We know dark matter does not interact normally with regular matter — otherwise we'd be able to see it — so that means most of the particles pass through us. But some might interact with a hydrogen or oxygen nucleus, changing their energies or spins. The researchers use a 70-kg human (about 155 pounds) as an example, and calculate how many particles may be careening around based on signals from the DAMA, CoGeNT and CRESST experiments. Of the billions of high-energy WIMPs passing through a body every second, fewer than 10 hit a body's nuclei in a given year. But lower energy WIMPs make impact much more frequently, around 100,000 collisions per person per year. That's about one per minute.