The machine known as the Tevatron is four miles around. Bison graze nearby on the 6,800 acres of former farmland occupied by the Fermi National Accelerator Laboratory in Batavia, Ill. Occasionally, physicists run races around the top of it.

It was turned on in 1983 to the sound of protesters who worried that its high-energy collisions between protons and antiprotons could bring about the end of the world or perhaps the whole universe.

For the next three decades it reigned as a symbol of human curiosity and of American technological might, becoming the biggest, grandest, most violent physics experiment of its time, devouring a small city’s worth of electricity to collide subatomic particles with energies of up to a trillion electron volts apiece in an effort to retrieve forces and laws that prevailed during the Big Bang.

The world as a whole never did end, but for American physicists a small piece of it has now. Last Monday the Department of Energy, which runs Fermilab, as it is known, announced that despite last-minute appeals by physicists, the Tevatron will shut down as scheduled in September.