Is Cosmology Solved?
Cowen, Ron, Science News
Scientists don't often make great debaters. Rather than dealing with absolutes in black and white, they tend to invoke qualifiers and caveats in shades of gray. But cosmologist Michael S. Turner, whose hand-drawn viewgraphs are so colorful that they have adorned the walls of an art gallery, isn't the typical scientist, and 1998 hasn't been the typical year for the study of the universe.
In an October forum--billed as "The Nature of the Universe Debate: Cosmology Solved?"--Turner, who is at the University of Chicago and the Fermi National Accelerator Laboratory in Batavia, Ill., put forth an assertion as bold as his drawings: For the first time in history, cosmologists have developed a consistent framework that integrates the origin, evolution, and current appearance of the universe.
Turner's opponent in the debate, Jim Peebles of Princeton University, took a more conservative view of recent progress in deciphering the cosmos. He prescribed caution in concluding that the key pieces of the cosmic puzzle have all been revealed.
The past year could mark a turning point for cosmology, Turner told a packed auditorium at the Smithsonian Institution's National Museum of Natural History in Washington, D.C.
Clearly, 1998 began with a jolt: Two rival teams studying the titanic explosion of distant, elderly stars overturned the prevailing belief that the cosmos has been slowing down its rate of expansion ever since the Big Bang. In fact, they reported, the universe is actually flying apart faster than ever
before (SN: 3/21/98, p. 185; 10/31/98, p. 277).
Although entirely unexpected, that recent finding and others appear to unify elements of a cosmic portrait that have emerged over the past decade, Turner says. Stitching together such disparate concepts as energy associated with empty space, invisible matter in the universe, and the curvature of the cosmos, the new reports may turn out to mark a watershed for cosmology. Their impact could be every bit as important as the discovery more than 3 decades ago of the whisper of radiation left over from the Big Bang.
In 1964, two physicists at Bell Laboratories in Holmdel, N.J., stumbled upon key evidence for the Big Bang. Scanning the sky with a radio receiver, they discovered a faint, uniform crackling. The pervasive nature of the signal and its intensity over a range of frequencies indicated that the radiation could not have come from the universe today. Instead, Arno Penzias and Robert Wilson concluded, it represents the radiation produced by the cosmos when it was young and extremely hot.
This radiation, known as the cosmic microwave background, is one of the cornerstones of the Big Bang theory. Along with measurements of the abundance of light elements forged just after the birth of the universe, the microwave background provides evidence that the universe began with the explosive expansion of a dense, hot soup of subatomic particles and radiation.
A fog of electrons pervaded the infant universe. For thousands of years after the Big Bang, radiation did not stream freely into space but was repeatedly absorbed and scattered by these charged particles.
About 300,000 years after the Big Bang, the universe became cool enough for the electrons to combine with nuclei. This lifted the fog, enabling radiation to travel unimpeded. Shifted to longer wavelengths by the expansion of the universe, this relic radiation is today detected as microwaves and far-infrared light. It provides a snapshot of the universe when it was 300,000 years old.
The Big Bang model has been phenomenally successful in explaining the events that took place beginning one-hundredth of a second after the birth of the universe. But by 1980, scientists trying to elucidate even earlier cosmic events were pushing the limits of the theory. The Big Bang model offers no explanation for the explosion itself, notes Turner. The dynamite that produced the Big Bang remains elusive. …