The physicist Enrico Fermi and others likened the furiously rising cloud in the New Mexico desert to a mushroom, and that became the shape now inextricably associated with nuclear explosions.

March 30, 2006 — -- A Pentagon test at a Nevada site this June will likely create the first mushroom cloud seen in the state since the United States ceased above-ground nuclear testing in 1963.

A massive, mushroom-shaped cloud of smoke was spotted near New Smyrna Beach on Wednesday, leading some beachgoers into thinking a major "explosion" took place not far from the beach. But is that ...