On the first Earth Day, in 1970, I was an 11-year-old kid living in Princeton, New Jersey. I spent the day with my friends gleefully crushing thousands of empty soda cans—our first awakening to the revolutionary concept of recycling. Many of us went home empowered to teach our parents a thing or two about their wasteful and polluting ways. Unlike the protests surrounding Vietnam and civil rights, environmentalism seemed to me to be a children’s crusade. This was our movement and Earth Day was our day. I was an immediate convert to the cause and have remained so ever since.

Beyond the pall of air and water pollution that in 1970 was the extent of our environmental concerns, there also loomed the ever-present threat of nuclear war. It appeared to me that the world bequeathed to us by our parents was a world gone mad, the evidence of which was all around us: Vietnam, riots, assassinations, poisoned air and water, and the Orwellian defense doctrine of Mutually Assured Destruction. The one bright spot for me was the fact that we were sending astronauts to the Moon. That was an awesome, hopeful and mind-expanding endeavor that gave me hope that humanity, for all its faults, had the ability to harness technology to peaceful and inspiring ends. Everything else was going to the dogs.

\When Christmas rolled around that year, my father gave my mother a super-8 movie camera, a gift that I immediately appropriated as my own. Come April, as a project for my 7th grade science class to celebrate the first anniversary of Earth Day, I made my initial foray into filmmaking with a three-minute documentary called “Pollution.” I didn't know it yet, but I’d found my calling. It was my destiny to become a documentary filmmaker.

Seventeen years later I was nominated for an Academy Award for a film called “Radio Bikini,” about the first nuclear weapons tests at Bikini Atoll in the Pacific. Overnight, I became a darling of the anti-nuclear movement, a righteous cause that had morphed out of the environmental movement of the 1970’s. Courted by activists bent on using my film about nuclear weapons to enhance their case against nuclear energy in the wake of Chernobyl, I was badgered repeatedly to advocate that the US government had intentionally irradiated US servicemen at Bikini in a conspiracy to study the effects of radiation on humans, and then covered it up.

Even though I knew (and stated publicly) that there was no evidence of purposeful intent, the activists who embraced my film had no use for evidence. Older than me by several years, and perhaps traumatized by duck & cover drills at school (which I had missed), their business was to spread fear and mistrust of all things nuclear, and to regard any conflicting information as a product of “The Establishment.” As the son of a Princeton University historian, I was raised to have a finely attuned bullshit detector and a deep suspicion of people who see the world in black and white. It was my first falling out with The Movement. As fate would have it, it would not be my last.

Twenty years after that I made a documentary film called Earth Days, a loving portrait of the rise of the modern environmentalism and the story of how Earth Day came about. At its premier as the Closing Night Film of the 2009 Sundance Film Festival, I took the stage to answer questions before a packed house of about 1,500 people. Out of the blue, someone asked me what my views were on nuclear energy as an environmentalist. I mentioned Radio Bikini, which had also premiered at Sundance, and said that my views had evolved a great deal in light of climate change and that I was no longer anti-nuclear.

Next to me on stage was Stewart Brand, one of the stars of the film, the founder of the Whole Earth Catalog and a legend in the environmental movement. Knowing Stewart had become a passionate advocate of nuclear energy, I asked if he’d like step forward to answer the question. As he held forth for five or ten minutes, making a cogent and eye-opening environmental argument for nuclear energy, I watched this left-leaning audience sit there aghast and yet utterly transfixed. I felt a palpable sense of liberation as Stewart happily blasted through one of the great taboos of environmental activism. It was as if the doors had been flung open on the stifling and depressing 20-year debate about how to solve climate change and we had suddenly been given a much needed breath of fresh air. Nobody wanted to discuss my film Earth Days anymore, I’m sorry to say. All anyone wanted to talk about was nuclear energy.

How horrifically ironic it would be if the one technology environmentalists were almost universally united against (a central tenet of The Movement) was in fact our best hope for saving the planet from the greatest environmental catastrophe of all time? The thought left me as thunderstruck as the first time I heard the Sex Pistols. Nuclear power was punk rock to the environment movement’s Crosby, Stills & Nash. This was a revolution against all that had gone wrong with environmentalism over many years. I determined then and there to make this the subject of my next film.

Four years later I was back at Sundance with a new documentary called Pandora’s Promise. It quickly thrust me into conflict with many of the very same people who had hailed me for making Radio Bikini many years before, and Earth Days more recently. And yet, given my background, reputation and environmental bona fides, I was as hard a target to discredit as were the extraordinary and brave people whose conversion stories on this issue I chronicled in the film, Stewart Brand among them.

I spent much of the next two years touring the world with the film, presenting it to environmental audiences, and making converts. I sometimes felt like a traveling preacher-man for a new religion, one based on hope, not fear; reason, not pseudo-science; advocating energy prosperity, not energy austerity. Wherever I went, I made surprisingly few enemies and met a veritable army of new friends who are now forming a movement.

Part of me is still that 11-year-old kid, inspired by technology, appalled by our degradation of the planet, determined to make a difference, and open to learning new things and forming new opinions based on new information. Environmentalists have rightly urged us to confront inconvenient truths, and yet the most inconvenient truth of them all is one they themselves can scarcely acknowledge. In opposing nuclear energy in the midst of a climate crisis, I believe they’ve made an error in judgment of historic and potentially catastrophic proportions. It is one of my missions in life to right that wrong—before it’s too late.