Dark Energy: the Plot Twist

In 1998, two teams of astronomers studying distant supernovae made a shocking discovery: the expansion of the universe isn't slowing down (as gravity should cause). It's speeding up.

Dark energy is even more mysterious than dark matter. It makes up about 68% of the universe's total energy content, and it acts like a repulsive force woven into the fabric of space itself — pushing everything apart on the largest scales.