When cosmic rays hit the upper atmosphere, they send high-energy particles, such as neutrons, showering down towards the surface. So an interesting question is how these neutrons influence things on the ground. Researchers have long known that high-energy neutrons can smash into atomic nuclei causing all kinds of damage to the structure of materials. This is one cause of errors in computer memories. Indeed, back in 2004, a group of researchers from IBM measured the flux of neutrons from cosmic ray collisions and used their results to predict the error rate in computer memories another electronic logic devices. Their predictions closely matched the observed rate of error, suggesting that neutrons are indeed an important source of problems in computing.

That finding has captured the imagination of Augusto González at the Institute of Cybernetics, Mathematics and Physics in Havana, Cuba. If background neutron radiation can cause errors in computer circuitry, then it ought to have a similarly destructive effect on another much more common information processing system–life. Evolutionary biologists have long known that spontaneous mutations occur at a rate that has a crucial influence on the nature of evolution. But exactly what causes spontaneous mutation has never been properly understood.

The question that González addresses is whether this mutation rate can be explained by the background neutron radiation. He does this by creating a mathematical model of the environment in which bacteria grow, which is essentially water.

He calculates that high-energy neutron would enter the water on a bacterial sample about once every 125 seconds. This high-energy neutron would then transfer its energy to water molecules creating a relatively short track of ions. He says that a single neutron would generate some 300 ions over a track length of about 100 nanometers and about 30 ions at a distance of 0.1 mm

Labels: Blinded by Stats

¶ 2:38 AM