There is a concept called quantum immortality, which many of you may have heard of. In brief, it suggests that nothing as such does not exist and an observer is always necessary as a fundamental element of the universe. It also says that, because the observer is essential, it cannot ever truly experience its own death - it will always find itself in a universe in which it survives. (This gets bastardized to mean souls etc., but it has nothing to do with souls and everything to do with probabilistic outcomes).
Which produces more questions than answers. Say that Lisa takes up smoking because of peer pressure from her friend at the age of seventeen. She dies at the age of 57 of lung cancer. If quantum immortality holds good, does this mean she simply never actually dies from the cancer? Does she find herself always in a world just before she develops n the cancer? Before she starts smoking? Before she meets her friend?
Johnny gets into a car accident at the age of 30. Does he therefore find himself in a world where he turns left instead of right? Where he doesn't get his license? Where cars are not invented? A world where he ends up as a vegetable in a hospital until technology is invented to heal him?