Though it may happen only once up to every 100 years, as estimated by the European Space Agency (ESA), the meteor airburst that generated a huge shock wave over the Russian city of Chelyabinsk last week served as an unexpected and explosive reminder of how little control humans have when it comes to our world and our universe.
Although the impact was large on a local level, injuring nearly 1,500 people and causing an estimated $33 million in damages, the impact was, as Discovery News' Ian O'Neill describes it, a cosmic flesh wound. Gone undetected, a larger body would have caused significantly more damage.
Even if there were a larger object headed toward Earth that posed a significant risk to a large number of people, and even if we could detect it, there is nothing tested and proven effective that we could deploy to mitigate that threat.
Threats from space aside, we really don't need to look beyond our planet for other reminders of how easily nature can turn against us, and there's not a whole lot we can do to push back.