The Moon doesn’t actually get smaller as it rises.
It’s an optical illusion, or a trick that’s played on our eyesight.
When we see the Moon on Earth’s horizon, our brain registers its size in comparison to objects on Earth: buildings, trees, the ocean.
It appears huge and much bigger than when it is high in the sky.
As it rises, our brain loses its earthbound scale of reference.
The Moon seems to grow smaller.
This phenomenon is known as the Moon illusion.