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Why did Irving Langmuir compare plasma oscillations to the motion of a jellylike substance?

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How scientists use lasers to learn about the universe — plasma Learn about the PHELIX (Petawatt High-Energy Laser for Heavy Ion Experiments) laser at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. PHELIX is used for plasma and atomic physics research.

In 1929, physicists Irving Langmuir and Lewi Tonks identified regions within electric discharges where electrons exhibited periodic variations, which they termed plasma oscillations. They compared these oscillations to the motion of a jellylike substance because the collective behavior of the electrons—moving together as a group in response to electrostatic forces—suggested the elastic, unified consistency of a gel.1

This analogy highlights the nature of plasma as a medium where particles do not act entirely independently. When electrons are displaced from their equilibrium position, the resulting positive charge exerts an electric force that acts as a restoring force, causing the electrons to oscillate as a whole about their equilibrium state. This organized, collective motion is a defining characteristic of the plasma state.23