On Christmas Eve 1968, the crew of Apollo 8, on its fourth orbit around the moon, saw the Earth rise above the lunar horizon.

Commander Frank Borman later wrote: “It was the most beautiful, heart-catching sight of my life, one that sent a torrent of nostalgia, of sheer homesickness, surging through me. It was the only thing in space that had any color to it. Everything else was either black or white, but not the Earth.” Artists, poets, philosophers and scientists were inspired by the image. The “Earthrise” photo appeared in the New Year’s issue of Time magazine, accompanied by poet James Dickey’s words: “‘Behold/The blue planet steeped in its dream/Of reality.”‘

On Christmas Day, in the New York Times, Archibald MacLeish wrote that the image of Earth would create a paradigm shift: “To see the Earth as it truly is, small and blue and beautiful in that eternal silence where it floats, is to see ourselves as riders on the Earth together, brothers on that bright loveliness in the eternal cold — brothers who know that they are truly brothers.”

The image fueled the fledgling environmental movement. The year 1970 saw the first Earth Day, and groundbreaking new laws partly inspired by the sheer fragility conveyed in the photo — and the love it generated. “The perspective expanded again, to embrace all life in the universe, and all time since the Creation,” writes Robert Poole in “Earthrise: How Man First Saw the Earth” (Yale University Press, $26). It is this expansion of consciousness that Poole calls “the unofficial space programme,” distinct from the technological race and competition with the Soviets to put men on the moon.

In this remarkable book, Poole also takes us back to Plato’s conjectures on what the whole Earth might look like; to Copernicus’ displacement of Earth from the center of the universe; to the first satellite images of Earth. He walks the reader through Buckminster Fuller’s vision of the “spaceship Earth”; James Lovelock’s Gaia hypothesis, in which the Earth is a complex system, a single organism “which has the capacity to keep our planet a fit place for life”; and the vision of Carl Sagan, who petitioned NASA to have Voyager carry a package of images and transmit photos of the Earth from the outer reaches of the solar system to give us a sense of how other intelligent beings might see our planet.

“Earthrise could be taken in two ways,” writes Poole, “either as a revolutionary new perspective of the Earth as a base for space exploration, or as an evocative portrait of home.”

While nostalgia was the dominant emotion created by Earthrise and the Blue Marble Apollo 17 photo in 1972 (“like our childhood home,” later wrote the photographer Harrison Schmitt, “we really see the earth only as we prepare to leave it”), many people, like Ray Bradbury, looked forward: “Let us forget the Earth. … you can’t stay in your mother’s womb forever … the only way the Earth can continue her life is by spitting you out, vomiting you up into the sky, beyond the atmosphere into worlds you cannot imagine.”

In “Earthrise,” Poole explores the evolution of a shift just when the enormity of the possibility of nuclear war threatened to shut down our collective imagination, just when we were most paralyzed by our ability to destroy the Earth. “One thing was obvious to all,” Poole quotes biologist Lewis Thomas: “while the moon was ‘dead as an old bone,’ the Earth was ‘the only exuberant thing in this part of the cosmos.’ “