IN MEMORIAM Rainer Kurt Sachs 1932–2024.

Rainer Kurt Sachs, a Professor of Mathematics and Physics at UC Berkeley, passed away in April 2024. He had two successful careers in science, one in general relativity and cosmology, and the other in the mathematics of radiation biology and carcinogenesis. Sachs made significant contributions to the analysis of gravitational waves and the prediction of minute angular fluctuations in the cosmic microwave background radiation. In his later career, he focused on understanding radiation-induced chromosome aberrations and modeling radiation carcinogenesis. Sachs was known for his modesty, attentiveness, and supportiveness as a mentor. A Memorial Colloquium will be held in his honor in October 2024. [Extracted from the article]