The 3-ton ruler

A specialized measuring machine at SLAC is helping scientists build precise detectors for the ATLAS experiment. When physicist Katy Grimm and her students began using SLAC National Accelerator Laboratory's coordinate measuring machine, they didn't know what to expect. The machine consists of a slab of granite about the size of a small dining table, with a large mechanical arm suspended above. It weighs more than 3 tons and cost nearly $200,000. It sits inside a clean room at SLAC, which means th...