WongKy said:
In theory this wouldn't destroy the earth, though it would cause massive death...it might not even wipe out all life on the planet even.
If done right, it could "bump" the earth out of it's current orbit at least a bit though, which could possibly end all life at least. Rememeber, the moon only has a bit over 1% of the mass of the earth. Hitting the earth with the moon would need to be done at precisely the right time to cause any change in it's orbit around the sun (if it's even possible at all, considering the moon is already in orbit around the sun as well, so the differences in speed would not be that great).
If you could reach out and grab the moon, pull back further into our solar system and then throw it at the earth, then you would probably get a decent reaction. But, if you simply used some method to change the moons orbit so it eventually degraded and collided with the earth, not only wouldn't you destroy the planet, but you might not even destroy all life on the planet either.
But......without the moon, the tides would not be nearly as strong as we currently have. I believe the sun would still cause there to be some tides, but I'm not sure if it would be enough to prevent stagnation and eventually kill off life in the oceans (which would eventually cause the planet to be unable to support life more then likely).
Add in the fact that a collision with the moon would throw up so much dust we would have probably very little sunlight getting through for many years, and all life might indeed be destroyed by collision with our moon.
Plus the wolves would be upset.