You are cleaning up in the machine shop when they fire up the reactor for the first time. This is an arcane new design that uses an artificial monopolar magnetic field to extract energy from weak force interactions. The reactor is right next to the machine shop, beyond a nine-foot-thick wall of lead and concrete. The reaction immediately starts to produce heptogazillionwads of neutrinos of all flavors, which, naturally, pass right through the shielding and hence through you.
The question is, would you notice anything from being bathed in a super-intense flux of neutrinos? Is there a level (density) at which they simply cannot avoid interacting with normal stuff in an observable way?
Obviously, if you have enough of them, you’ll get reactions. It’s just that, for neutrinos, “enough of them” is such a ludicrously large amount that you’d never expect to actually have anywhere near that many.
On the other hand, if you have a large (but realistic) number of neutrinos, and a large (but realistic) amount of target mass, then you can get some measurable effects. I’ve seen estimates, for instance, that one or two people on the planet might have “seen” supernova 1987a via neutrinos interacting with their eyes (it would have looked like a momentary pinprick of light).
I understand that in a type II supernova, during core collapse, a very short, intense burst of neutrinos is produced, and that this burst is high intensity enough that the pressure exerted by it can not be ignored in the modelling.
So yes, there is a level of neutrino flux that you could “feel” (and there’s probably a lower level that would cause fatal damage).
Yes; a large enough number of neutrinos will kill you in fact. However, we’re talking about far more neutrinos than a reactor could put out.
A supernova on the other hand produces enough neutrinos to kill a human who is as far away as one of the gas giants; “as far away as Saturn” I’ve heard.
That’s a lot of neutrinos. Apparently most of the force of a supernova’s explosion is generated by the tiny proportion of neutrinos that do happen to interact with the matter of the star.
Over 10% of a stars mass is more than you’re getting out of a reactor though, obviously.
The What If? column at XKCD tackled the supernova version of this question a while ago. Summary: if you were about 2 AU from a supergiant star that went supernova, the neutrino flux would be enough to give you acute radiation poisoning. Presumably, the reactor would have to have a similar level of neutrino flux in order to kill you.
Of course, if you’re that close to a supernova, you’re going to get a lethal dose of plenty of other things, too. The neutrinos might get you first, but it doesn’t matter much if the gamma rays or charged particles were just going to kill you a second or two later.
Hang on though. If there’s enough neutrinos that they’re going to interact with you, surely a monstrous number of them will interact with the planet first? The planet’s many orders of magnitude bigger than you are.
Oh yes, the neutrinos will fuck up the planet. But it still won’t be blocking more than a trivial fraction of the neutrinos. There will be more than enough getting through to the other side to fuck you up as well.
Some of those stars already have a radius in excess of 2AU. How do you define the distance to an object that has a difficult-to-define surface? If you decide to use the centerpoint of its sphere, that works at a ly, but at 2AU, you may find yourself inside the photosphere. At that distance, even scrith might not be enough to save you.
Well, every star has a difficult-to-define surface, including the Sun. It’s true that some stars are far larger than the Sun is, and might have a radius of more than 2 AU, but that doesn’t mean that you couldn’t define a distance of 2 AU past a nominal surface.
No matter what the size of the star might be, though, I insist that you and the star are equally distant from one another. Any point on the star you are measuring from is x distance away from any point on you, and vice versa.
I think that of all the astronomically massive things that live out in astronomyland, supernovae really take the cake.
To think that almost all the energy is ejected as neurtinos rarely interacting with normal matter and yet gives a huge explosion visible halfway across the universe… Truly staggering!
Also, I understand most of the glow we see is decay of radioactive cobalt and nickel (created by neutrino interactions, I presume). So what we have is a giant glowing radioactive cloud, visible halfway across the universe, which itself only represents a tiny fraction of the ejected energy. :eek:
The neutrino dose received by someone standing 50 feet from a 4-GWth nuclear reactor is about six hundred million times smaller than the average background dose from all sources at sea level.
That same person would get a neutrino interaction in his/her body about once every minute.
For supernovae: as leachim and others noted, neutrino interactions are thought to be central in supernova dynamics. They transport energy and momentum from the inner core to the outer material, and this neutrino-driven convection could provide the kick necessary to keep the explosion from stalling. This is still uncertain because as of today, no one has been able to get a supernova to explode in simulation. Neutrino-based explosions have been realized in 1D and 2D cases (that is, systems with imposed spherical or azimuthal symmetry), but fully 3D cases still stall out.
Unrelated to the explosion mechanism issue, the neutrino density gets so high in supernovae that neutrino propagation and flavor evolution is significantly modified by the presence of other neutrinos. That is, neutrino-neutrino interactions become important.
And as I recall, the energy released by colliding black holes is in the form of gravity waves. So make it the energy of 100 million* invisible* supernova.
Which begs the question: Supposing you had a magic shield that blocked all forms of radiation except gravitational waves (and also magically dissipated all of the energy and momentum absorbed in the blocking), how close could you get to that without getting fucked up?
That depends on the mechanical stress the human body can tolerate, which is something I’m not sure of. But at a first-order rough estimate, the relative stress will be approximately equal to one over the distance in hole-radii. That is, if you’re 10 radii away, you’ll get stresses of approximately 10%, and if you’re 100 radii away, you’ll get approximately 1%.