Werner Vogelsang, a physicist at the U.S. Department of Energy's Brookhaven National Laboratory. Vogelsang makes calculations based on a physics theory called quantum chromodynamics, which describes the interactions of subatomic particles, and compares his results to data obtained by scientists who perform experiments at Brookhaven's Relativistic Heavy Ion Collider (RHIC), to understand how protons get their spin - a fundamental question about elementary particles that has not been adequately answered, despite decades of study. Protons are made of smaller particles called quarks, which are held together by particles called gluons. Protons, quarks and gluons have an intrinsic property known as spin, similar to Earth spinning on its axis. Scientists collide polarized protons -- protons that mostly spin in the same direction -- at RHIC, and by "seeing" the products of these collisions via huge detectors, scientists hope to learn more about the proton's spin.