If you can explain these things. . .

... then go to the head of the class, because it seems that no one else can.

Some of the cases wander off toward tinfoil hat territory, but most are pretty solid. But here is one that seems to have been solved:

As it turns out, three percent of Americans say they have had a NDE, which is about 10 million people - not a small number at all. But not all of them were dying at the time; such experiences are known to occur in people suffering from Parkinson's Disease, for example. LiveSceience explains,

A variety of explanations might also account for reports by those dying of meeting the deceased. Parkinson's disease patients, for example, have reported visions of ghosts, even monsters. The explanation? Parkinson's involves abnormal functioning of dopamine, a neurotransmitter that can evoke hallucinations. And when it comes to the common experience of reliving moments from one's life, one culprit might be the locus coeruleus, a midbrain region that releases noradrenaline, a stress hormone one would expect to be released in high levels during trauma. The locus coeruleus is highly connected with brain regions that mediate emotion and memory, such as the amygdala and hypothalamus.

In addition, research now shows that a number of medicinal and recreational drugs can mirror the euphoria often felt in near-death experiences, such as the anesthetic ketamine, which can also trigger out-of-body experiences and hallucinations. Ketamine affects the brain's opioid system, which can naturally become active even without drugs when animals are under attack, suggesting trauma might set off this aspect of near-death experiences, Mobbs explains.

Finally, one of the most famous aspects of near-death hallucinations is moving through a tunnel toward a bright light. Although the specific causes of this part of near-death experiences remain unclear, tunnel vision can occur when blood and oxygen flow is depleted to the eye, as can happen with the extreme fear and oxygen loss that are both common to dying.

Altogether, scientific evidence suggests that all features of the near-death experience have some basis in normal brain function gone awry. 

So maybe the solution to the other mysteries is not far away, too.