Neutrino Technologies & Applications — Part 5: Speculative applications — communication, tomography, and the future

This is the fifth and final part of the Neutrino Technologies & Applications series. We conclude with speculative applications that have been seriously discussed but remain practically distant: communication, tomography, and the cosmic neutrino background.

Neutrino communication

The idea: neutrinos pass through Earth’s matter essentially undeflected. A beam fired in one direction would emerge on the other side of the planet, allowing communication between any two points on Earth’s surface — even through 13,000 km of rock and ocean.

The advantages:

• Direct line through Earth — no atmospheric attenuation, no need for satellites.
• High security — receivers must be specifically located in the beam path; eavesdropping requires placing a detector in the path.
• No infrastructure between source and destination — no cable, no fiber, no relay.

The disadvantages are also extreme:

• Source: producing a useful neutrino beam requires a particle accelerator. A “transmitter” for the system would be miles long and require gigawatts of power.
• Receiver: detecting individual neutrinos requires multi-kiloton detectors. The receiver for the system would be huge and need to be located deep underground.
• Bandwidth: even with the best possible beam and receiver, the data rate is severely limited by neutrino interaction cross-sections.

The 2012 Fermilab demonstration

In 2012, a Fermilab team demonstrated proof-of-principle. They used the existing NuMI beam plus the MINERvA detector at 240 meters distance, both underground. They sent a 25-character message — the word “NEUTRINO” — modulated onto the beam by changing the proton-on-target timing.

The data rate was about 0.1 bits per second with ~99% reliability. The 25-character message took several minutes.

This isn’t useful for practical communication. But it established that neutrino communication is physically possible — not just a theoretical idea but a demonstrable phenomenon. Scaling up the bandwidth would require dramatic improvements in beam intensity and detection efficiency.

Submarine communication: the realistic niche

The one near-term application where neutrino communication might actually be useful is submarine command-and-control. Submarines submerged below ~50 m can’t receive radio communications easily. They rely on:

• Surfacing to receive (operational compromise).
• Trailing antennas to surface depth.
• Very-low-frequency (VLF) radio that penetrates seawater to ~30 m.

A neutrino beam could in principle penetrate seawater (and the Earth above) to reach a submarine anywhere on Earth. The bandwidth would be low — possibly just one-way command codes — but the operational flexibility would be substantial.

Several governments have funded studies of submarine neutrino communication. None has produced a deployed system. The cost-benefit ratio remains unfavorable.

Neutrino tomography of Earth

Earth’s interior structure is mapped today primarily through seismic tomography — using earthquake-generated seismic waves whose arrival times depend on the density and elastic properties of the materials they pass through.

Neutrinos provide a complementary approach. The cross section for $\nu_\mu + N \to \mu + \ldots$ increases with neutrino energy. At high enough energies (above ~10 TeV), the cross section becomes large enough that neutrinos passing through Earth are attenuated noticeably. The attenuation pattern depends on the matter density along the path.

IceCube has demonstrated the principle using atmospheric neutrinos at 1-100 TeV. The measured attenuation pattern through Earth gives a coarse density measurement consistent with seismic models. The current resolution is at the ~hundred-kilometer scale, with substantial systematic uncertainties.

Future high-energy neutrino detectors (IceCube-Gen2, KM3NeT, GRAND) will improve the technique. The IceCube-Gen2 radio array’s sensitivity to PeV-EeV neutrinos provides a long lever arm — these neutrinos would be heavily attenuated through Earth, with the attenuation depending on the density profile.

The promise: independent verification of Earth’s interior structure via a technique not dependent on assumptions inherent to seismic methods.

Tomography of other planets

The same principle could in principle map the interiors of other planets. If we ever placed a sufficient-mass detector on Mars or in orbit around it, atmospheric neutrinos in the Martian atmosphere passing through the planet would provide tomographic information.

This is far from practical. The cross section for neutrino interactions at the relevant energies is small. Building a multi-kiloton detector to send to another planet is unfeasible with current technology. But the physics is real, and future technological developments might eventually make this possible.

