NASA is very confident that the world is not going to end on December 21, 2012 (as the Mayan calendar doesn't end on that day either), regardless of what some doomsayers are saying. The Mayan calendar is not predicting the end of our world on 12/21/2012, and a rogue planet isn't going to collide with Earth on that day either.
Further, other gloom-and-doom events are not being predicted by scientists for Earth on 12/21/2012. As far as professional (credible) scientists are concerned, that day -- December 21, 2012 -- will be just another day on our Gregorian calendar.
Yes, there is always a chance, on any given day, that a meteorite will hit Earth. Small ones go through our atmosphere all the time, and some of them even survive their fiery plunge to land on our surface.
Yes, indeed, there is always a possibility that a celestial body large enough do to harm to our planet will impact Earth at some time in the future. However, scientists are tracking such bodies and one large enough to actually do harm to Earth would be on the radar of these scientists.
As the NASA/YouTube video states, we don't need to talk with a scientist to verify this. We can do it ourselves. No foreign object appears in the sky, so no object is about to impact our world. It's as simple as that.
Recently, NASA scientists made a video called "Why the World Didn't End Yesterday". It is provided above and on YouTube (http://www.youtube.com/watch?v=2wimiRUHMI4).
It was meant to be released on December 22, 2012, after all of the hype about the doomsday predictions are over.
I'm guessing it was released early to calm fears in some people, just like the iTWire article Manufactured fantasy: 12/21/2012 Mayan doomsday prediction was written on December 4, 2012, to identify the concern NASA has, along with other scientific organizations and individuals, about the invalidity of these doomsday predictions.
Page two concludes.