16 19, Descartes was in the military camp in Newburg, a small town in the south of the Danube. This is a turning point in his life. He is immersed in deep thinking all day, thinking about mathematics and philosophy. 16165438+10/0. Descartes' eyes lit up and a spider crawling on the ceiling caught his attention. In the eyes of ordinary people, this spider may be as ordinary as usual. It was busy weaving a net near the corner of the ceiling, suddenly climbing up and down the wall and moving slowly in the air in the direction of silk.
Descartes was interested in this spider because he was thinking about solving geometric perfect numbers by algebra, but he encountered a difficulty, that is, how to represent points in geometry with several numbers in algebra? At night, his heart was filled with great excitement, and he fell asleep with a happy and anxious mood, which made him have nightmares and his mood could not be calm for a long time. Early in the morning, thinking of this spider hanging in mid-air, Descartes was suddenly enlightened in his meditation: Can we use the intersection of two walls and the intersection of the wall and the ceiling to determine its spatial position? He got up from the bed and drew three vertical straight lines on the paper, indicating the intersection of two walls and the intersection of the wall and the ceiling. Using a point to represent a spider in space can of course measure the distance from this point to three planes. In this way, the position of the spider in the air can be accurately marked. Descartes wrote: "The next day, I began to understand the basic principle of this amazing discovery." This means that he got the clue to establish analytic geometry.
Later, the coordinate system composed of these mutually perpendicular straight lines was called Cartesian coordinate system.