Sanity Check; June 1994; Scientific American Magazine; by Powell; 2 Page(s)

The farther astronomers peer into space, the more they come to appreciate the intricate structure of the universe at very large scales. In 1987 a group of observers inferred the presence of a vast accumulation of matter, nicknamed the "Great Attractor." Two years later another team discovered the "Great Wall," an aggregation of galaxies at least 500 million light-years across. New celestial surveys that take in larger chunks of the universe hint at still vaster gatherings of galaxies. Theorists find themselves hard-pressed to understand the origin of such enormous structures in a cosmos that, according to present knowledge, started out almost perfectly uniform. "The new surveys are very impressive," says Margaret J. Geller of the Harvard-Smithsonian Center for Astrophysics, "but the state of our ignorance is equally impressive."

Geller should know. Over the past decade, she and a number of colleagues--most notably John P. Huchra, also at the Center for Astrophysics--have produced information that has challenged the most ingenious theorizing. What the researchers do is measure the redshift (the stretching of light caused by the expansion of the universe) of thousands of galaxies. The redshift in turn indicates the galaxies' approximate distances from the earth.