yes this is true, but in a few years hopefully we will know where all the meterorites are (right now i believe the United states is the only country with scientist watching the skys looking for this type of thing, but they dont know the paths of all of the ones out there yet). And hopefully if this ever happends we will have buiilt sometype of space tugboat type ship and it will be able to grab on and then fire its jets and tug that rock saftley outta the path with the earth.