Don't think GRBs are all that worrisome, by comparison. It has recently been calculated that there is a 50-percent chance that a GRB-induced mass extinction on

Don't think GRBs are all that worrisome, by comparison. It has recently been calculated that there is a 50-percent chance that a GRB-induced mass extinction on Earth has occurred in the past 500 million years. This abstract: ( https://arxiv.org/abs/1409.2506 https://arxiv.org/abs/1409.2506 ) links to a PDF of the entire paper. So the probability in a human lifetime is magnitudes less than a supervolcano event or big asteroid impact. According to ( https://phys.org337426962/pdf.pdf https://phys.org337426962/pdf.pdf ): "The researchers don't believe a GRB striking the Earth could penetrate the atmosphere, but do believe one could destroy the ozone layer". We started to do that to ourselves more than once, not long ago. We are by far the highest-probability danger to Earth life. Chlorofluorocarbons: check. Nuclear weapons: check. Back to less-likely (inhuman) radiation sources: In the late 8th century, tree rings in the northern hemisphere 'recorded' a one-year atmospheric increase of 1% in carbon-14 ... 20 times normal. Cause: 'an extremely intense burst of high-energy radiation'. Cause unknown, but could have been ... a coronal mass ejection (the Sun). ( https://www.nature.com/news/mysterious-radiation-burst-recorded-in-tree-rings-1.10768 https://www.nature.com/news/mysterious-radiation-burst-recor... )