Anyone who has ever looked at the stars on a dark night has, at times, been awe-struck by their vastness and the greatness of space, yet only twelve men in history have been privileged to stand on the moon and look back towards the blue planet, as Earth has been described.  Standing on the surface of the moon, the Earth is some 229,000 plus miles away, and, according to Jim Irwin, one of those 12 who saw it from that perspective, the Earth appears to be the size of a walnut.