Clinically, we understand death to mean the state that takes hold after our hearts stop beating. Blood circulation comes to a halt, we don't breathe, our brains shut down—and that's what divides the states we occupy from one moment (alive) to the next (dead). Philosophically, though, our definition of death hinges on something else: the point past which we’re no longer able to return. Those two were more or less the same until about 50 years ago, when we saw the advent of CPR. Today, someone’s heart can stop and they can be dead, and then they can come back.
Modern resuscitation was a game-changer for emergency care, but it also blew apart our understanding of what it means to be dead. Without many people returning from the dead to show us otherwise, it was natural to assume, from a scientific perspective, that our consciousness dies at the same time as our bodies. Over the last few years, though, scientists have seen repeated evidence that once you die, your brain cells take days, potentially longer, to reach the point past which they’ve degraded too far to ever be viable again. This does not mean you're not dead; you are dead. Your brain cells, however, may not be.
“What’s fascinating is that there is a time, only after you and I die, that the cells inside our bodies start to gradually go toward their own process of death,” Dr. Sam Parnia, director of critical care and resuscitation research at New York University Langone Medical Center, told Newsweek. “I’m not saying the brain still works, or any part of you still works once you’ve died. But the cells don’t instantly switch from alive to dead. Actually, the cells are much more resilient to the heart stopping—to the person dying—than we used to understand.”
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