Tegmark then assumes that our observable Universe (the Hubble volume) has a diameter of 8x1026
m, and that a nucleon measures 2x10-13
m across, which gives the Universe a capacity of around 10118
nucleons, and therefore allows for 210118
possible ways of filling a Universe-sized space with nucleons. Small matters of cube roots and the diameter of the Universe are insignificant in the face of such a huge number, so he comes out with a final distance between identical copies of our Universe of (about!) 1010118
Similar reasoning leads him to suggest that identical copies of human beings are separated by about 101028
m, and that within 101092
m there is a volume of space 100 light-years in diameter which is identical to our own local space.