One rotation is 24 hours, 37 minutes and 22.6 seconds. Rotation refers to the movement of the object itself. The object will rotate along an axis passing through the object itself. This shaft is called "self-rotating shaft". Generally speaking, the axis of rotation will pass through the center of mass of a celestial body. Satellites, planets, stars and galaxies all rotate around their own axes. The rotation of the earth refers to the circular motion of the earth along a geocentric axis (rotation axis, also called the earth axis). This is rotation. The period of the earth's rotation is a planetary day, and the current value is 23: 56: 4. But in recent years, the earth's rotation period is slowly increasing (that is, the rotation speed is slowly decreasing), which leads to the need to adjust the global timer. For example, on June 65438+February 3, 20051,the global clock was unified by one second. This adjustment is called leap second.