Cosmic Ray Navigation

GPS is a handy modern gadget — until you go inside, underground, or underwater. Japanese researchers want to build a GPS-like system with a twist. It uses cosmic ray muons, which can easily penetrate buildings to create high-precision navigation systems. You can read about it in their recent paper. The technology goes by MUWNS or wireless muometric navigation system — quite a mouthful.

With GPS, satellites with well-known positions beam a signal that allows location determination. However, those signals are relatively weak radio waves. In this new technique, the reference points are also placed in well-understood positions, but instead of sending a signal, they detect cosmic rays and relay information about what it detects to receivers.

The receivers also pick up cosmic rays, and by determining the differences in detection, very precise navigation is possible. Like GPS, you need a well-synchronized clock and a way for the reference receivers to communicate with the receiver.

Muons penetrate deeper than other particles because of their greater mass. Cosmic rays form secondary muons in the atmosphere. About 10,000 muons reach every square meter of our planet at any minute. In reality, the cosmic ray impacts atoms in the atmosphere and creates pions which decay rapidly into muons. The muon lifetime is short, but time dilation means that a short life traveling at 99% of the speed of light seems much longer on Earth and this allows them to reach deep underground before they expire.

Detecting muons might not be as hard as you think. Even a Raspberry Pi can do it.

19 thoughts on “Cosmic Ray Navigation

  1. > Like GPS, you need a well-synchronized clock

    You don’t. Given enough satellites in view, GPS solves a set a of equations that will give you your position without any need for an external time source. Instead GPS itself will give you a high precision time source.

    1. Right, so the genius of GPS is that the satellite signal carries the clock and the satellite position. The muons can’t be similarly modulated so there has to be some extra side channel with this information, anyway. So i don’t understand what is the point of the muons-the triangulation could be off that side channel.

      1. It reduces the demands on the side channel. Triangulating off of it requires you have propagation to multiple receivers – a side channel only would require one communication link.

      1. You can solve your position with only 3 satellites if you have a really expensive local clock, or you can solve for 4+ satellites with a cheap clock that drifts badly over time, but is reasonably accurate over the short term.

      2. So I think there is a fundamental problem with your interpretation. You DO need a great clock across the system. The fact that the GPS satellites provide the clocking data for the receiver doesn’t mean the entire system doesn’t need a clock. In fact, many GPS receivers use the GPS clock info to discipline their local clocks and that is very effective. But to do the navigation, you do need to understand what time it is at your location using the exact same time as all the satellites. That doesn’t mean YOU have to generate that clock but you would if the satellites didn’t provide a way for you to work it out or, at least, the difference in the satellite times.

  2. Muons are my favourite subatomic particle! Why do they weigh 207 times as much as an electron? Nobody knows. Even string theory is silent on the subject – it uses an approximation where all currently known particles have mass zero.

          1. Because Copernicus was right after all – we ARE the center of the universe. That’s my story and I’m sticking to it, at least until some aliens show up to claim it.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.