Quantum Immortality

Following the conception and development of quantum mechanics, scientists proposed an idea based on it called quantum immortality. It boils down to this: No matter what sort of life-threatening situations you encounter, you'll never die. This is because of the “Many Worlds” hypothesis: You'll stay alive because there's always another timeline in which you didn't die, so your consciousness will continue on in that timeline. By extension, the people who die from your perspective are still alive and even conscious, just in an alternative timeline.

It sounds pretty cool, doesn't it? Of course, this is something of a simplification. You have to take into consideration that such dangerous situations don't have binary outcomes – it's not a simple “live or die” division. For instance, you can either die in or survive a car accident, but there are many different shades of the survival: You could be uninjured, or have some cracked ribs, or break an ankle, and so forth. The hypothesis doesn't guarantee that you'll be uninjured and in good health – it only promises that you'll be conscious and alive.

Then again, the definition of consciousness is kind of fuzzy. Are hospital patients stuck in a persistent vegetative state conscious? Sometimes they show neural activity that looks an awful lot like that of awareness and conscious thought. There's also locked-in syndrome, in which the patient can be verified as conscious, but they're paralyzed and can't move at all save for their eyes, and even that may be impossible if it's total locked-in syndrome. There are some unfortunate “survivors” of accidents and disease that end up in states like those; that said, they're still alive and conscious.

But don't worry – it's only a hypothesis, right? Besides, you can always write out a living will specifying to be taken off of life support should you fall into a vegetative state. Your next of kin would undoubtedly remain rational in such a situation, and would coolly choose to respect your living will instead of pleading for the hospital to bring you back to them, to keep you alive, and to save you at any cost. They'd never do something that selfish, right? Either way, even if we assume the worst – that the hypothesis is valid – then all you'd have to do is avoid injury and neurodegeneration for... well, all of eternity. That shouldn't be too hard.