The chances of the universe stopping its expansion and collapsing in on itself depend on the overall properties of the universe and the balance between the gravitational force and other factors, such as dark energy.
The ultimate fate of the universe is determined by the density of matter and energy within it. There are three main scenarios that describe the possible outcomes:
Open Universe (Continued Expansion): If the average density of matter and energy in the universe is below a certain critical value, the universe will continue expanding forever. In this case, the gravitational force is not strong enough to halt the expansion, and it will continue indefinitely.
Closed Universe (Big Crunch): If the average density exceeds the critical value, the universe's expansion could eventually halt and reverse. The gravitational force would overcome the expansion, causing the universe to collapse in on itself in a "Big Crunch" scenario. This would lead to a dense and hot state, similar to the early universe.
Flat Universe (Equilibrium): If the average density precisely matches the critical value, the universe's expansion would gradually slow down but never come to a complete halt. In this case, the expansion rate would approach zero asymptotically, creating an equilibrium state where the universe neither expands nor collapses.
The current understanding based on observations suggests that the universe's expansion is accelerating, primarily driven by a mysterious form of energy called dark energy. Dark energy acts as a counterforce to gravity, causing the expansion to accelerate rather than slow down. If this acceleration continues, it would make the scenario of a collapsing universe less likely.
It's important to note that our understanding of dark energy and the overall fate of the universe is still an active area of research. Ongoing observations and future discoveries may provide more insights into the long-term behavior of the universe and the chances of it collapsing or continuing to expand.