I'm not sure how much this has been covered on this board, but I have a few questions regarding the hypothetical doomsday scenarios involving the LHC. 1) I've heard that mini-black holes could be created at LHC, but that they are supposed to evaporate. How can we be sure that they will? Is it because there are numerous mathematical independent derivations of Hawking radiation? Is it because they are virtually demanded to be unstable by the laws of thermodynamics and QM? Is there any difference between the ones created in the lab and the ones created by cosmic rays? 2) Is there any evidence for strange matter in the universe? 3) Is the metastability of the vacuum speculative? Is there any evidence for or against it? People have argued that, because cosmic rays have been colliding for billions of years, they would have already triggered a transition to a true vacuum, and we wouldn't be here. Does this mean that the vacuum is not metastable? Could mankind ever trigger such a disaster, perhaps by making collisions more powerful than those found in nature? It's just that these scenarios have got me a little worried. Not necessarily because I'm afraid they will happen, but simply because they are possible. Please keep in mind that I know very little about theoretical physics or QM in your response. Thanks.