everything is stooopid
Every 250m years the sun, with its entourage of planets, completes a circuit of the Milky Way. Its journey around its home galaxy, though, is no stately peregrination. Rather, its orbit oscillates up and down through the galactic disc. It passes through that disc, the place where most of the galaxy’s matter is concentrated, once every 30m years or so.
This fact has long interested Michael Rampino of New York University. He speculates that it could explain the mass extinctions, such as that of the dinosaurs and many other species 66m years ago, which life on Earth undergoes from time to time. Palaeontologists recognise five such humongous events, during each of which up to 90% of species have disappeared. But the fossil record is also littered with smaller but still significant blips in the continuity of life.
Many hypotheses have been put forward to explain these extinctions (and the events may, of course, not all have the same explanation). The two that have most support are collisions between Earth and an asteroid or comet, and extended periods of massive volcanic activity. Dr Rampino observed some time ago that cometary collisions might be triggered by gravitational disruptions of the Oort cloud, a repository of comets in the outermost part of the solar system. That would send a rain of them into the part of space occupied by Earth. This has come to be known as the Shiva hypothesis, after the Hindu god of destruction. […]
In his latest paper, Dr Rampino speculates that the real culprit may be not stars, but dark matter—and that this might explain the volcanism as well.
