When comparing worst-case scenarios, we often think of the ultimate worst-case scenario as being that the universe blows up. Earth getting hit by a giant meteor or asteroid would probably be a close second.
I was certainly quite relieved earlier this week to hear that NASA lowered Earth's chances of getting hit by an 885-foot asteroid. Newly discovered in 2004, 99942 Apophis (original name was 2004 MN4) seemed to have a chance of hitting Earth (or the Moon) in 2029. Then again in April of 2036, scientists had calculated a 1 in 45,000 chance that Apophis could strike Earth. However, luckily for us, that threat has now been lowered to a 1 in 250,000 chance. Some day down the road, we're all going to be hearing about the Torino Impact Hazard Scale. Level 1 would indicate a very small chance of the worst-case scenario. If they start talking about the Level 4 threat level, we all might as well start partying like there's no tomorrow. In the meantime, let's send out some space probes that will put tracking devices on these annoying asteroids.