cosmic rays n.
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 the moon. 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.