Green fireballs are a type of unidentified flying object which have been sighted in the sky since the late 1940s. Early sightings primarily occurred in the southwestern United States, particularly in New Mexico. They were once of notable concern to the US government because they were often clustered around sensitive research and military installations, such as Los Alamos and Sandia National Laboratory, then Sandia base.
Meteor expert Dr. Lincoln LaPaz headed much of the investigation into the fireballs on behalf of the military. LaPaz's conclusion was that the objects displayed too many anomalous characteristics to be a type of meteor and instead were artificial, perhaps secret Russian spy devices. The green fireballs were seen by many people of high repute including LaPaz, distinguished Los Alamos scientists, Kirtland AFB intelligence officers and Air Command Defense personnel. A February 1949 Los Alamos conference attended by aforementioned sighters, Project Sign, world-renowned upper atmosphere physicist Dr. Joseph Kaplan, H-bomb scientist Dr. Edward Teller, other scientists and military brass concluded, though far from unanimously, that green fireballs were natural phenomena. To the conference attendees, though the green fire ball source was unknown, their existence was unquestioned. Secret conferences were convened at Los Alamos to study the phenomenon and in Washington by the U.S. Air Force Scientific Advisory Board.