Number 162 (Story #1), January 31, 1994 by Phillip F. Schewe and Ben Stein THE FIRST DIRECT OBSERVATION OF STRUCTURE IN THE COSMIC MICROWAVE BACKGROUND (CMB) has been made by a team of astronomers using a telescope at Tenerife, in the Canary Islands. Two years ago the Cosmic Background Explorer (COBE) detected structure in the CMB at a level of 1 part in 100,000 over angular swatches of 10 degrees. This structure, however, was inferred from statistical correlations in the underlying data and did not correspond to the blue and red clumps one saw in the famous COBE maps of the entire sky. The Tenerife measurements, in contrast, directly display primordial fluctuations in the temperature of the CMB (variations about an average value of 2.7 K) at a level of 2 parts in 100,000 over 5- degree chunks of the sky, for the portion of the sky covered by the Tenerife survey. These features would not correspond to any supercluster we would see today since the largest such structure would still subtend an angular size of less than 1 degree when projected onto the CMB. The Tenerife and COBE results are consistent with each other. For example, the quadrupole component of the CMB fluctuations is calculated to be 26 +/- 6 microkelvins for Tenerife and 17 +/-5 for COBE. (S. Hancock et al., Nature, 27 January 1994.)