writing a sci-fi and need some help with the sci-part... i'm all fi. so, it's not really about the science, but... sci-fi doesn't always need to be fact, of course, but i'd like to have something at least remotely plausible... thus, the loooooong stream of questions. scientists, please excuse my un-scientiness. 1. how long after world-wide nuclear war would the radiation still be present at dangerous levels? 2. if a giant volcano erupted (the yellowstone one?), would it essentially throw the whole world into darkness? and how long until 'the dust' settles? (if someone has a quick link to what exaclty could/would happen if that giant volcano erupted, let me know) 3. what world-wide event could essentially leave the earth in a state of untoxic (but technically low in oxygen because of lack of plants) air with a continuously black sky (blocking sun so there are no plants but possibly still the possibility of noticing the sun behind the clouds) for ever and ever and ever or at least a few hundred to a thousand years? 4. radiation causes interference, right? what else would make radio/walkie-talkie/computer/advanced technologies stop working? would they work again after the radiation goes away? basically, what can happen to make intelligent devices or long-distance communications (radio) stop working forever? as you might tell, basically i want to make my story where people can still live healthy, but have reverted back to simple machines with no prospects of redeveloping said devices. any help would be greatly appreciated. thanks in advance!