How to Shine Light Through Walls

What if you could shine a light at a massive wall and see the signal on the other side of it? That could be very useful for passing messages through massive object, i.e. you could be morsing through walls. Unfortunately, that doesn’t work since massive objects block photons, or do they?

Apparently, researchers at DESY came up with a strange sounding, but intriguing concept. The researchers used ‘hidden photons’ which are – so far – hypothetical particles predicted to exist in the supersymmetric extension of the standard model.

Now, hold on, you will say, not so fast. What is the standard model anyway and why does it need supersymmetric extensions?

The standard model in particle physics is a theory that postulates elementary particles and describes the way they interact with each other. Those interactions are also called fundamental forces. Actually, the standard model only describes three out of four known fundamental forces, i.e. gravity is not part of the standard model.

The elementary particles postulated by the theory have been experimentally confirmed (except one: the Higgs boson) to exist and make up all visible matter in the universe. So for example the theory includes electrons, photons, quarks, etc. Note that the proton or neutron are composite particles (composed of three quarks) and are not considered elementary particles.

Now, the standard model has certain things that are lacking and what physicists normally do when things don’t quite add up, they invent new stuff that makes things add-up.

So it is with supersymmetry, or the Minimal Supersymmetric Standard Model (MSSM) as it is called. This theory requires the doubling of the know elementary particles, each know particle gets is supersymmetric partner.

So, in this context the photon gets its (hidden) partner, the hidden photon. This particle is entirely hypothetical and has not been observed anywhere – at least not knowingly. There is some hope that it might show up in experiments in the Large Hadron Collider (LHC) at CERN.

Now back to the photon-through-walls thing.

Andreas Ringwald, the researcher at DESY, and his colleagues came up with a proof that if this hidden photon exists. It can be used to send messages through massive objects, as this hidden photon would need to have some rather interesting properties, namely they probably have a tiny mass (the photon has none) and would not interact with charged particles in conventional matter. Hidden photons could thus pass through even the densest materials.

The nifty thing about them is, that they are thought to be able to oscillate into normal photons and back, but they only do that in vacuum.

So Ringwald and his colleagues came up with a possibility and a proof that devices could be built that can send messages through ‘walls’ as thick as the diameter of the Earth, in fact they postulate that it would be possible with current technologies to send messages right through the Earth, unfortunately the ‘bandwidth’ would currently be limited to 1 bit/s (one bit per second).

There is an article on this phenomenon on the New Scientist website. The scientific work of Ringwald and colleagues can be found here (pdf).

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