1968 was a crazy year, its events moving at a horrific pace. The Tet Offensive. The My Lai Massacre. Bobby Kennedy announcing the news that the Rev. Martin Luther King Jr. had been assassinated. Bobby Kennedy’s assassination. Riots across urban America and outside the Democratic National Convention. The human drama seemed out of control in a way it hasn’t in the years since ― till now, of course.

Which is why it’s both heartening and sad to think of the event that brought 1968 to a close and opened a new set of possibilities. Apollo 8 was orbiting the moon, its astronauts busy photographing landing zones for future missions. On the fourth orbit, Commander Frank Borman needed a navigational fix and decided to roll the craft away from the moon, tilting its windows toward the horizon. The shift gave him a sudden view of the Earth rising.

“Oh, my God,” he said. “Here’s the Earth coming up.”

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Crew member Bill Anders turned the camera away from its lunar chores and pointed it homeward, snapping what may be the most iconic image ever taken. Borman said later that 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 simply black or white. But not the Earth.”

Back on Earth, the seeds of the modern environmental movement had already been planted. Rachel Carson had written Silent Spring earlier in the decade, beginning the process of wiping some of the shine off modernity. David Brower had led the Sierra Club through the great fight to save the Grand Canyon, turning it in the process into the first great green group. And soon there would be a major oil spill off the coast of Santa Barbara, and the Cuyahoga River would burst into flames. People were beginning to realize that there were limits to the abuse nature could take at the hands of growth.

But suddenly those limits were visible. Everything we had was there before us: a blue-and-white shimmering egg hanging in the monochrome void. You could see it aswirl with the motion of clouds, gloriously alive in the midst of the endless vacuum.

When we think of the Apollo missions, we often herald NASA’s accomplishments as technical. We put a man in orbit, and then we landed more on the moon. And yet one of the most important achievements of the decades of space exploration was artistic — this one photograph taken 50 years ago this month that showed us nothing about the rest of the galaxy and everything about our home.

It explained, I think, the tenor of the first Earth Day, which followed about 15 months later. Organized as a “national environmental teach-in” by Democratic Sen. Gaylord Nelson and Republican Rep. Pete McCloskey, the day used an image of Earth from space as its unofficial flag. The event drew 20 million Americans into the streets ― a tenth of the population at the time, probably the largest day of political action in American history.

Though it emerged from the fraught and divisive politics of the late 1960s, there was a sweetness to Earth Day. The event had a sense of unity because ― and this was the point made so clear in the Earthrise image ― we were clearly all in it together.

“Earth Day is the first holy day which transcends all national borders, yet preserves all geographical integrities, spans mountains and oceans and time belts, and yet brings people all over the world into one resonating accord, is devoted to the preservation of the harmony in nature and yet draws upon the triumphs of technology, the measurement of time, and instantaneous communication through space,” wrote Margaret Mead.

The effect of that unity was startling. Within the next few years, the Environmental Protection Agency was created and the Clean Water and Endangered Species acts were signed into law by President Richard Nixon, a man who lacked a scintilla of environmental awareness or interest but who responded to the movement overtaking Washington at the time.

That burst of legislation, emulated around the planet, was a remarkable recognition that we needed to control ourselves if we were to preserve that lonely, lovely sphere floating in the darkness.

“Limits to Growth,” a 1972 treatise based on simple computer models that flagged our fast-approaching planetary boundaries, was an attempt at a troubleshooting guide for what we’d begun to call “Spaceship Earth.” The Whole Earth Catalog, with a picture of the Earth from space on its cover, was the hippie-ish operating manual. For a while, it looked as if it all might take: By 1978, a decade after Apollo 8 returned to terra firma, pollsters reported that 30 percent of Americans were “pro-growth,” 31 percent were “anti-growth,” and 39 percent were “highly uncertain.” We almost built a new world.

But then we didn’t. The election of Ronald Reagan signaled that we’d taken the other fork, the one that would keep the old epoch rolling. There would be no more talk of limits: Instead, we’d push forward with the project of human expansion. We decided to care less about the earth as a whole and more about ourselves as individuals.

If you want a counter to Borman and Mead’s optimistic vision, consider this crabbed sentiment from Margaret Thatcher: “There is no such thing as society. There are only individual men and women and their families.” Pay no attention to the whole; think only of the parts.

In doubling down on our commitment to growth at all costs over the past five decades, we’ve managed to change that image of Earth rising in space in the most profound ways.

Fifty years is barely a blip in the vastness of astronomical time, but Earth now looks quite different when seen from space. In the Northern Hemisphere, the summer sea ice that once covered the Arctic is now half gone. Some of the islands of the Pacific have begun to disappear below rising seas. The great forests that covered South America and Africa are shrunken and ragged.

