Trajectory of the Sun in the galaxy, cosmic radiations and 62M Yr biodiversity cycle.

April 23rd, 2007

The 62M Yr bio-diversity cycle has been talked about for several years now. Using an exhaustive database of fossils created by Sepkoski, Muller and Rohde analyzed the fossil records and noticed the rise and fall in bio diversity every 62M yrs. This is what the graph looks like:

There is a claim that the above extinction is correlated with the trajectory of the solar system around the galaxy. Our solar system travels through the disk-shaped Milky Way with the rotational period to be about 225M yrs. The claim is that at regular intervals, the system’s wanderings take it up and down through the thin central portion of the galactic disk.

Meanwhile, The entire galactic disk, is hurtling through the hot gas that surrounds it at about 200km a second. The cosmic rays are continually generated in a shock wave produced where the galaxy’s “northern” or forward side collides with surrounding gases.

So every 62M yrs, as the solar system rises above the central plane it is closer to the source of the cosmic radiation.

“Cosmic rays themselves are not really that dangerous,” said Medvedev. “They create [charged particles] that propagate down through the atmosphere—especially muons that can go below the sea level.”

There is some evidence that one of the extinction episode, about 450M yrs ago, might have been caused by gamma ray burst, so this is not as far fetched.

But if this happens periodically, there should be some tell-tale signs of it. It would be nice to correlate the muon decay signature prevalence with the decrease in biodiversity finding. Considering that the biodiversity database is prone to sampling errors, and there are several other reasons why life may not have survived, I am not fully convinced, but this is an interesting theory.

According to this calculation, the next cosmic ray event is about 10M yrs. ahead of us.

By the way, this is unrelated to the Dinassaurs extinction, thats a different animal all together.

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