In this XKCD What If essay, Randall Monroe address the concept of a lethal dose of neutrinos. But on rereading it, it doesn’t seem to say exactly how the neutrinos would kill you.
Since the What If scenario involves being inside an exploding supernova, let’s suppose that you are protected from everything except the neutrinos.
How would they kill you?
Same as with other types of radiation, I suppose. The neutrinos interact with matter in your body; for that to have any discern you would need a lot of neutrinos because each one of them, on average, hardly interacts with anything, which is precisely Monroe’s point, but suppose there are enough of them to have a discernible effect. In doing so, part of the energy of the neutrinos is absorbed by that matter, which heats up. So it’d be tissue burns.
Neutrinos are electrically neutral and only interact via the weak force and gravitation, so they cannot directly do ionizing damage. They can produce a lepton (electron, muon, tau lepton) if it has sufficient momentum, and that can produce do ionizing damage if the resulting particle is energetic enough, but as noted in the XKCD comic the interaction is so rare that exposure to all of the other radiation would literally render you into component atoms long before the neutrinos would have any effect.
Stranger
How do you figure? It’s not like electrons interact only electromagnetically. Electrons are subject to the weak force, too, so there’s no reason that a sufficiently-energetic neutrino couldn’t knock an electron out of an atom. Sure, it’s highly unlikely, but that just means that you need a ludicrously large number of neutrinos. And yes, such a ludicrously large number of neutrinos would almost certainly be accompanied by a similarly ludicrous amount of other sorts of radiation, but it’s not too hard to come up with a contrived situation where all that other radiation is shielded.
I am hearing that in Rick Moranis’ voice.
How about trying it in Ray Stantz’s (Dan Aykroyd’s) voice?
Neutral current interactions are even more unlikely than lepton production, and because of the mass difference between an electron and a neutrino, the likelihood of getting enough interactions to do measurable damage is negligible outside of having courtside seats to a supernova. Just detecting neutrinos from solar emission requires a detector made of thousands of tons of fluid surrounded by extremely sensitive photomultipliers to capture the occasional emission.
Stranger
Right, we’re positing something like courtside seats to a supernova. Maybe with a pre-existing (old, cold, inactive) neutron star between you and the supernova, to block everything but the neutrinos.
High-energy neutrinos are so passé. To paraphrase Archimedes, give me a long enough particle accelerator and I can destroy the world.
What about a high density of cold neutrinos? Imagine a large number of gravitationally bound neutrinos with mean kinetic energy much less than their rest mass and no other matter or photons mixed in. A daring astronaut flies their spacecraft into neutrino cloud. Of course, the hull doesn’t really stop neutrinos, so they’re soon within the astronaut’s body. What density is lethal and what’s the cause of death?
Neutrinos have such low mass and enough weak interaction that getting enough density of them to create a gravitational gradient sufficient affect things on anything truly cosmic scale is virtually impossible; this is one of the reasons that cosmologists are pretty sure that the (missing) dark matter (MDM) isn’t just a flood of neutrinos. It is possible that some component of MDM are hypothetical ‘sterile’ neutrinos but current theory shows that they cannot be all of it.
If you really want a ‘fun’ hypothetical beyond-science-fiction weapon, consider a device that emits neutral mesons at relativistic speeds and then controls the decay such that they all decay inside the target. Because neutral mesons don’t interact electromagnetically, nearly all of the energy enters and is delivered within the target, irradiating it from within, probably in a big sploosh of thermalized tissue. Yick!
Stranger
While a neutrino can knock a single electron out, that wouldn’t really be called ionizing radiation, which refers more specifically to the extensive ionization from a charged particle passing through a material and depositing its energy over an extended path or region.
The electron that the neutrino knocks out, however, would do its own ionizing.
More generally, supernova neutrinos interacting in a human would lead to electrons, positrons, and protons moving through the tissues with energies of a few to tens of MeV, and all those secondary particles would do their own ionizing.
Yes, we know that already. But it’s not actually impossible, and so it’s interesting to ask what would happen. And if you don’t know the answer, it’s acceptable to not say anything.
Pardon me for posting.
Stranger
I think that was the Meson Accelerator ship to ship weapon in the Traveller RPG, it could by pass the ships shields. I think the also could use them as planetary defense weapons, burried deep below the planet surface for protection, but they could fire through the protective layer .
Another Cosmic Mega Eventᵀᴹ brought to you by the Cosmic Corporation, founders of Milliways, the Restaurant at the End of the Universe
My understanding is that the “easiest” way for a big dose of radiation to kill you—short of giving you a tumor that kills you years later—is by killing off stem cells (particularly in your bone marrow & GI tract) that you need to survive. You can read all the gruesome details in clinical detail here:
You can also get skin injuries, which manifest like a really bad sunburn, but won’t necessarily kill you: