50 years ago, CERN scientists collided particles in the first hadron collider ever built. On 27 January 1971, CERN’s Intersecting Storage Rings (ISR) produced the world’s first proton–proton collisions. Physicists had planned this machine in the 1960s, based on the idea that smashing two particle beams head on would give much higher energies than colliding a single beam of particles with a fixed target. This first hadron collider helped change the views of members of the physics community, who d