As for what the Janibekov effect is, there is a proverb: "Unless the sun comes out from the west." Although it is based on people's objective understanding of nature (the sun does rise in the east and west every day) falling phenomenon), but it also corresponds to another proverb, that is, seeing is not necessarily true. Combining this experiment with a series of natural phenomena we have observed can also prove that the earth is the only star in the solar system that spins in place, that is, the geocentric theory.

The tennis racket theorem, also known as the Janibekov effect, was invented by Russian cosmonaut Владимир Джанибеков (Vladimir Janibekov) on a rotating screw while working on the Salyut 7 space station in 1985. The nut was discovered by accident. A well-rotated nut will periodically change its direction of rotation, but there is no external force exerted on it in weightless space. Could it be that Galileo was wrong when he said that force is what changes the state of motion of an object? So first let us take a look at what this theorem is about.

If the three moments of inertia of a rigid body are not the same, it will tend to be stable when rotating around the main axis with the largest moment of inertia (the first main axis), or the main axis with the smallest moment of inertia (the third main axis). , rotation around the intermediate axis (second main axis) is unstable. This state of motion will be accompanied by rotation around the first/third main axis and has a tendency to gradually transform into rotation around the stable main axis.

Based on what we currently observe, there are no real rigid bodies in the observable universe, but the Janibekov effect does not require the target to be a real rigid body at all, and the impact of deformation is not so great that it cannot be used in calculations. It's okay if there are deviations. Things such as tennis rackets, remote controls, and smartphones can all exhibit the Janibekov effect on the earth and in the space station. The interstellar object 'Oumuamua is estimated to be an uneven long rod, which rotates and rotates based on changes in light intensity. If it does not rotate around the first and third main axes, its rotation posture may be unstable.

The Janibekov effect has nothing to do with gravity, air resistance, etc. You expressed it as "an object with small deformation is stable when rotating around the main axis with the largest moment of inertia (the first main axis) or the main axis with the smallest moment of inertia (the third main axis), and when rotating around the intermediate axis (the second main axis) Unstable" does not require a rigid body. Although the globe and the light bulb rotate in the same direction, due to the distance and different speeds, the light bulb in the video appears to be retrograde (the sun rises in the east and sets in the west, and Venus and Mercury are retrograde for the same reason).