Svensmark’s Cosmic Jackpot: “Evidence of nearby supernovae affecting life on Earth”
Posted on April 24, 2012 by Anthony Watts posted by Nadine
 Visible to the naked eye as the Seven Sisters, the Pleiades are the most famous of many surviving clusters of stars that formed together at the same time. The Pleiades were born during the time of the dinosaurs, and the most massive of the siblings would have exploded over a period of 40 million years. Their supernova remnants generated cosmic rays. From the catalogue of known star clusters, Henrik Svensmark has calculated the variation in cosmic rays over the past 500 million years, without needing to know the precise shape of the Milky Way Galaxy. Armed with that astronomical history, he digs deep into the histories of the climate and of life on Earth. Image ESA/NASA/Hubble
Note: I’m going to leave this as a sticky “top post” for a day or so. new stories appear below.
Nigel Calder asks us to republish this post for maximum exposure. He writes:
Today the Royal Astronomical Society in London publishes (online) Henrik Svensmark’s latest paper entitled “Evidence of nearby supernovae affecting life on Earth”. After years of effort Svensmark shows how the variable frequency of stellar explosions not far from our planet has ruled over the changing fortunes of living things throughout the past half billion years. Appearing in Monthly Notices of the Royal Astronomical Society, it’s a giant of a paper, with 22 figures, 30 equations and about 15,000 words. See the RAS press release at ras.org.uk
By taking me back to when I reported the victory of the pioneers of plate tectonics in their battle against the most eminent geophysicists of the day, it makes me feel 40 years younger. Shredding the textbooks, Tuzo Wilson, Dan McKenzie and Jason Morgan merrily explained earthquakes, volcanoes, mountain-building, and even the varying depth of the ocean, simply by the drift of fragments of the lithosphere in various directions around the globe.
In Svensmark’s new paper an equally concise theory, that cosmic rays from exploded stars cool the world by increasing the cloud cover, leads to amazing explanations, not least for why evolution sometimes was rampant and sometimes faltered. In both senses of the word, this is a stellar revision of the story of life.
Here are the main results:
- The long-term diversity of life in the sea depends on the sea-level set by plate tectonics and the local supernova rate set by the astrophysics, and on virtually nothing else.
- The long-term primary productivity of life in the sea – the net growth of photosynthetic microbes – depends on the supernova rate, and on virtually nothing else.
- Exceptionally close supernovae account for short-lived falls in sea-level during the past 500 million years, long-known to geophysicists but never convincingly explained..
- As the geological and astronomical records converge, the match between climate and supernova rates gets better and better, with high rates bringing icy times.
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