Prophecies and Probabilities

Since I normally do my weekly blog post at the weekend, it just occurred to me that this is my last opportunity to jump on the Mayan Prophecy bandwagon. The basic idea is that the world is going to end on Friday (21 December 2012), because more than a thousand years ago a Central American civilization called the Maya said that’s what would happen. Most of what I’ve read on the subject has been debunking the idea, with a lot of effort being put into proving that the Maya never actually said the world would end on Friday. This is really funny, because it suggests that if the Maya had said the world would end on Friday, then there would be serious cause for alarm, but actually it’s okay because they didn’t.

The Maya were a sophisticated and clever culture – they built pyramids like the one on the right, for example (photo courtesy of Paul Jackson). But history is filled with sophisticated and clever cultures. In the Western world, ancient Greece and Rome have been revered as paragons of wisdom and insight since the late Middle Ages. During the 18th and 19th centuries, other ancient civilizations were added to the cultural pantheon: Egypt, India, China and several others. But not the Maya. The idea that the teachings of the Maya should be heeded above all the others is (to put it politely) of recent manufacture. The most catastrophic event in Mayan history was the coming of the Spanish conquerors in the 16th century, which resulted in the near-total obliteration of their cultural heritage. If they didn’t foresee that clearly enough to prevent it, why believe their powers of prophecy are better than anyone else’s?

Anyone who wants to take the Mayan Prophecy seriously needs to explain why the Maya—of all cultures—got it right when no-one else did. And there’s a bigger thing they need to explain – why anyone should believe that a date-specific prophecy made more than a thousand years ago is going to come true. There simply isn’t a precedent. In the whole of history, date-specific prophecies of disaster conspicuously fail to come true.

There’s a reason for this. Macroscopic physical processes are probabilistic, not deterministic. You can’t predict when catastrophes will happen, because even the catastrophes themselves don’t know. There are plenty of big disasters that will happen, with certainty, at some point in the future – even “apocalyptic” disasters on a scale greater than anything in recorded history. A supervolcano, or a massive geomagnetic storm—particularly if coupled with a weakening of the Earth’s magnetic field—could destroy the infrastructure that holds the modern, high-tech world together. That might not literally be the “end of the world”, but it would be the end of civilized society. Events like that have happened before in Earth’s history, and it’s a dead cert they will happen again. But there’s inherent randomness in the system, so it’s impossible to determine exactly when they will happen. It may be a thousand years from now, or it may be next Thursday. Or Friday.

The Met Office can’t even predict the weather next Friday (except in terms of probabilities), so it’s ludicrous to suppose the Maya could predict some catastrophe—to the exact day—more than a thousand years in advance. Even if they were in contact with extraterrestrial aliens who had computer technology millions of years ahead of ours, they couldn’t predict something that is fundamentally indeterminate. On the other hand, it’s equally foolish to say—as some extreme skeptics have—that there definitely won’t be a world-ending catastrophe on Friday. That’s effectively saying that such a thing is less likely to occur on that day than on any other day. In other words, the extreme skeptics give special significance to that particular day just as much as the extreme believers do!