Under Earth's protective magnetic field, we don't usually need to worry too much about the health effects of cosmic radiation – although it's something that's known to impact astronauts in space, and even passengers travelling in airplanes.
But the same can't be said for our technological systems – fierce solar storms can wreak havoc on Earth's communication networks, and new research shows that even ordinary levels of cosmic radiation can have a disruptive effect on our personal devices.
"This is a really big problem, but it is mostly invisible to the public," says electrical engineer Bharat Bhuva from Vanderbilt University.
To see just how big the problem is, Bhuva and his team took 16-nanometre computer chips – the kind used in many of today's consumer PCs – and exposed them to a neutron beam, in an attempt to replicate what happens when cosmic radiation penetrates our atmosphere.
When cosmic rays collide with Earth's magnetic field, they create cascades of secondary particles – including energetic neutrons, muons, and pions.
Millions of these particles strike our bodies every second, and while they aren't thought to have any effect on our health, they can interfere with the operation of microelectronic circuitry.
In particular, when they interact with integrated circuits, they can actually alter or 'flip' individual bits of data stored in memory – a phenomenon that's called a single-event upset (SEU).
Most of the time, such an event probably wouldn't create much of a problem. An app running on your smartphone or PC might glitch somehow, making a miscalculation, but it's probably not something you'll notice for more than a moment.
But in some cases, SEUs could have drastic and potentially far-reaching consequences.
In 2003, a 'bit flip' in a Belgian electronic voting machine gave one candidate in the election an extra 4,096 votes, before the mistake was caught.
Even more worrying – the avionics system of a Qantas passenger jet malfunctioned due to a suspected SEU in 2008, forcing the aircraft into an abrupt dive that injured about a third of the passengers on board.
Bhuva's research was sponsored by a number of microelectronics companies, and the results are proprietary – meaning they're unlikely to be published any time soon.
But in a presentation of key trends in the findings at a meeting of the American Association for the Advancement of Science in Boston last Friday, he explained that as technology advances and transistors get ever smaller, the likelihood of SEUs due to cosmic rays is increasing.
"[S]emiconductor manufacturers are very concerned about this problem because it is getting more serious as the size of the transistors in computer chips shrink and the power and capacity of our digital systems increase," says Bhuva.
"In addition, microelectronic circuits are everywhere and our society is becoming increasingly dependent on them."
Ultimately, smaller transistors are more vulnerable to energetic particles, because they require less electrical charge to represent a logical bit – which means they flip between binary states (from 0 to 1, or vice versa) more easily when they're struck by cosmic rays.
On the other hand, today's transistors are smaller than ever, so they're actually less likely to be hit by flying energy particles. Contemporary transistors are also assembled in 3D designs, that help to make them less individually susceptible to SEUs.
But since today's computer chips include significantly higher numbers of these smaller transistors overall, at the device level, the risk of an SEU occurring is greater than ever, Bhuva says.
So, what's the solution? Unfortunately, shielding chips from energy particles isn't an option, as it would take more than 3 metres (10 feet) of concrete to prevent transistors from being struck. According to Bhuva, the answer is for device manufacturers to design systems that include three processors in place of one. In rare cases where two chips tell you one thing, and the third tells you another, majority rules – as the errant third result would likely be due to an SEU.
Plugging that hole will ultimately mean our devices run smoother than ever – but in the meantime, there's no need to lose any sleep over your smartphone being hit by a rogue particle strike.
"This is a major problem for industry and engineers," Bhuva says, "but it isn't something that members of the general public need to worry much about."
The findings were presented at the annual meeting of the American Association for the Advancement of Science in Boston last Friday.