Solar System's Path May Have Spurred Ice Ages

ImproperShutdown writes "Space.com reports that a physicist has found a correlation between the amount of cosmic rays reaching the Earth, as it passes through the spiral arms of the Milky Way, and the planet's ice ages over the last billion years. Apparently, as the Solar System passes through the higher density spiral arm regions, it receives more cosmic rays from the higher density of supernovae that have occurred in the region. This larger flux of cosmic rays ionizes the Earth's atmosphere more, which makes it more cloudy and cools down the Earth."

Comments

See, there they go again.

[Snafoo]

Once again our 'scientists' have managed to
misintepret perfectly clear statistical
data by imposing a faulty chain of causality.

Obviously, things are back-to-front. Ice ages
cause changes in the path of the solar system.

Duh.

This is not his first bad theory.

[Peter T Ermit]

Here at the APS site, there's an abstract. It looks like a bad paper -- one of a zillion theories that make mountains out of correlations. It's not even this author's first proposal of this sort. Five years ago, he suggested that the cosmic rays caused extinction events.

Sounds like this guy has a favorite hammer, and he's now convinced that everything looks like a nail.

100's of millions of years, not thousands.

[apsmith]

Some of the other posts (not having read the actual article presumably) and the space.com report itself seem a bit confused about the way the term "ice age" is being used here. Based on estimates (somewhat shaky, as was pointed out in another comment) of the galactic rotational speed of the spiral arms relative to stars like our Sun, this paper shows a surprising correlation over the past billion years between times our solar system was within a spiral arm, and periods of significant glaciation lasting 10's or 100's of millions of years.

According to the calculations in the article, the solar system has passed through the four spiral arms ("Orion" or Sagittarius-Carina, Scutum-Crux, Norma, and Perseus) a total of seven times over the last billion years, or roughly once every 150 million years. We've actually only recently left the Orion arm (heading for Perseus) so the cosmic-ray flux is still quite high, and according to the author's diagram, we are STILL experiencing a major glaciation period. Since the last "ice age" as we know them ended just over 10,000 years ago, that time scale is WAY to short to show up on the scale of this article. In other words, we're still in the middle of an ice age, as far as this paper is concerned.

While the thickness of the spiral arms is such that we pass through them in about 30 million years, the cosmic ray effects last 50-60 million years or more, depending on the level of star-formation within the arms at any given time. The author also notes that it is believed our galaxy had a peak in star production about 300 million years ago, and had much lower star production prior to about 1 billion years ago (until you get back to the 2-3 billion year period and earlier, for which we don't have much in the way of geologic records). In addition to the ice age records, the author also looks at records from iron meteorites radio-isotope dating to get another measure of cosmic ray flux in those periods, which also seems to correlate.

Anyway, interesting stuff, but on a time scale much bigger than we normally think about when we think of ice ages. The ice age before the current one according to this model dates to before the rise of the dinosaurs; go back a couple more and it's before we have any evidence of complex life on Earth!