==Example of the size of the IPv6 address space== 
 Here is one visualization. Imagine that the entire range of IPv4 address, 232 is represented by a typical human hair having a mean diameter of 70 μm. (There is a reference given on the human hair article which uses 70 to 80 μm as a typical experimental value.) Now, suppose we represent the size of the IPv6 address space in the same manner. Since there are 2128 addresses, we can see quickly that our example requires a distance of 296 x 70 μm. This is an enormously long distance. It is so long, in fact, that we need to convert it to light years for convenience's sake. 

 Assume  

  586,000,000 light-years 

 This is 10 times farther than it is to the center of the Virgo Cluster, which is nearby galaxy cluster. So if IPv4 is a hair on your head, then IPv6 is tantamount to the distance traveled by light in 586 million years.