Launched in 1989, the COBE satellite was designed to measure minute variations in the cosmic microwave background (CMB) in different parts of the sky. The COBE team, led by George Smoot at the University of California at Berkeley and Chuck Bennett at NASA's Goddard Space Flight Center, was the first to detect these variations in 1992.

Subsequent experiments like BOOMERANG, MAXIMA and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), which owe much to COBE, have since given cosmologists a new view of this temperature anisotropy. These measurements showed that the temperature variations were the "seeds" of the intricate large-scale structures, like stars and galaxies, which exist everywhere in the present-day universe.

The CMB was originally created when the universe was about 380,000 years old. Before this time, space was filled with a hot plasma of electrons and light nuclei, which meant that light could not travel very far without being scattered. But as the universe expanded, the plasma cooled enough to allow neutral atoms to form.

This "decoupling" of matter and radiation suddenly enabled photons to travel across space unimpeded, their wavelengths being stretched over time to produce a faint glow of radiation in the microwave region that we can detect today. The fact that the CMB has a perfect black-body spectrum with a temperature of around 2.73 Kelvin is one of the key pieces of evidence for the Big Bang

The Gruber prize is worth $250,000, half of which is awarded to project scientist John Mather, who was COBE's project scientist, with the rest being divided between the other 18 team members. The Peter Gruber Foundation, which was founded in 1993, supports five international awards, in cosmology, justice, genetics, neuroscience, and women's rights.