Those estimates typically confuse the 10^100 upper bound on the number of atoms in the universe with 2^100. The 2^128 number of addresses in IPv6 is clearly m

Those estimates typically confuse the 10^100 upper bound on the number of atoms in the universe with 2^100. The 2^128 number of addresses in IPv6 is clearly more than the latter, but dwarfed by the former. There are roughly 10^40 or so atoms in the universe per IPv6 address; by mass that's approximately one address for each combined biomass of earth. Earth mass divided by 2^64 is roughly 357 tons. There are roughly 2^33 humans on earth, so 2^64 is "only" a billion or two addresses per person; tha's far fewer addresses than the number of human cells out there.