It’s been well known for some time that there are regular mass extinctions of large numbers of earth’s species. Some of the mass extinctions are thought to be caused by asteroid hits. But there’s another set of extinctions that may be explained by a new theory:

“Recent work has revealed a 62 (+/-) 3-million-year cycle in the fossil diversity in the past 542 My, however no plausible mechanism has been found. We propose that the cycle may be caused by modulation of cosmic ray (CR) flux by the Solar system vertical oscillation (64 My period) in the galaxy, the galactic north-south anisotropy of CR production in the galactic halo/wind/termination shock (due to the galactic motion toward the Virgo cluster), and the shielding by galactic magnetic fields. We revisit the mechanism of CR propagation and show that CR flux can vary by a factor of about 4.6 and reach a maximum at north-most displacement of the Sun. The very high statistical significance of (i) the phase agreement between Solar north-ward excursions and the diversity minima and (ii) the correlation of the magnitude of diversity drops with CR amplitudes through all cycles provide solid support for our model. Various observational predictions which can be used to confirm or falsify our hypothesis are presented.”

In other words, the extinctions are caused whenever the Earth and solar system cross through the galactic plane as part of the regular motion of the sun around the center of our galaxy. As it crosses out of the plane, the solar system is exposed to inter-galactic radiation that the Milky Way’s disk normally protects it from.

If this is true, the “good” news is that our next scheduled mass extinction is about 7 million years from now. So it’s okay to put your assets into long term investments…

Read the rest here: [astro-ph/0602092] Do extragalactic cosmic rays induce cycles in fossil diversity?