Gravitational-wave astronomy: Observational results and their impact
  The successful construction and operation of highly sensitive
gravitational-wave detectors is an achievement to be proud of, but the
detection of actual signals is still around the corner. Even so, null results
from recent searches have told us some interesting things about the objects
that live in our universe, so it can be argued that the era of
gravitational-wave astronomy has already begun. In this article I review
several of these results and discuss what we have learned from them. I then
look into the not-so-distant future and predict some ways in which the
detection of gravitational-wave signals will shape our knowledge of
astrophysics and transform the field.
