The open or closed universe
can also be recently accelerated by the dark energy.
The fiery destruction scheduled for a closed universe was detailed in 1969 in a pioneering article by Martin Rees (now England's Astronomer Royal).
A closed universe is destined to collapse on itself.
A closed universe would keep the breadth of possibilities on a much shorter leash.
Nonetheless, cautions Burstein, "One massive group does not a closed universe
If there is enough mass, galaxies' mutual gravitational attraction will cause them to stop receding from each other, and the universe will end in a Big Crunch -- the closed universe
Gerard't Hooft of the Institute for Theoretical Physics in Utrecht, the Netherlands, has since written a paper purportedly proving that a closed universe
-- one filled with sufficient mass to reverse its expansion -- would necessarily collapse to a size smaller than any route one would need to take to circumnavigate two oppositely directed, speeding particles along a closed time-like curve.
Again, for gravity to be strong enough to stop and reverse the expansion of the universe, ultimately causing a recollapse -- which is how a closed universe
would behave--large amounts of dark matter must exist.
A closed universe will reach some maximum size and then eventually collapse, coming to what Tipler calls "a crunch singularity," a state in which temperature and density become infinite and the radius of the cosmos is zero.
In the closed universe, the cosmos must first reach its maximum size--we know it is still expanding now--and then start to collapse.
An ambitious example is "research and describe scientific hypotheses of the fate of the universe, including open and closed universes
and the role of dark matter and dark energy.