[In the following excerpt, Abramson gives a favorable assessment of Pale Blue Dot.]

Carl Sagan became a consultant to the National Aeronautics and Space Administration when it was still in its formative stage. During the more than three decades since, he has briefed astronauts for journeys to the moon, helped resolve some of the most intriguing mysteries about Mars and Venus and reigned as one of the principal gurus of planetary exploration.

Though honored for both public service and scientific achievement, Mr. Sagan is more renowned as a popularizer of space exploration. In 1978 he was awarded a Pulitzer Prize for his book The Dragons of Eden. In Pale Blue Dot he returns to familiar topics: the origin of the universe, the birth of the solar system, the development of life on Earth, the evolution and demise of stars and the prospect of life elsewhere among the galaxies. But this time he struggles to define a future for the human species after Earth, our "pale blue dot," and the rest of the solar system have met destruction in the dying throes of the sun.

Mr. Sagan's book offers lavish illustrations—telescopic images, pictures from robot space vehicles and paintings executed so perfectly as to be mistakable for the stunning photographs. With them, he marshals revelations by numerous planetary probes, especially two Voyager spacecraft now plunging through the Milky Way. Launched in 1977, the Voyager robots brushed past Jupiter and Saturn, and Voyager 2 went on to the neighborhood of Uranus and Neptune before heading out of the solar system. Together, they have sent back the equivalent of a 100,000-volume encyclopedia, Mr. Sagan says, including photographs of the two distant planets that previously had been nothing more than fuzzy dots taunting astronomers.

Unfortunately, the awe-inspiring work of the repaired Hubble Space Telescope is not included in Pale Blue Dot. More than Voyager, Mariner, Galileo or any of the planetary explorers, Hubble's recent discoveries have advanced what Mr. Sagan persuasively presents as the fundamental achievement of space science and exploration: humanity's changing perception of the universe and, consequently, of itself. The perception is still changing slowly, despite three decades of planetary probes and the tentative beginnings of human flight into space. But, after looking back to the humbling discovery that Earth is not the center of the universe and tracing the revelation of the cosmos as we know it today, Mr. Sagan soars to an inspirational, and evidently serious, conclusion that "a central element of the human future lies far beyond the Earth" and even beyond the solar system and our corner of the Milky Way.

People alive today may someday walk on Mars and on the asteroids near Earth. Extrapolating recent advances in technology, Mr. Sagan concludes that within a few centuries space vehicles may be able to travel near the speed of light. And, hundreds of generations into the future, he believes, their passengers will have evolved into a species significantly different from 20th-century earthlings.

"But unless we destroy ourselves first," he predicts, "we will be inventing new technologies as strange to us as Voyager might be to our hunter-gatherer ancestors…. In time, the designs will become more elegant, more affordable, more efficient. The day will come when we overcome the necessity of jumping from comet to comet. We will begin to soar through the light-years and, as St. Augustine said of the gods of the ancient Greeks and Romans, colonize the sky."

Mr. Sagan confesses that he argued with himself on the way to his remarkably optimistic prediction that humanity will one day travel beyond the solar system, colonize other worlds and perhaps even make contact with civilizations from other planetary systems. And well he might. Human space flight has enjoyed an uncertain beginning.

Although the Apollo moon landing project generated the enthusiasm and Federal appropriations that made robot missions to the planets possible, the project was the result of cold war competition, not a love of science or exploration. The space shuttle program has never been altogether certain of its objectives, nor has the much-debated and redesigned international space station.

When the Bush Administration offered a human mission to Mars as the next great American space objective, the idea was greeted with little enthusiasm from Capitol Hill or the public. Such an expedition, Mr. Sagan concludes, "is now probably too expensive for any one nation to pull off by itself," even if that were an appropriate national undertaking.

Not only is human flight expensive, but space accidents in the United States and the former Soviet Union have proved the enterprise to be dangerous by its very nature. And in the United States, there has been little political tolerance for accidents….

Mr. Sagan nominates the scientists and engineers who designed, built and operated the Voyager spacecraft as "role models for an America seeking excellence and international competitiveness," recommending that they be honored on postage stamps. Many of those involved in the Apollo program would echo that recommendation for Mr. Lovell's crew and the Mission Control team that got them back. Nearly 25 years later, the aborted moon landing mission is still widely remembered as NASA's finest moment.