Scientists have begun firing a beam of neutrinos through the Earth to a target 735 km (456 miles) away. This experiment will help the team understand how neutrinos can pass through tremendous amounts of matter, but barely interact. And if they’re lucky, they’ll catch the particles as they morph into different varieties: electron, muon and tau. One detector, at Fermilab, near Chicago, will sample the beam as it leaves the Main Injector. Another detector is stationed deep underground at the Soudan Mine in Northern Minnesota. Only muon neutrinos will be generated, so if the other varieties show up, scientists will know it happened in between the detectors.