What is DARK ENERGY?
Astronomers in the early 20th Century got the shocks of their lives when they discovered that galaxies appeared to be rushing away from us. Then came 1998 and the Hubble Space Telescope observations of very distant supernovae showed that, a long time ago, the Universe was actually expanding more slowly than it is today. Dark energy is the name given to an unexplained force that is the source of this expansion and it’s drawing galaxies away from each other, against the pull of gravity, at an accelerated pace.
Dark energy is a bit like anti-gravity. Where gravity pulls things together at the more local level, dark energy tugs them apart on the grander scale. We know how much dark energy there is because we know how it affects the Universe’s expansion. But it is an important mystery. It turns out that roughly 70% of the Universe is dark energy.