In 1964 Arno Penzias and Robert Wilson from Bell Labs in Princeton accidentally discovered an unexplained source of microwave noise using an antenna designed to detect radio signals bounced off the Echo satellite. At the time they could not possibly have imagined how momentous this finding would turn out to be. Indeed, they first attributed their anomalous background buzz to a pair of nesting pigeons who had coated the inside of their horn with "a white dielectric substance". Carefully removing this "foreground" did not, however, get rid of the noise, and -- to cut a long story short -- the existence of the cosmic microwave background radiation (CMBR) was established. Penzias and Wilson went on to share the 1978 Nobel Prize for Physics.
The existence of this universal background radiation is one of the major observational pillars supporting the Big Bang theory. The accurate black-body form of the CMBR spectrum is naturally accounted for by its production in a primordial fireball, during which the entire universe was hot enough to be ionized. In tandem with the other great breakthrough of observational cosmology - Hubble's discovery of the expansion of the universe - the properties of the CMBR have enabled cosmologists to paint a picture of a universe steadily expanding and cooling from an initial singularity of infinite density and temperature.
But the Big Bang model has always been open to the reasonable criticism that it is virtually impossible to test. Since the laws of physics fall apart at the initial singularity, cosmologists have never been able to calculate from first principles such crucial parameters as the density, curvature and expansion rate of the universe. Instead these free parameters have needed to be fixed by observations of distant galaxies and other sources that are difficult both to perform and to interpret.
In Echo of the Big Bang, science journalist Michael Lemonick tells the story of the CMBR in the developing context of modern cosmology, placing particular emphasis on the WMAP mission, which was launched in 2001. The author clearly has a flair for writing about popular science. His explanations of the (sometimes difficult) physics are admirably clear and the text is peppered with well turned phrases.
In the August issue of Physics World Peter Coles from Nottingham University recommends Lemonick’s book as a breezy and engaging introduction to the basics of Big Bang cosmology.