  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.
