Permanent magnets are placed in an environment without magnetic field, and their magnetism will gradually disappear with time! In the natural environment, the magnetism of natural magnets (such as magnetite) can be maintained permanently.

Couplets, also known as antithesis, door-to-door, spring stickers, Spring Festival couplets, couplets and so on. It is a antithesis written on paper, cloth or carved on bamboo, wood and columns. The antithesis of couplets is neat and even, which is a unique artistic form of Chinese.