This May, CERN’s Large Hadron Collider (LHC), the most powerful particle accelerator yet created by humans, is scheduled to start smashing protons into each other with unprecedented impact speeds. The LHC will explore the leading explanation that mass arises from ordinary particles slogging through an otherwise invisible but pervasive field of virtual Higgs particles. In this image by Maximilien Brice, a person stands in front of the huge ATLAS detector (center, near bottom of frame), one of six detectors being attached to the LHC. This was the February 25, 2008 Astronomy Picture of the Day.