When you gaze up at the sky on a clear night, the phenomenon you observe, where stars seem to appear randomly, is known as "autokinetic effect" or "stellar drift illusion." This effect occurs due to a combination of factors related to our perception and the nature of the stars themselves.
The autokinetic effect is an optical illusion that happens when you fixate your eyes on a single point of light in a dark environment. In this situation, your eyes are not provided with any visual references or cues to accurately determine the position or motion of the object you are observing. As a result, your brain struggles to perceive the exact location of the light source, and it appears to move or twinkle.
Furthermore, the stars themselves emit light that travels through the Earth's atmosphere before reaching our eyes. This atmospheric passage causes the light to interact with various factors such as air turbulence, temperature variations, and dust particles. These interactions can cause the stars' light to scatter and create the twinkling effect that we commonly associate with stars.
The autokinetic effect becomes more pronounced when you observe a specific star for a prolonged period. As your eyes attempt to lock onto the star, the lack of visual cues leads to the impression that the star is moving or appearing randomly in the sky.
It's worth noting that stars are actually enormous celestial bodies located at vast distances from Earth, and they maintain their fixed positions in space. However, due to the autokinetic effect and atmospheric influences, their appearance may seem to change when observed from our perspective on Earth.