What effect does dark energy have on the universe?

Dark energy plays a critical role in the dynamics of the universe, particularly in its expansion. The correct answer highlights that dark energy causes the universe's expansion to accelerate.

This phenomenon was first observed in the late 1990s when astronomers studying distant supernovae discovered that not only is the universe expanding, but the rate of that expansion is increasing over time. Dark energy is thought to make up about 70% of the universe and exerts a repulsive force that counteracts gravitational attraction. This repulsive force leads to an acceleration in the expansion of the universe, suggesting that galaxies are moving away from each other at an increasing velocity.

Understanding dark energy is crucial in cosmology because it helps explain various large-scale structures and the ultimate fate of the universe. The interplay between dark energy and the matter in the universe determines how the universe evolves, leading to open questions about its composition and long-term behavior. Hence, the identification of dark energy's role as an accelerator of universal expansion underscores its importance in modern astrophysics.