Complex sentence: John D. Reppy is a physicist who studies the quantum properties of superfluids at Cornell University as well as a notable rock climber of long standing, who established a number of widely known climbing routes particularly in the Northeastern United States.
Split into simpler sentences: John D. Reppy is a physicist who studies the quantum properties of superfluids at Cornell University. He is also a notable rock climber of long standing, who established a number of widely known climbing routes particularly in the Northeastern United States.