Asteroids are one of the most serious threats to life as we know it, but scientists have gotten pretty good at predicting exactly when and where the dangerous rocks will appear.
One massive space rock, called 99942 Apophis, is going to make a very close pass of Earth in 2029, and that flyby could determine the fate of our planet in the not-so-distant future.
Astronomer Alberto Cellino told Astrowatch, "We can rule out a collision at the next closest approach with Earth, but then the orbit will change in a way that is not fully predictable just now, so we cannot predict the behavior on a longer timescale."
The flyby in 2029 will be within 20,000 miles of Earth, which is close enough that the gravity of Earth is expected to alter the path of the asteroid in such a way that predicting its future passes will be much more difficult.