---
title: "Kapitsa’s helium flow: viscosity depended on how it was tested"
description: "Why did helium below the lambda transition defeat a single ordinary-viscosity picture?"
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[Cold liquids and superconducting order](https://sandboxphysics.com/stories/condensed-matter/#collective)

Materials · Measurements · Explanation

# Kapitsa’s helium flow: viscosity depended on how it was tested

Why did helium below the lambda transition defeat a single ordinary-viscosity picture?

Sandbox Physics · 2026-10-23

Nobel contribution: 1978-1

1. Prepare cold liquid helium
2. Drive flow through a narrow gap
3. Compare with other responses
4. Separate normal and superfluid motion

The narrow-gap experiment constrained dissipative flow. It did not imply that every probe of the liquid must see zero damping.

## A narrow gap tested an unusual flow

Kapitsa’s 1938 report examined helium below the lambda transition, where flow through a narrow gap implied extraordinarily low viscosity. Allen and Misener independently reported related superfluid behavior.

The result depended on the flow geometry and on checking the character of the motion. An unusually large heat transport signal had motivated the investigation, but did not itself establish a viscosity value.

Sources: [4] [3]

## Different probes couple to different motion

A two-fluid description permits a normal component with entropy and viscosity alongside superfluid motion. An oscillating object can therefore experience damping even when a narrow-channel experiment is dominated by the superfluid component. The descriptions concern different responses of one liquid.

Sources: [2] [3]

## Low-temperature engineering sustained the physics

Kapitsa also developed methods for producing and handling low temperatures. Stable cooling and sensitive flow measurements made systematic studies possible. The 1978 award recognized his low-temperature inventions and discoveries, a scope broader than one viscosity measurement.

Sources: [3]

## The source choice matters here

Kapitsa’s Nobel lecture discusses plasma and controlled fusion, so this helium article uses his original viscosity report and the official low-temperature award account. The linked pairing model supplies quantum-fluid context; it does not simulate the capillary apparatus.

Sources: [4] [3] [1] [5]

Continue with the physics

## Try the related models

### [Pairing across the crossover](https://sandboxphysics.com/labs/bec-bcs-crossover/)

Compare weak pairs with tightly bound pairs.

The teaching crossover does not predict a cuprate mechanism or helium-three order parameter.

## Sources and reading notes

1. [Ginzburg: On superconductivity and superfluidity (2003)](https://www.nobelprize.org/uploads/2018/06/ginzburg-lecture.pdf)

   The phenomenological order parameter, its effective charge and its range of validity.

2. [1962 award presentation: Landau’s liquid-helium theories](https://www.nobelprize.org/prizes/physics/1962/ceremony-speech/)

   Official contemporary account of collective excitations, neutron tests and second sound.

3. [1978 award: low-temperature inventions and discoveries](https://www.nobelprize.org/prizes/physics/1978/press-release/)

   The low-temperature award context. Kapitsa’s Nobel lecture itself concerns plasma research.

4. [Kapitza: Viscosity of liquid helium below the lambda point (1938)](https://doi.org/10.1038/141074a0)

   Original narrow-gap viscosity report; subscription preview and bibliographic metadata are publicly readable.

5. [Nobel Prize in Physics 1978: official award](https://www.nobelprize.org/prizes/physics/1978/summary/)

   Official attribution and award year. The observation or theoretical paper may be much earlier.

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