Thinking About Huge, Unlikely Risks

There have been fears that the new Large Hadron Colider (LHC) will generate a black hole when it is fully fired up, and the black hole will eat the earth. There was a similar fear before the first test firing, but we are still here. There were similar fears before the explosion of the first atom bomb, that it might set off a chain reaction in the atmosphere and destroy life on earth. (As if the threat were not enough with the tens of thousands of thermonuclear weapons in stockpiles around the world.)

New Scientist has an article pointing out that while the estimated probability of the black hole event is low, we have to weigh that fact by the confidence we have in the scientists who made the estimate.

In general if we have a set of non-overlapping alternatives -- A, B, C -- we can estimate the probability of X by the equation:

P(X) = P(X/A)*P(A) + P(X/B)*P(B) + P(X/C)*P(C)

So if we have two groups of scientists making different estimates of the probability of a catastrophe that will end life on earth we could estimate the probability that the earth will end by weighting the two estimates and comparing them with the case where neither group is right.

Of course the problem is that:

• We don't know the probability that the scientists are right,
• So we don't know the probability that neither group of scientists is right,
• Nor do we know the probability of disaster if neither group is right.

Still, the article has the right idea that we should consider not only the estimate of probability made by the scientists but also whether that estimate is trustworthy. In the case of the black holes, without knowing enough about the physics to judge the quality of the estimate, I don't see how there could be an accurate estimate.

On the other hand, the decision depends not only on the probabilities but also on the payoffs. In the case of a LHC, the downside is that it destroys the earth and all human life. The upside is that it might demonstrate that some current theories are right, or that the energy levels needed to demonstrate the accuracy of those theories is still higher than that reached by the LHC.

We can worry about the LHC and a very small probability of the end of the world. Or we can worry about an asteroid or comet hitting the earth; it is thought that the one that hit North America 13,000 years ago wiped out saber toothed tigers, mastadons and the Clovis culture human population; there are thousands of near earth orbit objects in space, and we don't know where they are. Or we can worry about another flu pandemic which is all but sure to arrive[ we are not sure about exactly when (a year, five, ten years, ....) or exactly how bad (one million deaths, five million, 100 million). Or we can worry about a new epidemic, another HIV/AIDS with a death toll in the tens of millions; new diseases emerge with distressing frequency. Or we can worry about World War III; the progression was 15 million deaths in WWI, 55 million in WWI,... Or we can worry about the economy and the likely damage to our friends and neighbors as well as the hunger and disease that the current global crisis will surely bring in its aftermath.

I don't have enough worry beads to allocate enough to all of these to do any good. So I choose not to worry about the LHC, but I hope someone is. As I hope that people are worrying about all the other disasters in our possible future.