Georg Cantor (1845- 19 18) is a German mathematician, the founder of set theory, and one of the great achievements of mathematics in 19th century. 1845 was born in Petersburg, Russia on March 3, and his father was a wealthy businessman.

In the 29th year of Cantor (1874), he published his first set theory paper in a mathematical magazine, and put forward the mathematical concept of "infinite set", which aroused great concern in the mathematical field. He introduced some concepts of infinite point set, such as cardinal number, potential and ordinal number. And try to distinguish different infinite discrete point sets from infinite continuous point sets in some way. He also built the real one.

Because the study of infinity often leads to some logical but absurd results (called "paradox"), many great mathematicians are afraid of falling into it and adopt an evasive attitude. During 1874- 1876, Cantor, who was less than 30 years old, declared war on the mysterious infinity. With hard sweat, he successfully proved that points on a straight line can correspond to points on a plane one by one, and can also correspond to points in space one by one. In this way, it seems that there are "as many" points on the 1 cm long line segment as there are points in the Pacific Ocean and the whole earth. In the following years, Cantor published a series of articles about this kind of "infinite set" and drew many amazing conclusions through strict proof.