<p>Twenty-five years ago this week, something went horribly wrong at Three Mile Island. Those very words are now synonymous with nuclear meltdown, but back then they merely referred to an obscure nuclear plant in central Pennsylvania. Human error and mechanical failure conspired to send the temperature in the reactor core soaring, threatening a blast of deadly radiation. All of America watched in apprehension. Politicians and regulators bickered, and the media whipped up a frenzy.</p>