Scientists pull electricity directly from Earth’s rotation

Physicists in the United States have built a small device that seems to pull electrical energy from Earth’s rotation itself. The tabletop experiment produced only tens of microvolts.

The team carried out the work in New Jersey with colleagues from NASA’s Jet Propulsion Laboratory. Their results hint that Earth’s spin and magnetic field could someday act as a constant, fuel-free energy source, if the effect scales up.

Electricity and Earth’s magnetic field

The work was led by Christopher F. Chyba, the Dwight D. Eisenhower Professor of International Affairs and astrophysical sciences at Princeton University.

His research explores how electromagnetic theory, the rules describing electric and magnetic forces, connects to energy and planetary environments.

The earth is wrapped in a geomagnetic field, the magnetic bubble around Earth created by moving metal in its outer core.

As the planet spins, that field stays mostly fixed in space, so any conductor attached to Earth moves through it all the time.

For decades, standard arguments in physics said that any voltage created this way would instantly disappear as electrons shifted to cancel the effect.

The researchers pointed out a loophole, showing that a specially shaped conductor might avoid that cancellation.

Their idea focused on a magnetically responsive shell that bends field lines while remaining a poor electrical conductor.

Such a structure could, on paper, keep Earth’s magnetic push from being completely balanced by the usual static charges.

Testing the theory

In the lab, that abstract shell became a hollow cylinder of about 1 foot long. The team made it from manganese zinc ferrite, a ceramic material that guides magnetic fields but barely conducts electricity.

They aimed the cylinder roughly north to south and tilted it so the long axis sat at about 57 degrees. In that orientation, it stayed perpendicular to both Earth’s rotation at Princeton’s latitude and the surrounding magnetic field.

Electrodes at each end let the researchers measure a constant voltage between the two faces of the cylinder as Earth turned. 

In their runs, the system generated tens of microvolts and its voltage reversed when they rotated the setup, matching the prediction.

A solid cylinder made of the same ferrite, with no hollow shell, produced no measurable voltage at any orientation.

Another shell designed so that magnetic diffusion, the slow spreading of magnetic fields in a conductor, did not matter also stayed quiet.

Physics and Earth’s magnetic field

At the heart of all of this is the Lorentz force, the rule that charges feel in electric and magnetic fields. When a conductor moves through a magnetic field, this force pushes electrons sideways and can, in principle, create a voltage around the circuit.

Normally, the electrons slide only a tiny distance before their own electric field cancels the magnetic push, so the current quickly dies away.

This cancellation happens in a short time, less than a billionth of a second, so Earth’s rotation seems useless as a power source.

The trick in this new device is to choose a shape and material where that perfect cancellation cannot happen everywhere inside the conductor.

That requirement shows up in a low magnetic Reynolds number, a measure of how easily magnetic fields slip through a moving conductor.

In this view, Earth’s magnetic field helps transfer a minute amount of rotational energy into the ferrite cylinder.

The planet very slightly slows while the device gains an equally tiny amount of electrical energy, keeping the total energy and angular momentum balanced.

Measuring the voltage

Because the voltages were so small, the group ran its main experiments in a dark underground room with very low electrical noise.

They later repeated the measurements in a residential building about 3.5 miles away, where interference made the data noisier but showed the same behavior.

One subtle background effect was the Seebeck effect, in which a temperature difference along a material creates its own voltage.

To handle this, the researchers constantly monitored temperatures at both ends of the cylinder and subtracted the expected Seebeck signal from their measurements.

When the cylinder pointed in its first orientation, the device produced a steady voltage close to the value predicted by the theory.

Turned 180 degrees, the voltage kept the same magnitude but flipped sign, while at 90 and 270 degrees it dropped to nearly zero.

By switching their meter into current mode, they also saw a steady direct current of only tens of nanoamps.

Even so, that product of voltage and current is many millions of times smaller than the power used by everyday electronics.

Possibilities for the future

Despite the excitement around the idea, the researchers stress that the work is still a very early step.

There are also formal critiques that argue the basic scheme cannot work, and the debate now continues in the technical literature.

If the effect holds up and can be scaled, future devices might power sensors or scientific instruments without any refueling needed.

The team even suggests that many small cylinders could be wired together, so that the voltages add up to something more useful.

For now, the most important next step is clear, an independent group must build a similar device and test the idea.

“The first thing that needs to happen is that some independent group needs to reproduce, or rebut, our results,” said Chyba.

The study is published in Physical Review Research.

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