| Currently the most powerful particle accelerator in the world. (It will be overtaken in 2008 when the Large Hadron Collider goes online at CERN). It is located at Brookhaven National Laboratory on Long Island, New York.
The machine accelerates either heavy ions, such as gold nuclei, or polarized protons. In either case the particles are accelerated through three booster stages (a linear accelerator, a dedicated booster stage, and BNL's Alternating Gradient Synchrotron) before being injected into the main ring. There they are accelerated to a maximum energy of 200 GeV (Giga-electron-Volts) for heavy ions, or 500 GeV for protons. Because the particles being collided all have the same electric charge they must be accelerated in two separate rings which cross at specified collision points. The rings are made of super-conducting electromagnets, and has to be cooled by liquid helium.
RHIC has space for six detectors. Four of these are currently occupied. There are two large detectors, called PHENIX, and STAR, and two smaller detectors, PHOBOS and BRAHMS. The large detectors are about three stories high, and are decorated with all manner of high speed fiber-optics connecting large arrays of high-speed electronics that control the data acquisition.
The facility also has three large computing farms, consisting of several hundred VA Linux machines. These are used to simulated the detectors for design purposes, and to analyze the data, an impressive feat considering that each of the large detectors is expected to produce about 300 TB of data each year.
There are two main goals for the collider. The first is the creation of a Quark Gluon Plasma, which will help us understand the nature of the force that binds quarks together to form hadrons (of which protons and neutrons are examples). Very little is currently known about this force. The other goal is to investigate proton structure. It is known that protons are made of three quarks, held together by gluons, but the details of how these produce the observed properties of the proton, such as mass, momentum, and spin, are largely unknown.
The detector started colliding ions on June 12 2000. The first collisions were amazing for two reasons: First, all the detectors observed collisions as soon as they started occurring which means that a giant multi-billion dollar project worked "out of the box". Second, the world was not destroyed. This point was very surprising for some who had been predicting that RHIC would do just that. Apparently there were actually three ways the world could have ended ("This is no cheap machine" as one research noted):
1: The high energy densities could have torn the fabric of space and time.
2: It could have created a small, stable, black hole.
3: It could have formed something called a strangelet.
It should be noted that the physics community did, in fact, analyze each of these possibilities as they were brought up and concluded that the probability of them occurring is fantastically small. | 
