Astronomers use Hubble to measure the Expansion Rate of the Universe
![](https://cdn.sci.esa.int/documents/34247/35306/1567213709205-i_screenimage_16076.gif)
Depicts: Theories on Universe expansion rate
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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.
Last Update: 1 September 2019