Major update published on 11 June 2014
One of the key features of Living Reviews is that its articles are kept up-to-date by their authors. A major update is considered a new publication. As such it is again subject to peer review and is issued with a new publication number.
Major revision, updated and expanded. Added new Section 2.3.3 on the Pioneer anomaly; split former Section 3 into new 3 and 4, and extended Section 3.3 on competing theories of gravity; added new Sections 5.3 and 5.4 on compact binary systems; added a new Section 8 on astrophysical and cosmological tests. The number of references increased from 299 to 454. Added two figures (8, 9) and updated Figures 1, 3, 5, and 7.