Pyotr Kapitsa measured extraordinarily small flow resistance in liquid helium below its lambda transition. Confining the flow to narrow passages made the failure of ordinary viscous-flow expectations experimentally striking. The observation helped establish superfluidity as a distinct quantum-fluid phenomenon. In a modern two-component interpretation, the low-resistance response does not mean that every component of the liquid has lost all viscous behavior; it motivates separating normal and superfluid contributions.[ref]
Viscosity of Liquid Helium below the λ-Point by Pyotr Leonidovich Kapitza. 1938 report, narrow-passage liquid-helium flow
Portrait of Pyotr Kapitsa
. Unknown photographer (Mondadori Publishers / Archivio Mondadori); 1930s; existing Commons adjustment by Materialscientist. Public domain in Italy: photograph copyright expired (PD-Italy). Source usage terms, via Wikimedia Commons. Source. Articles by others on the same topic
Pyotr Kapitsa, full name Pyotr Leonidovich Kapitsa, was a renowned Russian physicist who made significant contributions to various fields of physics, particularly in low-temperature physics and the study of superfluidity. He was born on July 8, 1894, in Kronstadt, Russia, and passed away on April 8, 1984.