cosmic rays

Notionally, the cause of bit rot. However, this is a

semi-independent usage that may be invoked as a humorous way

to handwave away any minor randomness that doesn't seem

worth the bother of investigating. "Hey, Eric - I just got

a burst of garbage on my tube, where did that come from?"

"Cosmic rays, I guess." Compare sunspots, phase of themoon. The British seem to prefer the usage "cosmic showers";

"alpha particles" is also heard, because stray alpha particles

passing through a memory chip can cause single bit errors

(this becomes increasingly more likely as memory sizes and

densities increase).

Factual note: Alpha particles cause bit rot, cosmic rays do

not (except occasionally in spaceborne computers). Intel

could not explain random bit drops in their early chips, and

one hypothesis was cosmic rays. So they created the World's

Largest Lead Safe, using 25 tons of the stuff, and used two

identical boards for testing. One was placed in the safe, one

outside. The hypothesis was that if cosmic rays were causing

the bit drops, they should see a statistically significant

difference between the error rates on the two boards. They

did not observe such a difference. Further investigation

demonstrated conclusively that the bit drops were due to alpha

particle emissions from thorium (and to a much lesser degree

uranium) in the encapsulation material. Since it is

impossible to eliminate these radioactives (they are uniformly

distributed through the earth's crust, with the statistically

insignificant exception of uranium lodes) it became obvious

that one has to design memories to withstand these hits.

[Jargon File]