shape, size, and motion—and that their interactions are governed by mechanical necessity rather than design. By reducing all observable change to these quantitative shifts in a vacuum, Democritus provided a rational framework for explaining the multiplicity of the physical world while maintaining the unity of being.132