Re: Atomic bug bomb!

Erik Max Francis wrote:

Logan Kearsley wrote:

Of course there is- neutrinos can do damage to your body by
transmuting the elements it's made of. You just need a stupidly huge
flux of neutrinos to get a noticeable effect, since absorption is so
low. If you were unlucky enough to be orbiting a star about to go
supernova, for example, the neutrino emissions would probably kill you
before anything else, seeing as how they can escape the core fairly
directly.

Yes, various calculations of the LD50 distance for a type II supernova put it at about ~1-10 au. Given that the neutrino pulse of is about 10^46 J, that puts the LD50 energy (not power) flux at about ~10^21-10^23 J/m^2.

An evaporating micro-blackhole ought to do the trick.

Not sure about that; as a primordial black hole shrinks, its temperature (and radiation power) rises, which means that the spectrum of radiation (including which type of particles) cycles through "heavier" types of radiation. A black hole on the verge of evaporation would likely be emitting the vast majority of its energy in radiation types other than neutrinos. Whether they'd still be enough total radiation to compensate for the shift isn't clear to me.

Actually, even putting aside the change in radiation types, it still wouldn't work if you want a rapid burst.

Take the best-case numbers and choose type II supernova LD50 lethality at 10 au, which, with a 3 x 10^46 J burst of neutrinos, gives an LD50 energy flux of 1 x 10^21 J/m^2 as a short-term, whole-body dose. To make it 100% lethal, you'll have to crank it up quite a bit. Say it only requires ten times as much, or 1 x 10^22 J/m^2.

Position your death hole near the surface of the Earth to minimize the distance to everyone on the planet; now the radiation emitted by the black hole has to be lethal at 12.7 Mm. Therefore, the neutrino pulse from the black hole has to be 2 x 10^37 J.

Black holes convert their mass-energy into Hawking radiation, so that means you need a black hole with a mass of 2 x 10^20 kg. But we need to catch the black hole as it's evaporating -- or, more specifically, make sure that for a relatively short period of time (since it's a short-term dose) it emits enough energy in the form of neutrinos to get the correct dose. But a black hole with a mass of 2 x 10^20 kg would only be emitting Hawking radiation at a rate of 2 x 10^12 W and wouldn't evaporate for another 7 x 10^44 s = 2 x 10^37 yr (power scales as 1/m^2; evaporation time scales as m^3)! And, of course, we haven't even addressed the issue of the radiation spectrum changing -- not all of its radiation will be in neutrinos.

So no, a primordial black hole evaporating nearby won't work.

--
Erik Max Francis && max@xxxxxxxxxxx && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis
Laws are silent in time of war.
-- Cicero
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