R. Stainforth

Deep in a Canadian mine, there's a barrel holding 3269 kilograms of liquid argon — a clear fluid that looks like very cold water. This barrel is the DEAP-3600 detector, and its job is to catch dark matter particles, which are thought to permeate the universe but barely interact with ordinary matter.

A pool of the purest water, into which tiny, almost invisible droplets occasionally fall. Each leaves a barely perceptible ripple, and capturing it requires years of patience. That is what the hunt for solar neutrinos looks like in the DEAP-3600 detector — a huge vat of liquid argon hidden deep underground.