Thisisthesecondeditionofabookonthephenomenological foundations ofmodern
cosmology. The ?rst edition was surprisingly well timed. In the
preceding 3 years, advances in astronomy had laid the foundations of the
dark-energy/dark-matter c- mological model. In 1998, observations of
type Ia supernova by the Supernova C- mology Project and High Z team
suggested that the expansion of the universe is accelerating. In 2000,
Boomerang and Maxima observed clearly the ?rst acoustic peak in the
anisotropy spectrum of the cosmic microwave background. The position of
the peak strongly suggested that the density of the universe was near
critical. These two observations reconciled popular in?ationary models
with the heretofore embarrassing insistence by astronomers that the
clumping of galaxies required that the mass density of the universe be
only about 25% of the critical density. The sup- nova data told us that
the rest was dark energy in the form of an effective vacuum energy or
cosmological constant. The so-called LambdaCDM model became the standard
model. Eight years later, the observational data has improved
tremendously as a c- parison of the ?gures in the two editions will
demonstrate. Surprisingly, all this incredible data has failed to ?nd
any clear failure of the?CDM model. Among the observational advances,
the most obvious comes from the WMAP satellitewho,
alongtheground-basedexperimentslikeACBAR, yieldedtheexquisite series of
peaks in the CMB temperature anisotropy spectrum shown in Fig. 7.1
