... do they really happen ?... well, the short answer is 'yes' ;)
One-in-a-million miracles happen, on average, 295 times per day in America alone, says Michael Shermer in this months’ Scientific American “Skeptic” column.
“I cannot always explain such specific incidents” Shermer writes, “but a principle of probability called 'the Law of Large Numbers' shows that an event with a low probability of occurrence in a small number of trials has a high probability of occurrence in a large number of trials”.
Shermer explains how, in their book ‘Debunked !', physicists Georges Charpak and Henri Broch present the application of probability theory to ‘miraculous’ events in an unusually enlightening way:
In the case of death 'premonitions', suppose that you know of 10 people a year who die and that you think about each of those people once a year. One year contains 105,120 five-minute intervals during which you might think about each of the 10 people, a probability of one out of 10,512 - certainly an improbable event.
Yet there are 295 million Americans. Assume, for the sake of our calculation, that they think like you. That makes 1/10,512 X 295,000,000 = 28,063 people a year, or 77 people a day for whom this improbable premonition becomes probable.
With the well-known cognitive phenomenon of confirmation bias firmly in force (where we notice the hits and ignore the misses in support of our favorite beliefs), if just a couple of these people recount their miraculous tales in a public forum, the paranormal seems vindicated. In fact, they are merely demonstrating the laws of probability writ large.
The full article is fascinating, and can be read here: Link