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 eva****ating 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 eva****ation 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 ****ft 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 eva****ating -- 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
eva****ate for another 7 x 10^44 s = 2 x 10^37 yr (power scales as 1/m^2;
eva****ation 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 eva****ating nearby won't work.
--
Erik Max Francis && max@[EMAIL PROTECTED]
&& 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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