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# How was geometry invented?

Geometry, the supreme branch of mathematics, studies different kinds of figures and their properties, and also how shapes, angles and distances are related. Elementary geometry is divided into two parts — plane geometry and solid geometry. Plane geometry deals with two-dimensional figures whereas, solid geometry deals with three-dimensional figures. The word ‘geometry’ comes from two Greek words — geo meaning ‘Earth’ and metry meaning ‘measurement’. Thus, geometry simply means, measurement of the Earth. The ancient Egyptians needed geometry for remeasuring the pieces of their land, which had been washed away by the floods in the Nile. They devised a method of marking the land with the help of poles and ropes. A pole was dug into the ground at a suitable place. A second pole was placed at another place and then the two poles were connected by a rope, which marked the boundary. With two more posts the area would be marked as a site for cultivation or building. And since their religion required them to build tombs for their dead, such as pyramids, so they needed geometry for construction purposes as well. In the beginning all geometry was intuitive. But in 600 B.C., a Greek teacher named Thales set about proving geometrical principles scientifically. In geometry, a truth is called a ‘theorem’. Thales discovered the proofs of some theorems and marked the beginning of demonstrative geometry. However, it was Euclid of Alexandria, Egypt, who gave geometry the status of a science. Around 300 B.C., he collected all geometric results known till then and set them in a systematic form in a series of thirteen books. These books were called ‘Elements’ and were used by the whole world for nearly 2,000 years. Based on these rules, Euclidean geometry was developed. As time passed by, other branches of geometry were developed that are: analytic, trigonometric, projective, Minkowskian, Non-Euclidean, and Riemanian geometry. It is an important subject of engineering. Many instruments such as compass, sextant and the transit, used by surveyors are directly related to principles of geometry.