The Possible Cosmic Culprit Behind Computer Errors
Cosmic rays—streams of charged particles—can negatively affect terrestrial technology.
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Ring! The bell sounds, signaling the end of the period. You rush to finish your essay, due in the five minutes before your next class. As your mouse hovers over the submit button, your screen buffers and then goes black. Your computer crashes, shattering your last hope of submitting your essay on time. Though most students would probably blame the spotty Stuyvesant Wi-Fi, there could be another (hidden) culprit behind the crash—cosmic rays.
Cosmic rays are radioactive energetic particles made up of subatomic particles. They travel through space at almost the speed of light (approximately 300 million meters per second). There are two types of cosmic rays: solar and galactic. Solar cosmic rays are emitted continuously by the Sun’s chromosphere, the layer of plasma between the Sun’s surface and its upper atmosphere. Their emission can increase during events like solar flares, in which energy stored in “tangled” magnetic fields is abruptly released. Galactic cosmic rays, on the other hand, originate from supernovas, or the explosions of stars toward the end of their life cycles. These events send electrons, protons, and atomic nuclei outwards until they interact with other matter. In the remnants of supernova explosions, galactic cosmic rays are accelerated. Galactic rays contain more energy than solar rays, which enables them to enter Earth’s atmosphere more easily.
Cosmic rays were first discovered by Austrian scientist Victor Hess in 1912. Before the 20th century, experts believed that all radiation came from natural substances on Earth, like uranium. Hess refuted this assumption in 1911 by completing 10 hot-air balloon journeys, monitoring radiation levels as he ascended. He observed that the high atmosphere contained more radioactive particles than the ground, meaning that the radiation source must originate from outer space rather than Earth’s interior or surface.
These particles were later dubbed cosmic rays and were found to affect electronics through single-event upsets (SEUs). An SEU occurs when a charged particle travels through a computer chip and causes an abnormal electrical charge, which, in turn, results in an incorrect output. This process is caused by interference semiconductors, which are materials used in computer chips that can conduct electricity. Semiconductors’ ability to route electricity is controlled by transistors, which then output binary numbers called bits. Transistors can turn on—letting energy travel through the semiconductor—or off, stopping the flow. When turned off, the transistor outputs a zero, but when on, it outputs a one. Consecutive bits then form strings, which the computer interprets as letters or characters.
Energy from cosmic rays can travel through semiconductors and turn the transistor on or off, generating an unintended bit. When an electrical current passes through the transistors in a computer chip, it can leave behind loose electrons, generating a current and outputting a one. Or, it can create new bonds between active electrons, stopping the current and generating a zero. Both of these scenarios, together called a bit-flip, may result in a string the computer cannot process, producing an error. These errors have a range of consequences depending on which bit is flipped. Incorrect bits could result in altered documents, a sudden termination of a program (leading to a computer crash), or no noticeable consequences.
The earliest occurrence of an SEU was in the 1970s when Intel introduced its newest system used to store computer memory, known as dynamic random-access memory (DRAM). However, seemingly random errors were produced, and inspection revealed that they were the result of radioactive ceramic casing. In particular, the facility manufacturing Intel DRAMs was built on the Green River in Colorado, located just downstream from an old uranium mill. Radioactive atoms from uranium leached into the river from the mill and eventually seeped into Intel’s ceramic packaging. The trace levels of radiation led to faulty outputs and multiple software errors. Radioactive nuclei emit alpha particles—consisting of two protons, two neutrons, and high energy levels—which interfered with transistors in the DRAM and caused a bit-flip. Cosmic rays, which contain alpha particles, are at risk of interfering with computer chips in a similar fashion as radioactive particles.
The theory behind cosmic rays was once again demonstrated by the Belgian election results of 2003. When reviewing the poll results, a town official was immediately concerned; a candidate had 4,096 more votes than the voting population. This specific number, exactly two to the 12th power, suggested that the incorrect poll results were due to a software error. After checking the computer’s software, analysis revealed that a bit was flipped in the thirteenth place of the vote counter, creating a one in the place of a zero. Software experts ran the same code inputted into this system and failed to recreate the error, leading them to believe that this mistake was due to a one-time, external event. The investigator pointed to cosmic rays as the reason behind the error.
Though cosmic bit-flips are uncommon, this problem is worsening as manufacturers continue to produce smaller computer chips since fewer particles are needed to generate the power to flip a bit. However, because smaller chips have advantages like faster processing times and lower prices, the response to bit-flips shouldn’t be to stop producing smaller chips but rather to take preventative measures. One precautionary response is error-correcting code (ECC) memory, which constantly surveys existing code and corrects any bits that would output erroneous code. This added layer of protection is one way to decrease the likelihood of bit-flips.
As the world becomes increasingly dependent on computers, the study of cosmic ray bit-flips serves as a reminder of the ever-present relationship between nature and technology. So, the next time you curse the Stuyvesant internet, remember the connection between our computers and the cosmos.