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Foreword by Walter Cronkite  
Introduction - The National Science Foundation at 50: Where Discoveries Begin, by Rita Colwell  
Internet: Changing the Way we Communicate  
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Astronomy: Exploring the Expanding Universe
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Astronomy: Exploring the Expanding Universe

Shedding Light
on Cosmic Voids

Even with more than 90 percent of its mass dark, the universe has revealed enough secrets to permit initial efforts at mapping its large-scale structure. Improved technologies have enabled astronomers to detect red shifts and infer velocities and distances for many thousands of galaxies. New research projects will plumb the secrets of nearly one million more. And yet, we have much more to learn from the hundreds of billions of galaxies still unexplored.

Gemini 8-meter Telescope - click for detailsHelping in the exploration is an ingenious method commonly used to estimate distances to and map the locations of remote galaxies, a method developed with help from NSF. R. Brent Tully of the University of Hawaii and his colleague at the NSF-funded National Radio Astronomy Observatory, J. Richard Fisher, discovered that the brighter a galaxy—that is, the larger or more massive it is, after correcting for distance—the faster it rotates. Using this relationship, scientists can measure the rotation speed of a galaxy. Once that is known, they know how bright the galaxy should be. Comparing this with its apparent brightness allows scientists to estimate the galaxy's distance. The Tully-Fisher method, when properly calibrated using Cepheid variable stars, is proving to be an essential tool for mapping the universe.

An Image of the Universe - click for detailsIn early 2000, researchers announced the discovery of a previously unknown quasar that qualified as the oldest ever found-indeed, as among the earliest structures to form in the universe. Quasars are extremely luminous bodies that emit up to ten thousand times the energy of the Milky Way. Eventually our maps will include everything we know about the universe-its newly revealed planets, the inner workings of the stars, distant nebula, and mysterious black holes. With our map in hand and our new understanding of how the universe began and continues to grow, we humans will have a better chance to understand our place in the vast cosmos.

PDF Version
Voyage to the Center of the Sun
New Tools, New Discoveries
At the Center of the Milky Way
The Origins of the Universe
The Hunt for Dark Matter
Shedding Light on Cosmic Voids
Visualizing the Big Picture
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