Space.com (August 27, 2009)
"Cosmic rays pour down on Earth like a constant rain. We don't much notice these high-energy particles, but they may have played a role in the evolution of life on our planet.
"Some of the mass extinctions identified in the fossil record can be linked to an asteroid impact or increased volcanism, but many of the causes of those ancient die-offs are still open for debate.
" 'There may have been nearby astronomical goings-on that drastically increased the radiation on Earth,' says Brian Fields from the University of Illinois.
"A supernova going off 30 light-years away could cause such a jump in radiation on our planet that could directly, or indirectly, wipe out huge numbers of species. Currently researchers are looking for possible evidence for this sort of cosmic foul play.
" 'Just finding dead beasties is not proof of a nearby supernova,' Fields says...."
This article is a pretty good summary of where we're at in the study of cosmic rays and the massive die-offs Earth has experienced over the last several hundred million years.
Good news, by the way: there's no about-to-go-supernova close enough to be a threat. On the other hand, we may be at a grandstand distance for watching Betelgeuse when it goes up. It looks like we've got more to be concerned about, finding out just how much time we've got before the Yellowstone caldera blows its cap again.
An interesting detail: 'Death Rays From Space' points out that the sun goes through this galaxy's spiral arms at regular intervals. Sci-fi role playing games notwithstanding, stars in the Milky Way galaxy aren't at fixed positions: they orbit the galaxy's center, and the spiral arms are zones of intense star formation that appear to be more 'fixed' than the stars.
There's a possibility - a debated one - that there's a connection between Earth's ice ages and passage through the spiral arms.
Interesting place, the universe: and my guess is that we've just started to understand how it works.
Related posts:
- "Lemming Tracks: All Betelgeuse, All the Time"
(June 10, 2009) - "Volcanoes, a Governor, Science, and the Next Yellowstone Caldera Blowout"
(February 25, 2009)
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