A day that many particle physicists had dreaded has arrived. Today, around 2:30 p.m. U.S. Central Daylight Time, researchers at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, will shut down their Tevatron collider, which has smashed protons into antiprotons since 13 October 1985 in order to produce new and fleeting subatomic particles. For nearly 25 years, the Tevatron reigned as the world's highest-energy atom smasher, until is was surpassed 18 months ago by the more-powerful Large Hadron Collider at the European particle physics laboratory, CERN, near Geneva, Switzerland. The demise of the Tevatron also leaves the United States with no atom smashers to search for new particles. (The nation's last collider, the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in Upton, New York, studies an exotic type of nuclear matter called a quark-gluon plasma.)
The Tevatron leaves a mixed legacy. In 1995, researchers used it to discover a particle called the top quark, a cousin of the up quarks and down quarks that make up protons and neutrons and the last and heaviest of the six known quarks. Some say that discovery merits a Nobel Prize; others say the top quark had to be there. Otherwise, the Tevatron never scored a surprising discovery to make physicists rethink their standard model of particle physics, researchers say. Fermilab will now try to redirect its efforts to studying the properties of elusive particles known as neutrinos. However, that new program will require billion-dollar investments, and it's not clear those funds will be available.
View an inventive video marking the shutdown.