Risk management is not a new idea: miners once used caged canaries as methane detectors. But modern technologies have made worldwide catastrophes imaginable — disasters so dreadful that we demand proof-in-principle that they cannot happen. Failures at nuclear reactors and chemical plants (such as Union Carbide in Bhopal, India) can kill or endanger many thousands of people. So the old protocol for risk avoidance — try it once; if it turns out to be dangerous don't do it again — is no longer acceptable. For example, scientists working on the Manhattan Project seriously considered whether a nuclear explosion could release enough energy to ignite the Earth's atmosphere. Their theories said no, and history has proved them right. But do we know enough about genetic engineering to proceed safely, or could someone unwittingly (or even deliberately) create a plague worse than the Black Death? For now, it's the physicists who are under the spotlight. The worry is that a new particle accelerator could trigger an irreversible process that would destroy our planet. It is a fair concern: one that must be raised, and one that has been answered decisively by scientists in the United States1 and in Europe2.
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