Full South Pole Telescope ( SPT) detector at Silicon Detector Facility (SIDET).
One of the goals of the SPT is to determine the masses of the neutrinos, which were produced in great abundance soon after the big bang. Though nearly massless, because neutrinos exist in huge numbers, they contribute to the total mass of the universe and affect its expansion. By mapping out the mass density of the universe through measurements of Cosmic Microwave Background (CMB) lensing, the bending of light caused by immense objects such as large galaxies, astrophysicists are trying to determine the masses of these elusive particles.
Original public domain image from Flickr