General relativity is the most beautiful physical theory ever invented. It describes
one of the most pervasive features of the world we experience—gravitation—in
terms of an elegant mathematical structure—the differential geometry of curved
spacetime—leading to unambiguous predictions that have received spectacular
experimental confirmation. Consequences of general relativity, from the big bang
to black holes, often get young people first interested in physics, and it is an
unalloyed joy to finally reach the point in one's studies where these phenomena may
be understood at a rigorous quantitative level. If you are contemplating reading
this book, that point is here.
In recent decades, general relativity (GR) has become an integral and
indispensable part of modern physics. For a long time after it was proposed by Einstein
in 1916, GR was counted as a shining achievement that lay somewhat outside the
mainstream of interesting research. Increasingly, however, contemporary students
in a variety of specialties are finding it necessary to study Einstein's theory. In
addition to being an active research area in its own right, GR is part of the standard
syllabus for anyone interested in astrophysics, cosmology, string theory, and even
particle physics. This is not to slight the more pragmatic uses of GR, including
the workings of the Global Positioning System (GPS) satellite network.