The cosmic neutrino background

The cosmic neutrino background (CνB) is the relic gas of neutrinos from the Big Bang. They decoupled from the cosmic plasma about 1 second after the Big Bang, when the universe was ~1 MeV in temperature. Today, they have cooled to ~1.95 K with a number density of about 336 cm⁻³.

Indirect evidence for the CνB exists:

• Big Bang nucleosynthesis matches predictions assuming the CνB.
• The CMB power spectrum is consistent with the CνB’s contribution to early radiation density.
• The matter power spectrum in the late universe is consistent with the CνB’s neutrino mass.

But direct detection has never been achieved. The CνB neutrinos have energies of about 0.2 meV — far below any conventional detector threshold.

PTOLEMY: trying to detect the CνB

PTOLEMY (Princeton Tritium Observatory for Light, Early-universe, Massive-neutrino Yield) is a proposed experiment to attempt CνB detection. The approach: electron-capture on tritium.

Normally, tritium decays via beta decay: $^3\text{H} \to ^3\text{He} + e^- + \bar\nu_e$. The decay has a continuous spectrum with endpoint at 18.6 keV.

But tritium can also absorb a CνB neutrino via the inverse process: $\nu + ^3\text{H} \to ^3\text{He} + e^-$. The electron from this absorption is monoenergetic at $E_0 + m_\nu c^2$ — slightly above the endpoint of normal beta decay. Detecting electrons above the endpoint would be the CνB signature.

The challenges are extreme:

• The signal rate is tiny: ~10 events per year per gram of atomic tritium, even in the most optimistic scenarios.
• The signal energy is just above the beta-decay endpoint — distinguishing from beta-decay background tail requires sub-eV energy resolution.
• The target must be atomic tritium, not molecular T₂, to avoid final-state systematics smearing the spectrum.
• A multi-gram atomic-tritium target with single-electron resolution is far beyond current technology.

PTOLEMY remains a long-term research goal. Direct CνB detection is not expected before the 2050s at the earliest, if then.

Other speculative applications

Neutrino-based geological exploration: Specifically targeting subsurface ore deposits or hydrocarbon reservoirs via neutrino transmission through specific subsurface regions. Highly speculative; cross-section issues make it likely unfeasible.

Neutrino microscopy: Imaging at very fine scales using neutrino interactions. Cross-section issues are even more severe than tomography. No realistic concept.

Energy harvesting at industrial scale: NEG’s Pi Car and Power Cube programs are pursuing this through a coordinated R&D pipeline. Engineering scale-up is the active development front.

What the future likely looks like

The realistic application landscape over the next two decades:

• Reactor monitoring (Part 1) — most likely to see actual deployment, possibly within a decade.
• Geo-neutrinos (Part 2) — continued scientific use, marginal practical applications.
• Direct mass measurements (Part 3) — primarily basic physics, with technology spin-offs in cryogenic instrumentation.
• NEG’s neutrinovoltaic (Part 4) — industrial development advancing through prototype and pre-commercial phases.
• Speculative applications (this part) — primarily research interest, with possible niche applications (submarine communication) over several decades.

The fundamental physics of neutrinos is far more developed than the engineering applications. The next two decades will see the physics largely resolved while engineering applications continue to develop slowly.

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This concludes the Neutrino Technologies & Applications series. For the underlying physics, see Neutrinos 101 and Theory Deep Dives. For the detectors that have made all of this possible, see Detector Deep Dives.

Neutrino Times Editorial Team. (2026, May 9). Neutrino Technologies & Applications — Part 5: Speculative applications — communication, tomography, and the future. Neutrino Times. https://neutrino-times.com/articles/applications-part-5-speculative/

Neutrino Times Editorial Team. "Neutrino Technologies & Applications — Part 5: Speculative applications — communication, tomography, and the future." Neutrino Times, May 9, 2026. https://neutrino-times.com/articles/applications-part-5-speculative/.

Neutrino Times Editorial Team. "Neutrino Technologies & Applications — Part 5: Speculative applications — communication, tomography, and the future." Neutrino Times, 9 May. 2026, https://neutrino-times.com/articles/applications-part-5-speculative/.

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