The universe is not only expanding – it is accelerating outward, driven by what is commonly referred to as “Dark energy.” The term is a poetic analogy to label for dark matter, the mysterious material that dominates the matter in the universe and that really is dark because it does not radiate light.
Two explanations are commonly advanced to explain dark energy.
For several decades cosmologies have successfully used a relativistic equation with dark matter and dark energy to explain increasingly precise observations about the cosmic microwave background, the cosmological distribution of galaxies, and other large-scale cosmic features.
The scientists apply sophisticated statistical techniques to the relevant cosmological datasets and conclude that if the dark energy term varied slightly as the universe expanded, it could explain the discrepancy.
One of the team’s major new experiments, the Dark Energy Spectroscopic Instrument Survey, could settle the matter. Explore further: New supernova analysis reframes dark energy debate.
Dynamical dark energy in light of the latest observations, Nature Astronomy.