Sub-atomic particles created by cosmic ray collisions have been used to create a “new kind of GPS.” In a new study, scientists at the University of Tokyo have shown how they used these high-energy particles to navigate deep beneath a building in an underground basement - something that would not be possible using the go-to Global Positioning System (GPS).
The first-of-its-kind feat is all thanks to muons, high-energy particles that are produced by cosmic rays hitting atoms in Earth's atmosphere. Muons “fall” to Earth in a constant shower, approximately 10,000 per square meter per minute, and move at the same speed regardless of whether they’re traveling through air, water, or rock.
“Cosmic-ray muons fall equally across the Earth and always travel at the same speed regardless of what matter they traverse, penetrating even kilometers of rock,” Professor Hiroyuki Tanaka, study author from Muographix at the University of Tokyo, said in a statement. “Now, by using muons, we have developed a new kind of GPS, which we have called the muometric positioning system (muPS), which works underground, indoors and underwater.”
Conventional GPS devices use data from satellites to locate a specific point on the Earth in a process called trilateration. Simply put, a GPS device is able to work its location on Earth by calculating its distance from satellite A, satellite B, and so on. This novel method works on a similar principle but uses the muon-detecting sensors as its reference point instead of satellites in low-Earth orbit.
The researchers carried out an experiment whereby four muon-detecting reference stations were placed on the sixth floor of a building while a person took a receiver detector to the basement floor. As the individual walked up and down the basement's corridor, they were able to track their movement with relatively good accuracy.
“The current accuracy of MuWNS is between 2 meters [6.6 feet] and 25 meters [82 feet], with a range of up to 100 meters [328 feet], depending on the depth and speed of the person walking. This is as good as, if not better than, single-point GPS positioning aboveground in urban areas,” added Tanaka. “But it is still far from a practical level. People need one-meter accuracy, and the key to this is the time synchronization.”
It’s hoped the accuracy could be improved through the use of chip-scale atomic clocks (CSACs), although the researchers say these are currently very pricey. As this technology becomes cheaper and more accessible, however, they anticipate that muometric wireless navigation systems could eventually become a common feature in smartphones.
The study is published in iScience.