Ask HN: Why don't transistors in microchips fail?
There is another mechanism called "Single Event Upset" (SEU) or "Single Event Effects" (SEE) (basically synonymous).  This is due to cosmic rays.  On the surface of the earth, the effect is mostly abated by the atmosphere  - except for neutrons.  As you go higher in the atmosphere (say on a mountaintop, or an airplane, or go into space) it becomes worse because of other charged particles that are no longer attenuated by the atmosphere.The typical issue at sea level is from neutrons hitting silicon atoms.  If a neutron hits the neucleus in some area of the microprocessor circuitry, it suddenly recoils, basically causing an ionizing trail of several microns in length.  Given transistors are now measured in 10s of nanometers, the ionizing path can cross many nodes in the circuit and create some sort of state change.  Best case it happens in a single bit of a memory that has error correction and you never notice it.  Worst case it causes latchup (power to ground short) in your processor and your CPU overheats and fries.  Generally you would just notice it as a sudden error that causes the system to lock up, you'd reboot and it would come back up and be fine, leaving you with a vague thought of, "That was weird".