Have you ever thought about that the Earth might collide with another planet? Because it seems to be possible for planets in a stable solar system to somehow get off track and run into each other.

Scientists at UCLA and Tennessee State University noticed a strange ring of debris and dust orbiting a star.  They thought at first that the star was young--only a few million years old--but then realized that it was billions of years old, like our sun.

So given the star's age and the distance of all that dust and debris from the star, that stuff should have coalesced into planets by now or been blown away into space.  So the theory is that the debris was caused when two planets collided and blew each other to bits.

Actually, many scientists think that when the earth was about a million years old, it collided with a body about the size of Mars, and that the resulting debris came to form our moon. So if we're ever struck by another planet, maybe Earth will get another moon.

Unfortunately, nobody would be around to see it.