Dark spots on the surface of the sun caused by magnetic storms.
Note: The number of sunspots goes through a maximum and minimum about every eleven years. During periods of maximum sunspots, the elementary particles associated with the spots cause disturbances in the atmosphere of the Earth and interfere with radio and television communication.
1. Notional cause of an odd error. "Why did the program suddenly turn the screen blue?" "Sunspots, I guess."
2. Also the cause of bit rot - from the myth that sunspots will increase cosmic rays, which can flip single bits in memory. See also phase of the moon.
[Jargon File]