The fall after he left Carleton, Paul continued his study of physics at Harvard, where he studied under Norman Ramsey, 1989 winner of the Nobel Prize in Physics.
Paul used the study of surface collision frequency shifts in the hydrogen maser to significantly improve the measurement of the hydrogen hyperfine frequency. Others later built on this work to develop a more accurate time standard, which is the basis for GPS and other time-related technologies.
After completing his Ph. D. in 1970, Paul held research positions at the University of Western Ontario and Corning Glass Works, before embarking on a 36-year career at the University of Michigan-Dearborn in 1973.
While at Dearborn he developed and taught most of the physics curriculum, conducted research on positrons with the atomic physics group on the Ann Arbor campus, and served as Chairman of the Natural Sciences Department and Associate Dean of the College of Arts, Sciences, and Letters. He was the recipient of three distinguished faculty awards recognizing his accomplishments in teaching, research, and service.
In 1986, he prepared the first edition of Physics: Principles and Problems, a best-selling textbook for high school students, which he carried through nine editions, the last of which was published in the fall of 2013.
Through this book, he was able to reach a generation of physics students and help them learn basic physics concepts. He also worked with faculty in science education at Dearborn to develop new science teaching methods for use in elementary schools.
He retired as emeritus professor of physics and science education in 2009. He was a fellow of the American Physical Society and treasurer of the American Association of Physics Teachers.
Paul was diagnosed with peritoneal cancer in 2008, a day after he taught his last class. He sustained three major surgeries and continued to work at his desk until two weeks before he passed away.
Many of you will have received emails from him. He was an active correspondent with Carleton alumni, physics teachers, and faculty colleagues. He was an avid reader and loved to share news with others interested in the topics he pursued.
He is survived by his wife of 47 years, Barbara, his brother Peter (Nancy), his children Eric (Christine Foley) Zitzewitz and Karin (Sean Pue) Zitzewitz, and his grandchildren Zachary, Zoe, and Alexander Zitzewitz, and Clara Pue.