Rene Descartes 

Also known by his Latin name, Renatius Cartesius. Rene Descartes was a French philosopher and mathematician. He wrote some works in Latin, but broke with philosophical tradition by writing in his native language as well. He lived and worked in many different European countries. Descartes developed the science of geometry into the discipline that most schoolchildren know today. He also invented the system of powers and created symbols for graphs ─ the Cartesian coordinate system. He is generally accepted to be the father of modern Western philosophy, coining the famous phrase «Cogito ergo sum» („I think therefore I am“).

Archimedes

The Greek mathematician Archimedes was the father of geometry. He discovered the value of pi, which is the ratio of the circumference of a circle to its diameter. Pi is used to calculate the volume of cylinders and spheres. Archimedes then looked for ways of measuring the volume and mass of irregular objects. Eventually, he discovered the principle of displacement: that an object put wholly or partly into water loses weight equal to the weight to water it displaces. One method of lifting water is known as the Archimedes's crew because it is thought that he invented it.

Aristotle

In the 4-th century BC in Greece, there were only a few schools, and none taught science. It was left to philosophers to come up with logical explanations of the world. Aristotle studied under the famous philosopher Plato, who regarded thought or the idea as the basis of all knowledge. Aristotle later decided that theories about the world must be based on the close study and classification of nature. Aristotle cataloged the known species of animals and plants, believing they were made of four elements; earth, water, fire, and air. He also believed that a fifth element, ether, surrounded the Earth.

Hypatia (Egypt) 

The first renowned woman of science was an astronomer and mathematician named Hypatia from Alexandria, Egypt. Her work was famed in many Mediterranean countries, but it came into conflict with the teaching of powerful Christian leaders, who ordered her to be murdered. For almost 1,000 years after Hypatia's death, the period in history known as the Middle Ages, few scientific advances were made in the Western world. Sadly, Hypatia is better remembered for the violence of her death than for her work in science.