CHICAGO--A new chapter in the study of the cosmic background radiation has just begun. At the Cosmo-02 meeting here (18 to 21 September), physicists announced the first detection of polarization in the radiation, the light left over from the very early ages of the cosmos. Although the much-anticipated result fits theoretical predictions, it heralds the start of a new approach for deciphering a cosmic message from the edge of the universe.
The cosmic microwave background (CMB) is the relic light that remains from the era when the first atoms formed, when the universe was just 400,000 years old. Now, the CMB looks pretty much the same in all directions, except for some very hard-to-detect hot and cold spots that are the signature of sloshing matter in the early universe. In 2000 and 2001, exquisitely detailed maps of those spots allowed scientists to divine the amount of matter and energy in the universe (ScienceNOW 30 April 2001). They even confirmed that the "shape" of spacetime was flat (26 April 2000).
Now a team using the Degree Angular Scale Interferometer (DASI), a microwave telescope based near the South Pole, has added another dimension to the map of the CMB: polarization, which is the orientation of waves of incoming light. Theorists had long suspected that light from the CMB might show preferred orientations in places because of the churning motion of the matter in the early universe. "We've detected polarization at a high level of confidence," says John Carlstrom, the leader of the DASI team. That will triple the amount of information available from the CMB, adds DASI team member John Kovac, a cosmologist at the University of Chicago. "It's like going from the picture on a black-and-white TV to color."
The detection is just a first step in the study of the CMB's polarization, but the result is a great relief to physicists that the faint signal isn't swamped by polarized light from other sources. "The Achilles heel of the whole polarization challenge is polarized space junk that could completely hose everything," says Max Tegmark, a cosmologist at the University of Pennsylvania in Philadelphia. The lack of noise, he notes, "bodes really well for the future of the field."