Dark matter: Time for detection

Abstract

Multiple lines of astrophysical evidence suggest that over one-quarter of the mass of the Universe takes the form of dark matter, with a density in our Solar System of roughly one hydrogen atom's mass per cubic metre. Most attempts to directly detect dark matter have focused on particles such as weakly interacting massive particles (WIMPs) or axions. Enormous detectors searching for dark matter have been built. They are looking for signals such as tiny flashes of light from collisions between dark matter and liquid xenon, phonons created by collisions in germanium, or microwaves generated by axions in a resonant cavity. Yet so far, dark matter has passed through the Earth undetected. An alternative explanation is that dark matter acts more like a classical, spatially dependent field. Writing in Nature Physics, Andrei Derevianko and Maxim Pospelov now suggest searching for such a field using a world-wide network of atomic clocks to register any changes in the their ticking rate as the Earth passes through dark matter.