Think Tank

09.12.2005

Top scientists pinpoint the critical developments of the last 25 years and predict wonders yet to come.

hat's surprised me most has been the extraordinary success of observers and experimenters in firming up the key numbers that characterize our universe. Theorists knew what the numbers were, but I for one didn't expect them to be pinned down so soon. We now have a consistent picture of how our universe evolved from its dense amorphous beginnings into the panorama of stars, galaxies, and clusters we see around us. Observations and computers have improved in step. Elaborate

simulations of "virtual universes" in supercomputers yield gratifying agreement with what astronomers actually observe in their surveys. As always in science, each advance brings new mysteries into sharper

SIR MARTIN REES, BRITISH ASTRONOMER ROYAL; PROFESSOR OF COSMOLOGY, UNIVERSITY OF CAMBRIDGE

focus. We have no idea why our universe is 4 percent atoms, about 25 percent dark matter, and the rest "dark energy." In the next 25 years, I'm hopeful that we'll learn what dark matter is. Dark energy is a far deeper problem, which won't be solved until we understand the bedrock quantum nature of space, on scales a trillion trillion times smaller than atoms. We'll also need advances in fundamental physics to decide another key question: Was our Big Bang the only one, or were there zillions of others, so that what we call laws of nature are just local bylaws governing a tiny patch of a physical reality far vaster than we've hitherto envisaged? But there will surely be great progress in what I'd call environmental cosmology, particularly in probing the "cosmic dawn"-the era when the first stars formed and the universe transformed from near-featureless uniformity into the intricately complex cosmic habitat in which we emerged.

he Wilkinson Microwave Anisotropy Probe has given us a snapshot of the universe in its infancy, a historic triumph of ideas and technology that will stand as one of the icons of 21st-century science. The image shows that the cosmos was nearly perfectly uniform except for tiny wrinkles in the distribution of energy. The pattern of wrinkles has given cosmologists a strong hint of how our universe was formed. Either it began in a Big Bang and underwent a brief period of extraordinarily rapid expansion, known as inflation, or space and time existed long before the Big Bang, and the pattern of wrinkles was created by events leading up to the bang. We have a chance of determining which picture is correct within the next 25 years by detecting gravitational waves (distortions of space that propagate through the universe) created just after-or just before-the Big Bang. In this way, we will come a giant step closer to answering the age-old question "Where did it all come from?"