If the universe has formed & originated by a Big Bang Explosion, then there must be empty space left in the center of the explosion site, as all the matter is travelling at tremendous speeds away ...
Miranda, a moon of Uranus is unique in that it has a very fractured surface Source: University of Oregon The surface is said to be jagged and fractured, with comparatively large disjointed cliffs ...
This is a follow up to: Is there a theoretical maximum size limit for a star? The answer there talks about the radiation pressure preventing a star from forming. What reaction is causing this ...