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kikisonic
2003-Jun-27, 06:28 AM
my freind said that he read that if there were a supernova anywhere close, high-energy neutrinos would interact with are bodys atoms to cause a kind of cancer. I think its improbible but I dont know. though the term high-energy neutrino makes no sence because neutrinos have mass.
so anyway could someone tell me if this idea makes any sence.

Eta C
2003-Jun-27, 12:55 PM
While there is some concern about what a neaby supernova would do (and that is still a matter of debate that I won't go into here) the source would not be neutrinos. These particles have an extremely low probability of interacting with matter (a small cross section to use the technical term) since they can only interact via the weak nuclear force. The Earth is continually bombarded by neutrinos that pass through it as if it weren't there. Every once in a while one will interact, but not frequently enough to kill the entire human race via exotic cancers.

As to the comment on energy, even if they have mass, they can have high energy. I think kikisonic is confusing high energy with high velocity. Since we now know neutrinos have mass (but a very small one) they cannot travel at c since only massless particles (e.g. photons) can do that. Nonetheless, a massive particle can have high energy. Witness the 1 TeV protons produced at Fermilab.

Hale_Bopp
2003-Jun-27, 01:44 PM
I seem to recall doing a back of the envelope estimation of the odds of a neutrino interacting with a human. I would have to work through the detials again, but I think I worked out an average person could expect one neutrino to interact with the body in a human lifetime. Remember, this is out of all the trillions of neutrinos that pass through your body each and every second from all sources (neutrinos from the Sun, the Big Bang, and every supernova that has ever exploded in the universe). A single neutrino interaction has miniscule energy.

So one more supernova, even a close one, is not going to change those odds too much (I think we caught on the order of tens of neutrinos for SN1987A in our detectors).

Rob

Grand Vizier
2003-Jun-27, 04:06 PM
I'm afraid, folks, that kikisonic (by the way, welcome to the board!) is not referring to a crackpot theory. I remember New Scientist doing a piece on this paper just after it came out in 1995:

http://tinyurl.com/ffnd


Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce inelastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a conventional model ofthe galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined...

But yes, it seems weird and improbable to me too. And pretty scary - there's no hiding or shielding in the case of neutrinos, you just have to move somewhere else in good time.

<SF>And, if this is true, a neutrino bomb would make the perfect genocidal planetbuster if you want to inherit the infrastructure and (most of) the ecology intact (prokaryotes will not be affected, eukaryotes will be damaged according to the size and complexity of their nuclei, I'd have thought).</SF>

Eta C
2003-Jun-27, 04:17 PM
I'm afraid, folks, that kikisonic (by the way, welcome to the board!) is not referring to a crackpot theory. I remember New Scientist doing a piece on this paper just after it came out in 1995:

http://tinyurl.com/ffnd


Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce inelastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a conventional model ofthe galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined...

But yes, it seems weird and improbable to me too. And pretty scary - there's no hiding or shielding in the case of neutrinos, you just have to move somewhere else in good time.

<SF>And, if this is true, a neutrino bomb would make the perfect genocidal planetbuster if you want to inherit the infrastructure and (most of) the ecology intact (prokaryotes will not be affected, eukaryotes will be damaged according to the size and complexity of their nuclei, I'd have thought).</SF>

I don't buy it. Fermilab has produced a beam of GeV neutrinos since 1973 and I haven't heard of any increased incidence of strange cancers in the Chicago suburbs downstream of the beam (Watch out Schaumburg!). Same goes for CERN near Geneva, BNL near New York and SLAC near San Jose. This also leaves out the continuous flux of MeV range solar neutrinos that have bombarded the earth since its creation. If a supernova is going to zap us, it's from a mechanism besides neutrinos.

dgruss23
2003-Jun-27, 05:04 PM
I don't understand why anybody would be concerned about neutrinos. Look at what scientists have to go through just to detect them. If the solar model is correct then according to one textbook I have 66 billion pass through every cm^2 of the Earth per second. They don't interact readily with normal matter - which is what we're made of.

Grand Vizier
2003-Jun-27, 05:19 PM
I don't buy it. Fermilab has produced a beam of GeV neutrinos since 1973 and I haven't heard of any increased incidence of strange cancers in the Chicago suburbs downstream of the beam (Watch out Schaumburg!). Same goes for CERN near Geneva, BNL near New York and SLAC near San Jose.

OK, I'll play devil's advocate. All quotes from the above citation. First, a near-supernova neutrino flux is going to be many orders of magnitude higher than anything produced in an accelerator:


Collapse models generallyhave difficulty in making stars explode, but predict neutrino fluxes that carryaway most of the binding energy released.

