Galaxies in the Young Universe; May 1997; Scientific American Magazine; by Macchetto, Dickinson; 8 Page(s)

Our conception of the universe has changed radically during this past century, as the powers of astronomical observation have steadily improved. Edwin Hubble¿s pioneering work in the 1920s led to the idea that a "big bang" gave birth to a universe that has been expanding ever since. Later studies revealed that the universe changed in other ways over time as well. Initially it was filled with exceedingly hot, dense, nearly uniform material. Now it is relatively empty. As astronomers look across millions of light-years, the matter they see is collected into a sparse handful of seemingly isolated galaxies. How this transformation occurred, and why the galaxies formed as they did, remains a central question in cosmology today.

Considerable effort has gone into examining galaxies nearby--those that are the product of some 10 billion years of evolution. In recent years, however, astronomers have made enormous progress in studying galaxies at cosmological distances-- namely, ones that existed when the universe was young. Thanks to the travel time imposed by the finite speed of light, scientists can peer directly into the past by looking out to greater distances. At this time, the light cosmologists can see left the most distant galaxies when the universe was less than one fifth its present age. With new instruments and techniques, the hope is to view distant "primeval" galaxies in the process of forming and to trace their evolution to the present day.