The 100th Nobel Prize in Physics was awarded to John Mather and George Smoot for recording faint echoes of the birth of the universe. Their precise satellite measurements of the cosmic background radiation, remnants of the sea of light emitted by the new universe, have confirmed fundamental predictions arising from the Big Bang theory, leading to its further acceptance as the standard model of cosmology.
The possibility that the universe began in an explosive burst was first seriously suggested in the 1920s, an idea sarcastically dubbed the 'Big Bang' theory by Fred Hoyle, a critic of the theory, in 1949. About the same time it came to be realized that if the dawn of the universe was indeed explosive, then a faint afterglow of this explosion might still remain, and be detectable. In 1964, Arno Penzias and Robert Wilson realized that microwave background radiation flooding into their radio receivers was indeed such a signature of the Big Bang. Owing to the interference caused by earth's atmosphere, however, it was impossible to see this radiation unimpeded.
In 1989, fifteen years after it was first proposed, NASA's COBE satellite was launched under John Mather's leadership to study cosmic microwave background radiation from orbit. Within minutes of starting its recordings, it confirmed that this diffuse radiation displayed precisely the expected frequency - wavelength relationships - the perfect 'blackbody' spectrum predicted to result from first light in the universe. In subsequent measurements, detectors on the COBE satellite under the direction of George Smoot were able to measure minute variations, or 'anisotropies', in the background radiation that are the faint whispers left behind by developing clusters in the expanding universe. Such traces of the earliest clumps of matter, which later went on to form large-scale objects such as galaxies and galactic clusters, were another key prediction of Big Bang theory.
There may yet be further cosmological evidence locked up in the cosmic microwave background radiation, and it is still the object of intense investigation - for instance, by NASA's current Wilkinson microwave anisotropy probe (WMAP) satellite and the European Space Agency's upcoming Planck mission, scheduled for launch next year.