this post was submitted on 24 Aug 2025
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Somebody please correct me if I'm wrong, but I believe due to the very low refractive index of about 1.0003, particles need tremendous energy to produce Cherenkov radiation in atmosphere. So the demon core flashes (while perhaps some negligible part Cherenkov) were probably mostly just from the ionization of the air, and subsequent nitrogen/oxygen fluorescence.
If my awful phone math is right, you'd need about 21 MeV of energy for an electron to produce Cherenkov radiation. I think the processes producing energetic electrons here (Compton scattering, some pair production, photoelectric effect, internal conversion, delta rays, and Bremsstrahlung cascade I believe) should regularly produce energies around 10 MeV at most (from Compton).
IIRC the flash wasn't discernable from being the air or the aqueous/vitreous humor in the eye.
I think it's been hypothesized that the eye jello allows for a much lower energy particle to to create the flash. They do know it's possible to induce it, but it's not exactly ethical to test the conditions that created the various criticality accidents to find out.
Oh cool! I hadn't considered that. The crystallin and vitreous humor in the eye do indeed have a refractive index similar to water, so Cherenkov radiation happens at less than 1 MeV IIRC, so it comes down to how much light would actually be produced in such a small volume. It does seem perfectly feasible!
So we can see radiation afferall
Sort of? Radiation refers to any ionizing wave- particle. This means ultraviolet, x-rays and gamma-rays are not possible to see.
Alpha and beta particles can only produce visible light if they are moving faster than the medium that light travels through. Because Alpha and Beta particles are massive they cannot reach c (speed of light in a vacuum) but in water, as being discussed, any velocity >0.75c will produce the light.
Electrons and positrons are a much lower mass and require much lower energy to get moving at a sufficient speed. This means beta decay is a candidate for it, but the beta decay of naturally radioactive elements is too low of an energy for this to be observed. In nuclear fission, the neutrons won't interact this way as they aren't charged. The immediate fission products, however, are usually of very high instability and some of these do decay by beta emission in a very short period of time.
Alpha particles, which are usually 5 mev, do not create the light, as they are much more massive. These are released from things like Uranium-238 to Thorium-234.