Shaviv hits the Phan

When I was back there in geology school, nobody talked about the Phanerozoic—the geologic time unit encompassing everything after the Precambrian. But more and more we're able to ask big-big questions about this big-big time period. In the July GSA Today, physicist Nir Shaviv and geophysicist Jan Veizer ask, Celestial Driver of Phanerozoic Climate? Their thesis is that CO2 is secondary to Earth's passages through the arms of our galaxy. Stimulating though not definitive. And geology has a history of pulling the rug from under the windy pronouncements of pure physicists.