星星會閃，是因為當星光進入大氣層時，經過不同溫度的空氣，會有不同程度的散射。（光線遇到冷空氣時，會跑彎多一點，而遇到暖空氣時，會跑彎少一點）當星光因散射離開我們眼睛，星星便好像暫時消失了；當星光剛好又再射進眼內時，星星就會重新出現，形成一閃一閃的效果。

Stars twinkle because they’re so far away from Earth that, even through large telescopes, they appear only as pinpoints. And it’s easy for Earth’s atmosphere to disturb the pinpoint light of a star. As a star’s light pierces our atmosphere, each single stream of starlight is refracted – caused to change direction, slightly – by the various temperature and density layers in Earth’s atmosphere. You might think of it as the light traveling a zig-zag path to our eyes, instead of the straight path the light would travel if Earth didn’t have an atmosphere.