Originally Posted by sabianq
"The Sun and planets move in a quasi-elliptical orbit between about 8.4 and 9.7 kpc from the galactic center, with a period of revolution of about 240 million years. The solar system Is currently close to and moving inward toward "perigalacticon," the point in the orbit closest to the galactic center. In addition, the solar system moves perpendicular to the galactic plane in a harmonic fashion, with a period of 52 to 74 million years and an amplitude of ~49 to 93 pc out of the galactic plane."
I don't think any of this is new or surprising to more advanced students of the galaxy. And the error bars in the harmonic component of the Sun's orbit are so large, one could fit any number of mass extinctions into such a broadly defined periodicity. BTW, Raup and Sepkoski discovered the periodicity of mass extinctions, and they hypothesized that another star or a 'companion' star to the Sun periodically sweeps through its nearest orbit and perturbs our system's Oort cloud, resulting in more Earth-orbit-crossing comets and asteroids. Such a "Nemesis" star has been searched for, but at this point, its existence may have been ruled out (since there is no star in the neighborhood with such orbital characteristics).
A rough galactic correlation is interesting, but correlation does not mean causation. I'd like to hear a plausible explanation of the mechanism of how galactic dynamics could cause terrestrial periodic mass extinctions before I check ebay for zirconium foil hats...