Stars don't twinkle it seems us to twinkle because of the rotation and revolution of earth.
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The twinkling of a star is due to Atmospheric refraction of starlight. The starlight on entering the atmosphere undergoes refraction repeatedly before it reaches the Earth.The atmospheric refraction occurs in a medium of gradually changing refractive index. Since the atmosphere bends starlight towards the normal the apparent position of the star is slightly different from the original one.  Also the position of the earth keeps changing due to rotation and revolving.....Since the stars are very distant they approximate point sized sources of light. As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers and thus comes the twinkling effect