What we see all around us, including ourselves, everything on earth, all the other planets and stars make up about 5% of our universe. Dark matter, which has as yet remained undetected, is believed to far outweigh visible matter, making up about 23%. Its existence is inferred by its gravitational effects on stars and galaxies.
The Swiss astronomer, Fritz Zwicky, first coined the term “dark matter” in the 1930s. He determined the mass and velocities of objects within the Coma galaxy cluster, and found that the velocities he calculated implied the cluster had much more mass than the observable light suggested.
It wasn’t until the 1970s, that U.S. astronomer, Vera Rubin, and her colleagues corroborated the existence of dark matter by studying the rotation of galaxies. According to her calculations, galaxies rotated too fast for the gravitational force of their visible stars to hold them together. These data pointed to the existence of vast amounts of unobservable mass, even 10 times more than visible, surrounding galaxies of stars. The work of Rubin and her team helped to firmly establish the notion of dark matter. What constitutes dark matter has remained a mystery until now, however.
The goal of the DEAP experiment is to directly observe and identify this dark matter component of the universe. This will be achieved by observing faint light pulses due to the elastic scattering of dark matter particles from argon nuclei.