Can Earth's rotation generate power? Physicists divided over controversial claim

Experimental effect and scale

• Commenters note the reported current (25 nA), voltage (17 µV), and power (~0.44 picowatts) for a 30 cm shell, emphasizing how vanishingly small the output is.
• Several people do rough calculations: Earth’s rotational energy is enormous (order ~10²⁴–10²⁵ J available for a 1-second lengthening of the day), so in principle there is “plenty” of energy, but the demonstrated device extracts an utterly negligible fraction.

Energy source and conservation laws

• A recurring debate: is the energy drawn from Earth’s rotation (kinetic energy/angular momentum) or from the magnetic field’s stored energy?
• Some argue that any macroscopic extraction must ultimately slow Earth’s rotation; others propose that the primary source is the magnetic field energy, with angular momentum returned to Earth when the field changes.
• Multiple replies stress that conservation of energy and angular momentum must hold for the full Earth–Moon–Sun system, and that tidal interactions already transfer angular momentum (e.g., to the Moon’s orbit).
• A few find the Nature article’s explanation of the torque and angular momentum bookkeeping unclear or possibly misleading.

Impact on rotation and magnetic field

• Using the authors’ own estimate (if this supplied all ~11 TW of global electricity), Earth’s spin would slow by only a few milliseconds per century, comparable to natural tidal and core-dynamics effects.
• Several comments compute that slowing Earth’s rotation by 1 second would correspond to thousands of times current annual global energy use, suggesting an extremely long usable horizon.
• Some worry that if the energy is drawn from the field itself, large-scale use might weaken the geomagnetic field faster than natural processes, with potential implications for cosmic-ray shielding, though this remains speculative in the thread.

Practicality and alternate uses

• Many treat the scheme as a fascinating physics curiosity rather than a practical power source, given the minuscule power density and likely materials/engineering limits on scaling.
• A few suggest niche uses: exploiting the effect for navigation or orientation (though others note we already can use the magnetic field directly, or gravity variations, for that).

Comparisons, analogies, and tangents

• The discussion repeatedly compares this to wind and tides as existing ways Earth’s rotation indirectly powers systems.
• Some recall the EmDrive controversy as a cautionary tale about tiny, hard-to-measure effects.
• There is a large side-thread on broader energy policy (solar, wind, nuclear, storage, waste), mostly agreeing that even if this effect is real, it is irrelevant to current energy planning.