If there is a consensus about anything among environmental activists, it's that's nuclear power is dangerous, and its tremendous downsides cancel out any possible advantages as a source of energy. Or at least that's how most people see the issue. The truth is there is a small but growing number of environmental experts who believe that despite well-known disasters such as Three Mile Island, Chernobyl, and Fukushima, it is possible to generate safe and cost-effective power using nuclear materials with a minimum of waste and without the inefficiencies of renewable methods such as wind and solar, which at current levels cannot meet public demand. A handful of leading voices in the environmental movement, among them Stewart Brand, Gwyneth Cravens, Richard Rhodes, and Michael Shellenberger, are now promoting nuclear power as a "green" energy source, and filmmaker Robert Stone (who presented a history of the ecology movement in the film Earth Days) gives them a chance to present their side of the argument in the documentary Pandora's Promise. The film received its world premiere at the 2013 Sundance Film Festival.