Dark matter is one of the biggest unsolved mysteries in modern physics. Astronomers are highly confident that it exists and estimate that it accounts for about a quarter of the universe's total energy content, yet scientists still do not know what it is made of.
Two leading possibilities are hypothetical particles known as ultralight axions and dark photons. In the mass range examined by the researchers, these particles would be extraordinarily light, roughly 19 to 21 orders of magnitude lighter than an electron.
Turning Earth Into a Giant Dark Matter Detector
Many traditional axion experiments try to convert axions into photons by exposing them to extremely strong magnetic fields inside laboratories. The challenge is scale. Even powerful lab magnets can only cover a relatively small region.
Researchers from Kyoto University, Hiroshima University, and Nihon University saw a way around that limitation. Instead of relying only on laboratory equipment, they asked whether Earth's own magnetic environment could be used as part of the experiment.
