Tim Appenzeller
The early universe isn't an empty canvas anymore. Not long ago, cosmologists could tick off on the fingers of one hand their certainties about how the universe began and evolved. They knew it had started with the big bang, they knew its age within a factor of 2, and they knew that at least some dark matter had influenced its architecture and motions. Most of the rest was the domain of theory. As cosmologist Craig Hogan of the University of Washington--himself a theorist--puts it, "Theory was in such good shape 10 years ago because there were no observations."
No longer. A battery of new telescopes, led by the Hubble Space Telescope and the 10-meter Keck Telescope--which has just been joined by a twin--together with new detectors and techniques, are filling in that canvas. By looking back to the most remote times or turning a keener eye on our own neighborhood, astronomers are getting the details about the universe's origins. Theorists must now contend with real measurements of its overall mass, its complements of ordinary and dark matter, and the structures, large and small, that took shape in its early years. There's much more to come. And as the stories in this Special Report show, reality can be bewildering.