If you put different filters on the camera, you could see other major changes. The atmosphere, for instance, now holds considerably more water vapor, which is what happens when you warm it up. And the oceans, still so heartbreakingly blue, now have a different chemistry, growing more acidic at a speed the planet has never witnessed in all its geological past.

The Great Barrier Reef, easily visible from above and the largest living structure on Earth, is now half dead, its corals killed off by the ever-rising temperature. Siberia is on fire, five degrees of latitude north of where it ever used to burn. And as I write this, California is fighting the biggest fire in its history, the smoke all but blotting out the region in aerial shots. There are dead zones at the mouths of our great rivers, extending ever farther out to sea as the tide of fertilizer washes off the field, and at one point this summer, you could see five hurricanes at once, swirling off the coasts.

The Lake Powell reservoir on the Colorado River shrinks during an 18-year drought. Images 1985-2018. (Courtesy of NASA, produced by Earthrise Media.)

This view will, of course, get darker as the decades unwind. It’s not hard to imagine that the view from space will soon show Florida truncated, Bangladesh inundated. The deserts will spread outward even farther than they already have, and the great ice sheets of the Antarctic, the largest physical feature on Earth, are in train to slide slowly ― and that’s if we’re lucky ― into the Southern Ocean.

We now increasingly think of space as an escape. Here’s Elon Musk: “Either we spread Earth to other planets, or we risk going extinct. An extinction event is inevitable and we’re increasingly doing ourselves in.”

Musk and a host of other plutocrats, including Jeff Bezos, Richard Branson and the late Paul Allen, have put their endless wealth where their fears are, underwriting our new round of space travel. But theirs is the emptiest of promises: no more than a tiny percentage of the population will ever make it off Earth (and given the latest research on the dangers to the human body of even the “short” flight to Mars, that may be optimistic).

If they do reach some other planet, it will be a barren place compared to our home. Find the most forbidding spot on Earth ― the top of the Himalayas, the center of the Sahara, the bottom of the Marianas Trench ― and it is a thousand times more hospitable than anyplace else in this solar system. We dig robotically through the sands of Mars in hopes we might find some faint sign of microbial life, even as we ― in the 50 years since Apollo 8 ― wipe out 60 percent of the animals on Earth.

Through the perverse glasses we’re now wearing, the black-and-white void of space has come to seem a more likely oasis than the gorgeous planet on which we were born.

Our salvation may lie in actually seeing that image again, and in realizing once again that we live on the one place we’ll ever live.

It’s actually hard to remember that Earth is a planet. We live in a house in a neighborhood in a city in a country, and all of these seem more real and daily to us than the big ball we inhabit. We rarely climb high enough to sense the curve of the Earth, and when we do, the flight attendant is usually asking us to close the window so our fellow passengers can concentrate on the movie.

A powerful hurricane completely destroyed this Pacific Island in 2018. (Images courtesy of Digital Globe, produced by Earthrise Media.)

I’ve had the vagabond good fortune to end up in many of the places where that planet-ness is clearer: on the endless lava plains of Iceland, or at the Rongbuk monastery in Tibet, the highest year-round human habitation on earth, where you stare straight up at Mount Everest, with its peak sticking into the jet stream and pulling a pennant of cloud out of that rushing atmospheric river. On the ice sheets of Greenland and the Antarctic, where millennia are made real by the mile of ice straight beneath your feet. Atop the volcano cones of the Sierras, where the wisps of smoke remind you of the boil beneath; on the fringes of Hawaii, where magma flowing into the Pacific creates new acreage. Beneath the waves on the timeless reefs. High up in the canopy of the rainforest.

These landscapes should provide us with a sense of permanence, but now all of them are in flux, making the effect just the opposite. That flux will be violent and chaotic, just one part of the ever-growing storms of our destabilized world. The victims of that chaos will be the people who have done the least to cause it; their plight is the best reason to embrace once again the vision of unity that came back to the Earth with those original images.

It’s clear by now that the only path to safety for the 99.99 percent of us who will never board a rocket lies in joining the fight for environmental justice. It’s the only battle we’re all in together. In a world riven by every kind of division, the one thing that really does unite us is our shared citizenship of that world. Donald Trump has been trying to turn “globalist” into a curse word, but if the Earthrise photo makes anything clear, it’s that we do indeed inhabit a globe. That’s our most basic identity.

I don’t know if it’s an identity we can still take hold of. It’s possible that we had our chance ― that the vision vouchsafed us in the drama of the 1960s was the last realistic chance, and that we let it slip through our fingers as we opened them to grasp at more wealth.

At least on a human timescale, we’ll never have a planet as intact and full of life as that one we glimpsed from space. Our trajectory is definitely downward. But there was so, so much beauty there, and there’s still so much left ― for now.