The word spiral comes from Greek, which means "winding" or "winding". For example, a plane spiral is a curve formed by winding outward from a fixed point. More than 2000 years ago, the ancient Greek mathematician Archimedes studied the spiral line. Descartes, a famous mathematician, first described the logarithmic spiral in 1683, and listed the analytical formula of the spiral. More interestingly, before his death, Jacques Bernoulli, a Swiss mathematician, asked someone to carve a humble abode-logarithmic spiral on his tombstone, and humorously wrote the epitaph "I will be resurrected after changing back to my original self".
If you are interested, you can observe cobwebs, because cobwebs are widely distributed and impressive spiral structures in nature. The structure of spider web fully shows what a wonderful little life spider is with the wonderful spiral concept! Banana leaves are also spirally arranged, and the included angles are 137 degrees, 30 degrees and 38 degrees. This arrangement of blades can make the blades get maximum illumination and good ventilation. In fact, the arrangement of plant leaves on the stem is generally spiral. In addition, the arrangement of sunflower seeds on the plate is also spiral.
Human hair grows obliquely from the hair follicle of the head, and it forms a vortex in a certain direction, which is called hair spin, and it can be divided into right-handed and left-handed ones. In fact, a hairpin is a hairpin that grows on the body surface and allows hair to grow in a certain direction. In wild mammals, hairpins can protect themselves and adapt to the environment. It can make rain drop in a certain direction, just like putting on a hemp fiber; They are closely arranged to avoid the bite of harmful insects; In addition, it also has a good thermal insulation effect. Although these functions of human hair have degenerated to a negligible degree, their shapes have always been maintained.
There are some special movements that produce trajectories that are also spiral. An ant crawls outward at a constant speed along the radius of the uniformly rotating recording center. As a result, the ant itself describes a spiral line. Bats fly down from high places according to the path of space spiral-conical spiral. Sometimes we have to take a spiral path to chase enemy ships or catch smuggling ships at sea. Some stars also have spiral orbits. After observing and studying the gas density in the middle of the Milky Way for three years, Dr. Naoko Nakai of Japan National Astronomical Observatory thinks that the Milky Way is spiral, that is, the stars spiral outward around the center of the circle.
Spiral is widely used in all aspects, such as mechanical screws, nuts, screws, and elastic turnbuckles of daily necessities. The rifling in the gun bore is also spiral, and even some stairs are spiral. Known as one of the "Seven Wonders of the World", the stairs of the Leaning Tower of Pisa in Italy are 294-level spiral. California designers also used the lighting principle of banana for reference to design a spiral building with 13 floors. It turns out that every room can get enough sunshine.