a single dish; instead, it looks at differences between the light falling on pairs of telescopes. Like water waves, light waves can interfere with each other, producing a complex pattern of intensity enhancements where the waves constructively interfere, and nulls where they destructively interfere. As light from a source washes over the array, an interferometer detects this interference pattern — hence the name. The source's structure on the sky can then be inferred from the interference pattern in much the same way that one might infer the size and shape of a stone thrown into a pond from the pattern of ripples left in its wake. The native resolution of an interferometer depends not on the size of the individual telescopes (as with a traditional single telescope), but on their separation. Pairs of telescopes with large separations provide sensitivity to small-scale structure, while short spacings are sensitive to large-scale structure on the sky. The 8 SZA telescopes are small enough to be placed very close together, which provides maximum sensitivity to the (large-scale) SZ signal from clusters. When the SZA was combined with the other telescopes in the CARMA array, which had longer separations and were sensitive to finer angular scales, it formed a complete picture of galaxy clusters at very high resolution. References Radio telescopes Interferometric telescopes Cosmic microwave background experiments Buildings and structures in Inyo County, California