Polarization in the cosmic

Polarization in the cosmic microwave background has been measured. The most fundamental properties of the CMB—which can reveal conditions in the universe when it was only about 400 000 years old—are its frequency spectrum and its angular power spectra of both temperature and polarization fluctuations. According to the modern theory of cosmology, the CMB microwaves received an orientation (polarization) just before the seething plasma that pervaded the cosmos in that early era finally became a neutral, transparent gas. Until now, the low level of polarization had allowed that quantity to escape detection. Using the Degree Angular Scale Interferometer detector situated at the South Pole, a group from the University of Chicago and the University of California, Berkeley, has acquired and analyzed enough high-quality data to actually see the CMB polarization. The observed value is consistent with predictions and thus strongly validates the underlying theory. (J. Kovac, et al. , preprint available at http://arXiv.org/abs/astro-ph/0209478 .)