A federal judge recently issued an injunction blocking stem-cell research funding. The probability that stem-cell research will quickly lead to life-saving medicine is low, but if successful, the positive effects could be huge. If one considers outcomes and approximates the probabilities, the conclusion is that the judge’s decision destroyed the lives of thousands of people, based on probabilistic expectation.
How do we make rational decisions based on contingencies? That judge didn’t actually cause thousands of people to die … or did he? If we follow the “many worlds” interpretation of quantum physics—the most direct interpretation of its mathematical description—then our universe is continually branching into all possible contingencies: There is a world in which stem-cell research saves millions of lives and another world in which people die because of the judge’s decision. Using the “frequentist” method of calculating probability, we have to add the probabilities of the worlds in which an event occurs to obtain the probability of that event.
Quantum mechanics dictates that the world we experience will happen according to this probability—the likelihood of the event. In this bizarre way, quantum mechanics reconciles the frequentist and “Bayesian” points of view, equating the frequency of an event over many possible worlds with its likelihood. An “expectation value,” such as the expected number of people killed by the judge’s decision, is the number of people killed in the various contingencies, weighted by their probabilities. This expected value is not necessarily likely to happen but is the weighted average of the expected outcomes—useful information when making decisions. In order to make good decisions about risk, we need to become better at these mental gymnastics, improve our language, and retrain our intuition."
Garrett Lisi, Uncalculated Risk