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

Supernova

[slug359]

I remember seeing this interesting program on a Discovery program ~ 2 years ago, covering exactly the same topic.
It also explained the effects of cosmic rays on space missions, from supernovas, and how more older stars are present in the 'arms' of the galaxy.

It also went into great detail about the effects cosmic rays had on the early space missions, leaving very very very tiny dents (albeit all over) the spacecraft.

Re:Supernova

[no reason to be here]

I saw something recently (i.e. sometime in the last three months) on discovery (or possibly the learning channel) that explored the connection between average global temperature and deep sea currents. apparently, so long as the deep sea currents continue on un abated, avg. temperatures stay stable from year to year, and temperatures don't get too extreme in different areas of the globe.
the last major disruption began around the end of the last ice age, and we humans have had an usually steady climate during our reign as king species.

Re:Global warming?

[dankelley]

Probably not. The timescale is wrong. Besides, the warming trend [difficult as it is to measure] seems to be consistent with CO2 emissions, linked through climate models in which we have [some, of not great] confidence.

Re:Global warming?

[anthony_dipierro]

Besides, the warming trend [difficult as it is to measure] seems to be consistent with CO2 emissions, linked through climate models in which we have [some, of not great] confidence.

It is also consistent with changes in the magnetic flux of the sun.

The question of global warming is still out.

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!