Cosmic rays actually do cause bit rot. A study in the 80s by IBM placed RAM testers in Boulder, Colorado, Leadville, New York City, and underground in Kansas City. Boulder had 5 times more errors than New York, and Leadville had ten times as many as New York. The elevation of the towns has a lot to do with it, since Leadville doesn't have as much atmosphere to absorb sub-atomic particles at 10,152ft. Boulder is at about 5,000ft. New York is at sea level. However, the shape of the earth's magnetic field has a lot to do with it, too. la Paz has a similar altitude to Leadville's, but is at a different latitude.

The sub-atomic particles that make up cosmic rays knock electrons out of orbit, generating just enough voltage to send a gate into the wrong digital state.

The effects get worse with smaller components. Makers of modern microprocessors have to be very careful about terrestrial radiation, as well. If their chip fab becomes radioactive, it will not turn out working chips.

All this stuff can be found in an IBM research journal somewhere. Specifically, the IBM Journal of Research and Development, Volume 40, Number 1.

So keep your smoke detector away from your chips!

corge = C = cough and die

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.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

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