“Dark energy” might sound like the kind of thing that ghost hunters would search for inside a haunted house. But dark energy has nothing to do with supernatural specters. It’s a real physical phenomenon. And it’s shaping our universe on the grandest scales.
Dark energy is a mysterious force that is driving our universe to expand faster and faster. No one knows exactly what it is. But scientists estimate that it makes up about 70 percent of everything in the cosmos. (Another 27 percent of the stuff out there is dark matter. The rest is ordinary matter, which includes everything we can see — from stars to you.)
Scientists need to understand dark energy to know how the universe evolved in the past — and what it will do in the future. While they might not yet have answers, scientists do have some ideas about how dark energy might affect that future.
Say dark energy keeps pushing the universe to expand at the same rate throughout time. In that case, our cosmos may slowly cool and fade to black. But if dark energy pushes the universe’s expansion even faster? The universe could eventually tear itself apart. And if dark energy weakens over time, the universe may someday collapse.
Recent data from the Dark Energy Spectroscopic Instrument, or DESI, hint that dark energy has weakened over time. But it’s possible that dark energy goes through phases of getting stronger or weaker. If so, maybe our cosmos yo-yo’s between expanding and contracting.
New telescopes on the ground and in space may also help answer questions about dark energy. But for now, our observations of the universe leave us on a real cliffhanger about the fate everything.
Want to know more? We’ve got some stories to get you started:
The universe: How will it end? Understanding how dark energy works is crucial to predicting the fate of the universe. (4/17/2025) Readability: 6.8
Mysteries about the universe abound, from its beginning to its end Dark energy is only one of the profound mysteries about our universe that has scientists scratching their heads. (10/20/2022) Readability: 8.2
Cool Jobs: Mapping the unknown Meet one cosmologist who uses exploding stars, or supernovas, to study dark energy. (4/21/2016) Readability: 7.4
Explore more
Cosmic timeline: What’s happened since the Big Bang
The long-awaited James Webb Space Telescope has a big to-do list
Physics Nobel rewards discoveries on cosmic evolution and exoplanets
The Vera Rubin Observatory is set to revolutionize astronomy
A map of 14 million galaxies and quasars deepens a dark energy mystery (from Science News)
Einstein’s gravity endures despite a dark energy puzzle (from Science News)
The largest 3-D map of the universe reveals hints of dark energy’s secrets (from Science News)
Activities
When we say the universe is expanding, what exactly does that mean? To help picture it, follow these NASA instructions for making a model of the expanding universe with a balloon.