Soon after Italian scientist Galileo Galilei expressed his belief that vacuums can exist (1638), scientists began studying the properties of air and partial vacuums to test the relative merits of Aristotelian orthodoxy and the atomic theory. The poem was printed in 1649 and popularized by Pierre Gassendi, a French priest who tried to separate Epicurus’s atomism from its materialistic background by arguing that God created atoms. The emergence of experimental scienceĭe rerum natura, which was rediscovered in the 15th century, helped fuel a 17th-century debate between orthodox Aristotelian views and the new experimental science. Aristotle’s conception prevailed in medieval Christian Europe its science was based on revelation and reason, and the Roman Catholic theologians rejected Democritus as materialistic and atheistic. Plato valued abstract ideas more than the physical world and rejected the notion that attributes such as goodness and beauty were “mechanical manifestations of material atoms.” Where Democritus believed that matter could not move through space without a vacuum and that light was the rapid movement of particles through a void, Aristotle rejected the existence of vacuums because he could not conceive of bodies falling equally fast through a void. Thus, Plato and Aristotle attacked Democritus’s atomic theory on philosophical grounds rather than on scientific ones. Science constituted only one aspect of their broad philosophical system. Like the later theologians of the Middle Ages, they wanted an all-encompassing theory to explain the universe, not merely a detailed experimental view of a tiny portion of it.

Instead, the Greeks used mathematics and reason almost exclusively when they wrote about physics. It was not based on observations of nature, measurements, tests, or experiments.

The Greek atomic theory is significant historically and philosophically, but it has no scientific value. 95–55 bce) wrote to popularize its ideas. Most of what is known about the atomic philosophy of the early Greeks comes from Aristotle’s attacks on it and from a long poem, De rerum natura (“On the Nature of Things”), which Latin poet and philosopher Titus Lucretius Carus ( c. According to Epicurus’s materialistic philosophy, the entire universe was composed exclusively of atoms and void, and so even the gods were subject to natural laws. The philosopher Epicurus of Samos (341–270 bce) used Democritus’s ideas to try to quiet the fears of superstitious Greeks. He argued that matter was subdivided into indivisible and immutable particles that created the appearance of change when they joined and separated from others. Democritus developed his atomic philosophy as a middle ground between two opposing Greek theories about reality and the illusion of change. The atoms of the soul were considered to be particularly fine. For example, sourness was caused by needle-shaped atoms, while the colour white was composed of smooth-surfaced atoms. In Democritus’s philosophy, atoms existed not only for matter but also for such qualities as perception and the human soul. Differences in atomic shape and size determined the various properties of matter. Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. His famous disciple, Democritus of Abdera, named the building blocks of matter atomos, meaning literally “indivisible,” about 430 bce. Leucippus of Miletus (5th century bce) is thought to have originated the atomic philosophy. The atomic philosophy of the early Greeks It was more than 2,000 years before modern physicists realized that the atom is indeed divisible and that it is not hard, solid, or immutable. Their speculation about a hard, indivisible fundamental particle of nature was replaced slowly by a scientific theory supported by experiment and mathematical deduction. The concept of the atom that Western scientists accepted in broad outline from the 1600s until about 1900 originated with Greek philosophers in the 5th century bce.

Atom theory