Philip A. Pinto, Associate Professor, Astronomy/Steward Observatory, University of Arizona
One of the greatest achievements of twentieth-century science is an understanding of the origin of matter. While hydrogen and helium were produced in the Big Bang, the origin of the heavier elements—the silicon in rocks, the iron in our blood, and the oxygen we breathe–lies in the lifecycle of stars. Nuclear reactions, which transform light elements into heavier ones, cause stars to shine and ultimately to explode, seeding the universe with their production. These newly formed elements, the building blocks of ordinary matter, play a central role in the formation of planets and the evolution of life.