文档介绍：Cosmic microwave background radiation
Lyman Page and David Wilkinson
Physics Department, Princeton University, Princeton, New Jersey 08544
The cosmic microwave background radiation (CMBR) is widely interpreted as the thermal afterglow
of a hot big bang. Measurements of the CMBR intensity as a function of frequency constrain the
history of cosmic energetics. Measurements of the anisotropy in the CMBR temperature provide a
snapshot of the distribution of fluctuations in the gravitational potential at the earliest stages of cosmic
structure formation. The authors review the interpretation of the CMBR emphasizing the status of
current observations and future observational prospects. Our knowledge of the CMBR will
dramatically increase in the first decade of the twenty-first century. [S0034-6861(99)05202-2]
I. INTRODUCTION II. MEASUREMENTS OF THE CMBR
Most astronomers and physicists now believe that we A. The spectrum
live in an expanding universe that evolved from an early
The temperature of the CMBR can be estimated by
state of extremely high density and temperature. Mea- noting that a substantial fraction (Ϸ24%) of the matter
surements of the spectrum and anisotropy of the cosmic in the universe is helium and assuming that it was made
microwave background radiation (CMBR) provide by nuclear reactions in the early universe. If so, at an age
strong evidence