Our Mathematical Universe: My Quest for the Ultimate Nature of Reality

by Max Tegmark

Quantum mechanics limits the variety even at a fundamental level. As we’ll explore in the next two chapters, quantum mechanics adds a sort of intrinsic fuzziness to nature that makes it meaningless to talk about where things are beyond a certain level of precision. The result of this limitation is that the total number of ways in which our Universe can be arranged is finite. A conservative estimate, erring on the high side, is that there are at most possible ways in which a universe the size of ours can be arranged.1 An even more conservative bound, known as the holographic principle, says that a volume the size of our Universe can be arranged in, at most, ways.2 Otherwise, you’d have to pack so much stuff into it that it would form a black hole larger than itself.