The twinkling of a star is possible because the?

Twinkling of stars occurs due to atmospheric refraction of light. As the starlight travels through the Earth's atmosphere, it encounters layers of air with varying densities and temperatures, causing the light to bend and change direction. This results in the slight shimmering or twinkling effect we observe in the appearance of stars. The twinkling is particularly noticeable for stars near the horizon, where the light has to pass through more of the Earth's atmosphere compared to stars higher in the sky.