In the early days of the universe, space was filled with exploding stars and spinning dust clouds – the same elements as the modern universe, but occupying a much smaller patch of galactic real estate! Planets in the neighbourhood of a stable star would have been constantly bombarded with intense waves of cosmic radiation, from both inside and outside their star’s system. Astronomers now believe as black holes formed and the universe expanded, this radiation became more dissipated and this played a crucial role in creating the right conditions for life to begin. Cosmic radiation ‘shreds’ DNA and other building blocks needed for life. When the universe was in its infancy and much smaller than it is today, it would have been awash with such radiation as star systems were established. These high levels of radiation would have then occupied a relatively confined space, making its effects more intense. However, as the universe expanded, the amount of cosmic radiation dropped – in terms of how much was being released but also how much space it had to fill! Additionally, as black holes grew they moved from spewing out radiation to also devouring it. This meant that the threat of radiation shredding DNA decreased, giving these building blocks more of a chance to develop and evolve. The theory has been put forward by Dr Paul Mason, an astrophysicist at University of Texas at El Paso. Presenting his research at the meeting of the American Astronomical Society in Kissimmee, Florida this week, the astrophysicist described the key mix of events which were needed. For example, supernovae – exploding stars which throw out masses of cosmic rays – were much more frequent during the galactic past! A nearby starburst would send out a tsunami of radiation. But as the universe grew, these events became more dissipated. In addition, the detritus from all those exploding stars also gave life a helping hand. Dying stars go into fusion overdrive, smashing together hydrogen and helium atoms to form larger, heavier elements before they are flung out into the cosmos.