{
  "id": 17689,
  "title": "Geophysicist identifies a maximum practical viscosity",
  "url": "https://urgent.news/2026/07/27/geophysicist-identifies-a-maximum-practical-viscosity",
  "topic": "science",
  "section": "Science",
  "published": "2026-07-27T08:00:40.000Z",
  "source": {
    "name": "Physics World",
    "slug": "physics-world",
    "url": "https://physicsworld.com/a/geophysicist-identifies-a-maximum-practical-viscosity/"
  },
  "original_language": "en",
  "account": "Geophysicist Masaki Yoshida from Ritsumeikan University in Japan has proposed a maximum practical viscosity of 10 28 Pascal-seconds (Pa s) for Earth's materials. This upper limit could provide insights into the geodynamics of our planet. Viscosity is a measure of a material’s resistance to flow, and it varies widely among different substances. For instance, gases like air and hydrogen have low viscosities, while liquids like water and glaciers exhibit higher viscosities. At the high end, Yoshida's research suggests that the viscosity of tectonic plates on Earth's surface could be as high as 10 70 Pa s, a value that effectively behaves like an infinite resistance to flow, akin to a rigid body. However, this posed a problem for Yoshida as he struggled to explain how these high-viscosity plates could bend and subduct into the mantle. To determine the effective viscosity of rocks under Earth's conditions, Yoshida analyzed satellite data of tectonic plate deformations and used both geodetic observations and laboratory experiments. By comparing regions under similar stress, he found that the maximum effective viscosity across Earth's geological history is around 10 28 Pa s. This upper bound offers a better understanding of the physical properties of matter and may help explain the emergence of plate motion on Earth, which began around 4 billion years ago.",
  "summary": "Boundary between materials that flow and those that don’t could shed light on Earth’s early history The post Geophysicist identifies a maximum practical viscosity appeared first on Physics World .",
  "key_points": [
    "High-viscosity tectonic plates behave like rigid bodies, posing challenges for subduction.",
    "Analysis of satellite data and experiments determines effective viscosity around 10^28 Pa s."
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}