BIO Space Sciences
Dark matter could sling lethal meteors at Earth, potentially causing mass extinctions like the cataclysm that ended the Age of Dinosaurs, Harvard scientists say.
Physicists think the mysterious, invisible substance called dark matter makes up five-sixths of all matter in the universe. It was first detected by the strength of its gravitational pull, which apparently helps keep the Milky Way and other galaxies from spinning apart, given the speeds at which they whirl.
Scientists have recently suggested that a thin, dense disk of dark matter about 35 light-years thick lies along the central plane of the Milky Way, cutting through the galaxy's disk of stars. The sun travels in an up-and-down, wavy motion through this plane while orbiting the center of the galaxy.
Researchers suggest this disk of clouds and clumps made of dark matter might disturb the orbits of comets in the outer solar system, hurling them inward. This could lead to catastrophic asteroid impacts on Earth, of the kind that likely ended the Age of Dinosaurs, said theoretical physicists Lisa Randall and Matthew Reece at Harvard University.
Past research has suggested meteor bombardment of Earth rises and falls in a cycle about 35 million years long. In the past, scientists have proposed a cosmic trigger for this cycle, such as a potential companion star for the sun with the dramatic name "Nemesis."
Instead of blaming a "death star" for these catastrophes, Randall and Reese point out that this cycle of doom closely matches the rate at which the sun passes through the central plane of the Milky Way. This hints that the galaxy's "dark disk" may be the actual culprit.
The scientists detailed their findings online April 20 in the journal Physical Review Letters.