Soon, clocks in the most remote locations may be accurately synchronized. A new device equalizes the clocks on the basis of cosmic rays, which can be measured everywhere on earth.
Timing is important. Not only when making a good joke, but also when it comes to weather forecasting, the electricity grid, communication and financial systems. A microsecond error can cause the power grid to become unbalanced or a financial transaction to go wrong.
Most systems use GPS for accurate timing. “But GPS signals are susceptible to both deliberate and unintentional disturbances,” says geophysicist Hiroyuki Tanaka from the University of Tokyo. Time-critical systems can use accurate atomic clocks to bridge periods when GPS cannot be contacted. But atomic clocks are often expensive and large. For example, a commercial cesium atomic clock costs almost half a million euros.
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Cosmic Time Sync
Tanaka now thinks he has a solution. His technique for exactly synchronizing the clocks of several devices is affordable, compact and robust. “If you want to disrupt the signal, you have to build a wall the size of a skyscraper or put up a huge electric magnet,” he says. In addition, it works underground and underwater. This is in contrast to GPS, where you cannot receive the signal from the satellites in some places.
The technique that Tanaka devised and tested uses cosmic rays. These are high-energy particles that race through the universe and sometimes collide with our atmosphere. The technique was therefore given the name ‘cosmic time synchronization†cosmic time synchronizationCTS).
Rain of particles
Cosmic rays collide with atoms and molecules in our atmosphere at an altitude of about fifteen kilometers. The collision of a single cosmic particle causes a shower of other particles, including so-called muons. Muons are the heavy brothers of electrons. They move through the air at nearly the speed of light and fly easily through water and rock. This is how they reach caves and the deep sea.
CTS devices detect these muons and see when they arrive approximately and how much energy and speed they have. Muons created by the same collision of a cosmic particle on the atmosphere can be recognized by their moment of arrival and energy. By sharing this information, CTS devices can confer with each other whether they are seeing muons from the same cosmic impact. If so, they can synchronize their clocks by counting back when the cosmic rays hit the atmosphere.
Initial tests with CTS devices showed that time synchronization is possible down to 0.0001 milliseconds.
Any phone CTS
You can repeat this time synchronization several times per hour. Cosmic rays are not very rare. There are about a hundred cosmic impacts per hour that produce measurable muons per square kilometer of Earth. It is worth noting that a single cosmic impact causes a particle shower that is only ten square kilometers in size. If you want to synchronize your clock with a clock outside that area, the device has to search for multiple, partially overlapping cosmic ray showers.
Tanaka is optimistic. “I think the CTS technology could be a good backup system for GPS that can be deployed easily and cheaply worldwide.” His goal is to develop a CTS device that can be built into smartphones. The current prototype is 20 by 20 centimeters in size and weighs one kilogram.
