The word “circle” derives from the Greek, kirkos “a circle,” from the base ker- which means to turn or bend. The origins of the words “circus” and “circuit” are closely related. The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, Sun, and a short plant stalk blowing in the wind on sand, which forms a circle shape in the sand. The circle is the basis for the wheel, which, with related inventions such as gears, makes much of modern civilization possible.

In mathematics, the study of the circle has helped inspire the development of geometry, astronomy, and calculus. Early science, particularly geometry and astrology and astronomy, was connected to the divine for most medieval scholars, and many believed that there was something intrinsically “divine” or “perfect” that could be found in circles. The compass in this 13th century manuscript is a symbol of God’s act ofCreation. Notice also the circular shape of the halo| Circles on an old astronomy drawing| Some highlights in the history of the circle are:

* 1700 BC – The Rhind papyrus gives a method to find the area of a circular field. The result corresponds to 256/81 (3.16049…) as an approximate value of π. * 300 BC – Book 3 of Euclid’s Elements deals with the properties of circles. * In Plato’s Seventh Letter there is a detailed definition and explanation of the circle. Plato explains the perfect circle, and how it is different from any drawing, words, definition or explanation. * 1880 – Lindemann proves that π is transcendental, effectively settling the millennia-old problem of squaring the circle.