Astronomers have discovered formations in space that may be left over from the "Big Bang" birth of the universe. And one of these may undercut an important tenet of cosmic theory -- namely that, on the large scale, the universe has a uniform structure.
Last December, George Smoot of the University of California and his colleagues on a joint project with the NASA Ames Research Center reported finding a supercluster of 30 to 40 galaxies spread over some 2 billion light years. That's an appreciable fraction of the 10 billion- light-year diameter of the observable universe -- a fraction that encompasses something like 1 percent of the universe's volume.
Smoot says there wouldn't have been enough time for such a supercluster to form since the "Big Bang" some 10 to 20 billion years ago. So he thinks the vast concentration of mass could have formed in the birth process itself.
Smoot and his colleagues infer the existence of the supercluster from data gathered by a NASA U-2 research plane -- data showing the movement of the solar system in relation to a sea of infrared radiation that permeates the universe and is itself left over from the "Big Bang." These data indicate that our own Milky Way galaxy is being pulled in the direction marked by the constellation Virgo at about 450 kilometers a second (a million miles an hour) by the gravitational pull of what the scientists take to be the supercluster. This supports earlier finding by others using X-ray and photographic data that suggest there is indeed a large-scale structure in that part of the sky.
Most cosmological theories assume the "Big Bang" was a more or less uniform event that has produced a uniform universe -- a theory that fits well with several kinds of data in astronomy and physics. Now that uniformity is challenged. "It is a paradox that the universe is so uniform, but yet appears to contain nonuniform structures on very close to the largest possible scale," Smoot observes.
More recently, Wallace L. W. Sargent and Peter J. Young of the California Institute of Technology and Alec Boksenberg and David Tytler of University College London have reported that diffuse clouds of hydrogen drifting between galaxies probably date from the cosmic birth itself. They have analyzed these hydrogen clouds by the way they absorb light from quasars (compact, extremely bright objects located at great cosmic distances). Well distributed throughout the universe, the clouds show the intergalactic medium to be cooler (about 300, 000 degrees C.) and more tenuous than had been thought.
As with Smoot's supercluster, the primordial clouds offer an opportunity for what the astronomers call "unprecedented insights" into the nature both of the present universe and of the fireball from which it emerged. Such discoveries are also a reminder of how little scientists do know of a universe that continues to challenge their assumptions.