After all was measured and accounted for, a voltage of 18 microvolts remained. This small potential disappeared when different cylinders were used, or the same cylinder was set at a different angle, suggesting it was being generated by Earth's rotation.

It's exciting and promising research, but we shouldn't get carried away at this early stage – and indeed the researchers themselves are being cautious. We're talking about a very small amount of electricity here, generated with a very specific experimental setup.

"Both papers [2016 and 2025] talk about how it might be scaled up, but none of that has been demonstrated, and it might well prove not to be possible," says Christopher Chyba.