The book Permutation City explores some concepts of immortality that would be immune to the heat death of the universe. In the book consciousness does not have

The book Permutation City explores some concepts of immortality that would be immune to the heat death of the universe. In the book consciousness does not have to be chronological in time or on any specific biological or synthetic hardware. It just has to be encoded in a physical state somewhere, and the next state can be anywhere else in time or space. One example is a person who deliberately set their consciousness on a loop, doing his favorite activity, climbing a skyscraper too tall to see the bottom or the top. Permanent flow state, not quite sure how long he has been climbing, feeling an adrenaline high. It may seem like a boring life, but for that person it's indistinguishable from a normal life that happens to be doing that action in the moment.