Cosmic rays coming from ultrapowerful sources in the distant universe can pose risks to humans on Earth — particularly frequent air travelers, who are routinely exposed at the high altitudes of commercial flights. Now, astronomers have used low-cost radiation detectors to begin mapping the radiation environment over African skies, in the first steps to protect the safety of airline crews flying over that continent.
Cosmic rays constantly bombard us from every direction in the sky. But the "rays" aren't exactly well named. Although the astronomers who first discovered cosmic rays thought they were a new form of radiation like X-rays and gamma-rays, further investigation revealed that cosmic rays are actually made of subatomic particles traveling at nearly the speed of light.
These cosmic rays typically come from the extremely distant universe, from ultrapowerful events such as supernovas and quasars.
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A typical cosmic-ray particle has the same kinetic energy as a fastball. That may not seem like a lot, but squished down to subatomic levels, that amount of energy packs a real punch. Cosmic rays can scramble electronics, damage data storage devices and even snip apart DNA. When DNA splits, it can cause replication errors and even lead to tumors. Scientists estimate that cosmic rays trigger a few percent of all cancers worldwide.
Thankfully, our planet offers several layers of protection against these threats. The first is Earth's magnetic field — the strongest among the rocky planets in the solar system — that simply deflects the lower-energy cosmic rays. The higher-energy ones barrel right through, however, making their way into our planet's atmosphere.
But once there, the cosmic rays usually strike a molecule of nitrogen or oxygen, releasing their energy in a shower of other particles. At sea level, cosmic rays or their lower-energy showers pass through the human body at a rate of about once every second.
The risks of cosmic rays
That's what happens at sea level; cruising altitude for airline flights is an entirely different matter. Without those tens of thousands of feet to offer protection, passengers and crews suffer far higher rates of cosmic ray bombardment. With higher rates comes a greater risk of DNA or cellular damage, and a corresponding increase in cancer rates.
The metal shell of the aircraft isn't much help in stopping the microscopic damage, either. While the metal will effectively block the cosmic rays themselves, as soon as they strike an atom, they will transform into a shower of subatomic particles that blasts through the cabin. That shower is almost as damaging as the cosmic rays themselves.
The only effective remedy is to limit exposure. Casual airline travelers have nothing to worry about, as their accumulated radiation dose isn't significantly different from what they experience on the ground. But frequent travelers, especially crews, face an increased radiation risk from their time spent at high altitudes.
The governments of the United States and Europe have mandated safety standards that limit the total exposure that airline crews can accumulate in their lifetimes. Combined with frequent monitoring of the radiation environment at high altitudes, airlines can keep their crews safe.
The monitoring must be frequent, because the cosmic-ray environment constantly changes depending on many factors, like Earth's magnetic field, the sun's activity and random cosmic variations.
Unmapped dangers
However, this monitoring program only covers the skies above North America and Europe. We have relatively little knowledge of the radiation environment above Africa. Although fewer flights cross that continent, until we understand the cosmic-ray environment, we cannot quantify the risk posed to airline crews.
A team of astronomers took the first steps in solving this problem, detailing their results in a paper accepted for publication in the Journal of Space Weather and Space Climate. Their setup was incredibly simple. They designed a dosimeter using a Raspberry Pi computer to measure the radiation exposure in any environment. Then, they brought the device on board two long-haul flights — one from Johannesburg, South Africa, to Frankfurt, Germany, and another from Munich to Johannesburg.
The researchers showed that their simple setup could accurately measure the radiation levels during the flight. They hope to expand the deployment of these simple devices to as many passenger aircraft as possible, allowing them to build up a network of monitoring devices that constantly map and update the cosmic radiation environment. From there, they hope to work with African governments to develop safety standards across their airlines.
