Final answer:
Gravity, despite being the weakest force, shapes the structure of the Universe due to its extensive reach across vast distances, governing the cosmic-scale structures and movements.
Step-by-step explanation:
Despite gravity being the weakest of the four fundamental forces, it has the most significant role in shaping the structure of the Universe. Other forces such as the strong nuclear force, even though much stronger, act at very short distances and thus don't influence the universe's large-scale structure.
Gravity's influence, although weak, extends over vast distances, making it the principal force responsible for the formation and movement of planets, stars, galaxies, and even clusters of galaxies. It binds these celestial bodies together and dictates their interactions over cosmic scales. In the quest for a Grand Unified Theory (GUT), physicists explore how these fundamental forces might relate, aiming to deepen our understanding of the universe's fundamental structures.