What characterizes an accelerating universe?

An accelerating universe is characterized by the phenomenon in which the rate of expansion of the universe is increasing over time. This means that galaxies are moving away from each other at an ever-faster pace rather than simply receding at a steady rate or slowing down due to gravitational attraction.

Observations, particularly those involving distant supernovae and the cosmic microwave background radiation, have provided compelling evidence for this accelerating expansion. The force driving this acceleration is attributed to a mysterious component known as dark energy, which appears to constitute a significant portion of the total energy density of the universe. Dark energy counteracts the force of gravity, allowing the rate of expansion of the universe to speed up.

Understanding this dynamic is crucial to modern cosmology, as it reshapes our perception of the universe's fate and the fundamental forces at play.