Image credit: NASA
This sounds like something from a science fiction movie, but it is a real threat to the whole planet. It can happen any time. A medium sized asteroid of a few kilometers in diameter crashing into the Earth can completely destroy our civilization and exterminate the whole human race, just like it happened to the dinosaurs.
But fortunately there are some ways to prevent all this. The human race is at the point that it can prevent it’s own extinction. There are numerous ways of deflecting such an asteroid to a safer orbit, but it has to be spotted years before potential impact, otherwise nothing can be done. Therefore, the world’s governments should fund research programs to track all asteroids that can be a potential threat. In such hard economic times this doesn’t look like it’s a priority to most governments, but it should!