I thought this was an interesting analogy for the IPV6 Address Space:
Putting the contrast into perspective, if one IPv4 address was one picometer (one trillionth of a meter) long, the entire IPv4 address space would be approximately 4.3 millimeters long–the length of an average-sized ant. If an IPv6 address were one picometer long, the length of the entire IPv6 address space would be approximately 3.4 billion trillion trillion kilometers, or 36 billion light years. The farthest visible object in the universe from the Earth is estimated to be 30 billion light years away. That's a very long distance; that's a great many IP addresses.