Observer is a soundtrack composed by Anti-General for the Three-Body animation. The theme is about the concept of the observer in physics.
In physics, the concept of the observer refers to the information needed when observing a physical system. This information may include the observer’s position, speed, and direction, as well as the measuring instruments used, and so on. The presence of an observer can affect the state of the physical system, so the concept of the observer is very important in physics.