A Huge Burst Of Gamma Rays Hit Earth--And No One Noticed
Artist's Conception of Neutron Star Collision NASA / Dana BerryScientists think a nearby collision of neutron stars could explain the undocumented onslaught of high-energy radiation in the eighth century Last year, Japanese scientists found evidence that, in 775 AD, Earth was hit with a sudden blast of high-intensity radiation--a blast carrying about 10,000 times the energy of the atomic bomb dropped on Hiroshima. Clearly, something catastrophic had occurred in Earth's cosmic neighborhood, but whatever it was, it apparently went undetected by the 350 million people living on our planet at the time: the historical records contain no mention of strange celestial events that year, catastrophic or otherwise. The event is recorded, instead, in the amount of radioactive carbon trapped in the annual growth rings of some of the world's oldest trees. Carbon's key radioactive isotope, carbon-14, forms when energetic particles enter Earth's atmosphere and collide with nitrogen atoms. Since trees...