The Big Bang theory describes the universe as continuously expanding, but this expansion does not apply to galaxies or planets. Instead, it refers to the movement of objects that are not strongly bound together, such as galaxy clusters, which gradually move apart over time. Within galaxy clusters, the gravitational forces are strong enough to prevent expansion among galaxies and other solid objects. Therefore, the term "expansion" specifically pertains to the increasing distance between larger cosmic structures. Understanding this distinction clarifies misconceptions about the nature of cosmic expansion.
