How photography helped physicist Bibha Chowdhuri see the invisible in the 1930s

Scroll.in | Kamayani Sharma

In 1938, Indian physicist Bibha Chowdhuri and D.M. Bose exposed samarium-soaked photographic plates at high altitudes in Sandakphu and Darjeeling to detect cosmic radiation and map subatomic nuclear disintegrations. Their experimental emulsion technique recorded 30 star-like tracks left by charged particles, establishing light-sensitive photographic plates as viable detectors of subatomic events.

She isolated cosmic particle trajectories. This methodology directly enabled scientists to differentiate heavy particles, including protons and mesotrons, based on track scattering patterns across varying elevations up to 14,500 feet at Pharijong. However, wartime supply disruptions during the Second World War severed access to specialized Ilford halftone plates from England, halting further cosmic ray experiments at the Bose Institute in Kolkata. While Nobel laureate Cecil Powell subsequently collaborated with Ilford Ltd in Bristol to refine these nuclear emulsions, Chowdhuri's pioneering research provided the essential empirical proof for photographic particle detection techniques.

Comment

The reliance of early high-energy particle physics on specialized industrial consumables—specifically Ilford Ltd's emulsion plates—exposed how peripheral scientific institutions were vulnerable to metropolitan supply chain disruptions. During World War II, the inability of the Bose Institute in Kolkata to procure Ilford halftone plates halted frontline cosmic ray research, shifting the momentum of subatomic particle discovery exclusively to British laboratories.

By institutionalising direct co-development contracts between Bristol University and Ilford Ltd, Western laboratories established an integrated industrial-academic pipeline that permanently raised entry barriers for non-Western research facilities. Consequently, facilities dependent on imported nuclear emulsions, such as the Tata Institute of Fundamental Research, were forced to shift toward cloud chamber apparatuses to bypass chemical supply bottlenecks.

Strategic Question for Discussion

Which carries more weight in determining early experimental dominance in particle physics — local theoretical innovation at institutions like the Bose Institute or direct access to industrial manufacturing pipelines like Ilford Ltd, and why?

While theoretical innovation allowed researchers at the Bose Institute to devise novel particle detection methods, access to specialized manufacturing pipelines proved decisive. Ilford Ltd's tailored emulsion production enabled Cecil Powell's Bristol team to achieve reliable, repeatable observations that secured international priority. The available evidence points toward industrial co-development as the primary bottleneck that dictated scientific priority in early mid-century nuclear physics.

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