IT IS ONE of the most important mysteries in cosmology—and getting greater on a regular basis. Ever since Edwin Hubble, an American astronomer, revealed observations of distant galaxies in 1929, scientists have recognized that the universe is increasing. For nearly 30 years they’ve recognized that the growth is accelerating (that discovery, made in 1998, was honoured with a Nobel prize in 2011). What they can’t agree on, although, is how briskly it’s presently rising.
