Prof. Brian Fields, Nuclear and Particle Astrophysicist presented the second Saturday Physics for Everyone (SPE) Lecture on Sept. 26.
The most massive stars are the celebrities of the cosmos: they represent a small fraction of all stars, but live extravagant lives and die in spectacular and violent supernova explosions. While these events are awesome to observe, they can take a sinister shade when they occur closer to home, because an explosion within a certain "minimum safe distance" would pose a grave threat to Earthlings. We will discuss these cosmic threats to life and show compelling evidence of a “near miss” supernova from 3 million years ago that rained its debris upon the Earth. This amazing discovery allows us to study supernova ashes in the laboratory and confirms that nearby explosions are a fact of life in our Galaxy. We therefore press further, presenting recent evidence that supernova explosions could have caused biological extinctions on Earth around 360 million years ago. We conclude with tests of this hypothesis, including the search for trace amounts of radioactive supernova byproducts in fossils that witnessed the end of the Devonian period.
