We can only live on earth because we have many things that other planets don't. For example were not so close to the sun like Mercury that it is so hot but were not far away from the sun like Neptune...
Nobody lives "in" the Earth (except possibly miners and cave dwellers), but many live "on" the Earth.As of August 2011, the estimated world population was 6,957,690,528.(nearly 7 billion, the...