The Return of the Phoenix Universe
  Georges Lemaitre introduced the term "phoenix universe" to describe an
oscillatory cosmology with alternating periods of gravitational collapse and
expansion. This model is ruled out observationally because it requires a
supercritical mass density and cannot accommodate dark energy. However, a new
cyclic theory of the universe has been proposed that evades these problems. In
a recent elaboration of this picture, almost the entire universe observed today
is fated to become entrapped inside black holes, but a tiny region will emerge
from these ashes like a phoenix to form an even larger smooth, flat universe
filled with galaxies, stars, planets, and, presumably, life. Survival depends
crucially on dark energy and suggests a reason why its density is small and
positive today.
