Atomism

Atomism (from ancient Greek atomos, meaning "uncuttable") is a natural philosophy that developed in several ancient traditions. The atomists theorized that the natural world consists of two fundamental parts: indivisible atoms and empty void. Atoms are indestructible and immutable and there are an infinite variety of shapes and sizes. They move through the void, bouncing off each other, sometimes becoming hooked with one or more others to form a cluster. Clusters of different shapes, arrangements, and positions give rise to the various macroscopic substances in the world.

References to the concept of atoms date back to ancient India and ancient Greece. In India the Jain, Ajivika and Carvaka schools of atomism may date back to the 6th century BCE. The Nyaya and Vaisheshika schools later developed theories on how atoms combined into more complex objects. In the West, the references to atoms emerged in the 5th century BCE with Leucippus, and Democritus. Whether Indian culture influenced Greek or vice versa or whether both evolved independently is a matter of dispute.

Of importance to the philosophical concept of atomism is the historical accident that the particles which chemists and physicists of the early 19th century thought were indivisible, and therefore identified with the uncuttable a-toms of long tradition, were found in the 20th century to be composed of even smaller entities: electrons, neutrons, and protons. Further experiments showed that protons and neutrons are made of quarks. At present, quarks, electrons, and other fundamental particles such as muons, taus, neutrinos, and gauge bosons show no experimental evidence of size or substructure. However, the possibility that they too might be composed of smaller particles cannot be ruled out. Although the connection to historical atomism is at best tenuous, these particles, rather than chemical "atoms", are roughly analogous to the traditional indivisible objects.