According to legend, in the era of Dayu's water control, Shaanxi Luoshui was often flooded. Floods destroyed houses, swallowed up rural areas and brought great disasters to people on both sides of the strait. Therefore, before the flood season comes, people will bring pigs and sheep to the river to worship the river god. Whenever people arrange sacrifices, a turtle will climb out of the river. People began to pay attention to this turtle. It was found that there were 9 large tortoise shells, 3 rows in vertical and horizontal directions.

These spots on the tortoise shell were later called "Luo Shu". Dayu divided the land of the motherland into Kyushu according to Luo Shu, formulated nine kinds of laws to govern the world, rectified the flood, and the river never overflowed again.

One year, the turtle climbed onto the shore again. Suddenly, a watching child exclaimed in surprise: "How interesting! Whether these points are added horizontally, vertically or obliquely, the calculated result is 15! "

This magical story is so popular in our country that it has even been written into the works of many ancient mathematicians. Uncle Luo does have its charm. After a clever arrangement of nine ordinary natural numbers, every three of them add up to eight formulas of 15, all of which are contained in one pattern, which is incredible.

In fact, we can work out the magic number 15 now. Because the sum of 1~9 is 45, if we divide it into three rows (columns), then each row is 45÷3= 15.

Luo Shu divided the square into nine squares because of the position of nine consecutive natural numbers, so it was renamed as "Jiugongsuan" in Xu Yue's Notes on Numerology in the later Han Dynasty. "Nine palaces count, that is, two or four are shoulders, six or eight are feet, three are left and seven are right, one is wearing nine shoes, and five is middle." Its structure is described in detail. Jiugong calculation is.

Mathematically, some patterns with wonderful properties like this are called magic squares. Luo Shu has three rows and three columns, so it is called the third-order Rubik's Cube. It is also the oldest Rubik's cube in the world.

There is a very simple method to construct a magic square of order 3. First, arrange the first nine natural numbers in a prescribed way. Then, write the four numbers outside the box in the space opposite it. In the same way, you can create a magic square of order 5. In fact, there is no unified method to construct the Rubik's Cube, which mainly depends on people's dexterity and wisdom. Because of this, the Rubik's Cube has won the love of countless people.

The Rubik's Cube not only attracts many mathematicians, but also attracts many math lovers. In Qing Dynasty, a scholar named Juck Zhang was fascinated by Rubik's Cube, but he later constructed a very unique set of Rubik's Cube. Six Numbers of the Turtle is one of Juck Zhang's representative works. The number 24 in the figure plays the role of 40, so that the sum of the numbers in each hexagon is equal to 75.

At the beginning of15th century, the Rubik's Cube spread to European countries. Its unpredictability and mystery soon drove thousands of Europeans crazy. Many famous mathematicians, including Euler, also became interested in the magic square.

In the past century, the Rubik's Cube has become more and more bizarre in form and nature. Nowadays, many people think that the most interesting Rubik's Cube belongs to the "Double Rubik's Cube". Mathematicians have not fully understood its mystery and laws.

The magic square of order 8 is a double magic square. Why is it called Double Rubik's Cube? Because the sum of eight numbers in each row, column and diagonal is equal to the same constant 840; And the product of eight numbers is equal to another constant 0580 1856000.

In the past, the Rubik's Cube was purely a mathematical game. Later, people gradually found that it contains many profound mathematical truths and found that it can be applied to many occasions. At present, many scientists in the world are racking their brains to study its laws. Some scientists even imagine that if our spaceship flies to a planet with advanced intelligent creatures, it may be used as a medium. What about the idea of communicating with each other 1977, the horizontal and vertical diagrams (fourth-order Rubik's Cube) were also taken into space by American travelers 1 and 2 spacecraft, as a special language of human beings, to convey the information and good wishes of human civilization to aliens who may exist in the vast universe! The rapid development of computer technology has injected fresh blood into this ancient discipline. Mathematicians made further research on it, and finally made it a new branch of mathematics with extremely rich contents-combinatorial mathematics.