On September 10, 2008, deep beneath the border between France and Switzerland, a small team of scientists held their breath as they pressed a button. Inside a 17-mile underground ring, an invisible stream of protons whooshed almost a full lap at 99.9999991 percent the speed of light. A cheer broke out in the control room. The Large Hadron Collider, the biggest and most expensive science machine ever built, had successfully fired its first beam.
The LHC was built by an organization called CERN with help from more than 100 countries and 10,000 scientists. The idea was to smash particles into each other at almost the speed of light to find out what the universe is really made of. Each of its giant detectors is the size of a cathedral and packed with sensors that record what happens when protons collide a billion times a second. In 2012, after four years of smashing, the machine spotted a new particle called the Higgs boson, which scientists had predicted for 50 years but never found. The discovery won a Nobel Prize.
Along the way the LHC also accidentally invented things you use every day. The World Wide Web was created at CERN by Tim Berners-Lee so physicists could share data more easily. The hospital scanners that detect cancer use technology developed for particle detectors. And every time the LHC restarts after an upgrade, scientists hope it might reveal hints about dark matter, the mysterious stuff that makes up 27 percent of the universe but has never been seen directly.
