The Interstellar Age:Inside the Forty-Year Voyager Missionby Jim BellDutton, 2015The two Voyager spacecraft that blasted off from Earth in 1977 are now billions of miles away. They've been flying through the dark all this time, angling higher and higher above the elliptic of the solar system, soaring out into the vastness of interstellar space. In tens of thousands of years, if they continue steadfastly on their way, they'll reach far stars lodged in constellations mankind has been mythologizing for 200,000 years. More than Sputnik or the Apollo missions, more than any roaring shuttle launch, more than the Spirit rover, or the Opportunity and Curiosity rovers, the Voyager craft are the most spectacular successes in the history of human exploration – indeed, in their durability and unassuming elegance and quiet pedagogy, the Voyager craft rank as two of the greatest creations of the human species.Those craft – their designers, their visionaries, their problem-solvers, their initial trials, their budgetary problems and trouble-shooting dramas – get a cheerily readable and authoritative history in Jim Bell's new book The Interstellar Age. Bell was there all along at every stage of the Voyager story, and he doesn't shy away from striking an appropriately heroic tone:

We are in the midst of a golden age of the exploration of space by people across our planet. About thirty active robotic missions are out there plying the ocean of space on our behalf, poised to make some of the most profound discoveries of all time. These missions let us vicariously see and hear and taste and touch the dirt and wind and ice of other worlds, following in the footsteps of the most grand and far-flung of them all, the Voyagers.

The Voyager craft famously bear greetings from their homeworld: gold plates that include long-playing phonograph records (LPs) suggested by Voyager scientist Frank Drake, LPs that include 27 pieces of music, 116 digitized photographs, a library of Earth-sounds, from spoken human greetings to the vocalizations of a variety of animals – and all of it, as Bell humorously points out, protected by complex technology and a little unexpected obsolescence:

The record was housed inside a circular gold-plated aluminum casing to keep it protected from radiation, which could slowly weaken and corrode the metal, and from erosion by high-speed micrometeorites, which could more quickly pit and gouge it. A stylus (needle) and its cartridge are included nearby, along with other information and instructions on the outside of the case for how to play the record. With the vinyl-music era now fading into history, it is perhaps ironic that not just intelligent aliens but most listeners of popular music today would require those instructions.

But the Voyager craft are far more famous for their visual abilities than their auditory ones; these craft have been taking pictures during the entirety of their working lives. Earlier spacecraft had been outfitted with cameras and dutifully taken pictures, but as Bell states with simple, partisan enthusiasm, “Voyager was different”:

Van Gogh-like tapestries of crazily colored, swirly clouds with vibrant tones of orange, yellow, and red on Jupiter, including the first close-ups of the Great Red Spot, began showing up on TV, on space posters, and in textbooks. The clarity of form and color and the simple elegance of Saturn's rings were revealed for the first time, including photos looking back from behind the rings, beyond Saturn, viewing the planet from a perspective impossible to achieve from Earth. And the large moons around Jupiter and Saturn were unveiled as alluring worlds – planets in their own right – one with active volcanoes (Io), another with plates of what appeared to be floating sea ice (Europa), and another with a thick, smoggy atmosphere that may be what the Earth's early atmosphere was like (Titan). It was a grand spectacle.

Bell rounds out his account with warm-drawn portraits of the key players in the Voyager story, from University of Iowa's Don Gurnett to the universally-beloved Andy Collins to the most famous figure associated with the program, Carl Sagan, the guiding muse behind all of Voyager's many poetic flourishes. As the craft sent back increasingly awe-inspiring photos of the home solar system they were leaving, it was Sagan, as Bell points out, who put it all in perspective for his classic TV show Cosmos:

As was his way, Sagan challenged and inspired us to internalize this new perspective, and to use it to guide our paths forward. “It has been said that astronomy is a humbling and character-building experience,” he wrote. “There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.”

Scientists at embattled NASA are still in touch with the impossibly remote Voyager craft, but it seems likely that by the time there's another chapter in the Voyager story to be written, there'll be no life on Earth around to write it, or at the very least that life will not be human. So Jim Bell's wonderful book is the whole of the story as it pertains to the human dreamers who sent these marvelous machines out into the void. It's a joyful and determinedly optimistic story – readers shouldn't miss it.