Supernovae point to expansion (Image: NASA/CXC/JPL-Caltech/Calar Alto O. Krause et al)

IT’S the ultimate sleeper agent. An energy field lurking inactive since the big bang might now be causing the expansion of the universe to accelerate.

In the late 1990s, observations of supernovae revealed that the universe has started expanding faster and faster over the past few billion years. Einstein’s equations of general relativity provide a mechanism for this phenomenon, in the form of the cosmological constant, also known as the inherent “dark energy” of space-time. If this constant has a small positive value, then it causes space-time to expand …