PHOTO: MAXIMILIEN BRICE/CERN

The 7000-ton Atlas detector at CERN, the European Organization for Nuclear Research, in Geneva, is the centerpiece of the biggest particle physics experiment ever undertaken. Atlas is built into the large hadron collider, or LHC, the massive machine that is our best hope for solving such basic mysteries as what gives mass to matter.

Atlas is really four detectors nested within one another. In August, the last of the outermost detector's eight 100-ton, 25-meter-long superconducting magnets [orange-striped tubes] was installed. When completed in 2007, the LHC will knock together protons that are traveling at 99.999999 percent of the speed of light. Protons crashing at that speed cause an eruption of fundamental particles, re-creating conditions similar to those just after the big bang. Atlas will see about a billion collisions per second, generating data at a rate equivalent to 20 telephone conversations by everyone on Earth all at once. Somewhere within that mountain of data will be answers to many of particle physics' most difficult questions.