Asked by: Anon
If we disregard a religious afterlife, physical immortality means not succumbing to disease, old age or trauma. It’s entirely plausible that we might eventually have cures for all the diseases around today, but new diseases will emerge. We can’t eliminate all bacteria and viruses because they’re a fundamental part of the ecosystem, but organisms that are benign today might mutate into something more harmful in the future. Avoiding ageing is harder.
The mechanisms that program our cells to die have evolved as a necessary part of running a multicellular body. Without programmed cell death, you have cancer; with it, you grow old and die. There are some organisms that don’t appear to age: tardigrades, for instance, or the jellyfish Turritopsis nutricula. But it’s limited to simple organisms; vertebrates can’t do this. But even with cures for all diseases and perpetual youth, physical trauma will get us all in the end. If you don’t get hit by a bus, you’ll be swallowed up when the Sun becomes a red giant, or dissipate when the Universe cools below the energies required to keep electrons and protons together.