Task & Purpose's The Navy is testing a GPS-like device that doesn’t require satellites “The future is extremely bright for this line of research." begins:

The Navy is researching a new technology that could help sailors and Marines navigate in places where the Global Positioning System just doesn’t work.

Unlike GPS signals, cosmic ray muons are a natural source of radiation that can pass through rock, buildings and earth and can be used at high latitudes north of the Arctic Circle, where GPS satellites do not work well due to their orbital constraints, the Office of Naval Research wrote in a press release on Tuesday.

and later:

“Cosmic-ray muons (or atmospheric muons) are ubiquitous and universal,” researchers wrote in a study of muons published in the journal Nature in 2020. “[B]y utilizing this universality and relativistic nature, cosmic muons have a potential to be used for positioning the receiver detector located underwater or underground three dimensionally with a great accuracy.

That Nature Scientific Reports article (Tanaka, Hiroyuki K. M. 2020) Muometric positioning system (μPS) with cosmic muons as a new underwater and underground positioning technique is pretty challenging to read.

Several cosmic ray muons are produced in an air shower, each produced by a single very high energy cosmic ray proton or heavier nucleus.

But they come randomly, and the showers are fairly well localized. So I'd like to ask:

Question: How can cosmic ray muons be used to replace GPS for positioning information in 3D on Earth?


2 Answers 2


From what that paper says, it's based on the flight time of highly-relativistic muons between a reference detector at the surface and the final detector under the water. There are three or more reference detectors arrayed on the surface with positions and time-references determined by GPS. Presumably the underwater detector also needs to know what time it. The final picture shows a cable joining the surface detector and the underwater detector (which seems to somewhat defeat the purpose). It also talks about taking ~100 days to make a measurement.

It seems like this paper is aimed at making very accurate measurements of slow seafloor movements. Otherwise, I'm not sure how one would do this. EM waves (laser beams?) and pressure waves (sonar) probably don't propagate well enough or with sufficiently reliable velocity, especially in water with temperature and salinity gradients, etc. The muons supposedly travel very close to the speed of light, >0.9999999c.

It doesn't sound like it will be very useful for submarines :-(

  • $\begingroup$ It sounds like such a system could be used to accurately survey the position of some other resource (a sonar beacon, perhaps) that might be more useful to submarines. $\endgroup$
    – Dave Tweed
    Jan 29 at 23:25
  • 1
    $\begingroup$ Now if you could use a modulated muon beam to send time signals from the surface detector to the underwator detector ... (neutrino beams are used for communication in Joe Haldeman's science fiction novel The Forever War ...) and physics.stackexchange.com/questions/199606/… $\endgroup$
    – Ben Bolker
    Jan 30 at 1:31
  • 1
    $\begingroup$ @Ben Bolker We could move a 100 foot thick slab of lead in and out of the path - and that wouldn't be too difficult if we're only allowed one bit per 100 days. $\endgroup$
    – Roger Wood
    Jan 30 at 2:49

(speculative answer)

If you have a muon detector with good angular resolution, the sky has some pretty much distinctive features in cosmic ray brightness, visible well underground.

Marine people are used to looking at constellations and determinging their position.

Another option is to use something similar to muon tomography and look for known features above or around you.

  • $\begingroup$ Did you read the article linked in the question? The principle is described in great detail. $\endgroup$
    – asdfex
    Jan 31 at 18:16

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