It was long thought that q was positive, indicating that the expansion is slowing down due to gravitational attraction. This would imply an age of the universe less than 1/ H (which is about 14 billion years). For instance, a value for q of 1/2 (once favoured by most theorists) would give the age of the universe as 2/(3 H). The discovery in 1998 that q is apparently negative means that the universe could actually be older than 1/ H. However, estimates of the age of the universe are very close to 1/ H.