Earth Used as Dark Matter Detector, Reveals Mysterious Signals

Scientists have transformed Earth into a giant dark matter detector. This new approach uses the planet's magnetic field and atmosphere. Researchers from Kyoto University, Hiroshima University, and Nihon University led the effort. They searched for ultralight axions and dark photons, two hypothetical dark matter particles.

Traditional dark matter experiments use strong magnetic fields in laboratories. These experiments cover small regions. The new method leverages Earth's natural electromagnetic environment. The Earth-ionosphere cavity acts as a natural resonator. This amplifies electromagnetic waves within the target mass range.

The research team developed a new theoretical framework. This framework accounts for the electrical conductivity of the atmosphere. It allowed reliable predictions up to 30 Hertz. The model predicted that axion signals would vary by location. Dark photon signals, however, should appear with consistent strength globally.

Researchers analyzed ten years of geomagnetic measurements. Data came from the British Geological Survey's Eskdalemuir Observatory. They removed artificial noise from the data. They then searched for steady signals within narrow frequency ranges. These signals are characteristic of dark matter. Statistical analysis was applied to the results.

This method set new limits on how strongly axions interact with light. These limits are one hundred times tighter than previous ground-based experiments. The dark photon search identified several signal candidates. Their origin is currently unknown. These signals have not been confirmed as evidence of dark matter.