Another way of thinking about it:
* Stars in the Milky Way: 400 Billion
* Galaxes in the universe: 2 Trillion
So (4x10^11)x(2x10^12)=8x10^23 stars in the universe.
* Size of IPv6 address space: 3.4x10^38
Find the ratio between addresses and stars:
* 3.4x10^38 / 8x10^23
IPv6 offers about 430 trillion times more addresses than estimated stars in the universe.
From Tom Coffee's presentation "An Enterprise IPv6 Address Planning Case-Study"