Twinkling of the Stars is due to the phenomenon of 

Solution

When a ray of light travels from one medium to another it ‘bends’. This phenomenon is referred to as refraction. The atmosphere of the earth is made of different layers. It is affected by winds, varying temperatures and different densities as well. When light from a distant source (a star) passes through our turbulent (moving air) atmosphere, it undergoes refraction many times. When we finally perceive this light from a star, it appears to be twinkling.