Dr Gopalan has done pioneering work leading to establishment of the chronologies of several critical rock suites of the Indian subcontinent through indigenous development of high precision mass spectrometer facilities, and meticulous design of experiments. Establishment of the ages of solid bodies in the solar system, of basaltic volcanism in the sea of Tranquility on the moon, and of granite activity in three distinct phases in the Precambrians of Rajasthan, and elucidation of the stratigraphic relations of the Precambrians of Madhya Pradesh are some of the significant contributions made by him.