Why do stars twinkle?
The change in intensity of light coming from the stars is called twinkling of stars.
The twinkling of stars occurs due to atmospheric refraction of star's light.
The Optical Density of Air continuously changes from one moment to another
When atmosphere refracts more starlight towards us, stars appear to be bright
When they reflect less light, star appear to be dim
Hence, the star light reaching our eyes change continuously and stars appear to twinkle.