For anyone who wants to learn more (and
why am I reading this stuff when I have a bunch of homework to do!) the EPA has a very good introduction to the subject
here. There's a lot of cool information there, and I've only read a couple of pages of it (sorry but way too busy!), but the key takeaway I think is that probably the
worst possible size for our grief nanoparticles is 1-2 microns, as you start getting into the realm of Rayleigh scattering and the scattering efficiency starts to go up relative to the mass/volume of the particulate matter. 2.5-5 microns seems to be a bit better, but what we really want to do, I think, is break our Grief down until it hits the molecular or atomic scale.
Once you get down to the nanometer scale, as far as I can tell Grief particles will basically affect visibility about as much as free air does. On the other hand, at that point you need to start paying attention to the concentration of particles in the air, because our Grief particles will basically be
displacing the air, and if we displace too much air then the people around us (and cars, and plants, and open flames, and everything else that uses air to breathe) will start to asphyxiate.
So, let's assume that we've broken our particles down to say 1 nanometer diameter spheres, each with a volume of 5 10
-28 m
3. Now, air can normally hold roughly a mole (6.02 * 10
23) particles per 22.4 liters; the total volume in our 100-meter radius hemisphere is 2094395 m
3 which is ~2.1*10
9 liters, thus we can hold 5.6*10
31 particles. Now, I for one would rather only displace say 1% of the air at the
most: this will give us a total cloud capacity of 5.6*10
31 * 0.01* 5 10
-28 ~= 1,200 m
3 of 1-nanometer spheres of Grief. We can also add in a few 5-micron spheres, as those seem to hit another local minimum in terms of scattering efficiency, but I'll leave that as an exercise for someone else.
Someone mind checking my math and my assumptions?
