4850 Feet Below: The Hunt for Dark Matter

Merging Galaxy Cluster Abell 520. Photo credit: NASA.
Merging Galaxy Cluster Abell 520. Photo credit: NASA.

In rural South Dakota, physicists descend an abandoned mineshaft—the deepest in the U.S.—to almost a mile underground in search of the most elusive of particles: dark matter. The rest of this story unfolds in a new online video, “4850 Feet Below: The Hunt for Dark Matter,” part of the Science Friday Big Questions Digital Video Series supported by the John Templeton Foundation. Science Friday began as a radio show in 1991 by host and executive producer Ira Flatow, and is one of the nation’s most popular science broadcasts, carried on nearly 400 stations with 1.5 million weekly listeners. “4850 Feet Below” outlines the extraordinary quest to try to solve one of the biggest mysteries in astrophysics.

The hunt for dark matter takes place 4,850 feet below ground to reduce background noise. On the surface of the Earth, cosmic rays pass through the volume occupied by the human body every second. At the bottom of the mine, that equals about one cosmic ray every three months. That’s the level of silence required to detect the most likely candidate for dark matter: weakly interacting massive particles, or WIMPs.

The instrument being used to hopefully prove the hypothesis is called LUX, the Large Underground Xenon Experiment. Essentially, it is a large tank filled with the element xenon that will light up when struck by dark matter. In order to detect such events, the xenon is monitored very closely—an undeniably difficult task given the circumstances.

Although not yet directly detected, research suggests that the existence of dark matter is inferred due to gravitational effects on visible matter, radiation, and the structure of the universe. Gathering the signals to prove that dark matter exists, and that it is comprised of WIMPs, would be a milestone and a historic moment in the story of physics. For now, the search for dark matter continues, 4,850 feet below the surface of the Earth.

Watch the video here.