Here's why:

* Size: The sun is a giant star, with a diameter of about 1.39 million kilometers. The moon is a relatively small celestial body, with a diameter of about 3,474 kilometers.

* Mass: The sun is about 333,000 times more massive than the Earth. The moon is only about 1/81 of Earth's mass.

While the moon appears larger in our sky than the sun, this is an illusion caused by its closer proximity to Earth. The sun is much farther away, making it appear smaller, even though it is vastly bigger.