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A loophole in a result from classical electromagnetism could allow a simple device on the Earth’s surface to generate a tiny electric current from the planet’s magnetic field.

It might seem that classical electromagnetic theory would hold few surprises, but two researchers argue that one aspect of received wisdom is wrong. They show theoretically that a device, sitting passively on the Earth’s surface, can generate an electric current through its interaction with the Earth’s magnetic field. The power from the proposed device would be measured in nanowatts, but might, in principle, be scaled up.

A century-old experiment showed that if any electromagnet with cylindrical symmetry (the symmetry of a bar magnet) rotates about its long axis, its magnetic field does not rotate [1]. There is a component of the Earth’s magnetic field that is symmetric around the rotation axis (which is not aligned with the magnetic poles), so according to this old principle, the axisymmetric component does not rotate. Any stationary object on the Earth’s surface sweeps through this component of the field, which is constant at any given latitude.

A system for generating electricity from the geomagnetic field and rotation of the earth is presented. The earth rotates through the geomagnetic field to form a potential difference between first and second terrestrial charged bodies. The first and second charged bodies are spaced apart in a direction substantially normal to the earth’s surface. The system comprises an electrical load, a first current path, and a second current path. The electrical load has a supply input and a ground output. The first current path is coupled to the first charged body and to the supply input of the electrical load, for supplying the potential difference to the electrical load. The second current path is coupled to the ground output of the electrical load and to the second charged body. As a result of this arrangement, an electric current related to the potential difference is generated in the electrical load.

Entitled “The Problem of Increasing Human Energy — With Special References to The Harnessing of The Sun’s Energy”, it was published by his friend Robert Johnson in The Century Illustrated Monthly Magazine for June 1900 soon after Tesla returned from Colorado Springs where he had carried out an intensive series of experiments from June 1899 until January of 1900.

The exact title of the chapter where he discusses this device is worth giving in its entirety:

Interstellar object ‘Oumuamua — that strange, cigar-shaped chunk of rock from somewhere a vast distance beyond the Solar System — is, new research has concluded, absolutely, positively not an alien spaceship.

OK, well, probably not. We can’t tell for sure without closely examining the thing, and it’s passed beyond our reach now. But, after carefully reviewing all our observations of the object, the international team of ‘Oumuamua scientists has concluded that everything we know about it is consistent with a natural origin.

We already mostly knew this. But a paper last year from Harvard astrophysics enfant terrible Avi Loeb briefly suggested the possibility that the rock was an alien probe. It was like a spark to dry tinder, honestly, and other scientists have been running around with buckets ever since.