# Platonic Solids - Historical significance

### polyhedra regular geometry hexahedron

The term platonic solids refers to regular polyhedra. In **geometry**, a **polyhedron**, (the word is a Greek neologism meaning *many seats*) is a solid bounded by **plane** surfaces, which are called the *faces*; the intersection of three or more edges is called a *vertex* (plural: *vertices*). What distinguishes regular polyhedra from all others is the fact that all of their faces are congruent with one another. (In geometry, congruence means that the coincidence of two figures in space results in a one-to-one correspondence.) The five platonic solids, or regular polyhedra, are: the **tetrahedron** (consisting of four faces that are equilateral triangles), the hexahedron, also known as a cube (consisting of six **square** faces), the octahedron (consisting of eight faces that are equilateral triangles), the dodecahedron (12 pentagons), and the icosahedron (20 equilateral triangles).

The regular polyhedra have been known to mathematicians for over 2,000 years, and have played an important role in the development of Western philosophy and science. Drawing on the teaching of his predecessors Pythagoras (sixth century B.C.) and Empedocles (c. 490-c. 430 B.C.), and contributing many original insights, the Greek philosopher Plato (c. 427-347 B.C.) discusses the regular polyhedra, subsequently named after him, in *Timaeus*, his seminal cosmological work. Plato's narrator, the astronomer Timaeus of Locri, uses triangles—as fundamental figures—to create four of the five regular polyhedra (tetrahedron, hexahedron, octahedron, icosahedron). Timaeus's four polyhedra are further identified with the four basic elements-the hexahedron with **earth**, the tetrahedron with fire, the octahedron with air, and the icosahedron with **water**. Finally, in Plato's view, the regular polyhedra constitute the building-blocks not merely of the inorganic world, but of the entire physical universe, including organic and inorganic matter. Plato's ideas greatly influenced subsequent cosmological thinking: for example, Kepler's fundamental discoveries in **astronomy** were directly inspired by Pythagorean-Platonic ideas about the cosmic significance of geometry. Platonic geometry also features prominently in the work of the noted American inventor and philosopher R. Buckminster Fuller (1895-1983).

See also Geodesic dome; Kepler's laws.

## Resources

### Books

Coplestone, Frederick. *Greece and Rome.* Vol. 1, *A History of* *Philosophy.* Garden City, NY: Doubleday, 1985.

Kline, Morris. *Mathematics in Western Culture.* London: Oxford University Press, 1964.

Koestler, Arthur. *The Sleepwalkers.* New York: Grosset & Dunlap, 1959.

Millington, T. Alaric, and William Millington. *Dictionary of* *Mathematics.* New York: Harper & Row, 1966.

Stewart, Ian, and Martin Golubitsky. *Fearful Symmetry: Is God a Geometer?* London: Penguin Books, 1993.

Zoran Minderovic

## User Comments

over 3 years ago

I Sreeram of class 8 studying in Delhi Public School,Nacharam Secunderabad.Math is a subject which it makes easier,Brain sharpa and physical mentally.If we practice everyday in 1 hour we can score good marks in exam.That's why we have to work hard,if we work hard we will go up in life. And please encourage the child to do a lot of reading when the exams appear in November 7,2013.Thursday

almost 10 years ago

THis is good information but why are each of the soids related back to fire water wind and fire?