5th force of nature: Scientists to hunt dark matter with new physics

Scientists at ETH Zurich are conducting highly precise ion trap experiments to search for a hypothetical fifth fundamental force of nature that could help explain dark matter, an elusive form of matter known only through its gravitational effects. Unlike the four established forces—gravity, electromagnetism, and the strong and weak nuclear forces—this proposed fifth force is theorized to act between neutrons in an atomic nucleus and orbiting electrons, mediated by a new, unknown particle. The team uses precision atomic spectroscopy on different calcium isotopes, which have the same number of protons but varying neutrons, to detect tiny shifts in energy levels that would indicate the presence of this force. The experiment involves trapping single charged calcium isotopes with electromagnetic fields and measuring the frequency of light emitted during energy transitions with unprecedented accuracy—100 times more precise than previous attempts. Complementary studies in Germany involving highly charged calcium ions and nuclear mass ratio measurements support the findings. While the observed deviations in energy shifts cannot be fully explained by known nuclear effects, alternative