
Physicists like me don’t fully understand what makes up about 83% of the matter of the universe — something we call “dark matter.” But with a tank full of xenon buried nearly a mile under South Dakota, we might one day be able to measure what dark matter really is.
In the typical model, dark matter accounts for most of the gravitational attraction in the universe, providing the glue that allows structures like galaxies, including our own Milky Way, to form. As the solar system orbits around the center of the Milky Way, Earth moves through a dark matter halo, which makes up most of the matter in our galaxy.