A "Perfect" Liquid at RHIC

Evidence to date suggests that gold-gold collisions at the Relativistic Heavy Ion Collider (RHIC) are creating a new state of hot, dense, matter different and even more remarkable than had been predicted.
-- by Karen McNulty Walsh

Photo of magnets at the Relativistic Heavy Ion Collider

Since 2000, the Relativistic Heavy Ion Collider (RHIC above) has been performing beyond expectations. Built and operated with funding from the U.S. Department of Energy’s Office of Science, RHIC has produced discoveries that have captured worldwide attention from both scientists and the public.

Photo of BRAHMS detector


Photo of PHENIX detector


Photo of PHOBOS detector


Photo of STAR detector


In doing so, RHIC research has shone a spotlight on U.S. leadership in science. And the exciting scientific output of RHIC has just begun.

Looking back

Like a giant “microscope” peering deep into the inner space of atomic nuclei, RHIC also effectively serves as a “telescope,” looking back in time to explore matter as it is thought to have existed fractions of a second after the birth of the universe. Inside the 2.5-mile-circumference particle accelerator, two beams of gold ions circulating at nearly the speed of light collide head on, developing enormous energy density in a tiny volume.

Under these conditions, the quarks and gluons that make up protons and neutrons in ordinary atomic nuclei are expected to be free for a fleeting instant — just as scientists believe they were microseconds after the Big Bang, before joining together to form protons, neutrons, and eventually, atoms, stars, planets, and people. This is much farther back in time than any telescope surveying the sky will ever be able to reach. Using sophisticated detectors known as BRAHMS, PHENIX, PHOBOS, and STAR, RHIC’s researchers take “snapshots” of this early universe substance and study how it evolves.

Understanding matter at such a fundamental level will teach us about the forces that hold the universe and everything in it together. Earlier physics studies on the basic structure and properties of matter have yielded countless, unforeseen advances and many technologies we now take for granted — things like personal computers based on state-of-the-art electronics, medical tools that help diagnose and treat disease without surgery, and telecommunications devices that allow us to talk with friends and colleagues around the world using a device smaller than a human hand. Of course, no one can predict what, if any, practical applications the knowledge gained from RHIC will yield, but we’ll never know unless we delve deeper into the mysteries of matter.