The lensing study shows that the universe is expanding at rates slightly slower than, but similar to, rates calculated from the HST Key Project to measure the size and age of the universe. The distance scale was one of the primary science problems the HST was built to address. That findings from the gravitational lensing study and the HST Key Project agree is good news. The new research shows a slow enough expansion to explain the ages of the oldest globular star clusters, as long as the universe has a low density.
Low density is indicated by a variety of pieces of evidence.
Until recently, astronomers have been confounded by discoveries of some globular star clusters older than the calculated age of the universe. The bad news is that a slowly expanding, low density universe spells trouble for the favorite version of the big bang theory. The big bang ultimately traces the birth of the universe back to an explosion of unimaginable violence and power. The big bang theory can only be patched up in three ways, each of which is unpalatable, say astronomers who report the new results. Theorists can explain the old, low density universe by appealing to special conditions in the first fractions of a second of the big bang.