Abstract
The universe is incredibly massive. Nevertheless, its mass must be spectacularly fine-tuned for life to be possible. Exactly how massive the universe is remained unknown until astronomers focused the Hubble Space Telescope on a patch of sky no bigger than a tenth the Moon's (angular) diameter, and held it there for some 278 hours. This Ultra Deep Field (see figure) successfully imaged all the galaxies (at least those bigger than dwarfs) that exist in that region.