A few weeks ago, I came across an article which made me rethink not only the world of IT, but the world in general.
Now, typically, I don’t like writing about stuff I’ve read elsewhere without linking to said article, but in this case, I simply cannot remember where I saw the article, so this time I cannot provide a link (sorry!)
Anyway – the crux of the article was that some computer glitches, or crashes have been know to be caused, not by user error, or by bad programming, but by Alpha Particles causing memory bit flips.
OK – what?
Alpha particles are composite particles comprising of two protons and two neutrons tightly-bound together. The particles are emitted from the nucleus of some radionuclides during radioactive decay.
The term alpha particle was coined by Ernest Rutherford during his studies of the properties of uranium radiation in 1899. He observed the radiation having two different characters, the first he called “α radiation” and the second, more penetrating radiation he called “β radiation”.
After five years of experimental work, Rutherford and Hans Geiger determined that “the alpha particle, after it has lost its positive charge, is a Helium atom“ . Alpha radiation consists of particles equivalent to doubly-ionized helium nuclei (He2+) which can gain electrons from passing through matter. This mechanism is the origin of terrestrial helium gas.
Alpha particles occur naturally in many ways. The best-known source of them is from the alpha decay of heavier atoms. When an atom emits an alpha particle in alpha decay, the atom’s mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by two, as a result of the loss of two protons – the atom becomes a new element. Examples of this sort of nuclear transmutation by alpha decay are the decay of uranium to thorium, and that of radium to radon.
The nuclear reactions observed in stars produce many alpha particles – typically these have been referred to as alpha reactions.
Extremely high energy helium nuclei make up about 10 to 12% of cosmic rays.
Alpha particles may also be produced by scientific particle accelerators, although convention is that they are not normally referred to as alpha particles, but rather as energetic helium nuclei.
So what does this have to do with bit flips and Blue Screens of Death (BSOD)?
Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation. The particles travel somewhere between 5 to 7% of the speed of light (approx. 20,000,000 m/s) and because they are highly ionising, alpha particles are unable to penetrate very far through matter and are brought to rest by a few centimeters of air or less than a tenth of a millimeter of biological tissue.
However, The Alpha particles in cosmic rays have sufficient energy to alter the states of circuit components in electronic integrated circuits, causing transient errors to occur – such as corrupt data, or incorrect performance of CPUs.
This has long been a problem in electronics at extremely high-altitude, such as those used in satellites, or in some cases, aircraft, but with transistors becoming ever smaller, this is becoming an increasing concern in ground-level electronics as well.
In 2008, data corruption in a flight control system caused a Quantas Airbus A330 airliner with 315 passengers to twice plunge hundreds of feet on it’s journey between Singapore and Perth. The sudden altitude drop resulted in injuries to multiple passengers and crew members. Cosmic rays were investigated among other possible causes of the data corruption, but were ultimately ruled out as being very unlikely
In 2010, a malfunction aboard the Voyager 2 space probe was credited to data corruption probably caused by a cosmic ray.
Studies by IBM in the 1990’s suggest that computers typically experience about one cosmic-ray-induced error per 256 megabytes of RAM per month.
To alleviate this problem, Intel has proposed a cosmic ray detector that could be integrated into future high-density microprocessors, allowing the processor to repeat the last command following a cosmic-ray event.
So what is a bit-flip, and how does an alpha particle cause one?
Modern semiconductors store their binary bit-values as the presence or absence of electrons in a semiconductor well
The bits are flipped from 0 to 1 or vice-versa by passing an electrical charge through the circuit.
It is entirely possible that occasionally, a crash of a computer system can be attributed to a cosmic ray alpha particle passing through the CPU of your computer at exactly the right time, affecting the exact right part of memory to cause negative electrons to accumulate in the well, causing the bit to flip, thus corrupting the memory and cause the glitch.
Whilst I cannot provide a link to the article I read, I did come across this YouTube video whilst researching this phenomenon which explains all about the alpha particles and the effects they can have on computer systems – Take some time to watch the video, it contains some fascinating events which have happened as a result of Alpha particles.
So, next time your PC dies suddenly, it might not be your fault, or Microsoft’s buggy program code – it could just have been one of those 1 in a million events caused by the cosmos.
