NASA scientists are baffled about the possible origins of booming sounds heard across the world in recent times.
64 locations internationally have reported hearing sudden, sonic-boom noises without the presence of aircraft in the vicinity, or any other identifiable source.
The latest unexplained event happened over the skies in Alabama earlier this week. The phenomenon was powerful enough to shake houses and make windowpanes rattle.
Theories range from a normal sonic boom produced by an aircraft reaching the speed of sound to ground explosions. However, no such events were reported at the time of the unexplained phenomena.
Locations such as Alabama and Idaho in the United States, Cairns in Australia, and Wales in the United Kingdom have been affected by the strange booming sounds.
Scientists so far remain at a loss to explain the phenomenon, but conspiracy theorists and alien invasion aficionados have jumped up to put their own theories forward, speaking of the coming of Armageddon and alien craft testing new weapons.