The ultimate fate of the universe is determined by its total energy density, the distribution of matter and energy within it, and the influence of key physical forces, particularly dark energy. Current cosmological models suggest several potential end states, each depending on these initial conditions. If the expansion continues indefinitely, it may lead to a "heat death," a scenario where the universe becomes increasingly cold, diffuse, and low in usable energy as all matter eventually decays or disperses. Alternative theories include a "Big Crunch," which posits that the gravitational forces of all matter will eventually overcome the expansion, causing the universe to contract back into a singularity, or a "Big Rip," where the accelerating expansion overcomes all fundamental forces, tearing apart galaxies, stars, and ultimately, atoms themselves. Observations regarding the accelerated expansion suggest that models favoring perpetual expansion are currently the most supported.