[In the following review, Morrison offers praise for Pale Blue Dot, concluding that "no recent book has done better at making plain the subtle nature and fascination of scientific investigation."]

This book opens with a generous gift to us all. It was made early in 1990, when the space probe Voyager completed its scripted dozen-year tour of duty. Well beyond Neptune and far north of the plane of the solar system, the craft received a final set of new commands, no part of the original mission. Look back, Voyager, to the now distant inner planets! Carl Sagan and a few others had argued and waited years for the Jet Propulsion Laboratory and NASA to schedule a shoestring effort to snap just one candid portrait of the earth among the planets. They succeeded brilliantly.

The spacecraft recorded a mosaic of 60 frames, planets against the sky. It sent the bits to far-off earth; that slow video transmission from past its design range took three months. The four planets in clear view would at best be mere dots of light. (The glare of the sun only six light-hours away from the camera masked nearby Mercury. Pluto and Mars happened to be poorly placed. Uranus and Neptune were so faint that they required long exposure; they could not help themselves from moving, so their images are streaked.) Our earth entire is seen as one bright bluish dot in the image that faces the title page.

The cloud-and-sea-marked blue marble we know well from closer space views dwindled to a featureless dot once the telescopic camera was carried a few thousand times farther away. The earth was for the first time put into the same perspective as the other planets in the sky. In 1957 a metal ball from a human workshop had been set into the heavens; mere speed transformed it into something celestial, "shining, circular, and perpetual" in orbit. Aristotle was denied and Newton confirmed. One after another the planets became close-up scenes, real places, a red Mars landscape looking not unlike the Arizona desert. Here they are at last as wandering stars: the earth, too.

Anyone can now see at once that Copernicus was right. The earth is only one planet among planets; blue, yes, but then icy Neptune is blue as well. Sagan eloquently draws an inference about this our home. "On it everyone you love … every human being who ever was, lived out their lives … Every hunter and forager, every hero and coward, every creator and destroyer of civilization…. Every saint and sinner in the history of our species lived there—on a mote of dust suspended in a sunbeam."

Around us stretches a vast cosmic darkness, studded with countless pools of myriads of suns. Only the abstract laws of physics seem to bring any order; no Designer is visible, no Parent seen to care for us. Yet the universe of science is no petty place; it is dauntingly large, old, diverse, even humbling. A religion to match our awesome data, Sagan thinks, may someday emerge. We are not center stage. "We have not been given the lead in the cosmic drama. Perhaps someone else has. Perhaps no one else has … a good reason for humility." The self-serving conclusion is what the author mistrusts above all.

After this high thinking, Sagan catches his readers up in a dozen exciting, personal, even audacious reviews of what we have found and may yet seek in space. Colorful and fresh space images are plentiful in these pages, along with paintings, diagrams, maps and some graphs, but no equations at all. Many of these treat issues Sagan has been close to. Here he is more than an author; he is an original researcher, articulate and engaged.

A sample of three out of many rich topics will have to suffice. One is a witty little essay. The French use a mild expletive, sacre-bleu. Translate it: Good heavens! Like our "geez," it is a euphemism for invoking Deity. The earth's distant signature is that sacred blue. Yet just outside the air, astronauts see a black sky with stars, even in sunlight. All airless moons and asteroids share black skies.

Molecular light scattering from the density fluctuations of any molecule is preferentially blue; what scatters is removed from the direct path, so that the long low light of any sunset is rendered in red hues. Venus has an atmosphere so thick that down at ground level it is always sunset, as the sky color reported by the Venera landers confirms. The meager sky above the rusty deserts of Mars looks pale salmon, colored by the long-lasting residues of finest dust, stirred up into the high air by windstorms. The two giant planets are certainly dark at the prodigious depths of their atmospheres. All we see there from without is the cloud layers that lie highest. The unearthly blue skies of Neptune and Uranus are puzzling; easy answers do not appear quite to work. Does some unknown blue stuff lie there inside? Sacre-jeune, sacre-rouge, sacre-noir! For this reader, awe of plenitude arises from this game of words.

Are we alone in the Milky Way? The most ambitious of searches for radio signals from putative distant sharers of our own scientific curiosity has been pressed for seven years by Paul Horowitz of Harvard University; it was financed by private gift, largely from Steven Spielberg of E.T. The modest radio dish in use is surplus, but the student-built multichannel receiver is world class, automatically monitoring eight million simultaneous narrow-frequency channels.

Signals that rise far above the noise are the candidates for our attention and are tested for origin from interference or for electronic fault. A few are culled from 60 trillion observations over the entire sky. Not one of the finds repeats. One fact, says Sagan, co-author of the analysis, "sends a chill down my spine." Of the 11 best candidates, eight lie within or close to the band of the Milky Way, where most stars collect. A fair bet against that happening by chance should pay off at better than 100 to 1. Probably these are rare, nonrepeating chip errors; without repeats or other structure we remain ignorant and very properly withhold belief. We will keep on listening, now without federal support. "Science offers little in the way of cheap thrills. The standards of evidence are strict. But … they allow us to see far, illuminating even a great darkness."

This book glowingly communicates current wonders and large issues still ahead, like future "interplanetary violence" against the earth by collisions both random and intentional. It displays openly the hopes and judgments of one gifted, adept and devoted human being, surely sometimes right and sometimes wrong. No recent book has done better at making plain the subtle nature and the fascination of scientific investigation.