This Norwegian valley has rocks on either side of the river that act like a giant battery. That may explain its ghost lights

The Hessdalen lights in Norway remain an unresolved luminous mystery first reported in 1811.

Scientific monitoring since 1984 has narrowed the field, pointing to geological and electrical processes rather than the paranormal.

Leading theories include radon-driven ionization, piezoelectric effects in quartz, and a possible natural battery formed by minerals on both sides of the river.

The case remains a classic example of a phenomenon without a definitive explanation, but one that is now much better understood.