As a high-school student, Harry Weerts finished reading his physics textbook, but was left with more questions than answers. His quest to find those answers led him from his native Netherlands to the forefront of particle physics in the United States. (See CV)

From the start, Weerts had no doubt that he would study physics at university. But it was a riveting class about neutrino scattering at the RWTH Aachen University in Germany that compelled him to do both his masters and his PhD at the same university, working on neutrino experiments at CERN, the European particle-physics lab near Geneva, Switzerland.

His biggest career decision, he says, was to move to the United States and work at the Tevatron — the world's highest-energy particle accelerator — as a postdoc at the Fermi National Accelerator Laboratory (FermiLab) in Batavia, Illinois.

From there he took a faculty position at Michigan State University in 1983, where he was able to spend the next 20 years working on one of the two large-collider experiments designed at the Tevatron. He oversaw the programme — which continues to collect data today — since it began running in the 1990s.

A self-described “lucky guy”, Weerts was part of the team working at the Tevatron that in 1995 discovered the largest elemental subatomic particle: the elusive top quark.

Always on the lookout for the next big collaborative project, Weerts recently took a year's sabbatical at FermiLab to champion the International Linear Collider — the proposed particle accelerator that would be able to create high-energy collisions between electrons and positrons.

Most recently, he decided to put off retirement and give up his tenure at Michigan State to serve as director of high-energy physics at Argonne National Lab in Argonne, Illinois. This decision was driven by his belief that the younger cohort should conduct the experiments and that it is the duty of the more senior scientists to lead their field in new directions.

“I feel I owe it to my research field to help define the next big project in particle physics,” Weerts says. Being a director at Argonne enables him to make this contribution at an administrative level, he adds. And with so much left to discover, he wasn't quite ready for retirement just yet.

“Only 4% of the Universe is made out of the stuff we've studied for the past 2,000 years,” he says.