It remains a classic moment in United Nations history. Israeli Prime Minister Benjamin Netanyahu used the dignified setting of a General Assembly speech in the fall of 2012 to raise the specter of an Iranian nuclear bomb. He displayed a cartoonish drawing of what he said was an Iranian bomb with a lighted fuse on top and asked: "How much enriched uranium do you need for a bomb? And how close is Iran to getting it?" He called his crude drawing a "diagram."

The catcalls came immediately. Jon Stewart of The Daily Show waved a copy of the Israeli drawing that night and said, "Bibi, bubbe, what's with the Wile E. Coyote nuclear bomb?" Stewart showed his antidote to the bomb: a cartoon drawing of a giant magnet.

Fifteen months earlier, in a report for the New Yorker, I disclosed that a highly secret National Intelligence Estimate, whose conclusions were unanimously approved by delegates from seventeen American intelligence and counterintelligence agencies, found that there was no conclusive evidence that Iran had made any effort to build the bomb before or after the American invasion of Iraq in 2003. (A similar unproven allegation, that Iraq possessed an undeclared nuclear and chemical weapons arsenal, was used by the administration of George W. Bush and Dick Cheney to justify the invasion in the wake of the September 11 attacks of 2001.)

As in 2012, there is still no evidence that Iran, which does utilize low levels of enriched uranium to run its sole nuclear power plant, has the capacity to produce the needed amounts of highly enriched uranium for a bomb. Nor is there any evidence of a secure facility capable of fabricating enriched uranium into a solid nuclear core that could trigger a bomb. The American intelligence community has spent years, without success, searching for signs of an underground fabrication facility with ventilation holes that could surface many miles away—in Iran's more than 600,000 square miles. It's been decades of searching for air holes.