Americans John C. Mather and George F. Smoot won the 2006 Nobel Prize in physics on Tuesday for work that helped cement the big-bang theory of the universe.

Mather, 60, works at the NASA Goddard Space Flight Center in Greenbelt, Md., and Smoot, 61, works at the Lawrence Berkeley National Laboratory in California.

Their work was based on measurements done with the help of the NASA-launched COBE satellite in 1989. They were able to observe the universe in its early stages about 380,000 years after it was born.

Ripples in the light they detected also helped demonstrate how galaxies came together over time.

"The very detailed observations that the laureates have carried out from the COBE satellite have played a major role in the development of modern cosmology into a precise science," the academy said in its citation.