In fact a significant fraction of the stellar mass is irradiated as neutrinos. Given how small they are, this is a lot of the wee beasties. For all we know, a supernova offers a 1:10^6 or higher risk of contracting neutrino-induced cancer compared with being near an accelerator (and I think you'd have to be within a certain angle of the beam, actually), and so, perhaps, *no* accelerator-induced cases have yet occurred (we couldn't identify them at that rate against the background rate, if they did).

Secondly, higher energy particles - you mention GeV neutrinos - are not necessarily the most likely to interact with biological material:


...This is due to the increasing awareness that highlinear-energy-transfer (LET) radiations (alpha particles, fission neutrons,ions) may be responsible for unique biological effects [13-15]. Plainly stated,the (unrestricted) LET is the amount of energy dissipated by a radiation perunit path length.The nucleus of a cell, specifically the genetic material, is far moreradiosensitive than the cytoplasm. Chromosomal change can result frombreaks and other types of damage to the DNA chain, leading to mutagenesis.Of special importance are those radiation insults that create irreparablegenetic damage without inactivating the cell, which then can become the"founder" cell of an aggregation of mutant or cancerous cells. Not all types ofradiation are equally effective in producing important damage at thechromosomal level. Low-LET radiations such as gamma and x-rays dispersetheir energy over longer distances than their high-LET counterparts, whichhave characteristic densely-ionizing tracks. There is now a wide consensusthat the critical property of radiations at low doses is determined by thisspatial pattern of energy deposition over dimensions similar to those of DNAstructures (few nm).

[...]

Several observations are in order. First, the stopping power Stof an ion displays a broad maximum (at ~ 4 MeV for O in water) and it is thereforepossible to have identical values of LET for two very different energies. Thenature of the damage induced may however be quite dissimilar. For instance,the high-energy LET-counterpart of an 80 keV oxygen ion in water is at ~ 200MeV. This is in the energy range generally explored in acceleratorexperiments, where energy losses are almost entirely due to ionization. Thecontribution to Stby direct atomic collisions at lower energies is considerable(see table), and these collisions are of special interest because the energyimparted to an atom is likely to cause disruption of the DNA molecule with amuch higher effectiveness than an equivalent delta-electron producedthrough ionization. This may make neutrino-induced recoils even moreeffective than other forms of high-LET radiation in producing the densedamage responsible for the special biological effects detected.




This also leaves out the continuous flux of MeV range solar neutrinos that have bombarded the earth since its creation.

See above, with regard to accelerators - who knows whether there may not be a risk of 1:million, 1:billion or whatever of cancer from solar MeV neutrinos? We would have no way of isolating such cases from the background cancer rate.


If a supernova is going to zap us, it's from a mechanism besides neutrinos.

I'm inclined to agree. But supposing, for example, a huge neutrino flux didn't act as a dinosaur-killer, but simply doubled or tripled the cancer rate for a generation? That would be a tiny blip in the evolutionary record - but it would certainly be significant for us. Fortunately, it depends on the range, and we have no close supernova candidates right now. It's nice to be able to write off one source of doom easily :)

Eta C
2003-Jun-27, 06:51 PM
I'm thinking about this, but a few comments about the quotes.

The mechanism he's proposing is two stage:
1: high energy neutrino interacts (via weak neutral current) with a nucleon in the body. This causes a high energy ionized particle to be produced.

2: This ion then damages DNA and other organic matter. These are the "LET's" referred to in the article.

It's this second stage that is heavily energy dependent. No one really denies that ionizing radiation can have an effect. The question is whether the burst of neutrinos from a supernova will be intense enough to give a high probability of the first reaction occuring to cause a problem. Given the very small cross section for this reaction, the flux will have to be large.

I've got to do a little research to find the neutrino flux (particles per square cm) from an accelerator pulse, but my gut feeling is that it can be prettly large. Also, don't forget that the SN neutrino flux is attenuated at it travels. Inverse square can be a powerful thing when light years are involved.


So the bottom line questions are:

What is the neutrino flux from a supernova as a function of range?

What is the flux from an accelerator, the sun?

What is the cross section for a neutrino to interact with the nucleus of an atom?

Is this high enough to produce a significant number of LET's and cause cellular damage?

Research in progress. Will get back.

Grand Vizier
2003-Jun-27, 06:58 PM
So the bottom line questions are:

What is the neutrino flux from a supernova as a function of range?

What is the flux from an accelerator, the sun?

What is the cross section for a neutrino to interact with the nucleus of an atom?

Is this high enough to produce a significant number of LET's and cause cellular damage?

Research in progress. Will get back.

Cool - those are good questions. (Also in terms of potential detectable cancers, (I'm guessing at none :wink: ) how directional is the neutrino output from an accelerator, and how many people at the sites mentioned could it affect - that's a hard one, I think) I was about to do some of the same research but have had to get back to work :( (apart from the odd simple post).