* Atomic units are incredibly small: Atomic units are designed to describe the size and energy of atoms and electrons. They're based on fundamental constants like the mass and charge of an electron.
* Astronomical distances are vast: The distance from Earth to the Sun (an astronomical unit or AU) is roughly 149.6 million kilometers. This is a tremendously large distance compared to the size of an atom.
Imagine trying to express the length of a football field in millimeters! The numbers would be unwieldy and meaningless in the context of the measurement.
Instead of atomic units, we use astronomical units (AU) for distances within our solar system, and light-years for distances between stars and galaxies. These units are much more practical for expressing the vast distances in space.
