That suggests to some that once every 26 million years something beyond Earth dramatically impacts our planet. Five major extinctions, including that of dinosaurs, have occurred over the past 570 million years. Cosmic rays may have played a role. Just when you finally thought you knew what wiped out the dinosaurs, three scientists have a new explanation that offers a whole new twist.
Dinosaurs rank at the top of billions of species that thrived and then vanished forever.
The mass extinction has perplexed scientists ever since they began digging up fossils of creatures no longer on Earth. David M. Raup, a statistical paleontologist at the University of Chicago, estimates that between 5 billion and 50 billion species existed at one time or another on this planet, compared to about 40 million today. The latest, and one of the most intriguing, forays into the debate comes from three scientists at the Israel Institute of Technology. Astrophysicists Arnon Dar, Ari Laor and Nir Shaviv speculate that radiation from the collision of distant stars caused some mass extinctions. In the last few seconds of a binary neutron star's life, the two stars spiral together and form a black hole surrounded by a hot, dense disk that blasts powerful jets.