Mike Wall, Space.com (September 22, 2010)
"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...."
The article's got a picture that illustrates how our star bobs up and down, relative to the galactic plane, as it goes around the center of our galaxy. The motion is a bit like that of a carousel's horses.
So, should we be digging in, building fallout shelters: like Americans did back in my 'good old days?' ("Cold War, United States History)
Eventually, maybe: but according to the article, we don't need to rush. The next era of peak radiation is due in maybe 10,000,000 years. Okay: compared to how long life's been on Earth, that's not all that long. Compared to, say, the expiration date on milk containers? Like the Lemming said, there's no need to rush.
Mr. Wall does a pretty good job of outlining what's happened in terms of biodiversity over the last 542,000,000 years. Basically:
- Lots of animals and plants died Species
- Occasionally died out
- Life went on
These days, that's a bit noteworthy. In the Lemming's opinion.
- "Ecological Disaster - a Quarter of a Billion Years Ago"
(December 14, 2010)
- "Ecological Disaster - a Third of a Billion Years Ago"
(September 30, 2010)
- "Life on Other Worlds: Evolution, Orbits, and the Galactic Environment"
(August 13, 2009)
- "Re-Thinking This Galaxy's Habitable Zone"
(September 23, 2008)
- "The Sun as a Swinger? Cardiff U's Title is Better for Mass Extinction Article"
(May 12, 2008)
Related posts, at