This app simulates the trajectories of nearby asteroids that are potentially dangerous to Earth. You can watch in real time where they are, were, or will be at any given time.
All trajectories of the asteroids shown here are based on real data from NASA's Near Earth Object Program:
http://neo.jpl.nasa.gov/

This version includes data from all asteroids known by NASA whose trajectory comes closer than 0.02 AU to Earth's orbit, and which size is larger than 50m in diameter, for a total of 1121 asteroids.
Notable asteroids:
- 16960 (1998 QS52)
- 3200 Phaethon
- 2201 Oljato
- 4179 Toutatis
- 1981 Midas
- 85713 (1998 SS49)
- 177049 (2003 EE16)
- (2000 TU28)
- 216985 (2000 QK130)
- 99942 Apophis
- (2007 TU24)
- (1997 XR2)
- 292220 (2006 SU49)
- (2004 TN1)
- 2007 VK184
- And over 1000 more!

Besides the asteroids, you can also watch the following planets:
- Mercury
- Venus
- Earth
- Mars
- Jupiter

NOTE: Asteroid trajectories are inherently unstable, so they are difficult to predict far into the future. The trajectories calculated by this app cannot be considered 100% accurate, particularly for dates far into the future.