The four major problems in the world refer to the proof of cubic product, bisecting any angle, turning a circle into a square and "Goldbach conjecture".

1. Cubic multiplication refers to making a cube with a ruler and gauge to make its volume twice that of a known cube.

2. bisecting any angle means bisecting any angle with a ruler method.

3. Turning a circle into a square means making a square with a ruler method, and its area is equal to that of a known circle.

4. The proof of Goldbach conjecture is the proof of even number and prime number correlation theorem. If this theorem is proved, Goldbach's conjecture can be proved.