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The Rest Is Science
The Rest Is Science

Polymetalic Nodules Are Weird

May 13, 2026 • 31m

Summary

⏱️ 6 min read

Overview

Hannah Fry and Michael Stevens explore fascinating scientific topics including polymetallic nodules from the ocean floor, the mysteries of handedness and ambidexterity, lightning strikes on tall animals, and how humidity affects temperature perception. The episode features their signature blend of rigorous science and playful banter, culminating in an unexpected discussion about sexy accents.

Polymetallic Nodules: Ancient Ocean Treasures

Hannah presents a mysterious black rock called a polymetallic nodule, recovered from the Atlantic Ocean floor. These potato-sized formations take millions of years to develop, growing around seeds like shark teeth or meteorite fragments at just one millimeter per million years. The rocks contain concentrated rare metals essential for electric car batteries and can even generate natural electrical charges that oxygenate the ocean floor, creating a paradox about mining them for green technology.

  • Polymetallic nodules form at the ocean floor through hydrogenous precipitation, one of Earth's slowest geological processes
  • The rocks accumulate at approximately one millimeter every million years, with seeds dating back to dinosaur times
  • Nodules contain manganese, nickel, and cobalt - the same rare metals needed for electric car batteries
  • Clusters of nodules can generate 1-2 volts of electricity, splitting seawater into hydrogen and oxygen
  • The CIA once used nodule mining as a cover story to retrieve a sunken Soviet submarine during the Cold War
" They accumulate at about one millimeter every million years. It's unbelievably slow. "
" These grapefruits that are sitting at the bottom of the ocean that have been there since the time of the dinosaurs. "
" There is this kind of paradox that's going on at the moment, which is that to make cars greener, maybe we should do this really quite environmentally damaging thing. "

Deep-Sea Mining Dilemma

The discussion returns to the environmental implications of mining polymetallic nodules. While these rocks contain exactly the metals needed for green technology like electric car batteries, extracting them could severely disrupt deep-sea ecosystems. The hosts wrestle with this paradox of needing to do environmental damage to enable greener technology on land.

  • Polymetallic nodules contain the exact rare earth minerals needed for electric car batteries and green technology
  • Mining these nodules would likely be quite disruptive to marine life despite their abundance
  • The ocean has already done the work of concentrating rare metals together through natural processes over millions of years

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