Ground zero The term ground zero ( sometimes also known as surface zero as distinguished from zero point ) describes the point on the Earth ' s surface closest to a detonation . In the case of an explosion above the ground , " ground zero " refers to the point on the ground directly below the detonation ( see hypocenter ) . The term has often been associated with nuclear explosion s and other large bomb s , but is also used in relation to earthquakes , epidemics and other disaster s to mark the point of the most severe damage or destruction . The term is often re - used for disasters that have a geographic or conceptual epicenter . Trinity , Hiroshima , and Nagasaki . The origins of the term " ground zero " began with the Manhattan Project and the bombing of Japan . The Strategic Bombing Survey of the atomic attacks , released in June 1946 , used the term liberally , defining it as : " For convenience , the term ' ground zero ' will be used to designate the point on the ground directly beneath the point of detonation , or ' air zero . ' " William Laurence , an embedded reporter with the Manhattan Project , reported that " Zero " was " the code name given to the spot chosen for the atomic bomb test " in 1945 . The " Oxford English Dictionary " , citing the use of the term in a 1946 " New York Times " report on the destroyed city of Hiroshima , defines " ground zero " as " that part of the ground situated immediately under an exploding bomb , especially an atomic one . " The term was military slang , used at the Trinity site where the weapon tower for the first nuclear weapon was at " point zero " , and moved into general use very shortly after the end of World War II . At Hiroshima , the hypocenter of the attack was Shima Hospital . The Pentagon . The Pentagon , the headquarters of the U . S . Department of Defense in Arlington , Virginia , was thought of as the most likely target of a nuclear missile strike during the Cold War . The open space in the center is informally known as ground zero , and a snack bar located at the center of this plaza was nicknamed " Cafe Ground Zero " . World Trade Center . Since 2001 in the United States , especially in the media , " Ground Zero " is generally understood to mean the site of the World Trade Center , which was destroyed in the September 11 attacks . The phrase was being applied to the World Trade Center site within hours after the towers collapsed . It appears that the first use of the term on a mainstream North American media outlet in reference to the September 11 attacks was at approximately 11 : 55 am when an eye witness who claimed to be a Fox News freelancer referred twice to ground zero . He may also have been the first person to suggest the cause of the collapse of the towers was due to " structural failure due to fires " . At 4 : 41 p . m . , in an interview with Peter Jennings on ABC News , attorney and survivor of the attacks Tom Humphreys ( spelled " Humphries " on air ) said , in reference to the collapse of the South Tower , that The next known reference occurred at 7 : 47 p . m . ( EDT ) on that day , when CBS News reporter Jim Axelrod said : The term " Ground Zero " was simultaneously used by NBC News reporter Rehema Ellis when her own report was aired on NBC at around the same time as Jim Axelrod ' s report on CBS News . She said : Rescue workers also used the phrase " The Pile " , referring to the pile of rubble that was left after the buildings collapsed . Even years later , the term " Ground zero " has become a shorthand for the site , even after construction on the new One World Trade Center and the National September 11 Memorial & Museum were well under way . In advance of the 10th anniversary of the attacks , New York City mayor Michael Bloomberg urged that the " Ground zero " moniker be retired , saying , " . . . the time has come to call those 16 acres what they are : The World Trade Center and the National September 11th Memorial and Museum . "