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Wednesday, December 29, 2010

Earth Biodiversity Pattern May Trace Back to Bobbing Solar System Path

Most discussions of cosmic ray extinction events focus on nearby gamma-ray burster supernova events, which will likely be the subject of an upcoming post here. The article below, however, examines a completely different possibility. The sun's path around the Milky Way galaxy periodically places it in direct exposure to cosmic rays from the Virgo Cluster of galaxies. The periodicity of this event is 62 million years, which seems to coincide strikingly well with the periodicity of terrestrial biodiversity. Note that this does not coincide with the 27 million year periodicity of the Oort body extinction events. The latter are very rapid occurrences, whereas the former take place on the scale of millions of years.


SPACE.COM--- A puzzlingly regular waxing and waning of Earth's biodiversity may ultimately trace back to our solar system's bobbing path around the Milky Way, a new study suggests.
Every 60 million years or so, two things happen, roughly in synch: The solar system peeks its head to the north of the average plane of our galaxy's disk, and the richness of life on Earth dips noticeably.
Researchers had hypothesized that the former process drives the latter, via an increased exposure to high-energy subatomic particles called cosmic rays coming from intergalactic space. That radiation might be helping to kill off large swaths of the creatures on Earth, scientists say.
The new study lends credence to that idea, putting some hard numbers on possible radiation exposures for the first time. When the solar system pops its head out, radiation doses at the Earth's surface shoot up, perhaps by a factor of 24, researchers found.

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