A hazard is an event which imposes a threat of damage and destruction on life and property. In MEDC's particularly, there are several methods in place to reduce the destructive impact of a hazard. Prediction of hazards, education of the people at risk and building restrictions on vulnerable areas all contribute to lessen the number of deaths, casualties and destruction when the hazard strikes. But what type of hazard? These preparations are effective but only on relatively small scale hazards, for example an earthquake. If an earthquake can be predicted early enough the area can be evacuated, if the people have been educated they will know how to react in this situation and a minority of properties will be damaged if building restrictions have been imposed to prevent any construction along the fault line. But what happens if a larger more destructive hazard, for example, a comet was...