Some say volcanoes triggered the dinosaurs’ decline a million years before the infamous asteroid hit 66 million years ago. Others say the dinosaurs slowly starved after the asteroid’s impact generated a dust cloud so thick it blocked out the sun for months. Many would have been incinerated by thermal radiation in the hours after impact, researchers report July 28 in the Journal of Geophysical Research: Biogeosciences. Instead of escaping into space, that heat would have been trapped by the dust cloud and radiated back to Earth’s surface. About an hour later, the radiation would have dissipated, and the dust cloud would have blocked out the sun.