New York ? Two Americans won the Nobel Prize in physics Tuesday for measuring the oldest light in the heavens, a feat described as “one of the greatest discoveries of the century” that convinced skeptics of the big-bang theory of the universe’s origin.

George F. Smoot, 61, of Lawrence Berkeley National Laboratory in Berkeley, Calif., and John C. Mather, 60, of NASA’s Goddard Space Flight Center in Greenbelt, Md., will share the $1.4 million prize equally for their work.

They were the chief architects of a NASA satellite observatory named COBE, for cosmic background explorer. Launched in 1989, the spacecraft measured feeble remnants of light that originated early in the history of the universe, about 380,000 years after the big bang, nearly 14 billion years ago. Until then the universe was opaque to light, making it impossible to directly observe anything older.

Smoot and Mather’s findings revealed the ancient seeds of stars, galaxies and other celestial objects.

“It’s the farthest out we can see in the universe and it’s the furthest back in time,” said Phillip F. Schewe, a spokesman for the American Institute of Physics.

The big-bang theory predicts that this primordial light should display a classic “blackbody” spectrum, an indicator that the whole universe started out at a uniform temperature before expanding into the much less homogeneous state we now observe. That is exactly what COBE found.

“It’s just a magnificent verification of the big bang,” said Lawrence Krauss, a professor of physics at Case Western Reserve University in Cleveland.

John C. Mather, an astrophysicist at NASA's Goddard Space Flight Center, shows some of the earliest data from the Cosmic Background Explorer satellite during a news conference Tuesday at NASA headquarters in Washington, D.C. Mather and George F. Smoot on Tuesday were awarded the 2006 Nobel Prize in physics.

The measurements also revealed tiny ripples in the light’s intensity, representing “lumps” no more than 0.001 percent richer in matter than the space around them. From those humble origins arose massive galaxies and galactic superclusters hundreds of millions of light-years across.

In announcing the prize, the Royal Swedish Academy of Sciences noted that life itself depends on the existence of those tiny fluctuations, because without them matter would be spread uniformly and thinly throughout space.

“It is one of the greatest discoveries of the century. I would call it the greatest,” said Per Carlson, chairman of the Nobel physics committee. “It increases our knowledge of our place in the universe.”

“We did not know how important this was at the time when it happened. We only knew it was important,” Mather said.

They weren’t the only ones. When Mather and Smoot presented their observations at a 1992 physics meeting “there was an audible gasp in the hall,” Schewe said.

When their results were published that year, famed cosmologist Stephen Hawking called it “the greatest discovery of the century, if not of all time.”