These are not the probabilities you are looking for
There has been an increasing buzz in the papers regarding the impending launch of the Large Hadron Collider (LHC). Some of this concerns the possibility that it will lead to a disaster which destroys the world. This certainly sounds unlikely, and people who seriously suggest this are typically brushed aside with official calculations about the chance that the LHC will indeed destroy the world in any of the ways that have been suggested. For example, it is said that the chance of it destroying the earth though the creation of a particle called a strangelet is only about 1 in 50 million and the chance of it creating a black hole which does not evaporate is much less than this. However, these are not the probabilities we are looking for.
The problem is that the calculations don’t consider that the physical theories they are using could themselves be incorrect. For example, a hundred and twenty years ago, the scientific consensus held that Newtonian mechanics was the ultimate physical theory. If they had to calculate the chance that an experiment could lead to the curving of space and time, they would have said there was no chance at all. Indeed they would have also calculated that there was no chance of modern electronics or lasers existing, since both are impossible classically. They would have been at least as certain of this as the directors of the LHC are, and they would have gotten it wrong. We could be in just such a situation and with the highest possible stakes at risk.
There is, however, one large dissimilarity between now and then. In the late 19th Century, there was a huge amount of evidence in favour of Newtonian mechanics and only a few nagging lose ends that hadn’t been explained. Now, however, we are genuinely uncertain about our physical theories. Indeed, we are so uncertain as to spend more than 3 billion euros building the LHC in order to find out more. Moreover, we know that our current theories are false because they don’t correctly merge Relativity Theory and Quantum Mechanics. That is, we know that we don’t presently understand what happens with tiny objects that are extremely dense and/or moving near the speed of light. Since this is exactly what is occurring in the LHC, we have significant reason to distrust the probability calculations. They tell us the chance of the LHC destroying life on earth given that the underlying theory is completely correct, but what we really want to know is what the chance is given our uncertainty in the underlying theory. This is impossible to calculate precisely, but will be much higher than the stated odds. Considering the stakes, it is thus highly irresponsible for the LHC’s management to give so much emphasis to these misleading probability calculations, when the real chance is clearly higher.