Question about neutrinos

If you had a sample of pure carbon 14, could you change the decay rate by bombarding it with neutrinos or starving it if same?


Are you referring to results like Sturrock et al. 2010 that found a possible correlations between radioactive decay rates and the sun’s rotation or activity? I think these results are still unconfirmed and unexplained, though there seem to be mounting evidence for it.

I see some creationists are already using this to attack the validity of radiometric dating. But these (possibly) observed effects are so small as to be negligible for radiometric dating.

Neutrinos can induce beta decay-- That’s usually how they’re detected, in the rare instance that they’re detected at all. But the cross-section for neutrinos to interact with anything is abysmal, so any change in the decay rate is going to be very small.

Yes, this is possible (the bombarding part; starving it doesn’t make any sense). Here are some back-of-the-envelope estimates for the sort of partial rates you’re talking:

Partial rate per nucleus due to natural decay: 4x10[sup]-12[/sup] Hz
Partial rate per nucleus induced by electron neutrinos from the sun: 10[sup]-32[/sup] Hz
Partial rate per nucleus that could be induced by the most powerful neutrino beam we’ve got: 10[sup]-28[/sup] Hz

So, the effect is super puny in practice. In case the notation above doesn’t convey the puniness: If you put your block of carbon-14 in front of the most powerful neutrino beam we have, you would induce one additional decay for every 40,000,000,000,000,000 decays that occur naturally.

Another cute way to think about this: It isn’t that the neutrino interaction rate is fundamentally too small. After all, both natural beta decay and neutrino-induced beta decay are governed by the weak force. It’s just that radioactive nuclei can undergo natural decay at any time whereas neutrino-induced decays can only occur if a neutrino happens to be passing by.

I guess the sun is our biggest local source of natural neutrinos. But there should be tons of neutrinos from other stars, too, back to the big bang?

Is the “night” (that is, non-sun parts) sky neutrino-dark? Is this Obler’s paradox again? By that I mean, if we lived in a non-expanding steady-state universe, would the whole sky be bright as the sun, both in light and neutrinos?

Is it the case that all nuclear decay is caused by a neutrino changing the flavor of a quark?

Yes, there are neutrinos all over, some from stars, and some primordial. Just because the Sun is the brightest local source doesn’t mean it’s the only source.

No. Alpha decays don’t involve any neutrinos at all, nor does neutron emission or spontaneous fission (technically, alpha decay is a form of spontaneous fission).

Beta decays do involve neutrinos, but in that case it’s far more often an antineutrino emitted from the decay than an incoming neutrino that gets absorbed. Likewise for positron emission or electron or positron capture, with negative signs added as appropriate.

Does all beta decay involve neutrinos?

Well… There’s something called “neutrinoless double beta decay” that’s predicted by some models, but conclusive evidence of it has never been observed. And even there, you probably get virtual neutrinos internal to the decay process.

But other than that, yes, absolutely, beta decay always involves neutrinos.

Chronos’s answers might already have clarified this for you, but note that beta decay isn’t caused by a neutrino (or antineutrino) changing the flavor of a quark. Rather, a quark spontaneously converts into another quark while emitting an electron and an antineutrino (or a positron and a neutrino for the less common beta+ decay). The neutrino or antineutrino is a product of the decay and not really a cause.

The process you propose in the OP could be said to be caused by a neutrino, but that process is typically not called beta decay. If the incoming particle is an electron-type antineutrino then it’s usually called “inverse beta decay”, and for other cases it depends on the context as to what you might call it (most commonly a mouthful: “charged current quasi-elastic scattering”).

Olber’s paradox has the same resolution for neutrinos as it does for photons. As for “where are they?” – folks are looking. The target of interest is the diffuse supernova neutrino background, or DSNB. There are more neutrinos in the DSNB than from regular stellar output since most of the energy in supernovae (99%) goes into neutrinos. The expected rate is just below current experimental bounds, so there is some hope that upcoming measurements will actually see this flux of neutrinos.