Asteroid Buzz

You probably didn't notice but two small asteroids came close to Earth on Wednesday. (http://www.nasa.gov/topics/solarsystem/features/asteroid20100907.html). 

Their orbit took them within the moon's orbit of the earth. Small means 10 to 20 m in diameter.

 Image credit: NASA/JPL-Caltech

This apparently happens all the time but until recently we didn't know. The rate of asteroid detection has escalated recently as shown by this movie:

Asteroid Discovery From 1980 - 2010

Most of those asteroids are pretty far from Earth, but there are a lot  too close for comfort.

Ignorance was bliss.

PS: This will not be on the exam.