Cosmological acceleration

Cosmological acceleration refers to the finding that the universe is expanding at an increasing rate. Originally, scientists expected gravity to slow the expansion over time, but observations of distant supernovae showed the opposite: galaxies are moving away faster and faster. This acceleration is thought to be caused by a mysterious energy called dark energy, which makes up about 68% of the universe. It behaves like a kind of repulsive force, pushing galaxies apart and causing the universe's expansion to speed up as time goes on.