128 bits is enough to allocate 170 unique addresses to every milligram of matter in the Solar System (~99.9% of which is the Sun, about 2 * 10^33 grams). I thin

128 bits is enough to allocate 170 unique addresses to every milligram of matter in the Solar System (~99.9% of which is the Sun, about 2 * 10^33 grams). I think that's a more useful measure than the volume of the Solar System, which after all is mostly empty space. After all, what's the smallest (lightest) device which can benefit from having its own IPv6 address?