Assuming an asteroid is on an imminent collision course with Earth, there are a number of ways we might prevent it. The asteroid could be slowed down, sped up, or by slightly changing its trajectory just enough so that it does not intersect with Earth’s orbit when and where Earth happens to be.
Humanity faces a variety of natural disasters on a daily basis. Volcanoes, earthquakes, hurricanes, and tornadoes claim the lives of roughly 60,000 people every year. And a major disaster – such as a supervolcano eruption – could threaten the continued existence of mankind altogether.