[flingo]

Cosmic rays can come from any angle, and even pass through the entire earth without impacting anything. (millions of them are zipping through you and your RAM, right now! electrons barely dodging out of the way in time.)

I think (but have no reference) that the amount of cosmic rays the planet blocks by being in the way is dwarfed by the effects of the magnetosphere and solar rays.

[Balgair]

Slight nit-pick: Neutrinos are the ones that are zipping through you and the Earth. They interact with things very rarely and have no real charge anyway. The rays you'd worry about with computer hardware are photons (gamma rays) with high energy enough to create new charged particles. Also other charged particles like muons and their decay cascades.

[raducu]

Watching an alcohool fog chamber is such a cool experience.