The theory and observation of the cosmic microwave background have changed the status of cosmology within the physical sciences. What was once a backwater of elegant speculation without observational constraints is now seen by many as a precision tool for measuring fundamental properties of the universe.
We know that the universe is flat to within 1%, and that the vast majority of matter and energy in the cosmos is in an unknown “dark” form that cause its expansion to accelerate. Stunning images representing the temperature of the cosmic background radiation obtained by the COBE satellite in the early 1990s and the WMAP satellite - which released its first data in February this year - have allowed cosmologists to see what could be the seeds of galaxy formation. And the next generation of experiments will open a new window on the universe by measuring the polarization of the cosmic microwave background.
Pedro Ferreira from the Department of Astrophysics at Oxford University discusses the significance of the cosmic background radiation in more detail in the April issue of Physics World.