Here's why:

* Inertia is the tendency of an object to resist changes in its motion. It's directly proportional to an object's mass.

* The Sun is significantly more massive than the Moon. The Sun's mass is about 333,000 times greater than the Moon's.

This means it takes much more force to change the Sun's motion compared to the Moon's. Even though the Sun is constantly moving in our galaxy, its massive inertia makes it appear relatively stable from our perspective on Earth.