  Globular clusters are ancient stellar populations with no star formation or
core-collapse supernovae. Several lines of evidence suggest that globular
clusters are rich in planets. If so, and if advanced civilizations can develop
there, then the distances between these civilizations and other stars would be
far smaller than typical distances between stars in the Galactic disk. The
relative proximity would facilitate interstellar communication and travel.
However, the very proximity that promotes interstellar travel also brings
danger, since stellar interactions can destroy planetary systems. However, by
modeling globular clusters and their stellar populations, we find that large
regions of many globular clusters can be thought of as "sweet spots" where
habitable-zone planetary orbits can be stable for long times. We also compute
the ambient densities and fluxes in the regions within which habitable-zone
planets can survive. Globular clusters are among the best targets for searches
for extraterrestrial intelligence (SETI). We use the Drake equation to compare
globular clusters to the Galactic disk, in terms of the likelihood of housing
advanced communicating civilizations. We also consider free-floating planets,
since wide-orbit planets can be ejected and travel freely through the cluster.
A civilization spawned in a globular cluster may have opportunities to
establish self-sustaining outposts, thereby reducing the probability that a
single catastrophic event will destroy the civilization or its descendants.
Although individual civilizations within a cluster may follow different
evolutionary paths, or even be destroyed, the cluster may always host some
advanced civilization, once a small number of them have managed to jump across
interstellar space.
