Democritus, an ancient Greek philosopher, was not the first to propose an atomic theory, as his mentor Leucippus originally proposed it. Democritus adopted the theory, developed it further, and provided a more detailed and systematic view of the physical world.
According to Democritus' atomic theory, everything is made up of atoms, which are physically indivisible: atoms are indestructible, eternal and invisible, small and unable to be diminished. He posited that atoms occupy space and differ in size, shape, magnitude, position and arrangement. In his model, atoms are homogeneous.
Using this as a basis to the physical world, Democritus was able to explain all changes in the world as changes in motion of atoms, or changes in the way the atoms were packed together. The theory explained physics and combined mathematics, since its structure was quantitative and subject to mathematical laws.
The Democritus theory elaborated further on how nature behaves. According to the theory, nature is a highly complex mechanism. When it comes to qualities such as warmth and taste, atoms differ only in quantity and the properties of these qualities are only by convention. According to Democritus, atoms and the Void are the only things that actually exist.
In his theory, he explained that by atoms moving randomly and colliding to form larger bodies was how the universe began. According to Democritus, the world always existed, will forever exist and is filled with atoms moving about randomly.