Astronomers use Hubble to measure the expansion rate of the Universe
An open Universe expands forever because it does not contain enough mass, and so does not have enough gravity to slow down the expansion of space.
A closed universe contains enough mass to halt the expansion, and eventually collapses.
A universe with a 'critical density' of matter in space is exactly balanced between these two alternatives, and expands at an ever-slowing rate.Credit:
About the Image
|Release date:||9 May 1996, 19:00|
|Size:||500 x 639 px|