Number 95 (Story #1), September 22, 1992 by Phillip F. Schewe and Ben Stein STUDIES OF THE COSMIC MICROWAVE BACKGROUND (CMB) can provide information about the inflationary expansion of the early universe. A few months ago Lawrence Krauss and Martin White of Yale asserted (Phys. Rev. Lett., 10 Aug.) that variations in the CMB may be due in part to gravitational waves (tensor perturbations) and not just to matter-density fluctuations (scalar perturbations). A new paper by theorists and experimenters, including George Smoot of LBL, Paul Steinhardt of the University of Pennsylvania, and Michael Turner of the University of Chicago, examines the likely contributions of tensor and scalar perturbations to the CMB variations for the case of several different inflationary models. They conclude that a combination of large-angular-scale data from the Cosmic Microwave Explorer (COBE) and small-angular-scale data from other CMB detectors might be able to distinguish scalar from tensor effects. (R.L. Davis et al., Phys. Rev. Lett., 28 Sept. 1992.)