Most models of dark energy hold that the amount of it remains constant. But about 10 years ago, cosmologists realised that if the total density of dark energy is increasing, we could be headed for a nightmare scenario - the "big rip". As space-time expands faster and faster, matter will be torn apart, starting with galaxy clusters and ending with atomic nuclei. Cosmologists called it "phantom" energy. To find out if this could be true, Dragan Huterer at the University of Michigan in Ann Arbor turned to type la supernovae. These stellar explosions are all of the same brightness, so they act as cosmic yardsticks for measuring distances. The first evidence that the universe's expansion is accelerating came from studies of type la supernovae in the late 1990s.
展开▼
