There's only one group of people who really know what happens when you die: the dead. And since the dead won't be revealing their secrets anytime soon, it's up to scientists to explain what happens when a person dies.
Death, just like life, is a process, scientists say. The first stage of this process is known as clinical death. It lasts from four to six minutes, beginning when a person stops breathing and the heart stops pumping blood. During this time, there may be enough oxygen in the brain that no permanent brain damage occurs. Other organs, such as the kidneys and eyes, also remain alive throughout clinical death.
In the second stage of dying, known as biological death, the cells of the body begin to degenerate, and the body's organs — including the brain — shut down. Doctors are sometimes able to stall biological death by inducing hypothermia — cooling the body to below its normal temperature. This method can stop the degeneration of cells and has been used to revive cardiac-arrest patients.
These stages of death are well understood, but what remains elusive is what happens to a person once he or she is both clinically and biologically dead. To get some insight into this mystery, researchers turn to the study of near-death experiences (NDEs).
According to the Out-Of-Body Experience Research Center in Los Angeles, more than 8 million Americans have reported NDEs, which occur when a person is either clinically dead, near dead or in a situation where death is likely or expected.
Many people who have had near-death experiences report similar sensations: feeling as though they were floating outside of their bodies, moving rapidly through a tunnel toward light or seeing deceased loved ones.
Researchers continually study NDEs in an effort to make sense of the biological and neurological processes that may be behind such events. Some studies claim that NDEs are just another form of lucid dreaming, while others link these experiences to oxygen deprivation in the brain.