It is largest science experiment ever conducted. The Large Hadron Collider (LHC) at CERN, the European Organization for Nuclear Research, took a quarter of a century to plan and about $10 billion to build. Housed in a 17-mile underground ring, the LHC has been designed to accelerate particles at temperatures colder than that of deep space to a velocity approaching the speed of light. Beset by a series of hiccups and delays, the CERN scientists on Nov. 29 finally recorded a benchmark achievement, powering up a proton beam to an energy of 1.05 trillion electron volts (TeV), overtaking the Tevatron accelerator at Fermilab in Illinois as the world's most powerful accelerator. Eventually the machine will power up to as much as 7 TeV, causing collisions of such high energy that they will re-create the conditions in the seconds after the Big Bang. Amid the by-products of these collisions, physicists will be searching for signs of a hypothetical subatomic particle called the Higgs boson, which according to current theory is responsible for imparting mass to all things in the universe. Other scientists are hoping for even deeper clues, like confirmation of an ambitious theory called supersymmetry. Let the physics begin.