Earlier this month humanity witnessed something most of us would never dreamed of witnessing before--a 10-tonnes spacerock smashed into Chelyabinsk, Russia, injuring thousands.
But why didn't NASA do anything to prevent the crash? We have employed highly-sophisticated telescopes on earth as well as above us, in the sky, and we have literally thousands of eyes peering at the sky at all time. So why didn't anyone spot that piece of rock? Physicists have been discussing methods of avoiding giant-dino-killing-asteroids for decades, and yet this event acts as a grim reminder that we're not entirely ready to face the inevitable.
Currently the responsibility of spotting giant killer asteroids rests upon the shoulders of United Nations Committee on the Peaceful Uses of Outer Space. It composes of scientists from NASA, the European space agency and the world's other space agencies.
But who do you think should be in charge of defending earth against asteroids? Or better, invading aliens?