At its most basic, dark energy is the opposite of gravity, a mysterious force stretching the universe ever wider. As for dark matter, it’s called that for a reason. Before this year, all the objects astrophysicists knew about shared one attribute–they gave off light. Dark matter is “everything else that has mass that we can’t see,” Kennedy says. His simpler explanation: “It’s just a collective term for stuff we don’t know a lot about.” But our knowledge, like the universe, is expanding at a rapid rate. In February a satellite captured pictures of what Science calls “the most ancient light in the universe.” Physicists used the clues to calculate the shape of the universe (flat), its precise age (13.7 billion years) and the speed of its expansion (71 kilometers per second per megaparsec). Now, if they could just explain what a megaparsec is, we’ll all know so much more than we did last year.
