What phenomenon causes a bright planet viewed very low in the east to appear to twinkle or shimmer more noticeably?

Answer

The planet being viewed through the thickest layer of the Earth's atmosphere

When planets are viewed very low above the horizon, their light passes through the thickest layer of atmosphere, introducing turbulence that makes the light appear to shimmer more noticeably.

What phenomenon causes a bright planet viewed very low in the east to appear to twinkle or shimmer more noticeably?
astronomyplanetskymorning