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The rise and fall of species on Earth might be driven in part by the undulating motions of our solar system as it travels through the disk of the Milky Way, scientists say.
Two years ago, scientists at the University of California, Berkeley found the marine fossil record shows that biodiversity—the number of different species alive on the planet—increases and decreases on a 62-million-year cycle. At least two of the Earth’s great mass extinctions—the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago—correspond with peaks of this cycle, which can’t be explained by evolutionary theory.
The galactic bow shock is only present on the north side of the Milky Way’s galactic plane, because that is the side facing the Virgo Cluster as it moves through space, and it would cause superheated gas and cosmic rays to stream behind it, the researchers say. Normally, our galaxy’s magnetic field shields our solar system from this “galactic wind.” But every 64 million years, the solar system’s cyclical travels take it above the galactic plane.
The boost in cosmic–ray exposure could have both a direct and indirect effect on Earth’s organisms, said KU paleontologist Bruce Lieberman. The radiation could lead to higher rates of genetic mutations in organisms or interfere with their ability to repair DNA damage, potentially leading to diseases like cancer.
I don't know about the Ordovician extinction event, but I thought there was fair evidence that the Siberian Traps caused the Permian Extinction, or were at least a well timed coincidence if not, and pretty destructive too.
Originally posted by iori_komei
62-million-year cycle. At least two of the Earth’s great mass extinctions—the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago—correspond with peaks of this cycle, which can’t be explained by evolutionary theory.
But every 64 million years, the solar system’s cyclical travels take it above the galactic plane.
I do feel I need to stress that this is only a hypothesis as of now, it is not
a theory, and is not necessarily the truth.
Personally though I think it's a good hypothesis that may just be the truth.
for National Geographic News
April 20, 2007
Cosmic rays produced at the edge of our galaxy have devastated life on Earth every 62 million years, researchers say.
The finding suggests that biodiversity has been strongly influenced by the motion of the solar system through the Milky Way and of the galaxy's movement through intergalactic space.
Mikhail Medvedev and Adrian Melott, both of the University of Kansas, presented their new theory at a meeting of the American Physical Society earlier this month.
The theory offers the first explanation for a mysterious pattern previously noted in the fossil record.
"There are 62-million-year ups and downs in the number of marine animals over the last 550 million years," Melott said.
The pattern includes a rise and fall of marine animal diversity every 62 million years and a weaker cycle of rising and falling marine diversity, which repeats every 140 million years. The researchers think that expanding and retreating glaciers may explain the 140-million-year cycle, but they are stumped over what drives the 62-million-year cycle.
The declines in the 62-million-year cycle correspond with some of the best known mass extinctions on Earth.
Among them are the die-off caused by the asteroid or comet widely believed to have doomed the dinosaurs 65 million years ago and the "Great Dying" of 250 million years ago. During the Great Dying, some unknown cause wiped out most life on Earth.